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DIY: Brake Booster Replacement

49K views 50 replies 22 participants last post by  1stoutm5 
#1 · (Edited)
A couple weeks ago, I had some serious brake malfunction after some rain and a carwash. Thanks to the fine members of this forum, it was deduced that the compartment where the booster is located had filled with water, and water was sucked into the booster as a result. For those who don't know, the booster basically is an circular container with a diaphragm in the middle. Engine vacuum lowers the pressure on the master cylinder side of this diaphragm to assist the driver pushing the brake pedal down. When it filled with water, I think some water even got sucked into the vacuum lines to the engine. An old thread I found was detailing one members experience with this issue, where enough water was sucked into his engine to cause hydrolock and enough damage to cause his insurance to buy a new engine!

Needless to say, this is a potentially serious problem and it all has to do with the drain hole in the bottom of this compartment getting clogged with debris (not even big debris either!) and filling up with water. It only takes a few minutes to access this compartment, and although the drain hole is obscured by the booster you can at least reach down there and try to get stuff out of there or check if any water is accumulating. Now, onto the actual DIY:

PARTS NEEDED: Brake Booster (P/n 34331165541), Booster gasket (p/n 35111165132), master cylinder o-ring (p/n 34311165092), 1-2 pints DOT4 brake fluid

For the booster you can either get the BMW branded one for like $600 or Pelican has a TRW Lucas branded one (exact same unit) for $330. I opted for the cheaper one.

First thing you're going to want to do is remove the driver's side cabin air filter and filter housing. When you do that, this is what you'll see:



As you can see, underneath the filter housing there's this compartment where the booster and brake master cylinder sit. In my case this filled with water probably both due to rain we got, and after the carwash it filled up enough so as to suck water into the booster somehow, and probably into the vacuum line as my car died while idling and braking right after the wash and a couple times after.

Anyway, first thing you'll want to do is remove the cap to the tank along with the brake fluid level sensor harness. Then, remove the brake fluid from the expansion tank/reservoir using some sort of vacuum deal. I suppose a turkey baster would work here too. Theres a filter deal down in the expansion tank too that prevents you from getting all of the fluid out, but try to get as much as you can out, as it prevents it from coming out later.



Notice also that the tank is divided; there is another small section where the clutch slave line attaches. The fluid in there cant be removed until you remove the line to the clutch, and then it'll just fall out. I had trouble getting the clutch line out, and found that I had to cut s small notch in the end so it was wide enough to clear the flange deal at the end of the plastic protrusion on the expansion tank it hooks up to. You can see what I mean here:



Now that the clutch line is removed, you have to remove the expansion tank. There is a line running out of it that attaches to a hydralic line you have to pull off, but once you do that you can reach under the master clynder and unhook the two plastic latches on either side of the master cylinder, once you do that tilt the tank away from the engine and pull and it'll pop out of the master cylinder. I still had some brake fluid in there so it would be wise to put some shop towels underneath to catch. Worst case is it'll drip down into the compartment where you can clean it up later. Here's the master cylinder with the tank removed and the tank sitting out of the car, you can see the hose coming out of the bottom that I was talking about is circled:





Next you have to remove some cover pieces, first one snaps off above the divider deal (its removed and was where the red circle is) where the brake lines and vacuum line head toward the engine, and the second one that is below the wipers you unscrew the one screw and lift it out:





Next you can pul out the vacuum line from the booster, it'll just pop out. Now comes the fun part. Before you can take the booster and master cylinder out you have to unscrew the two brake lines on the other side of that divider deal. There isn't much clearance, but I managed to get two wrenches on there. Hold the big middle coupling steady as you unscrew the fitting on either side. I found that a normal wrench wanted to strip the fittings, so I used those wrenches that are shaped like a nut. The fitting size is 11mm and the the middle coupling is 15mm. The last thing you want to do is strip these hydraulic lines, so please be careful.



Once they are out, you can remove the brake lines from the master cylinder. These come off rather easily. Here's a shot of the master cylinder/booster with all the brake lines removed:



It's worth noting that the TIS calls for you to seal the brake lines and master cylinder openings so as to prevent dirt from entering. I used duct tape for this purpose, and just used care overall to prevent that from happening.

Next you have to go into the drivers footwell and remove the trim piece above the pedals. There are three screws and another fastener deal that you just turn a quarter turn to undo. You can then lift the panel down, and you'll see the wires that attach to the gong, which can be removed:



The trim panel then comes out, and you'll see the other end of the brake booster. The TIS calls for you to remove the brake light switch (circled in green), which I did but I'm not totally sure if it was necessary. It's very easy to remove though, it just slides out. Then you have to disconnect the clip (circled in red) that keeps the pin coming from the brake pedal attached to the booster:



The TIS also calls for you to undo the recoil spring from the brake pedal, but I found that to be difficult and not needed. Now you have a clear shot at the two nuts that hold the booster in place (circled). You can see them along with the pin to the booster and the retaining clip removed. To remove these two nuts you'll need a deep socket rachet and patience. I found for the top one you I only had clearance to turn the wratchet about an inch, so it took a while:



Now the booster comes out pretty easily. Take care not to bang around the master cylinder or anything and not to damage any brake lines but it basically just slides right out. As you can see below, the drain hole in my compartment was quite full of sludge, and you can't even see the drain hole:



All clean, now you can see the drain hole:



Now you can unscrew and remove the master cylinder from the old booster.

When I removed the booster, it was FULL of water. Not just clean water either, but dirty sludgy water. I didn't get a shot of me pouring it out of the old booster, but here's a picture of some that got on the ground. The yellow stuff is the brake fluid, and the black oil looking fluid next to it is the some of the water that came out of the booster! Also, I got a shot of the inside of the booster, which as you can see was disgusting:





When the master cylinder is removed, replace the oring and reinstall into the new booster. Torque the nuts to 26Nm, and put on the new gasket. Here's the new booster with master cylinder attached:



From here, it's just a matter of putting everything back together in reverse order. The brake lines are suppose to be torqued to 18Nm, but I don't know how one could use a torque wrench to do it so just tighten them fairly tight but don't overdo it. Again, use care not to get any dirt into the lines or master cylinder during reassembly. I found that putting everything back together took half the time as taking it all apart.

Once everything is back together, you have to refill the expansion tank with new DOT4 fluid and bleed the brakes. Although one is supposed to use the GT1 near the end of the bleeding process to cycle the DSC/ABS pumps, I didn't have one so I suppose I missed out on cycling the old fluid out of those. Hopefully it's not too big of a deal.

I'm totally not mechanically talented, and this is easily the most complicated thing I've ever attempted on a car. As it required a special tools and a lift to bleed the brakes, I ended up doing all the work at a place called First Gear Garage, located in Eden Prairie, MN. They've been open for like 7 or 8 months, and you basically rent out a bay or a lift by the hour. They provide you with tools and everything to get the job done. It's a very cool, clean shop and I wouldn't have attempted it out of the garage at home. Serious props to these guys!

Here's a couple shots of the shop. They were actually doing a free brake clinic today where they teach you how to maintain your brake system, replace pads, bleed, etc. It's cool concept for a business. Here's a couple shots of the garage and clinic in progress:





Like I said, if I can do this than anyone can do this. I don't have much experience at all, but with the proper tools and some common sense I got it done. My brakes are so much better now, even better than before the booster became flooded with water. If you have any comments/questions please let me know.
 
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19
#5 ·
I did clean up the spilled fluid as best I can, especially inside the compartment where some dripped. The guys who run the shop helped with that. as well They keep the place very clean and mopped up and cleaned up any mess left from people who were working in there during the day, whether it was metal shavings from a guy removing and installing a new exhaust or oil drops or what have you.

As for bleeding the clutch slave, I didn't do it. The TIS doesn't call for it either, but I suppose it would be prudent to do so. I may go rent a pressure bleeder from an auto parts place or go back to their shop to do that. For those in the know, is that a necessary thing to do after this job? The line from the expansion tank to the clutch slave is slightly inclined, so any air could feasibly be displaced by the new fluid and bubble up to the tank before reaching the clutch cylinder.
 
#6 ·
Get your system bled properly (with GT1)

At first opportunity (Do NOT put this off), get your car into a shop with a GT1 and someone who knows
their way around our car. The entire brake hydraulic system and ABS/DSC system must be bled exactly
as called out in the TIS. Right now you have no DSC and if the ABS is engaged, you will then have a very
soft, mushy brake pedal. If you have the opportunity to watch while the procedure is being done, you
will be amazed at the amount of trapped air that comes out.

Really, your car is "less-than-safe" as it sits right now, so please get this done.

Be sure they bleed your clutch system as well, since it will undoubtedly have air in that system as well.
In fact, I always make it a point to bleed/flush the clutch whenever I do the brake fluid, given the fact
that it is so easily done.

Regards,
Alan
 
#7 ·
At first opportunity (Do NOT put this off), get your car into a shop with a GT1 and someone who knows
their way around our car. The entire brake hydraulic system and ABS/DSC system must be bled exactly
as called out in the TIS. Right now you have no DSC and if the ABS is engaged, you will then have a very
soft, mushy brake pedal. If you have the opportunity to watch while the procedure is being done, you
will be amazed at the amount of trapped air that comes out.

Really, your car is "less-than-safe" as it sits right now, so please get this done.

Be sure they bleed your clutch system as well, since it will undoubtedly have air in that system as well.
In fact, I always make it a point to bleed/flush the clutch whenever I do the brake fluid, given the fact
that it is so easily done.

Regards,
Alan
Interesting. The TIS procedure has you basically do each corner again after an initial bleed while cycling them via DIS, so basically I could just commence from that point, saving the shop some time. I definitely have read many threads here where people bleed the system at home sans the GT1 and the common thought seemed to be "there'd be old fluid in the pumps but not much," however you claim it's a large safety issue. I wish I could figure out how to successfully make a the cable to connect to my laptop where I have the GT1 software installed so I could do this myself to see, but I'll call the local dealers and BMW shops to see what they'd charge for the GT1 portion of the bleed.

Anyone else have thoughts on this? I didn't realize this could be so dangerous. Surely there are some here who have bled the brakes on their own w/o a GT1 and lived to tell the tale?
 
#15 ·
This is a great writeup and it helped me along today as I swapped out my booster and master cylinder. However, in the interest of shared knowledge I'd like to add a few things (hopefully without offending the OP!)

1 - When removing the booster assembly, you can omit the stage where the OP mentions undo-ing the two hydro lines that are a pain to get to. The ones closest to the engine, outside of the booster bay. You will have enough articulation inside the bay to move the hydraulic lines out of the way without removing those outside and nearest to the engine. Removing the three lines from the rubber housing that mates them to the top of the bay will aid further in ease of R&R of the unit.

2 - When under the pedals inside the car, the only things you need to mess with are the two bolts that attach the master cyl assy. to the firewall and the safety clip that attaches the pedal to the piston. You can access the bolts with a deep drive socket, a small extention, a wobbly joint, and a large extension (in that order from firewall to your hand). The safety clip is removed by lifting the tab on the back flat end and pushing the clip away from the pin. A small screwdriver aids in this.


Hope this all helps. This honestly is a super easy job and shouldn't take more than 2 hours (including taking pictures for facebook, drinking 2 coffees and cleaning the general area around the booster if you're OCD like me). Much less risk involved if you stay away from the lines closest to the engine, since the OP mentioned he almost stripped them. They look like knuckle-busters anyways, so why bother :)
 
#18 · (Edited)
A couple weeks ago, I had some serious brake malfunction after some rain and a carwash. Thanks to the fine members of this forum, it was deduced that the compartment where the booster is located had filled with water, and water was sucked into the booster as a result. For those who don't know, the booster basically is an circular container with a diaphragm in the middle. Engine vacuum lowers the pressure on the master cylinder side of this diaphragm to assist the driver pushing the brake pedal down. When it filled with water, I think some water even got sucked into the vacuum lines to the engine. An old thread I found was detailing one members experience with this issue, where enough water was sucked into his engine to cause hydrolock and enough damage to cause his insurance to buy a new engine!

Needless to say, this is a potentially serious problem and it all has to do with the drain hole in the bottom of this compartment getting clogged with debris (not even big debris either!) and filling up with water. It only takes a few minutes to access this compartment, and although the drain hole is obscured by the booster you can at least reach down there and try to get stuff out of there or check if any water is accumulating. Now, onto the actual DIY:

PARTS NEEDED: Brake Booster (P/n 34331165541), Booster gasket (p/n 35111165132), master cylinder o-ring (p/n 34311165092), 1-2 pints DOT4 brake fluid

For the booster you can either get the BMW branded one for like $600 or Pelican has a TRW Lucas branded one (exact same unit) for $330. I opted for the cheaper one.

First thing you're going to want to do is remove the driver's side cabin air filter and filter housing. When you do that, this is what you'll see:



As you can see, underneath the filter housing there's this compartment where the booster and brake master cylinder sit. In my case this filled with water probably both due to rain we got, and after the carwash it filled up enough so as to suck water into the booster somehow, and probably into the vacuum line as my car died while idling and braking right after the wash and a couple times after.

Anyway, first thing you'll want to do is remove the cap to the tank along with the brake fluid level sensor harness. Then, remove the brake fluid from the expansion tank/reservoir using some sort of vacuum deal. I suppose a turkey baster would work here too. Theres a filter deal down in the expansion tank too that prevents you from getting all of the fluid out, but try to get as much as you can out, as it prevents it from coming out later.



Notice also that the tank is divided; there is another small section where the clutch slave line attaches. The fluid in there cant be removed until you remove the line to the clutch, and then it'll just fall out. I had trouble getting the clutch line out, and found that I had to cut s small notch in the end so it was wide enough to clear the flange deal at the end of the plastic protrusion on the expansion tank it hooks up to. You can see what I mean here:



Now that the clutch line is removed, you have to remove the expansion tank. There is a line running out of it that attaches to a hydralic line you have to pull off, but once you do that you can reach under the master clynder and unhook the two plastic latches on either side of the master cylinder, once you do that tilt the tank away from the engine and pull and it'll pop out of the master cylinder. I still had some brake fluid in there so it would be wise to put some shop towels underneath to catch. Worst case is it'll drip down into the compartment where you can clean it up later. Here's the master cylinder with the tank removed and the tank sitting out of the car, you can see the hose coming out of the bottom that I was talking about is circled:





Next you have to remove some cover pieces, first one snaps off above the divider deal (its removed and was where the red circle is) where the brake lines and vacuum line head toward the engine, and the second one that is below the wipers you unscrew the one screw and lift it out:





Next you can pul out the vacuum line from the booster, it'll just pop out. Now comes the fun part. Before you can take the booster and master cylinder out you have to unscrew the two brake lines on the other side of that divider deal. There isn't much clearance, but I managed to get two wrenches on there. Hold the big middle coupling steady as you unscrew the fitting on either side. I found that a normal wrench wanted to strip the fittings, so I used those wrenches that are shaped like a nut. The fitting size is 11mm and the the middle coupling is 15mm. The last thing you want to do is strip these hydraulic lines, so please be careful.



Once they are out, you can remove the brake lines from the master cylinder. These come off rather easily. Here's a shot of the master cylinder/booster with all the brake lines removed:



It's worth noting that the TIS calls for you to seal the brake lines and master cylinder openings so as to prevent dirt from entering. I used duct tape for this purpose, and just used care overall to prevent that from happening.

Next you have to go into the drivers footwell and remove the trim piece above the pedals. There are three screws and another fastener deal that you just turn a quarter turn to undo. You can then lift the panel down, and you'll see the wires that attach to the gong, which can be removed:



The trim panel then comes out, and you'll see the other end of the brake booster. The TIS calls for you to remove the brake light switch (circled in green), which I did but I'm not totally sure if it was necessary. It's very easy to remove though, it just slides out. Then you have to disconnect the clip (circled in red) that keeps the pin coming from the brake pedal attached to the booster:



The TIS also calls for you to undo the recoil spring from the brake pedal, but I found that to be difficult and not needed. Now you have a clear shot at the two nuts that hold the booster in place (circled). You can see them along with the pin to the booster and the retaining clip removed. To remove these two nuts you'll need a deep socket rachet and patience. I found for the top one you I only had clearance to turn the wratchet about an inch, so it took a while:



Now the booster comes out pretty easily. Take care not to bang around the master cylinder or anything and not to damage any brake lines but it basically just slides right out. As you can see below, the drain hole in my compartment was quite full of sludge, and you can't even see the drain hole:



All clean, now you can see the drain hole:



Now you can unscrew and remove the master cylinder from the old booster.

When I removed the booster, it was FULL of water. Not just clean water either, but dirty sludgy water. I didn't get a shot of me pouring it out of the old booster, but here's a picture of some that got on the ground. The yellow stuff is the brake fluid, and the black oil looking fluid next to it is the some of the water that came out of the booster! Also, I got a shot of the inside of the booster, which as you can see was disgusting:





When the master cylinder is removed, replace the oring and reinstall into the new booster. Torque the nuts to 26Nm, and put on the new gasket. Here's the new booster with master cylinder attached:



From here, it's just a matter of putting everything back together in reverse order. The brake lines are suppose to be torqued to 18Nm, but I don't know how one could use a torque wrench to do it so just tighten them fairly tight but don't overdo it. Again, use care not to get any dirt into the lines or master cylinder during reassembly. I found that putting everything back together took half the time as taking it all apart.

Once everything is back together, you have to refill the expansion tank with new DOT4 fluid and bleed the brakes. Although one is supposed to use the GT1 near the end of the bleeding process to cycle the DSC/ABS pumps, I didn't have one so I suppose I missed out on cycling the old fluid out of those. Hopefully it's not too big of a deal.

I'm totally not mechanically talented, and this is easily the most complicated thing I've ever attempted on a car. As it required a special tools and a lift to bleed the brakes, I ended up doing all the work at a place called First Gear Garage, located in Eden Prairie, MN. They've been open for like 7 or 8 months, and you basically rent out a bay or a lift by the hour. They provide you with tools and everything to get the job done. It's a very cool, clean shop and I wouldn't have attempted it out of the garage at home. Serious props to these guys!

Here's a couple shots of the shop. They were actually doing a free brake clinic today where they teach you how to maintain your brake system, replace pads, bleed, etc. It's cool concept for a business. Here's a couple shots of the garage and clinic in progress:


Like I said, if I can do this than anyone can do this. I don't have much experience at all, but with the proper tools and some common sense I got it done. My brakes are so much better now, even better than before the booster became flooded with water. If you have any comments/questions please let me know.
Hi! Could you please help me? I'm stuck... I disconnected brake lines but I just can't remove master cylinder from brake booster. Do I need to pull them out as one piece? There is absolutely no clearance to take out master cylinder... How did you do it? Thanks!
 
#19 ·
The booster and master cylinder come out as one piece, you can take them apart once they are both out.

I just realized the pictures in this thread no longer work. I'll try to fix that today and repost with pictures.
 
#22 ·
I put a zip file containing the TIS and pictures I took on filedropper. You can find it here: http://www.filedropper.com/booster
Thannnnnnks!!!!!!! That's what I was missing! :) You have such a nice DIY!
I noticed that according to TIS there has to be some hose running through upper cover under the booster.
I don't have anything there (like on your pic) but the scheme does. Do you have anything there?


 
#23 ·
TIS often uses the same diagrams for multiple cars, so there can be minor differences between diagrams and what's under your hood. The photo above is from my car, and as you can see I don't have anything in there.
 
#24 ·
Nabio, any chance you still have those pictures?

I think either my Master Cylinder or brake booster needs to be replaced as my pedal suddenly takes much more effort and travel to stop the car. Pressure isn't completely gone like with a bursted brake line. I can tell that the pressure to the pedal returns but it isn't that strong.
 
#26 ·
brake boost/engine hydrolock

I second the Hydro lock from water being sucked up in the vac lines. In 2002 my 1998 540i was acting up periodically where the engine seemed to be misfiring. I had taken it to BMW three previous times over this issue and even reported to them that the issue seems most common after a rain. They could never seem to figure out although each time they reported that they thought they fixed the issue. The third time I picked the car up I was in a hurry as I was going on a business trip so they washed it after service and when I drove it off within a mile I had misfire issues, so I took it back and got a loaner to take on my trip. When I got back again they said my car was ready and they would call me after it had been washed but after several hours and no call I called them back only to be delayed further. Finally the next day they called and said there were some issues and needed me to come in. What I found was after they washed the car they experienced hydro lock, broke a rod and it punched a hole in the engine block. <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:eek:ffice:eek:ffice" /><o:p></o:p>
The cause of the problem… previously there was a wiring issue and part of the harness runs thru the brake boost box. Tree leafs and other debris have a tendency to collect in that area just under the hood, “which is not an issue.” The issue is when you pull the top off the box and allow some of that debris in the box it can cover the weep holes in the bottom backing up water as it runs down your windshield submerging your brake booster, and the rest is history. <o:p></o:p>
 
#27 ·
Quick question just to flesh this out in my mind, the drain hole in the bottom of the cavity, is this just a hole allowing water to drain wherever, or is there some sort of hose directing the water somewhere. I only ask as checking this drain is something I hope to check this weekend, and a hole would clear from the top but if there's some hose underneath, then I want to clear that also, though not sure how. Is running hot water through these things still good for clearing drains like this?
 
#28 ·
I don't remember if there is a connecting hose under the box for the drain holes but I would think if the holes are clear and after running some water into the box and finding it to drain well then everything should be good. If you find there is a line attached I would think straightening out a wire hanger and pushing it thru should clear any debris.

good luck!!
TC
 
#29 ·
Agreed, many thanks :)
 
#31 ·
I recently had some similar problems that were mentioned above on my '02 M5. I purchased 2 used brake boosters/master cylinders for about $150 total. This job was relatively easy, but just time consuming. I followed the guide pretty closely, so I will say that it is a great write-up.

One thing i did to try to keep air out of the ABS module was press the pistons out on 1 front caliper and one back caliper. I took some old playing cards and made them a little thicker than the backing plate on the pads. I then wrapped them with electrical tape. I removed the pad on the side without the piston and installed the cards. I then put them back on the car (bolts hand tight) and pressed my brakes until they got tight on the rotors. Be sure to do this before removing any of the brake lines, fluids, etc. After I completed the brake booster swap and had all lines hooked up, I filled the resevoir with fluid about halfway up the screen. I then removed the calipers and pressed the pistons in hoping this would push the air back to the resevoir, thus keeping it from the ABS module when I bled the brakes. When I did this at each caliper the fluid level rose in the resevoir. Maybe this worked and maybe it didnt, but I thought it was worth a shot.
If you do get air in the ABS module and you go drive/brake on a dirt/sandy road to activate the ABS, will it remove the air from the module?

I am attaching a video and pictures of the plugged drain hole below the brake booster. I am working on taking the brake booster apart and will attach those pictures when complete.

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#34 · (Edited)
I believe I too need to replace the brake booster but throwing out some symptoms, and some possible variables into the mix.

I've had my e39 2002 525i since about 10/2012. Brakes were perfect for about 6 months'ish. I've replaced pads, rotors (rebuilt caliper seals), etc. over time. a few months leading up to that time, I had pre-symptoms of failed ABS (shuttering) but would be rare and brakes fully functional. Eventually I got the tri-fecta, but brakes worked 100% still. Just throwing that out there to preface that I still haven't fixed the ABS issue (not for a lack of trying though). So I don't think that is my current issue.

Also, I've bled my brakes around 2013'ish. The fluid is full (max and a little higher), but does look dirty. So yah, I guess I could bleed the brakes but don't think that's it.

Ok, so around the winter of 2013, I came out to "odd" braking (after a heavy rain). Odd being hard at first but quickly went soft/mushy, and squeaky, like a wet sneaker). . I read up and sure enough, cabin filter area was flooded way high and full with leaves clogging small drain. I corrected and brakes were better, but not perfect. Looking back, they've been getting worse and worse.

Now, just this week, while I don't have the watery squeak that came with a flooded cabin (no rain/car wash in weeks either), I have the similar, but not exact symptoms though: Somewhat mushy to half way, but pedal doesn't go all the way down, but if I push hard, it will go pretty far down to floor, and it doesn't squeak now (since drain hole fixed). And with average driving around town, braking seems almost normal. It definitely doesn't drop to the floor. Braking is there, but have to really step on it.

When I start car and go right away, and come to a stop, I have to use moderate pressure to stop. Quick stop is unlikely. But, after car warms up a little and I pump brakes often while going down a side road, braking improves, but not great by any stretch. But I could probably get a quick stop out of the car.

I'm in TX and it seems the hotter out (daytime), the worse it is too. I'm wondering, like an engine, the vacuum inside the booster is degraded with hot engine compartment air?

Anyway, hoping some of this rings a bell to folks in a rough determination that it's the brake booster more than something else.

Oh, one quick question, did anyone have to replace those factory hose orings, or use fuel line clamps?
 
#35 ·
If you are sitting at idle and you press the brakes as far to the floor (and hold it) as you can will the car sputter and act like it wants to stall out?

Is it really hard to press the brake pedal? There is a valve on the vacuum line going to the booster that could be bad. Its easy to check without removing the booster. I am not sure how it fails though. I am assuming closed, but dont quote me.

Also, I would pretty much guarantee that your booster still has water in it. The only way all the water came out of mine was to take it apart.

I have a used booster that should fit your car if you need one.
 
#38 ·
Hi,

At idle, I can't push to floor (or at least I don't think they go to floor). It moves about 2" to 3" max. Pressing VERY hard, it won't go all way down and car doesn't hiccup at all. It presses what I think is normal for few inches, but guess that's too much? After that, it's VERY hard and won't go any more, but also car needs more to stop. I think the valve you are referring to is the suction jet valve and from what I've read, if it failed, the car would likely throw a vacuum code (don't have any codes).

I think I'll take to a shop and maybe they can do the pressure test.
 
#37 ·
There's an easy way to tell if your booster is bad or full of water: hook up a brake pressure gauge (0-2000 psi) to a front caliper bleeder port. With the brake pedal pressed down hard, engine not running so no booster effect, maybe 700-1000 psi. With engine running and a good booster, maybe 1500-2000 psi.

They're cheap, and if you can't do it, any brake shop will have one.
 
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