tech: It's 10AM. Do you know where your brake fluid reservoir is? - The Unofficial BMW M5 Messageboard (m5board.com)

greg · 1st November 2002, 07:57

So I put the EBC pads in today. (See this thread.) 32,000 miles and the rears were down to about 25%. (The fronts were replaced by the dealer a few months ago under warranty for a different reason.)

So I found it somewhat amusing that I had never really noticed the complete lack of a brake fluid reservoir anywhere in view in the engine compartment!. I looked in all the usual places under the hood - no reservoir! I looked in the manual. It says only "The brake fluid reservoir is located under the microfilter housing on the driver's side of the vehicle." I look again, under the filter - but in the engine compartment - no reservoir. I mean - I know what brake fluid reservoirs look like - has BMW changed the rules and put it in one of those big metal cannisters with a black lid? No. Couldn't be. now think. Really. Don't cheat.

Do you know where it is?

Well I do. Now, anyway. You really do have to remove the air filter box (not just the filter itself) to access the reservoir!!!

Step 1:

Disconnect the outlet plumbing by lifting the 3 retaining clips. The plastic piece to which these clips are attached is actually a ring that floats around the tube. Knowing this will be helpful in reconnecting it later.

Step 2:

Disconnect the hood switch wire, and flip the metal bail up and over to the left to free the cover. Lift the front of the cover up, and then remove by sliding it forward. Note that the back of the cover has tabs which protrude through both the filter box and the plastic frame behind it. Knowing this will be helpful in repositioning the filter box later.

Step 3:

Squeeze the funny looking clip shown here, while pulling up on the front of the filter box. You do not need to remove the filter element first, but you did already because you were curious - no biggy. On my car the rubber seal around the front and inside edges of the box was actually glued to the rubber seal running fore and aft - however it comes away easily and will reseal when replaced without needing new glue. Note that the outboard, rear corner of the box has to come out from under and behind the frame. Knowing this will be helpful in repositioning the filter box later.

Ahhhh. There's the sucker!

TCM · 1st November 2002, 08:08

Yes, BMW sure does hide that reservoir well. Always takes awhile for a person to find it for the first time. Glad to see you made out well.

V-10 4 Me · 1st November 2002, 17:38

Just curious if your resevoir was in fact low? I also need to check out mine. It is been about 2 years and time for BMW to change out the fluid.

It's funny that I haven't even thought about it...

Aussie2U · 1st November 2002, 18:46

Nice writeup & pics Greg. When my car was just a few months old, I took it on it's first track day. When the track's tech inspection guy looked under the hood, he asked where the brake fluid resevoir was. When I said down underneath that black box, he shook his head and said "great job BMW, make my life more difficult...". He sent me on through knowing the car was new & crossing his fingers I suppose.

greg · 1st November 2002, 18:48

Quote:

Originally posted by Ocean-Side M5
Just curious if your resevoir was in fact low? I also need to check out mine. It is been about 2 years and time for BMW to change out the fluid.

It's funny that I haven't even thought about it...

I think the systems are usually designed to carry enough fluid so that you won't run out as the fluid moves to the pistons to compensate for pad wear. In fact, if you never ADD fluid, then when you install new pads, you won't overflow the reservoir as you push the pistons back in, as long as you pump the pedal after each wheel.

In my case, the dealer had replaced front pads and rotors, and topped up the reservoir, even though they didn't replace the rears, which were pretty low. So when I compressed the rear piston for each wheel, the fluid level in the reservoir came back up to over "max". Had I not removed some fluid, doing the other rear would have caused an overflow. This would be especially bad in the M5, because you can't see the sucker. Next time you opened up the compartment, you'd find all that paint gone and the metal underneath rusting. I used a simple syringe too remove some fluid.

pmiranda · 1st November 2002, 22:06

Another bit of trivia: the same reservior supplies fluid to the clutch master cylinder. If you get as far as Greg did, you'll see a black hose running from the reservior into the firewall. I haven't looked for it, but apparently the clutch master cyclinder is inside the car by your feet! This is good to know, since if it leaks (like it did in my old Acura), you will start wearing out the clutch and you will never notice because it drips in or behind the carpet way back up in there. If you ignore the warning of the service dept. (like with my Acura, thinking they were pulling a fast one) and just look under the hood and think "leak, what leak" then you will completely wear out your clutch in under a month, making a ~$200 clutch master cylinder repair a $2000 clutch disk replacement.

JEM · 2nd November 2002, 07:28

Great pics, the only comment that I'll add is that once you've done it once, you'll find it takes a whole three minutes to pull out the filter housing.

BKH · 14th March 2006, 08:39

double post

BKH · 14th March 2006, 08:41

Un-ffffing believable! My "brake fluid low" warning goes off tonight...with only minutes to spare before they close I get to a Pep Boys and buy fluid...then pull into my hotel parking lot and spend 10 minutes looking for a brake fluid reservoir that I never did find. So now I'm in my room and pull up Greg's most helpful thread. Had I not seen this I would have spent another 10 minutes in the morning looking at the same things in the engine compartment all over again and then headed off to the nearest dealer. Thanks Greg!