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Did a thermostat replacement today (a lot of pics)

255K views 554 replies 154 participants last post by  baicc 
#1 ·
Replaced the thermostat on hdhntr23's Beast today. Too bad he had to work, or I would have watched him do it! Oh well, not too bad, just under 2 hours. Would have been less if I wasn't getting text messages every 5 minutes.....

Thank you to DouglasABaker for some helpful advice.

Thermostat





Thermostat housing removed



Here you can see 3 of the 4 O rings that should be replaced. The other is a tube that goes inbetween them, it has 2 Orings on it, one on each end.







The before mentioned tube is here in the middle. Remove it and replace the 2 Orings. I then put the tube on the thermostat housing for the reinstall.





New thermostat installed





Some of the old radiator fluid



 
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#2 ·
Thanks for the PICS and advice.
Inside 2 hours of your time equates to 2 six packs of your favorite brew in return.!
Where did you buy the new thermostat - BMW dealer or other - how much where the parts?
 
#4 · (Edited)
Parts were about $230. I bought them at the dealer. Thats not including the lap dances and meals Im going to have to buy Tim on the 17th. That DOES however include about 3 sets of O rings in case any ripped.

Did you also replace the temp sensor? Curious - I didn't, now I'm thinking I should have for preventative maintenance.
Yes the top temp sensor was replaced too. That part total was including the sensor. If I hadnt already, I wouldve also replaced the lower temp sensor, near the bottom of the radiator.

Yeah I had to work, and Tim's schedule got changed, it originally was planned for me to do it with him YESTERDAY, so to make up for it, Im going to go up there tomorrow and help with yet another clutch install!!!! Id say my full day off tomorrow will make up for not taking a half day yesterday.

For real Tim thanks! You are SO the MAN.

Lap dances on me bro!!! Err wait... Ill BUY lap dances hahaha.
 
#7 ·
I believe hdhntr23 and I have the same SES fault code which is "low temp". Mine comes up every few days and then seems to reset on warm 80 deg ++ days in central Ohio. Last winter it stayed on from November to March. Temp gauge hangs out at about 11 o'clock on the dial. Plenty of threads on the topic but very few replacement with "pics". So, thanks goes out to tim for keeping us current on DIY's.
 
#9 ·
The code I was getting on the Peake was a 69 (hehehe I typed 69)... anyway thats "coolant temperature implausibility". It wasnt for PM, this job isnt one of those that one would do JUST for PM. Maybe replacing your sensors but not the T-Stat.

Hope this helps
 
#11 ·
As crazy as it sounds it drives much smoother than it did before. Nice strong pull even steady acceleration.
 
#13 ·
What was the parts list? $230 bucks for a $20 thermostat and $2 worth of O-rings is a bit steep. I know BMW parts tend to be on the expensive side, but come on.
 
#14 · (Edited)
What was the parts list? $230 bucks for a $20 thermostat and $2 worth of O-rings is a bit steep. I know BMW parts tend to be on the expensive side, but come on.

look at that t-stat - looks way different then any "normal" one

RealOEM.com BMW E39 M5 Waterpump - Thermostat

books for ~145 bucks, holy crap!

and the o-ring on it must be made out of unicorn horn @ 47bux

temp ensor is a 25 dollar part, not too bad

+ all the misc orings

the t-stat is really what gets expensive, yikes

tischer comes out to about 160 bucks + coolant
 
#17 ·
Oh and the big O ring that goes inside the T-Stat housing, its made of a wicked hard plastic/rubber on top of a metal ring. I saw the carnage on Friday @ my boy Tim's house and the old one had to be ripped out with pliers.
 
#18 ·
I'm really not surprised at the cost, but I still think it ridiculous. I noticed the T-stat was relatively huge, and weird compared to most others I've ever seen. But we gotta pay to play, right?
 
#22 ·
...
Here you can see 3 of the 4 O rings that should be replaced. The other is a tube that goes inbetween them, it has 2 Orings on it, one on each end.



Great job on the writeup guys - glad you got it all taken care of :)

One slight correction: That is actually 2 of the 6 (six) o-rings that should be replaced. Each of the tubes shown is also removable and has an o-ring on the other end as well. In total there are 3 removable tubes, each with 2 o-rings.

If the t-stat housing has not been removed before, it is very likely that the pipes will be "frozen" and will seem like they are part of the housing (or block), but they are not. If you can manage not to move them at all during dis/re-assembly, then you can probably avoid replacing them. This, however, is very difficult, so I would err on the side of replacing all 6 of them while I had it apart.

d-
 
#24 ·
Great job on the writeup guys - glad you got it all taken care of :)

One slight correction: That is actually 2 of the 6 (six) o-rings that should be replaced. Each of the tubes shown is also removable and has an o-ring on the other end as well. In total there are 3 removable tubes, each with 2 o-rings.

If the t-stat housing has not been removed before, it is very likely that the pipes will be "frozen" and will seem like they are part of the housing (or block), but they are not. If you can manage not to move them at all during dis/re-assembly, then you can probably avoid replacing them. This, however, is very difficult, so I would err on the side of replacing all 6 of them while I had it apart.

d-
Oops, didn't know that. They must have been frozen pretty damn good, I pulled like hell to get them out......
 
#23 ·
200+ miles so far and no leaks!
 
#26 ·
FYI, cooling the heads first is not particularly new. Ford/Yamaha did it on the SHO V-8s starting in 1996 model year. It was bit unusual then, but not new. I've had several "regular" T-stats fail in the open mode, but that is probably less common that failing closed. Having it designed to fail open is a good idea. Which probably means mine will fail closed... ;-)
 
#32 ·
Ah, of course! Thanks. :)

Chuck
 
#34 ·
Sorry for the stupid question but why not do the water pump as well when you're already there for preventative maintenance (or do ours not fail)?
 
#35 ·
2 or 3 reasons for me at least...

1. most importantly it wasnt cost effective for me to do it right now.

2. Im under the impression that they arent connected or in the same housing vs. most standard setups (I may get corrected on this one sorry if its wrong)

3. Tim has done enough for me I didnt want to have him worry about that right now anyway.
 
#37 ·
Do our water pumps fail often or it's not an issue?
The reason I ask is that my friend's just blew up on his e46 M3 and he is worried about engine damage from the possible overheat.
 
#38 · (Edited)
In all the years I've had the E39 M5 (and been on the board here), I can't really recall any water pump failure issues ever being discussed...of any significance anyway. Apparently, the M5 pump design is much more robust than the 540i/E46/E36, etc, where you need to proactively replace by ~60k. That being said, the E39 M5 is now old enough that some people are really getting up there in miles. I wonder if tranck has ever done his water pump?
 
#40 ·
Im under the impression that they arent connected or in the same housing vs. most standard setups (I may get corrected on this one sorry if its wrong)
The thermostat resides in the upper portion of the water pump. However, as others noted, there aren't a lot of posts about water pump failures on this board, so either nobody bothers to report them, or they're not quite the issue they are on other BMWs. Still, when I had my t'stat changed recently (at over 105k miles), I went and did the pump, too. My car is my daily driver and I just didn't want to get stuck somewhere with a cooling problem. On tear-down found that the pulleys/tensioners were well-worn, too. The coolant reservoir looked like it was on its last legs, and so I changed that out. Also changed most if not all of the rubber parts that had to come out at the same time (hoses, belt).
 
#45 · (Edited)
Wait, we have to use BMW specific coolant too? I just refilled mine with Prestone after doing this the other day.
You should use BMW approved fluid. Too many variables with seals and metals for me to take the chance just to save a few dollars. If you go aftermarket, I'd seriously look into Zerex G-05. Supposedly it's factory fill for many European cars these days, only w/o the huge dealer markup. Zerex G 05. There is a Pat Bedard article on this on Car and Driver online.
 
#46 · (Edited)
So how hard would it be for me to drain ALL of the coolant and refill it with the BMW stuff? When we did the t-stat replacement, we didn't drain the block, so right now there's just an amalgamation of fluids in there - old BMW coolant, new Prestone coolant, and DI water. I really don't want to have to take it to someone; that's the whole reason I did it myself. I guess I should have researched the coolant issue beforehand.

Edit: After some research, it looks like I just have to pull the radiator plug and the plugs on both sides of the block and refill 50/50 with coolant/water. I need 6.5 quarts of coolant since we have a 13 quart capacity, right?
 
#48 ·
If youre going to drain it from the block I suggest new crush washers when you do.
 
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#50 ·
Yes Douglas. It is MANDITORY that if you drain from the block you get new crush washers. That would suck to get the thing drained all the way then only to realize you didnt buy 2 $.60 parts. So while youre buying the MANDITORY OEM coolant ask them for some crush washers for the block.
 
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