DIY: Thermostat (manual M54)

[nathancarter]

Here's a DIY for easily replacing your thermostat. It's written for the M54 motor with a manual transmission attached, but only minor adjustments are necessary if you have something different.

Tools needed:
Socket set - 10mm & 13mm, specifically
Flat-head screwdriver
Philips-head screwdriver #2 or #3
Torx screwdriver or socket - T25 I think
Torque wrench (optional)
Side-cutter plier (optional)
Fan pulley counter-holder and 32mm slim wrench (if you have an automatic transmission)
Ramps and/or jack stands - the supplied trunk jack is NOT sufficient.
CLEAN bucket, at least 2 gallons
Cheesecloth for straining coolant (if re-using coolant)


Notes:
- If you have over 75k miles, I would HIGHLY recommend doing a cooling system overhaul - water pump, thermostat, expansion tank, hoses.
- If you are certain your coolant is less than about a year old, you can re-use it, which I did here. Otherwise, all new coolant is recommended, so you'll want to drain the block using the third drain plug on the side of the block. I won't cover that here.
- Automatic transmission has a couple of different steps to get the fan out of the way.
- Automatic transmission only has one blue drain plug, not two.




































(This last photo is underneath the car, looking forward)

Notes on installation and finishing up:
- DON'T over-tighten the drain plugs in the bottom of the radiator or they'll crack.
- I put a tiny bit of grease on the hose ends of the new thermostat, to ease future removal of hoses. I don't know if this was a good idea.
- Torque for the thermostat bolts is very low - about 10 N-m I think (Bentley manual doesn't specify)
- Since we only drained the radiator, bleeding shouldn't be necessary. SLOWLY strain the coolant from your bucket through a few layers of cheesecloth back into the expansion tank. If you spilled any, top off with distilled water. It may help to loosen the bleed screw (located behind the radiator cap) when refilling, but if you do so, be careful not to over-tighten and crack it.
- Wash off any spilled coolant with clean water or it'll leave a crusty residue when it dries.
- Watch for leaks and monitor coolant level over the next few days.

If you elect to replace all your coolant, here's a useful link:
BMW325i.NET - Maintenance - Coolant Change

[blackswan]

Thanks for this awesome resource!!

[sammk]

Count me in as yet another beneficiary..

[BobSC]

One of the best DIY's I've seen. Thanks for doing this and with the great pics!

[ninjarider]

Thanks nathan for this superb DIY post. Really helped me change my thermostat and coolant. I also referred to http://www.bmw330ci.net/maintenance/coolant.php to flush out coolant from the engine block. The whole process took me half a day, but that's because I had to wait for the car to cool on a hot day, took me a while to get it on ramps, and I overtightened a thermostat bolt, shearing it off completely !

I hope this helps others .. I did not use a torque wrench, so the 8.8 rated thermostat 10mm bolts will shear off if you overtighten them, so be careful (I obviously didn't read nathan's post close enough), after facing some resistance on a ratchet, stop, it is enough to hold the seal. Thankfully, a part of the bolt was sticking out of the engine block, and it rotated and I was able to unscrew it out !

[jbenjamin]

Thanks Nathan, that was a very thorough post. I need to change my thermostat soon, I am getting a code 168 Electrical thermostat mechanical fault. I will be using your post to get the job done.

JB

[BirdmanFerrari]

Nathan,
Thanks for taking the time to put this together. One of the reasons the BMW community is so great is because of stuff like this!

Best,
Birdman

[robmpulse]

You stated several times that this is manual specific info. Can these not be followed to change an auto car?

[nathancarter]

The majority of the process will be the same for an automatic. The difference is in the fan - Step 9, above. The manual has an electric fan that is VERY easy to remove; the automatic has a fan that's attached to the front of the water pump, and driven by the belt. See the rusty threaded part in the photo for step 10? The automatic fan is threaded onto there. To remove it, you'll need a slim 32mm wrench. It's also REVERSE THREADED which can trip you up if you're not paying attention.

If you need a hand with it, let me know. Bring it over one evening or weekend morning and we can get it knocked out. The local BMWCCA chapter is also having a DIY event in a few weeks:
http://www.motorsportreg.com/index.c...6BD5F9006A2A8C

[robmpulse]

The majority of the process will be the same for an automatic. The difference is in the fan - Step 9, above. The manual has an electric fan that is VERY easy to remove; the automatic has a fan that's attached to the front of the water pump, and driven by the belt. See the rusty threaded part in the photo for step 10? The automatic fan is threaded onto there. To remove it, you'll need a slim 32mm wrench. It's also REVERSE THREADED which can trip you up if you're not paying attention.

If you need a hand with it, let me know. Bring it over one evening or weekend morning and we can get it knocked out. The local BMWCCA chapter is also having a DIY event in a few weeks:
http://www.motorsportreg.com/index.c...6BD5F9006A2A8C

Thanks for the info. I actually got around to doing it last Sunday. Was pretty straight forward. As you said, the only difference was the mechanical fan.

For others doing this, I did not need a "slim" wrench. I used a regular sized 32MM. Also, no holder is needed. If you turn it tot he point the pulley is just about to slip on the belt, then tap the wrench with a hammer a couple times, it breaks loose and then can be spun off with no problem.

Also, there is no need to drain the coolant. The amount of fluid loss is very minimal when you take the hoses off. I only needed to top it off with less than a gallon of coolant when done. Unless, of course, it's time for a coolant flush. But even then, it's better to flush it properly than just to drain the radiator and refill.

From start to finish only took about 15 - 20 mins.

[johnhansen]

Great post, didn't take too long at all to get it changed out and saved me a ton of money. Thanks for the info!

[fiat84]

My Bentley e39 manual page 170-17,18 states "Thermostat housing to cylinder head 10 Nm(89 in-lb) for the M54, M52 TU engines = 7.3 foot-lb

Autozone states all M6 bolts are 88 inch-lb torque.
http://www.autozone.com/autozone/rep...00c152801b2c86

[ImmortalSix]

Consider me helped, too -

E83 with an M54B25 and a 6MT, was pretty much the same. I didn't have to take the fan out.

BMW's weird blue coolant is $25 a gallon.

I used a Wahler thermostat.

Thanks a lot!