DIY: Thermostat Replacement with pics

Since I had some problems with the coolant temp and coolant leak from the thermostat, I decided that it would be a good time to replace it. For a replacement unit, I used a spare themostat which I got 2 years ago from dealership.

The replacement process is done on a M54B22 engine but it's the same accross the M54 series engines. Cars with auto transmission have a bit more work to do because of the mechanical fan in the way.

Leaky t-stat


Bleeder screw for proper system venting


3 push/lock pins removed for the fron air intake


Remove T20 bolt, 2 plugs shown here and push/lock pin on opposite side to remove fan.


Connection was very tight and I was afraid that I would break something




"New" Thermostat


Spraying some good amount of WD-40 to break loose the connections


With a flathead screwdriver, pry the metal release tab upwards for both hoses




Thermostat plug release spring needs to be pushed down to release connector


To remove the thermostat: Remove the 11mm nut that holds the engine hoist bracket, remove the 13mm bolt of the lower part of engine hoist bracket, and the 3x10mm bolts that hold the thermostat on the block.


Have some rags below the thermostat as coolant (around 1.5L) will be spilled. You don't want coolant on the engine belt. It's oily and can make the belt slip. There were marks of there the coolant was leaking which I thoroughly cleaned before proceeding.


Old thermostat with messed seal


Aparently the plug was messed too, rust, coolant, dust particles and one wire which was barely making contact. As I further pulled the connector the wire was cut. Somebody please explain to me what the sensor/electrical component inside the t-stat does?


To prevent future coolant leaks, I applied some high temp RTV silicone sealant as per application instructions.


Used OEM coolant. Nitrite Free




Assembly is just the opposite process, not difficult, took me total of 2 hours.

The Bentley manual describes draining the coolant first.

It also explains that the wires inside the thermostat are actually heaters. They go on to explain their purpose and function.

Good reading to do before undertaking this repair.

Not sure I would have applied the orange goo...


.

Overall a good DIY, particularly the pix. That said, I'm also not sure I'd go with the silicone sealant on the face of the block. The gasket does the job just fine when properly torqued and when you need to remove the T-stat again it's going to be much more messy to do.

Originally Posted by bmwbun

The Bentley manual describes draining the coolant first.

It also explains that the wires inside the thermostat are actually heaters. They go on to explain their purpose and function.

Good reading to do before undertaking this repair.

Not sure I would have applied the orange goo...


.

Yes, they heat up an element inside the t-stat to open it under heavy load conditions where the coolant around the cylinders would boil before a conventional t-stat would open. It says to drain the coolant to prevent leaking on the belts etc. Good thing to do if you don't plan to clean the mess afterwards. I used a good engine cleaner and after everything dried, some baby powder on the belts. When sprayed with coolant and not cleaned, the belt will slip.

Originally Posted by grafiksguy

Overall a good DIY, particularly the pix. That said, I'm also not sure I'd go with the silicone sealant on the face of the block. The gasket does the job just fine when properly torqued and when you need to remove the T-stat again it's going to be much more messy to do.

I wasn't sure either if I would use silicone gasket sealant, but apparently the gasket doesn't do it's job properly BMW used a very thin piece of rubber gasket which does wear out even if properly torqued. The silicone gasket sealant sticks on the engine block but not on the composite material of the t-stat so if you ever need to remove the t-stat you just pull it out, and use a scrapper to remove silicone from the engine. I used this silicone gasket in numerous applications such as my valve cover gasket, oil pan (in another car) etc. Better to take an extra hour scrapping silicone from the engine block rather than having coolant leak on the engine/belts.

Thanks for the comments

I think my thermostat is broken as I'm sometimes get hot air into the cabin and sometimes not.

How long does this take to do and did you need any special tools besides the ones shown in your DIY?

If you have a manual it takes an hour the first time and you only need basic tools, 10,11,13mm sockets, torgue wrench, T20 bit, big philips screw driver (bleed screw).

You might want to check some other things before replacing the thermostat, such as properly bleeding the system, checking the connection on the heater water valve next to the airbox, climate control system etc. A faulty thermostaty will not usually cause the symptom you describe

Good job paraklas as usual. Just some minor corrections if you don't mind:
- the Torx screw for the fan shroud is a T-25, not a T-20. A T-20 fits but there's a chance the screw head gets rounded.
- the thermostat electrical connector release spring is an easy push-on to release. Squeezing with index finger and thumb does the trick.

dont forget to bleed off after everythign is done, otherwise, you will get an overheat experience. Bleed off cap is a small black plastic cap next to the thermostat cap.

Great pics!!! This is on my to do list for the week. Thank you for taking the time to help....Step by step photo's is a plus..

I agree with the RTV idea. I installed a new thermostat when I did a cooling system rebuild, torqued the thermostat to 10NM, etc., and it weeped slightly. I re-drained the radiator at the right side lower plug, removed the shroud and fan, disconnected the upper and lower hoses from the thermostat, RTV'd the mating surface exactly like in the photo here, and no more leaks....

Thanks for the diy paraklas! It was really easy to do, the only problem i had was the push/lock pin thing on the other side of the fan, that thing didn't want to budge so i just butchered it haha.

Just did my thermostat on my automatic (mechanical fan) E46. Everything went well except for getting of the fan. There is an expensive tool sold my a number of sites but Puri 13's method http://forum.e46fanatics.com/showthr...ht=fan+removal worked like a charm. The wrench and hammer worked great! I did slide a thin piece of sheet metal between the wrench and the hoses so that they would not get damaged. I hit it (hard) 3 times and the rest was easy. Replacing it, Once you get a 1/4 turn on the shaft, it will just spin on. Got a 1 1/2 open end wrench at Auto Zone for $11 for the job. Puri 13, great idea and savings! Thanks a lot!

wow i didnt know it was that easy! thanks for the write up!

Replacing a thermostat is very simple.. BMW has these part always in stock because they fail freqently.. very nice D.I.Y

Advance Auto Parts has a Fan Clutch Wrench set that are loaners. I replace the thermostat today on my automatic 330 ZHP vert. The fan nut was not that tight. Please remember it is a left hand thread. The car was showing service engine soon light. Code P00128. Advance turned of the SES light when I returned the wrenches.
Temperature comes up really fast. Head center on the guage. NAPA sell a German made thermostat for $ 49.99 on line and I paid $ 52.00 in the store.
Thanks for the DIY it really helped.

n00b questions alert:

1) what do i need to do with the bleeder screw? or is it in the pic just for to indicate where it is?

2) do i just press up the push/lock clips? they seem delicate so i want to make sure what i'm doing before applying undue force

3) how do i remove the top and bottom connectors after applying WD40?

4) do i have to flush the coolant or can i just use lots of cloth, collect the coolant leakage and top it up once DIY is completed?

5) what's the best way to mininize coolant leakage when i remove the t-stat. 1.5L is quite a bit that could affect the underlying belt.

Originally Posted by Sharky06

dont forget to bleed off after everythign is done, otherwise, you will get an overheat experience. Bleed off cap is a small black plastic cap next to the thermostat cap.

what's bleed off? can you please explain.

Originally Posted by paraklas

If you have a manual it takes an hour the first time and you only need basic tools, 10,11,13mm sockets, torgue wrench, T20 bit, big philips screw driver (bleed screw).

You might want to check some other things before replacing the thermostat, such as properly bleeding the system, checking the connection on the heater water valve next to the airbox, climate control system etc. A faulty thermostaty will not usually cause the symptom you describe

for the t-stat, other than the obvious symptom of the temperature gauge not aligning up at the center, vertically, i've read that the cabin takes unusually long to warm up.

Just did this a few days ago, now I have heat and my car gets up to temperature within a few minutes. Thank you so much for your writeup, made my job MUCH easier!!

bump for answers