DIY: (E9x) M3 Thermostat Replacement

[noremaC]

About to attempt this. With labor costs from $400-600, that's highway robbery. Don't understand how DIYer's are doing this in 3hrs and professional indy shops are quoting 5-6.

Question - the ECStuning replacement kit (https://www.ecstuning.com/b-assemble...1537836155kt1/) comes with 1 liter of coolant, while the genuine replacement kit comes with a gallon. Assuming I should get more coolant than 1 liter? If so, how much? It also says to dilute 50:50 with distilled water. Meaning, if we needed to refill with 2 gallons total, you need 1 gallon of water : 1 gallon of coolant.

I am going to attempt the method Lunker325 did - purchased the transfer pump for $10 on Prime.

Also doing the temperature sensor as well (is this located in the tstat housing as well)?

Thanks for the fantastic DIY and awesome thread contributions!!!

[Bimmer Barney]

This is covered under CA Emmissions Warranty on a 2011. Just had mine covered under that 7/70 Warranty.

[Richbot]

I used less than a gallon of 50/50 mix when I replaced the radiator, hoses, and t-stat. I would think if you're just doing the tstat without draining a liter (two liters when mixed into 50/50) ought to get you there

Sensor is in the tstat housing

[exclusivedetails]

If I am only replacing the coolant sensor, do I still need to drain or siphon out the coolant?

[M3MPH1S]

Originally Posted by exclusivedetails

If I am only replacing the coolant sensor, do I still need to drain or siphon out the coolant?

You might spill a very very small amount, but that's not going to affect anything. I wouldn't bother even siphoning.

[Ginlaan]

Just finished this job on my 08 m3. No idea where the times come from that people are saying it takes to do this job. From first bolt to last bolt 1 hour 35 minutes and that was with taking a dunkins run as well to get coffee. You could easily do this job under a hour.

I work in the industry and even Mitchel labor guide has the time at 4.5 hours for R&R as well which boggles me why.

[GT172I]

How the hell did you get the thermostat housing back on those rear pipes without shearing the o-rings?

I literally used a carpenters clamp across the thermostat to the 90 deg turn on the coolant pipes to get it on only to discover it tore the o-rings and leaked out ~1 gallon of coolant into the V and down the back of the engine.

Got new o-rings but cannot for the life of me get the housing seated without bulging out and tearing the o-rings. I've got through 3 of them so far and have used assembly lube, coolant and even dish soap to try to lubricate the o-rings. I think the housing end has a slightly rounded lip so might be better without shearing but I can't get it seated even pushing and wiggling the damn thing with all my strength. I'm worried about pushing the car off the jack stands.

Any advice whatsoever would be greatly appreciated

[pbonsalb]

I used a tiny bit of grease as the lubricant. Obviously make sure nothing is in the way in the receiving end. Maybe lightly lubricate that area as well. It did take some effort to get them in.

[GT172I]

Originally Posted by pbonsalb

I used a tiny bit of grease as the lubricant. Obviously make sure nothing is in the way in the receiving end. Maybe lightly lubricate that area as well. It did take some effort to get them in.

Thanks for the advice, I realized it was really just one of the o-rings that had been fighting me with a vengeance so I pulled it out and was going to try my last spare with some grease like you mentioned and noticed that the offending o-ring was swollen much larger than the others/new one. Either it absorbed something I put on it trying to lube it up or it was just a bad o-ring but after swapping in the new one and with a tiny bit of lube it went on much easier.

FYI for the future folks attempting this DIY, get at least 5 (maybe 6) of those o-rings to replace the 4 squashed/dried out ones in there and check for consistency between the new ones since it's a tight fit.

Cheers

[Lor443]

The OP mentioned that step 6 is optional, is it possible to change the thermostat and sensor without draining the coolant and just topping off what you lost when removing the thermostat housing?

[pbonsalb]

The problem is the mess you make if you just let coolant spill all over the front of the engine onto the belts and pulleys. I suppose you could rinse it down after. I drained down some, maybe 2-3 quarts.

[Lor443]

Originally Posted by pbonsalb

The problem is the mess you make if you just let coolant spill all over the front of the engine onto the belts and pulleys. I suppose you could rinse it down after. I drained down some, maybe 2-3 quarts.

Did you drain it using the plug under the car or siphon it out from the reservoir under the hood?

If I just vacuum some out from the reservoir under the hood would that work to lessen the mess?

[Lor443]

Originally Posted by pbonsalb

The problem is the mess you make if you just let coolant spill all over the front of the engine onto the belts and pulleys. I suppose you could rinse it down after. I drained down some, maybe 2-3 quarts.

Also, if I just siphon some of the coolant out, change the thermostat and sensor and then refill am I good?

Do I need to touch the bleed screw or just siphon and refill?

[pbonsalb]

I don’t know that you can get enough out of the high mount expansion tank but siphoning it would help reduce the spill when you remove the thermostat. Draining from the radiator drain plug is better.

I try to be neat. Maybe others are just opening up the housing and letting coolant spill out and then hosing down the front of the motor.

Some is going to spill no matter what.

[Lor443]

Originally Posted by pbonsalb

I don’t know that you can get enough out of the high mount expansion tank but siphoning it would help reduce the spill when you remove the thermostat. Draining from the radiator drain plug is better.

I try to be neat. Maybe others are just opening up the housing and letting coolant spill out and then hosing down the front of the motor.

Some is going to spill no matter what.

Understood that I would have to deal with some spill. If i just siphon out whatever I can and then refill without touch the bleed screw would I be fine?

[pbonsalb]

You don’t need to bleed a high mount expansion tank. It is self bleeding. I don’t know why it even has a bleed screw. Once the engine has gotten hot enough to open the thermostat and then cooled back down, you could remove the cap to release any air that migrated up to the tank.

Siphoning the expansion tank alone probably won’t lower the engine coolant level to below the thermostat. It should reduce the spillage. Let us know what you find. I have not read the whole thread but there is probably insight from others. I did this a year ago and drained the radiator. There is a drain on the lower driver’s side. I did not have much spillage.

[Lor443]

In the middle of this job right now. I lost the metal fastener that holds the attached small tube into place. Is there anything I can use to sub it with? Also anyone have the part number for this?
Photo in link:
https://s.amsu.ng/9TOzkVGpknWN

[pbonsalb]

You need to find that metal clip for the small hose from the expansion tank to the thermostat housing. It probably fell down onto the front undertray. You could check realoem to see if it is sold separately but I doubt it. You might be able to buy a complete used hose with clip on eBay.

[Lor443]

Originally Posted by pbonsalb

You need to find that metal clip for the small hose from the expansion tank to the thermostat housing. It probably fell down onto the front undertray. You could check realoem to see if it is sold separately but I doubt it. You might be able to buy a complete used hose with clip on eBay.

Looks like I'm gonna need to buy a new hose. It went flying out when I was loosening the hose and I can't find it.
How likely do you think it is to fall out while driving? Not gonna have the hose for a couple of days.

Also I had almost zero spill after siphoning the expansion tank. A little bit less then a gallon came out.

[pbonsalb]

Likely to come off due to system pressure. Maybe you could bend a finish nail or piece of coat hanger or something as a temporary clip.

[Lor443]

Originally Posted by pbonsalb

Likely to come off due to system pressure. Maybe you could bend a finish nail or piece of coat hanger or something as a temporary clip.

Thanks!
I scanned with Carly today to clear my thermostat code. I noticed 2 new codes, 1 for the Temperature Sensor which I am assuming is normal since I changed it, and 002AFB Intake Bank 1.

I cleared all codes but is it normal the temperature sensor code would come up after changing the sensor? I made sure it was plugged in well before closing up.

Also, does the 002AFB have to do with any of this?

Please let me know.

[pbonsalb]

Make sure you go through a warm up cycle with cabin heat on full to circulate the coolant while getting the engine hit enough for the thermostat to open. You will feel the upper hose get hit and full. Then loosen cap so air in the system from when you drained it that may have since been pushed around the system can vent out. Loosening the cap will key it out. The system is self venting so there is no special bleed process like on an E36 with low mount tank. The self venting just gets air into the expansion tank where it naturally goes to the top. You still have to let it out. Typically this happens naturally as you are checking the coolant level after draining and refilling.

https://www.newtis.info/tisv2/a/en/e...-check/Hq5CpsJ