DIY: Thermostat Replacement with pics

Originally Posted by xlash

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.

1. 2nd picture. You can use a large philips screwdriver to loosen it a bit. No need to remove it completely. If you haven't touched that area yet, better buy a new screw since it's plastic and can easily break.

2. Yes you press them to lock. They are delicate yet very cheap. I bought a bag of 100 and I just replace them when they start to break.

3. Pry the spring with a flathead screwdriver till it pops then wiggle the hoses to break loose and pull. Pretty straightforward when you see how the spring mechanism works.

4. Use a cloth to prevent spilling on the belts. Top it off with a 50/50 mixture of coolant/distilled water. No need for flush.

5. You can drain some beforehand through the radiator plug located below the radiator. You will need ramps and to take the splash cover out to do that. Or you can remove the temperature sensor located in the lower radiator hose. This way you will loose the coolant but it won't go on the belts. Nothing you can do to keep it inside the engine.

6 - If you have a dog, make sure to not let lick the coolant (it's sweet and poisonous). Wash away any spilled coolant

The bleed-off (or bleed or bleeder) screw is used to let the air escape from the system as you fill it up with antifreeze/distilled h2o. You just unscrew a little ways (you don't have to remove it compeltely, fill the radiator expansion tank with fluid to the correct mark, and then tighten the bleed screw back down. Drive the car a little, let the car cool down and repeat the fill-up bleed-off process a couple to a few times until the system runs at the proper level and air isn't trapped in the system anymore. Then the heater works correctly and you don't overheat the motor.

Originally Posted by paraklas

5. You can drain some beforehand through the radiator plug located below the radiator. You will need ramps and to take the splash cover out to do that. Or you can remove the temperature sensor located in the lower radiator hose. This way you will loose the coolant but it won't go on the belts. Nothing you can do to keep it inside the engine.

I would recommend that you do not remove this part unless you have a replacement unit on hand. This is because the unit has most likely not been changed and the seal is (at least) the same age as the seal on the tstat you are replacing. Pull this out and you risk a leak.

The write-up is good - as said before though, I would not put silicone sealant on the mating surface. Future replacement is going to be difficult because you'll have to free the surface of the old compound.

Think about it this way - BMW builds millions of cars. They are all built this way from the factory and I've never seen a dealership washing spots of coolant where the cars were parked, nor has mine or any of my friends leaked over time. IF the bolts are torqued down properly the surface will seal appropriately all the way around. This looks like someone may have changed this before you got to it. The leak looks like the result of someone without a torque wrench who over-tightened the bolts. Initially it would seal but over time the housing may distort slightly causing the leak.

Thanks for the write up, paraklas. I used this to swap out my thermostat today and it was a piece of cake.
You mentioned above that you bought a bag of the push/lock clips for the fan and air intake shrouds. Did you pick that up from a dealer or did you find those online somewhere?
Thanks again for the info!

Originally Posted by xlash

what's bleed off? can you please explain.

I just replaced my thermostat today. It was stuck open. Also, the gasket had deteriorated along the bottom. Here's the bleeding procedure I used and everything looks good. Make sure to check your coolant level when your engine has cooled after your next drive.

Coolant Bleeding procedure.
Open sealing cap. Set heater control to maximum temperature. Set blower to low level. This opens the heating valves and sets the auxiliary water pump in operation. Run engine and briefly press accelerator pedal three to four times (approx. 4500 to 5000 rpm) to flush engine cooling circuit. In doing so, do not run engine for longer than approx. 30 seconds; otherwise coolant will heat up and expand. If the coolant level drops in the expansion tank during this operation, top up expansion tank with coolant up to edge. Screw on sealing cap and warm up engine until thermostat opens.
http://forum.e46fanatics.com/showpos...6&postcount=35

so many writeups on this subject and they are all the friken same none of them tell you have to get the friken cooling fan off for automatic trans

Originally Posted by mrhappyface

so many writeups on this subject and they are all the friken same none of them tell you have to get the friken cooling fan off for automatic trans

Google is your friend.
http://www.bimmerfest.com/forums/sho...d.php?t=388656
Basically get the fan tool, or use a wrench and a hammer to loosen the nut (reverse thread).

Just an FYI, NAPA has Wahler (made in Germany) thermostats for $49.99 (part #423206). Not sure if equal to OEM quality, but I've heard good things about Wahler.

Mine (Wahler) has been installed for almost 2 years, also considering that the actual thermostat is held by metal prongs instead of composite (OEM) makes me feel more confident on its reliability.

If their is splashed residue around the area of my radiator fill reservoir does that mean that leak could be from the thermostat?


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Originally Posted by Sforza209

If their is splashed residue around the area of my radiator fill reservoir does that mean that leak could be from the thermostat?

I just replaced my thermostat last weekend. I have so much heat from my vents now!
I used RTV sealant to prevent any leaks in the future. The old gasket has melted/deteriorated in some places. In my case, the problem was that the thermostat was stuck open.

If you have leakage around your reservoir, then could be that your reservoir is cracked, your coolant overheated and the pressure cap released some pressure/coolant, or maybe your bleed screw is not tight/leaking.

Try cleaning up the area and pinpointing where it's coming from.

I think the RTV is unnecessary. It'll be a real mess next time. I replaced my t-stat 100K miles ago and no leaks yet.

Jabela's bleeding procedure is more complicated than needed. With fan on low and heat full hot, simply pour the coolant in very *slowly* until it comes out the bleeder screw. That should be all except for maybe a top-off after your next drive that fully warms it up.

Originally Posted by jabela

I just replaced my thermostat last weekend. I have so much heat from my vents now!
I used RTV sealant to prevent any leaks in the future. The old gasket has melted/deteriorated in some places. In my case, the problem was that the thermostat was stuck open.

If you have leakage around your reservoir, then could be that your reservoir is cracked, your coolant overheated and the pressure cap released some pressure/coolant, or maybe your bleed screw is not tight/leaking.

Try cleaning up the area and pinpointing where it's coming from.

Thanks man. I had been planning a good thorough cleaning of that area but just couldn't find the time. Also. Since my radiator light keeps coming on I have to keep refilling the radiator fluid. If I dont fix the problem soon I can just see the radiator fluid bill stacking up. Is it ok to just put water in my radiator? My car is always parked In the garage and I live in cali so it doesn't get below freezing. Thanks


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Originally Posted by havnfun328

I think the RTV is unnecessary. It'll be a real mess next time. I replaced my t-stat 100K miles ago and no leaks yet.

Jabela's bleeding procedure is more complicated than needed. With fan on low and heat full hot, simply pour the coolant in very *slowly* until it comes out the bleeder screw. That should be all except for maybe a top-off after your next drive that fully warms it up.

Well, considering the gasket deteriorated on the original thermostat and it started weeping coolant, it's good insurance. I'll probably have to scrape it off the block next time I replace it, but I had to do that anyways to get all of the OEM gasket residue off to get a clean surface mount to.

As for the bleeding, yes it may be overkill, but it worked very well. When I checked the next day I didn't have to top it up at all.

+1 on the RTV. It doesn't stick on the thermostat so you can take out easily and you can scrap it from the engine block.

i just did my thermostat,by the way taking the fan was pretty easy all i needed was 32 mill wrench from sears and a long screwdriver.my question is, does ses go away on its own after i put the new thermostat.

excellent write up!

I have a few questions :

1. My bolts for my thermostat seem corroded, shall I spray them with wd-40 before attempting to open them? What precaution can take not to break them?
2. If I dont want to drain the coolant, how much litres will leak when I remove the thermostat? Will cloth ot container be more suitable to catch it?
3. If I do go ahead and drain the coolant, will I need to drain the radiator with the blue screw from under the car and drain the coolant out the engine?

Thanks in advance.

Originally Posted by AU Terry

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.

Hey AuTerry
I have a 330ci '01 Conv and have this same problem "Temperature comes up really fast. Head center on the guage..." mines reaches hot in a matter of 15-20minutes. I also have a small leak on one of the hoses, i just need to find it. I keep on filling the radiator with antifreeze every other day. PLEASE ADVICE what to change? did you Change any Censors? Thanks

Anyone, please advise. What to change. Thank you...


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U have to find the leak u r letting air into the system which causes overheating (boiling water idea) check the air relief valve right above reservoir. Again find the leak u can damage the heads if it gets to hot