Thermostat housing leak..

[BMWLOCO]

I've been having a persistent Thermostat housing leak from the bottom of it. I recently replaced the hoses and clamps at the bottom of the t-stat thinking this would solve the issue, but it only reduced it. After the job, I cleaned it up again and still have minor seepage from the bottom side of the thermostat housing. I was able to tighten the bottom bolt up a little more, but don't want to break it. Should I just go at it? FRAGILE?

I placed form RTV sealer in that area, but that just minimized it slightly. Now it's coming down from the side again.. RTV it all around?

Is there some sort of gasket other then the rubber o-ring that goes in there? I recently replaced the T-stat and the o-ring when I did the water pump and the timing belt.

Any help will be appreciated..

Thanks in advance!

[paperplane94]

Iv'e got the same issue.

OP are you sure your two temp sensors aren't leaking, mine were.

Also check to see if its leaking where the housing mates to the engine head, there is a gasket there too(#4 below), A mirror will be very helpful here.

It looks like the only things in the housing are the O-ring( 8 ), gasket where it mates to head(4), and 4x AL washers for the two sensors and the two plugs(15,13,3). Then there are the hoses. Did you check the small hose underneath that leads to the throttle body?


YES THE HOUSING IS MADE OF AL, so it is very fragile! no over-torquing.

I could definitely see how a bead of RTV around the mating surface would help. I would have done mine already if bleeding was not such a pain.
Please get back here if you find a fix!:D

[BMWLOCO]

I've been looking at the area with a mirror, but never suspected it might be from the top temp sensors. I'll check that out tomorrow and tighten if needed. I see seepage from the matted area under the big o-ring. More to follow.. Thx..

[AnimalE30]

Don't go to town on the three bolts on the housing unless they're new. I snapped the top one leading to a midnight drill and tap fest. Was no fun.

The bottom temp sensor can be tricky to tighten. Remove the wiring harness from the injectors to get at it better.

Also if its time, replace your thermostat and thermostat o-ring. May solve your leak as well.

[jlevie]

As mentioned above, first determine the source of the leak. If from the thermostat seal or the gasket between the housing and block, new seals may be needed. Or the sealing surfaces may be corroded and a new housing and cover may be necessary.

[BMWLOCO]

I replaced the Thermostat and housing O-ring a few months ago, when I did the timing belt, etc.. They did throw in the gasket that goes in on the back, but I didn't replace it.

I'll follow up hopefully this evening..

Thanks so far!

[jaysee]

when i changed my tstat i put the gasket in b4 the tstat, it sealed but not right, i had to take it off and put it on right.. wasnt leaking bad just seeping out and driping. r you sure u didnt make the same mistake?

[BMWLOCO]

You know, it might be the issue. I have an auto-x this weekend with my son. Although it's just seeping and dripping a little, I don't want to tackle it this weekend.

Thanks again, I'll update ASAP..

[Ceeker]

you're problem most likely isn't the o-ring. or the two sensors up top. I barely had my tightened and had no like after running the car to op temperature. I would get some RTV gasket sealant. take off the housing. Some thermostat housings come with a small spout that is pressed into the housing on the bottom. These often corrode because it isn't sealed in any way. they get brittle and can also break off- had that happen a good few times. if yours is loose it could very well be leaking from this spout. Gently remove, clean surface and Use JB-weld to repair it. You won't get any leaks from that area afterward. if you don't have this spout or it is built into the housing. Replace the rectangular #4 gasket in the pic above and put a thin coat of sealant on both the head and housing side while still wet and bolt it down. if the housing mating surface is corroded the RTV will fill it - taking up any imperfections that might contribute to minor leaking. also double check the hose clamps for tightness.

[funcrew]

This may not apply to you, but I bought a China-made T-housing that was such a bad quality casting that it would likely have leaked upon installation. Bought a Genuine BMW one that was much better made.

[BMWLOCO]

SOLVED! (I think)

Rubber ring was in BEFORE the T-stat and not after, like it says in the above diagram. Cleaned up the surface and flipped the parts and DONE.. Refilled with coolant and washed down the area. Ran it for a few.. We'll see later on today.,,,

Thanks to all that helped.