Author Topic: Thermostat Housing Issue (Read 5056 times)

sporkfan · « **on:** June 29, 2010, 07:05:01 PM »

I replaced the radiator and thermostat today trying to calm down an unstable temperature gauge. The system bled properly, but now I've got a hiss and some steam coming from the top right bolt of the four on the thermostat housing.

I've tightened the bolt as much as I comfortable doing with the aluminum and such. Am I missing something or could the thermostat housing itself be cracked.

jscribble · « **Reply #1 on:** June 29, 2010, 08:28:05 PM »

I just had a similar problem, the gasket on my bleeder screw split, and likes to steam on me when it gets warm. A brass one (with new o ring) is 4.25 from pelican parts. Worth a look.

dkbmxer002 · « **Reply #2 on:** June 30, 2010, 12:23:08 AM »

do NOT over tighten haha, i snapped one into the head and was never able to get it out.

sporkfan · « **Reply #3 on:** June 30, 2010, 07:19:02 AM »

I've got another thermostat housing that I can use. I'm going to order another gasket and give it another go tonight.

I will add that drilling a hold in the thermostat does make bleeding a lot easier.

sporkfan · « **Reply #4 on:** June 30, 2010, 06:20:55 PM »

New thermostat housing and gasket, cleaned the bolts to get all of the RTV off and the same issue.

My bleeder screw is happy and the system is holding pressure...well atleast until all of it oozes out of the thermostat housing. All four bolts were torqued to 11 lb/ft.

Any ideas?

monko141 · « **Reply #5 on:** July 01, 2010, 08:48:25 PM »

My guess is that there is some RTV in the bolt hole and it won't allow the bolt to go in as far as it needs to.

sporkfan · « **Reply #6 on:** July 02, 2010, 05:13:46 AM »

Quote from: monko141;94146

My guess is that there is some RTV in the bolt hole and it won't allow the bolt to go in as far as it needs to.

I had the same assumption and tried to throw a few more washers on that bolt to move it further up the hole, and still had the same issue.

locknload · « **Reply #7 on:** July 03, 2010, 08:27:00 PM »

Do you have the o-ring in there?

sporkfan · « **Reply #8 on:** July 04, 2010, 12:21:02 PM »

Yes, the o-ring is on the thermostat. I'm reaching my wit's end on this thing,

I just purged it again thinking that it was some air behind the thermostat, but again, I get the hissing once the system gets up to pressure.

Anybody want to buy a 318is with a custom interior?

locknload · « **Reply #9 on:** July 06, 2010, 09:57:42 AM »

About all I can suggest is remove the housing & re check the block face and housing face to make sure there isn't something there (old gasket material, metal sliver, dent, etc). If the gasket survived the removal, put a light coat of RTV on both sides of the gasket & see if that doesn't do it for you. It is possible you have 2 bad housings, it is BMW plastic after all.

sporkfan · « **Reply #10 on:** July 07, 2010, 08:07:17 PM »

They were both aluminum housings.

locknload · « **Reply #11 on:** July 08, 2010, 10:25:32 PM »

If you're sure everything is assembled properly (0-ring between tstat and tstat cover, not between tstat and block) and it still leaks, then it seems the cover(s) must be warped or otherwise damaged. It is odd that it didn't leak before you disassembled it. And you are sure the leak is coming from the tstat and not the pump or some other source? If you have a very flat surface and some 600 grit sandpaper, you could try sanding the gasket face of the tstat cover to true it up a bit.

Cobra Jet · « **Reply #12 on:** July 09, 2010, 11:39:22 AM »

question - is your thermo housing:

A) the original one to the engine

OR

B) a replacement

If it's a replacement, is it a genuine BMW part, or is it one that is reproduced by some offshore company? There is a definite problem w/ the offshore repops - there are a few threads about this as well... The only definitive thermo housing to use is a genuine BMW replacement - of which at most Dealers is around $30...

If it's the original part, it may have a stress fracture near or around that specific area that is not totally visible and only will "appear" once the part has expanded due to heat or normal operating temps. If original, I would replace it with a new one.

DO NOT overtorque the bolts to that housing - you're going to end up snapping one or more - then you'll be back on here asking how to remove the busted threads (or where to get a new timing cover assembly due to cracking it). The cover is aluminum and it's very easy to damage it if over torquing ANY of the bolts going into it.