thermostat housing gasket - silicon or no?

[romeox929]

as question states, I assume it would be helpful to add a layer between block-gasket and gasket-housing. I haven't noticed any mention to use it at bmwe34.net or bentley manual, so any input on this one would really help out. TIA :help

EDIT: sorry, i have a 1991 525i with a m50 motor.

[FWinNH]

No need. The oring will seal the connection quite nicely. No muss, no fuss...

[calmloki]

Doing the same job on my '93 525iT tomorrow. I don't think BMW uses silicone or gasket sealer much of anywhere. However, I'm going to the not-made by-BMW aluminum casting thermostat housing and don't trust the mating surface to be perfectly flat as BMW parts seem to be, so i will probably use a thin smear between the gasket and the housing, but not against the head. Other thoughts?
Tom Walrod

[632 Regal]

NO SILICONE it corrodes aluminum after time.

if theres an O ring theres no need for anything. if it has paper gaskets use permatex spray gasket or similar.

[FWinNH]

I have the aluminum t-stat covers on both my M50 and M60 engines and both sealed up nicely with just the o-ring (profile type gasket on the 6 cyl).

[calmloki]

Good deal - didn't consider the O-ring for the thermostat. I'll go sans goop.
Tom

[Akhil]

found it was leaking nad had to drain and redo it with t-stat/water pump sealant. I don't know it has silicon or not, but its says "Water Pump/ T-Stat sealant" and safe for entire cooloing system. It cost a $1 only. I won't do t-stat without this sealant after this experince.


Hope this help.
Akhil

[romeox929]

theres an O-ring that goes around the thermostat itself and a separate gasket (paper?) that goes between the housing and the block. I guess permatex wouldn't worsen things, only make better?

[FWinNH]

theres an O-ring that goes around the thermostat itself and a separate gasket (paper?) that goes between the housing and the block. I guess permatex wouldn't worsen things, only make better?

Not on an M50 engine it doesn't. Are you sure you don't have an M20? I thought the 525 in 1991 was an M20.

[romeox929]

Not on an M50 engine it doesn't. Are you sure you don't have an M20? I thought the 525 in 1991 was an M20.

I don't know when they started producing m50's for 525's, but I'm positive I have a M50.

[FWinNH]

I don't know when they started producing m50's for 525's, but I'm positive I have a M50.

OK, you're right (of course - it's your car) The last of the M20's was produced in August 1990. So I assume that yours was built post September '90.

And sure enough yours does apparently have a paper gasket rather than the profile gasket (also shown in the below drawing). I would definitely use some permagasket compound or something similar.

http://www.realoem.com/bmw/showparts.do?model=HD53&mospid=47404&btnr=11_1503&hg=11&fg=35

[632 Regal]

Bill R like Hylomar.

[Dave M]

Bill R like Hylomar.

I'm through half a tube of the $hit putting my car back together (none on the head gasket ;) )

Dave M

[calmloki]

After doing the waterpump and thermostat housing replacement on my M50 '93 525iT I would (and did) go with no goop at all. The M50 is all compressible rubber rings. Just clean mating surfaces well. Not leaking yet...
Tom

[Derek A.]

I thin coat of RTV on the metal not sealing surfaces will help to prevent leaks down the road, especially of there is pitting present on the aluminum.

The real early M50's used a paper gasket. After that its all profile gaskets and o rings.

[Kalevera]

No RTV. Many an engine is destroyed by some idiot goobering it up with the stuff. It has its uses, but the tstat cover is not one of them. Use a scotch brite pad or a new razor blade to clean the aluminum, the rubber profile gasket and tstat O ring prevent leaking, but things need to be flush.

These engines only need a TINY dot of RTV at gasket junctions between covers (ie - pan/block/lower timing cover gets a dot on each side on the outboard side of the gasket during a pan gasket job). For some reason, people think that RTV can universally replace the use of an actual gasket. To make matters worse, they put more than a dot on the motor to form some kind of seal that won't leak, and neglect the fact that just as much squeezes in as what squeezes out. The stuff solidifies and turns into strings of goob, which proceed to clog tiny and necessary coolant passages, overheating the car and trashing the head. Or it can get in the oil (pan gasket scenario) and lunch the bottom end.

So, no RTV. And I doubt you'll need hylomar in this situation, either. Clean, bolt, and go. If you still have leaks, then there's a pitted or damaged surface that merits replacement, anyway.

best, whit