Oil thermostat in engine case leak

[porscheboy1]

Hi guys.

I have been restoring a 1978 911 SC for about 3 years and it is now in the road. After breaking in the cams I drove 50 miles and inspected the outside of the engine. No oil leaks underneath but it appeared that the oil thermostat in top of the engine is leaking. I have good sight and working access to; the engine top since I have installed PMO carburetors. The top of the engine was wet, the MSD6AL was wet, the fuel pressure control unit was wet and the top insulation in the engine compartment was wet. I thought that I might have damaged the O ring on the thermostat when I installed it so I ordered another one from our host. Victor Renz red. I installed this. The oil pressure switch for the warning light is new and appears not to be leaking. I took it out and added some pipe thread tape for good measure. I also replaced the engine crankcase breather cover gasket , although this is a low pressure application. I don't know of any other place from which the oil can be coming. I cleaned all the oil off and drove another 50 miles. The leak is still there. I have some Dow Corning Molycote 55 rubber O ring lubricant. Should I try that. What else should I do?

Thanks in advance for your advice.

Regards,

John

[Flat6pac]

I had thermostat gaskets that would leak so what I started doing was putting a pass of 574 between the o ring and the top inside edge of the thermostat. Worked for me in the past.
Bruce

[porscheboy1]

Thanks, what is 574?

[Flat6pac]

Loctite 574 is a building sealant available from Pelican.
Bruce

[porscheboy1]

I will try that.
John

[fanaudical]

When you get the t-stat out, carefully check the bore in the engine case for any scratches or corrosion that runs near the O-ring sealing depth. My case had some deep scratches and corrosion pitting (found during rebuild). I filled those with JB Weld and carefully honed the surface smooth again.

[KTL]

Shouldn't need to use teflon tape on the oil pressure warning switch (idiot light in the oil pressure/temperature combo gauge) because the switch has a tiny aluminum sealing washer to prevent oil leakage. Thread size is M10 x 1.0 in case you're curious.

Also i'd recommend using thread sealant paste. That tape can tear apart upon threading things together and can clog up oil passages

[chrismorse]

If the case is Mag, (?), be very careful tightening the thermostat.

Dad passed his 74 to me and after I dumped the ac to install a Carrera cooler, I had a very bad afternoon.

All warmed up, I was passing an even more elderly driver, when I saw a huge cloud of blue smoke behind the car - OIL.

Shut it off and coasted to the side of the road oil everywhere - It seems that the studs pulled out of the case dumping about 12 quarts of oil in about 3 seconds.

My supposition is that the thermostat stud threads in the mag case were "pulled" at some point in the cars life.

chris