can't stop coolant leak on engine

[morriss]

Ever since I changed out the original thermostat months back, I've had a constant drip drip from where the thermostat housing (PET = "regulator housing cap") mates to the bridge (PET= "regulator housing"), along the bottom edge. Yes, I put the new o-ring on TOP of the new thermostat and tightened the bolts as far down as they would go.
Well, Saturday I was attempting to calibrate the WUR with the fuel gauges when the drip turned into two steam vents that covered everything in coolant. Today I pulled the regulator housing cap off and it appeared that someone had put water from the hose in the radiator because along the lip there was a build-up of what looked like hardened calcium. So I took the dremmel to it and to the housing (still mounted on the engine) and carefully cleaned them both. It took about an hour to clean the build-up off all the various surfaces/ lips / ridges. Nice and clean, put it back together, and it still leaks. It seems like there should be a gasket or something where the two pieces come together to stop any leaks, but Porsche doesn't call for one, for whatever reason.
So, what's the answer? I don't want to white trash fix it with a tube of gasket maker, so what's the correct way to make the leak stop?

[Mrmerlin]

both pf the mating surfaces should be smooth that includes where the thermostat seats its possible that there has been corrosion in this area and it has changed the surface enough to cause the leak. You might try removing the water outlet( the part thats connected to the lower hose) and then take a piece of 220 grit on a flat piece of metal and work the surface of the water bridge down, this will increase the sealing pressure of the outlet against the O ring seal. You may have to buy a new O ring as well .
If you do the surfacing to the outlet portion then any amount of metal you remove from the protruding ridge will decrease the amount of sealing pressure

[bwmac]

If it is the style of cap to O-ring seal that I am thinking of, where the O-ring is to be squeezed into a slot or grove. Then your choice is to file the cap or housing where ever the o-ring sits so that there is more squash. Now you can use a fatter o-ring which is my first choice, but if the housing is getting pitted then it should be filed smooth. caution, filing is not easy to get flat. I mark the surface lightly with a small punch making little equal dents all the way around. then file till they are equally removed. Thats how i do it. a good sealer at the auto parts store is called aviation gasket sealer and i think its by Permatex

http://www.permatex.com/products/Automotive/automotive_gasketing/gasket_sealants/auto_Permatex_Aviation_Form-A-Gasket_No_3_Sealant_a.htm

[Mrmerlin]

also make sure you have to correct O ring you could have a thinner o ring and this is the cause of the leak

[morriss]

Thanks for the info Merlin and bwmac. I got the thermostat and o-ring from Roger, so I'm confident the o-ring is correct. I guess it wouldn't hurt to call him and ask him about a fatter one though.
Merlin- I dremmel brushed the groove that the thermostat sits in on the outlet portion too - I mean I got every nook and cranny on both the engine outlet portion and the water outlet cap.
I will try the sand paper next and hopefully Roger will have a fatter o-ring.
Thanks again gentlemen.

[MPDano]

Yeah, if you look at my Engine. You'll see mega RTV. I've used it for years and never had an engine leak on me. Remember, these cars are very old and have lots of corrosion. Especially since most PO's didn't use the correct type of Coolant. Heck, I didn't know until this Forum. I too had normal Coolant in mine. Corrosion causes pits, lots naked to the eye and a normal seal won't seal correctly. I suspect this is your issue.

If you do put RTV with your O-Ring, make sure you give it the recommended time to properly dry before starting the car. I like the Red RTV as it's High Temp.

[Mrmerlin]

Please tell me your putting the belt covers on that green engine???

[morriss]

Okay, sanded both the housing on the engine and the housing cap with 220 grit sandpaper. There is still one big pit on the cap though. If I keep sanding, I'm afraid I'll take the lip down too far. Here's a pic of it. Will the red RTV take care of this?

[MPDano]

Yup. no problem. Like I said, make sure you let the RTV dry fully before starting it up. I usually let it sit at least 24 hours.

[Maleficio]

RTV is the answer to many problems.

[morriss]

Put the red RTV on and buttoned up about an hour ago. I'll report back tomorrow.

[MPDano]

Originally Posted by morriss

Put the red RTV on and buttoned up about an hour ago. I'll report back tomorrow.

It will seal up. Just give it a lot of time for the silicone to properly harden. I usually do a minimum 24 hours on all my cars.

[morriss]

Success! No leaks. Thanks Dano, bmwac, and Mr. Merlin. Now, back to setting the WUR.