1921 Peugeot Coolant Outlet Seal

[MochetVelo]

My 1921 Peugeot engine has a cast coolant outlet/elbow on top. The mounting surface is flat and it's difficult to seal. The elbow mounts with two studs. I tried a gasket and also a high-temp polyurethane sealant. Any ideas on how to get this to seal? I see a hi-temp carbon buna-NB gasket material at McMaster-Carr.

 

Phil

 

 

 

 

[Larry Schramm]

Looking at the elbow it does not look like it is flat.   The photo appears that there the ends are higher than the center.

 

If it was mine, I would consider taking the top elbow and either put it in a mill and make sure it is flat or if you have a large belt sander put it on that to be sure it is flat.  Then look at the engine side with a straight edge and feeler gauges to ensure it is flat.  

 

You should not need to take off much material to make sure it is flat.  After you confirm both surfaces are flat, then you should be able to use some standard gasket material. 

 

This is what I use for those applications.

 

Are you near A2?

[MochetVelo]

I think the camera makes the elbow look bent, but it is flat. I will try feeler gauges, however, and I might bring it to a machine shop. That is actually a new stainless elbow I had cast. I made an aluminum one previously (like the original) but it corroded quickly. 

 

Phil

[Fordy]

Get yourself a sheet of flat thickish glass and varying grades of wet rub paper. Start with a coarse grade and some lubricant (water will do) and using a circular motion slowly grind down the "flat" surface. This will very quickly highlight any deviation from a true flat surface. If there are any points that show no contact with the abrasive then you need to keep going until it does. Probably only a couple of thou in it but enough to leak.

[Terry Harper]

Try a cork gasket (1/8") with shellac sealant on both sides. (assemble while wet) Make sure both surfaces are clean and oil free.  I would not be surprised if that was the material originally used by the factory.

Edited December 16, 2022 by Terry Harper (see edit history)

[MochetVelo]

That sounds logical, Terry. When I see close-up photos of these engines, I often see tell-tale coolant trails emerging from the elbow (see below).

 

Phil

 

 

 

 

[Marty Roth]

On 12/16/2022 at 4:19 AM, Fordy said:

Get yourself a sheet of flat thickish glass and varying grades of wet rub paper. Start with a coarse grade and some lubricant (water will do) and using a circular motion slowly grind down the "flat" surface. This will very quickly highlight any deviation from a true flat surface. If there are any points that show no contact with the abrasive then you need to keep going until it does. Probably only a couple of thou in it but enough to leak.

Great advice,

This is exactly the method I used many years ago to save the oil pump on our 1927 Chevy Roadster, dramatically enhancing the diminished oil pressure. After the "fix", we toured cross-country tens of thousands of miles

[MochetVelo]

My leaking coolant problem is solved thanks to a suggestion from my restorer friend Walter Higgins:

 

Clean mating surfaces, then apply a 1/8" - 3/16" bead of Permatex 22071 "Water Pump & Thermostat Housing Gasket Maker" to one surface.

Align the parts and press down the coolant elbow slightly to create about a 1/16" gap (do not tighten). Allow to set overnight, then tighten the joint. 

 

I refilled the radiator and ran the engine with no leaks. The Permatex is gray in color. 

 

Phil

Edited March 19, 2023 by MochetVelo (see edit history)

[Mark Gregush]

Overlooked step when using any number of sealers esp silicon type: Don't seal all the way and allow to setup over night before fully tightening.