Some of you may remember that last year at about this time I had a coolant leak that turned out to be a tiny crack in the neck of the surge tank. I replaced the surge tank with a repop from Greg Donahue and sealed the flange/manifold interface with Permatex water pump sealant (which was highly recommended by several people here). This worked fine until early this year.

This year it has started leaking again, apparently from the flange/manifold interface. Does anyone have any ideas why it would start leaking again and how to go about preventing it? It seems to only leak just as the engine is started up until the thermostat opens (water flow through the water neck is greater than the leak rate) and after the engine shuts off and cools down. It is not a big leak (maybe a 2" puddle under the car), but I don't like it happening again. I don't plan on fixing it until the weather cools down and cruise season is about over. Would drilling a hole or two (1/8") in the thermostat help with releaving pressure on the flange as things warm up and cool down, allowing a little coolant flow until the thermostat opens?

Sorry for the long post.

 

That Permatex, is it silicone based like RTV?

If so, did you let it "skin" before assembly? If the RTV doesn't "skin" (a thin layer that cures), I've had many things leak within a year or less. Waiting 20 minutes for that skin to form, then assembling makes a world of difference.

Besides that, did you use a gasket ? Is it possible the gasket crushed enough that the bolts came loose? Are they loose now?

 

did you use the rtv made for use with antifreeze?

 

This is what I used:

http://www.permatex.com/auto/autouh....&item_no=22071

The instructions say to assemble immediately before it skins over. It is made specifically for water pumps and thermostats. It is a gasket maker so a paper gasket is not used. Both bolts are tight.

 

Jeez Bill, some people lose motors and trannys, you have persistant leaks. How do you get off so easy?

I don't think the hole in the thermostat will solve the problem, but it won't hurt a thing if you do try it. I've seen applications that have a small hole in the top of the thermostat to help evacuate air from the cooling system while filling.

It's still my opinion that a leak-is a leak-is a leak, regardless of rate or operating condition. You just happen to be more observant than most. Refresh my memory: does the tank have a support bracket, or is it supported by the waterneck? I keep thinking (haven't seen my ol '64 for two decades) that the waterneck mounts with two bolts, is the pattern horizontal or vertical? A tank filled with coolant (8 lbs/gallon?), or a bracket that's off a little would have leverage against the seal area. It's also possible the thermostat slipped enough during assembly to interfere with the seal area.

I'm a Hylomar fan myself. Sealed many gaskets with it, no problems. Cleans up with a little acetone on a rag, no more scraping (woo-hoo). One thing it will not do is hold pressure. If your parts don't fit up well enough to make a good mechanical seal, it's not the stuff to use.

BTW, Your Gal looks GOOD in red!

 

Interesting.

Since you didn't use a gasket, if it possible the thermostat is interfereing with tightening it down all the way? (raised lip around the outer edge of the thermostat?).

Assuming, I think, that the tank bolts up where the thermostat sits?

By the way, I'd never use a "gasket maker" if there is a gasket available for the purpose.

Curiouser and curiouser...

 

I also drive a 64 Galaxie, I would go with what krewat is saying, it may need the gasket. Also on mine the bracket has come loose and has cracked the neck.

 

The tank is supported by a bracket that is soldered to the tank and water neck. It is mounted to the intake manifold by two bolts on the diagonal. The tank is a new reproduction purchased about this time last year. It did not start leaking until early this spring when I started on the bodywork. After driving the car in and out of the garage a few times it started to leak. I really don't think the thermostat slipped.

Thanks on the paint. I like it too.

 

No. The thermostat sits in a recessed area in the flange. It is at most flush with the flange.

Personally, I think the newer sealers are better than a thin paper gasket as they fill in uneven spaces and allow some give or flex that a paper gasket doesn't. But that's only my opinion and don't want to turn this into a gasket/no gasket debate.

 

See my response to Krewat regarding my thoughts on the gasket.

As I said in another post, the surge tank was purchased brand new from Greg Donahue last year. It is solidly built. Better than the original. Everything is tight.

After thinking about it some more and discussing it on the network54 FE list, I mentioned that the intake manifold was powder coated and that when I replaced the surge tank last year, some of the coating on the mounting surface on the intake had cracked. I cleaned and sanded it down, but I am now thinking that possibly another crack has appeared and I will have to sand down the entire mounting surface.

I will say that I am 99.9% sure the leak is at the flange/manifold interface as there is no evidence of coolant higher up on the water neck, the tank itself, the mounting bolts, or any of the hoses. I can feel a wetness on the underside of the flange starting about 3/4 of the way up. So ..... once the weather cools down and things slow down, I will pull the tank and see what's up. Until then I will keep a close watch on my coolant level.

 

One other thing. Last year's leak was a lot worse than this one. I actually saw the coolant squirting out of the crack in the water neck when the car was first started. Once everything warmed up, the crack closed and the leak stopped. As it cooled down, it leaked again. This leak is more of a slow dribble when the car is started and after it is shut off.