Coolant leak-how to proceed?

[madkaw]

Well it's been one of those days. Played around with my carbs and went for a spin. I noticed my engine has been pinging more lately and I needed to check my timing, so I turn around back home and get hard on the gas-everything good!

I get home and smell coolant and it is running down the drivers side of the block front to rear. It's coming out good, but the car is running fine.

I shut it down and look for leaks. It is about impossible to see under the thermostat housing, which is my first suspect. Then thinking about all that pinging---WHAT IF its my HG:cry:

I can't find where it's coming from, so I start it back up. No leak, car idles perfect. So I wait for the thermostat to open, but this engine just runs cool I guess, and can't seem to get the thermostat to open. I take this oppurtunity to check my timing-23 degrees initial-WTH. Now I am more serious about HG.

I take the car for a spin and that gets the thermostat open and here comes the leak. Look again and I can't be sure. Now if you are a lucky enough owner of triples with a shorty Mikuni manifold you will know that the intake manifold HAS to come off to get to the thermostat housing-suck!

So I look again and with the dizzy removed it's easier to see but still I can't be sure.

Any trouble shooting ideas BEFORE I take it apart and make the car incapable of running?

[240260280z]

I have seen thermostat housings corrode. Take the hose off first to have a look. I have also seen leaks due to loose hose clamps.

Maybe do a compression test on #1 too.

[EuroDat]

I would think its the thermostat housing. The leak seems to start once the engine is nice and warm, which creates pressure in the cooling system through thermal expansion. I dont think the thermostat opening makes any differance, its the thermal expansion causing the pressure which causes the leak.

You cant remove the thermostat housing because of the carbs, but can you remove the top housing with the radiator hose? That way you can inspect the internals of the lower housing without removing it. I would suspect its corroded through.

Chas

[zKars]

Take the upper rad hose off and check for split in the hose and make sure the clamp is tight....

[Zed Head]

I just fixed some very light seepage around my thermostat by re-tightening the bolts. I replaced my thermostat a few months ago and I guess the new gaskets compressed after some heat-cycling, or I was just afraid to over-tighten the soft aluminum in the first place. Same scenario, it only leaked when hot, closed up when cold. Might be worth a try. I have EFI and can reach all of the bolt heads without removing anything, with some long extensions and contortions (for the ones in to the head).

Mine was a tiny leak though, only identified by smell and wetness, no actual dripping.

[madkaw]

Well I cooled off a bit and starting thinking like you guys. I've decided that changing the stat housing gasket was easy and logical step first. Haven't taken a spin yet , but see what that does. The gasket seemed wet on removal but I didn't drain the block - so it got coolant on it during removal. Still, it did look a bit suspect. Bolts were tight and hose looks good. Gasket surface on housing lid sanded flat. Keep my fingers crossed .

Thanks for the ideas guys

[240260280z]

You will never forget this photo

[Mikes Z car]

I think I can fix that with some JB Weld...

[Stanley]

Mine's leaking too, on the other side (only, I hope). Fairly sure it's corrosion on the big hose barb that takes the lower radiator hose. Saw how bad it was when I changed radiator hoses -should have installed a new inlet at that time. Figured it would be too much of a chore to get the old corroded inlet out of there. Never do that. Guess it only leaks when it's hot. My engine usually runs on the cool side, except stop and go on the freeway on a hot day - when you can't pull over and check it. Felt a little moisture there though.

Wonder what's the best radiator hose without going silicon? Those braided OEM imitations are expensive and look a little thin.

[madkaw]

Blue,

awesome photo.

Well replacing the gasket did not help. I will double check, but I think the hose is fine. The neck on the housing had some very minor corrosion, but I believe the hose seals up. It looks like the fluis is below that. So now I guess I get a pressure tester and see if I can get it to leak with the dizzy out so I can see where it originates????????

[mlc240z]

Worst case, thermostat housing is only $32 at MSA.

[madkaw]

No, worse case is 6 hours of work to replace it.