Oh boy...I'm afraid to ask this question 'cause I think I know the answer.

I bought an X-11 350 car a few weeks ago. Very clean car, runs pretty well ( a bit too much cam). After I test drove the car and bought it, we found a small puddle (8" round) of coolant that had come from the blow by hose at the radiator cap. The radiator didn't seem very hot. We all wondered if the thermostat was stuck. We pulled the housing and sure enough there was the thermostat stuck closed. No big deal. They said they'd put a new thermostat in before it shipped to me. They did.

The car arrived here this past week. And after rides I'm still getting small puddles of coolant. Here's the part that concerns me: After nearly two hours of cooling down the radiator still had pressure in it when I lifted the vent on it. This pressure vented in a few seconds and spiited a bit more coolant doing so. Also, I tried starting the car completely cold with the radiator cap off. I could see foamy bubles starting to collect at the top of the radiator. I seem to remember if you see bubles in the coolant you may have a leaky head gasket. Am I remembering correctly ? My concern is that I have a leaky head gasket that's ending up pressurizing my coolant system. BTW...the cap is 1 16 lb. cap and was also supposed to be replaced by the dealer. Can't say for sure.

So...sound like a head gasket issue to you guys ?
Or do you have other ideas ?

I can't absolutely say for sure that the motor isn't overheating because I don't have guages yet, but I'm pretty sure it's not.

Use a block tester, also known as a combustion leak tester, to determine if you have exhaust gases in your cooling system. A combustion test kit can be found at your local NAPA, auto parts store. The part number is 700-1006. The price for this part is less than $50.00. Exhaust gases in your cooling system can suggest a head gasket leak, a cracked block, or a warped head, etc. A leaking head gasket can create excessive heat and pressures exceeding the ability of the radiator’s cooling capacity, and should be repaired immediately to avoid additional costly repairs. Head gasket leaks are generally secondary to another problem, such as a clogged or leaking radiator. Make sure you identify and repair or replace the original problem or the vehicle may overheat and cause the head gasket to fail again.

To do the test, add the blue detector fluid to the (block-tester) plastic container according to the directions, and place it onto the radiator filler neck. The squeeze bulb is placed on top of the reservoir and squeezed repeatedly (Some block testers, have a tube that connects to a vacuum line instead of a squeeze bulb). Squeezing the bulb will draw air from the radiator through the test fluid. Block tester fluid is normally blue. Exhaust gases in the cooling system will change the color of the fluid to yellow, indicating a combustion leak. If the fluid remains blue, exhaust gases were not present during the test. The vehicle should be started and at operating temperature before performing the test. Vehicles with head gasket leaks may overheat, and purge hot water and steam out of the radiator. Perform this test, at your own risk, and do not do the test, unless you are experienced and are wearing clothing and equipment to protect you from burns, or injury.

Sometimes, engines with a head gasket leak show steam, water or white smoke exiting the exhaust pipe. Other symptoms include coolant in the oil, or oil in the radiator coolant.

If you are keeping the anti freeze level too full it will burp out the excess every time you refill it. It should be down in the radiator where you can see maybe 2 open copper fins. That allows for expansion under heat. If its too full, when it expands it burps the excess out the overflow tube. I learned this the hard way. :)

Thanks Mike & Jim,

I'm hoping it is as simple as the level being too high. The dealer did top off all the fluids in the car in preparation for me buying it. Maybe the bubbles I'm seeing are just incidental air moving around in the cooling system. I'll let the level drop a bit and see if it stops. If it doesn't I'll try the block tester to confirm a leaky head gasket.

Mark

My '69Z (all stock/original) likes the coolant level about 1-1/2" below the "full cold" embossment on the side tank; runs at 170*-180* all the time, but if it's filled (cold) any higher than I noted, it'll puke some coolant during hot-soak after shutdown. If I leave it at its "happy level", it never pukes a drop. If the cooling system is doing its job and it runs at normal temperatures, it'll find its own "happy level" - leave it there.
:beers:

Thanks alot guys.
I don't remeber leaving that much expansion room in old coolant systems (non expansion tank systems).
I thought the old systems ran at higher pressures than today and contained the expansion.

Can you tell it's been over 20 years since I built my '72 ?
HAHAHAHA !

At least all my standard sockets are being put to use on something other than my Harley !