365 blown head gasket?

That would make sense if you also get oil in the coolant.

 

Fill with water and while car is warming up (idle speed) check engine compartment with the aid of a torch check for leaks could be a failed mechanical seal in water pump or a hole in a water transfer hose?

 

Make sure you get all the air out of the system before you go on a ride.
Start with the engine cold and the expansion tank full; turn the heater on; open up any vent there may be in the cooling system (on the thermostat housing?) and squeeze repeatedly the large rubber hose that takes the water from the engine into the radiator.
Idle the engine and while squeezing the hose keep an eye on the level in the tank; have a jug of distilled water mixed with antifreeze ready.
Once the coolant warms up and the thermostat opens up, the air will start to bubble out from the circuit and into the tank: be ready to top up the tank.
Continue to squeeze the hose until they are too hot to touch and there is no air left in the system.
Turn the engine off and place the cap on the expansion tank.

Before you start all this, make sure the car is parked in a such a way the tank is the highest point of the cooling circuit.

Good luck

 

Pressure test cooling system. Other things can cause this too.

 

+1

This is both the easiest and the most reliable / predictive way I know of to tell whether a head gasket is causing a coolant leak.

Also, it is important to run the p-test separately under BOTH conditions ----- engine HOT & engine COLD ---- in order to make the determination accurately. As some minor leaks may only be present at either extreme.

 

There is only one thing that can cause the water to escape under pressure: gas formation.

This can form from either of the following: 1) steam from overheating (hotspots in the engine from insufficient cooling or insufficient water circulation), or 2) combustion gas being forced into the cooling system, pushing out the water.

Does it spit water from the tank with the cap off when the engine is cold? Does the exhaust steam a lot when it is started from cold, and does the engine run irregular if that happens? If yes then there might be a head gasket issue.

It can be many other things too. What is the temperature on the gauge when this happens? Insufficient cooling and hotspot formation can be caused by a clogged radiator, defective waterpump not pushing (enough) water, or even air trapped in the engine. All of these will cause water to pour out eventually.
When filling, air in the system may prevent you from filling it completely. It seems as if no more water can be put into the cooling system, but in fact the air in there keeps you from filling it properly. Squeezing the hoses while filling may help.

 

I believe there is a chemical test that can determine if there are combustion chamber gas components in the coolant.

I have had it happen where a blown head gasket will leak hot, high pressure gas into the coolant and cause it to boil over but no oil is seen in it or coolant in the oil. (If the gasket leak is between the combustion chamber and coolant pathway only you will see this.)

 

what model is this car?
what type of motor(SOHC?), if a 245...simply change th thermstat(GM 180 degree F),
oncew a KNOWN good t-sta is functioning, and all other valves are either all open or all closed...while driving(fans NOT a functioning factor here), check by touch temp of radiator-look for cold spots-lastly....have local garage use exhaust gas anylizer to "sniff" the expansion tank...if CO present you have to take the engine apart.
Likely all the way apartas car is 45-50 yrs old...

 

You mean there is no spring on the radiator cap with a metal end plate that seals inside the neck of the tank? I have heard of these falling apart and the spring falls into the tank.

Does your car have one surge tank that you keep about 1/2 - 2/3 full? That should have a pressure cap (with a spring) on it.

If your car has a second tank, which is the reservoir tank into which the first tank overflows when it is hot, then the first tank should have a pressure cap.. The second one does not because when it overflows it dumps onto the ground.

If you do not have a pressure cap somewhere in the system and the tanks are full the car will dump coolant onto the ground when it warms up.

 

The cap on the radiator is just a flat cap with a gasket. The cap on the small tank in front of the radiator has the pressure cap on it. It sounds like you have the wrong cap on the radiator and that you do not know what you have on the small tank.

 

The chemical test takes 60 seconds and you'll know for sure it's the head gasket.

 

I agree, search youtube, there are many videos talking about this.

 

There is no mystery. You need diagnosis

 

Great news!!!