Chrysler Repair: Coolant exits from filler bottle shortly after starting, coolant system, radiator shop

Question
When I start my 95 lhs and let it run for about 3 mins or so coolant will start to come out of the over flow. The coolant is only warm when this happens. I can put my finger in the coolant reservoir right as it is coming out of the over flow. I put the cap back on and shut the engine off and it comes out even more. Can anyone help.

Thanks scott.

Answer
Hi Scott,
It is not likely that the temperature of the coolant in the engine is so high as to raise the pressure in the system due to expansion of the coolant, which what usually causes some coolant to temporarily enter the bottle (and then gets sucked back when the system cools down and the fluid contracts). I assume the the temperature gauge is still in the normal range or lower when this starts to happen, correct?
Rather because this happens so quickly after start up my thought is that the engine itself is pressurizing the coolant system due to a leak in one of the two head gaskets. When that happens the pressure in the combustion chamber can 'communicate' to the cooling system passageways that also flow across the gasket between the block and the cylinder head.
Do you notice excessive white smoke coming out the exhaust (and which smells of coolant) when you first start the engine from cold? That would be another sign of such a leak as would a milky color of the engine oil. If you do have those symptoms then you would want to figure out which bank of cylinders has the leak so as to focus on that side to replace the gasket. You might tell that by checking the compression of the individual cylinders, or even just removing all the spark plugs and having a helper crank it over (when cold) will reveal a sputt of coolant from one of the six spark plug holes at the first turn of the crank. Also a 'wet' spark plug would be suspicious when you remove them.
It is also the case that there is a tester sensor that a radiator shop would have to detect the presence of exhaust gas in the cooling system, if you can't definitively prove this theory.
Let me know if you find it to be the gasket. It might be the case that the gasket is not actually torn but rather that the head bolts are not as tight as they should be in which case you could correct that without removing the cylinder head, etc.
Roland