foamy coolant

hi,

my friends '90 wagoneer started running hot recently. we checked and found the pressure bottle dumping coolant around the coolant lines. when we released the pressure and had it running w/o cap, we saw the return coolant being all foamy...

how can air get into the system (and plenty of it)? could the head gasket be broken and gas from the combustion chamber gets pushed into the coolant lines? shouldn't the foam be either oily (not) or smelling of gas (neither)?

any other ideas?

thanks, guys,

micha

Foamy tends to say that you have a head gasket leak. Take it to a mechanic and have him use a sniffer to test for hydrocarbons in the radiator.

How foamy? I have seen foam in mine too, but both of mine hold pressure now and do not overheat, once I fixed all the hose, bottle, and cap leaks.

Have you tried just replacing the leaky hoses and bottle cap to see if the overheating is due to pressure loss from leaky hoses and a leaky cap? Also check the radiator and water pump seal.

Usually a head gasket pressure leak will over pressure a sealed cooling system and leak, forcing coolant out of the bottle cap even with good, new hoses, caps, bottles, and radiators....But you can not tell which it is unless you replace any defective cooling system parts first and retest it.

as foamy as water out of a sink faucet with the little screen thingy attached...
too foamy for a small leak in a hose. plus, that usually pushes water out of the leak instead of sucking air into it.
(and the bottle cap is new and the hoses are not old and look good)

i suspected the cylinder head gasket. it seems to be this way.

In that case sounds like a head gasket.