There's a little test kit you can use to test your coolant for the presense of combustion gasses. Like this:
http://www.etoolcart.com/index.asp?P...OD&ProdID=1687
If you don't have a head gasket problem, here are other possibilities:
- Trapped air. If for whatever reason air becomes trapped in the back of the heads/engine, it will create an air pocket that won't necessarily find its way out of the engine. The back of my intake manifold is drilled/tapped for this reason, and twin lines run forward to the water neck allowing a little coolant flow to bypass the heads and keep this area clear of air pockets. You could try jacking the nose of the car high and running it; that might help.
- Stuck thermostat. Thermostats do stick; and when they do...you could overheat.
- Fan wiring. Is it possible you have your pushers and pullers working against eachother? Try powering each fan individually and make sure they're all pushing air from nose to tail through the radiator core.
- Collapsed lower hose. Is the lower radiator hose collapsing when the thermostat opens? Weak hoses with no internal spring reinforcement can do this; and when they do, coolant flow stops. Also, I've seen internal plies of multi-ply hose collapse leaving the outer shell looking OK. This failure mode will drive you to drink.
- Timing retard. Is the timing advance grossly retarded? Did someone accidentally time the engine ATC instead of TDC? If so, the additional retard will create a ton of combustion heat.
- Water pump. Did the impeller seperate from the shaft? Seen that. Pulley is turning; impeller is not.
Hope some of that might help.
Byron
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