Help, it wont stay cool

[WesLaub]

After putting in BJs aluminum radiator and electric fan the temp ran nice and cool. A week or two later it started running warm then hot on the fwy under load but on side streets or parked the temp dropped and ran fine. My mechanic thinks its running lean but nothing he does has changed the problem. He even put in a new t-stat, no help. HELP. Any suggestions are appreciated.

Wes

[Ryan]

if it ran fine before, and now is running hot, then it is possible that you have a pocket of air inside the cooling system, the waterpump isn't working properly, or you are running lean. Also, if your timing curve is off, it'll also heat up the engine.

[jeeping1974]

if it is a bad water pump, I would recommend replacing it with a high flow water pump as they work really well with an alum radiator.

[WesLaub]

Timing was checked, OK. The radiator cap sets well above the motor making it easy to get the air out. Didn't think about the water pump being bad, it was new 3yrs ago. Very low miles since I put in the water pump (Autozone). Any way to tell if the water pump is bad (no leaks).
Thanks

Wes

[jeeping1974]

there is a weep hole usually that is on the drivers side of passenger side behind the pulley that would start to "weep" coolant out of it. Did you pressure check the cap and system also?

[Ryan]

3 years, pump "should" be ok, especially if you don't have any weeping out of it. I'd go back to air pocket / timing / mixture. Did he tune it by ear, or was it hooked up to an Air Fuel Ratio gauge?

[Stuka]

Yeah, timing by ear is no good. Need a vacuum guage or a timing light. The AFR helps, but is kind of redundant to the vacuum guage. Running lean (vacuum leak, carb set wrong) could really cause it to run warm.

Did you try to get the air out of the system by start it cold with the radiator cap off, then letting it run until the thermostat opens. You will see air start to come through.

[tom malone]

wont stay cool

if ran cool after the radiator installation for two weeks it does not have an air pocket. assuming it has the correct amount of coolant and no leaks. i would look at the radiator hoses and make sure they are not collapsing when the engine rpm is up causing it to heat up, slow down the problem goes away. also check the thermostat even though it is new it could defective, buy a quality,part i have seen the go bad. the lower hose is usually the culprit. alos it doesnt happen to often but the empeller in the water pump could be spinning on the shaft at speed, auto zone part likely. t malone

[mrtazwrench]

if ran cool after the radiator installation for two weeks it does not have an air pocket. assuming it has the correct amount of coolant and no leaks. i would look at the radiator hoses and make sure they are not collapsing when the engine rpm is up causing it to heat up, slow down the problem goes away. also check the thermostat even though it is new it could defective, buy a quality,part i have seen the go bad. the lower hose is usually the culprit. alos it doesnt happen to often but the empeller in the water pump could be spinning on the shaft at speed, auto zone part likely. t malone

It should have a spring in the lower hose to prevent collapsing, make sure it was not removed, or not installed in a new hose. Not likely with 3 year old pump and low miles, but I just removed one that at some time had poor coolant in it and the impeller was eaten away to a flat disc, it did not overheat, but had no flow through the heater core.

[WesLaub]

Thanks to all for suggestions. I tried everything

New waterpump, Flow Kooler.
Lower hose with spring.
BJ's aluminum radiator and electric fan.
Failed smog (to rich because my mechanic friend thought it might be running lean)
Remote oil filter (thought about remote oil cooler)
And anything and everything else we could think of.

Final conclusion:
Maybe one or both heads cracked leaking combustion gases into water jacket under load.
Rebuild motor?
Shoot self(or drive GW off cliff, I'd jump before going over)

Wes