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Over heating

i have a 1999 chevy lumina with a 3.1v its has been over heating and i dont have a clue to what else it could be. i have a new thermostate. a new water pump. my radiator is good. and i bypassed my heater core so i know its not that either. anyone who knows to what it is please answer my question. thx

Are you losing any coolant? Could be intake manifold gasket or head gasket problems.

oh no sorry i forgot that part too. i just replace the upper and lower intake manifold gaskets. so no it is not leaking any coolant

Under what conditions is it overheating?
Have you checked your fan operation?
How do you know your radiator is good? It may not be leaking, but its could be clogged.

Have the radiator flow tested. Also have it checked for internal blockage. A shop with a pyrometer can “map” the temperatures in your radiator and tell of it’s dissipating heat properly or clogged internally.

another possibility is a headgasket leak. That can be checked with a simple pressure leakdown test.

A hose could be clogged. Sometimes the inner liner will seperate and collapse.

Radiator caps can fail too. They whould hole pressure up to their rating, typically about 16psi. The cap’s rating will be stamped into the underside somewhere.

Replacing parts before doing diagnosis usually cost much more than doing the diagnosis up front. Haynes repair manuals will walk you through the stpes.

my fans are clicking on but they seem like they are taking too long to click on. also i poured this gasket seal stuff thru the radiator so i didnt know if that could add up to it over heating. but i flushed the system and it seemed to flush thru. my radiator i flushed and i put a garden hose to it and it cam out perfectly. but i havent seem any leaks so i dnt think that it is that. but i went to go into drive and it also stalled too.

The fans can be tested to see if they turn on at the proper temperature.

Water will flush through a half-clogged radiator, but a half-clogged radiator will not dissipate the heat sufficiently. That’s not a good way to test the radiator. A radiator shop can do it properly.

If the radiator is half clogged, the gasket seal stuff could have contributed to the problem.

The stalling may be unrelated.

The bottom line here is that I think you need to see a qualified shop and get this diagnosed. Otherwise you’ll keep spening money on parts and may not get it fixed until permanent damage has occurred to the engine. I wouldn’t want to see that happen.

how much does an average diagnostics test cost? and where can i get one? they only places close to me is advanced auto parts and auto zone

Why did you pour gasket seal stuff though it?

To find a shop look in the yellow pages for a “radiator” shop

that is what the directions said on the bottle. its seemed to work for a while.

What directions for what bottle? It seemed to work for what for a while? I didn’t mean why did you pour it in as opposed to doing something else with it. I meant why were you using it at all? What problem were you trying to solve with it?

my car was leaking coolant thru the lower intake manifold gasket but i got that fixed now. that was why i was using it.

Ok -then what mountainbike mentioned is probably right - that stuff probably gunked up your radiator. Think about it - its job is to clog stuff. If it didn’t clog stuff it couldn’t stop a leak.

that is true. i just need to find a place that can do the diasnostic test. but a mechanic said he thought it could be my catalytic converter. is that true?

The “diagnostic testing” is simply going through the checks necessary to find the actual cause of the problem. Some of the steps require specialized equipment and/or fittings, some do not. But it’s well worth doing the diagnostic checks.

Typically a problem of this nature can be diagnosed with an hours of shopp time, perhaps a bit more. Typically shop time will cost about $100/hr.

what about the catalytic converter could that be it?

Nope. A bad cat converter causes a whole different set of symptoms.

I’m recommending strongly that you discontinue guessing and get it diagnosed, but should you decide to continue changing parts until it stops overheating my suggestion would be to change the radiator and radiator hoses next. They’d b eth enext most likely candidates.

Note that if it still overheats I disavow any responsibility. I’m only suggesting the radiator and hoses because you seem to want to keep trying parts and I’d hate to see you spending money on wild guesses like the cat converter. At east the radiator has a reasonable probability of being the cause.