Overheating Mystery

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C

Carbonics

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Aug 27, 2006
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513
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California
2000 Kia Sephia, 72k

car started overheating yesterday...

upper radiator hose is hot on both ends, so it must be circulating, right?

coolant sprayed out of overflow tube.

fans work

full of coolant

raplaced radiator cap thinking it might have been bad, same thing.

only thing I can think of is maybe water pump belt slips? discount tire said they needed to be replaced, but they seem fine to me and they all rotate just fine with the alt, PS, water, ac... turning on heater in the car blows super hot heat so water pump must be circulating through the heater core.... im lost.
 
didn't check the thermostat, from what I have read - if the entire upper radiator hose is hot then it's circulating hot coolant from the engine, and if only the engine side of the hose is hot and not the radiator side then it is closed...so I went by that, which is a far cry from removing the thermostat - I plan on doing that tonight...

the book says to drain all the coolant out, but people have told me you don't have to - just refill what came out.

your take?

it has to be the thermostat, everything else checks out fine.
 
not like a faucet, just some did.... no water in the oil or oil in the coolant.

so, i removed the thermostat housing, swapped thermostats, put in new gasket with RTV, tightened it back up and #@$%! thing leaked coolant still, probably should have let the rtv dry but it had a gasket and it leaked way too much to me.

i tried tightening it up but cracked the housing, nice one....will try and get a new housing and go again.

how do you tell if the thermostat is bad with it removed?
 
just ordered a new housing, what makes you think it's a head gasket? there is no oil in the coolant and no water in the oil.... car only has 72k and has been well taken care of.

when I removed the thermostat housing and looked inside the block it was brand new shiny looking, kind of surprised me.
 
It may also have been that the thermostat wasn't opening far enough...perhaps just far enough to heat the hose up, but not far enough to circulate enough coolant, fast enough to keep things cool.
 
how do you guys suggest I tighten the housing back on? the reason I overtightened it is because coolant/water came out pretty fast from the seal.

should I just put the gasket on, apply the RTV, tighten it up and let it sit 24 hours before adding water? it was my assumption that the RTV was just an insurance policy and that the gasket itself did the sealing.
 
Sounds like a trip to your trusted neighborhood mechanic is in order...
before your $10 repair becomes an engine replacement.
smirk.gif
 
headgaskets leak compression,not just oil and water.a leakdown tester or radiator gas test will tell the tale.leave the stat out,see what happens[after you repair the housing].I had an lt 1 that ran like a frenchman from a fight,but coolant bubled in overflow tank all the time.no oil or water ever mixed,but gasket was blown.you eliminated the thermostat by verifying the upper hose was hot.that means coolant is flowing.
 
Unfortunately neither the 72k miles or taking excellent care of a vehicle is a guarantee against headgasket failure. Sometimes it could just be a bad head/block; sometimes it's just bad luck.
 
Headgaskets can go one of twenty different ways; one of which is exhaust winding up bubbling into the coolant. The heat from this exhaust as well as the pressure will be too much for the system to take.
 
I suspect eljefino and baby huey have it right as well. If your coolant tank is overflowing in what seems like too short a time to have overheated your engine, you likely have a headgasket leak.

A radiator shop can chemically sniff your coolant for hydrocarbons. If they find any, it's confirmed.

This happened to me the last time I rebuilt a ford 302 v8. Neither head gasket showed any sign of a leak, however, 2 new gaskets later, the problem was solved. Glad I shelled out for ARP head bolts on that one.
 
I'm 99% sure it's not the thermostat. Those are usually designed to fail in the open position and if anything, your car won't warm up rather than overheat.
 
There are no usuallies with thermostats. If it is 7 years old, replace it and hope that it isn't the head gasket.
 
ThirdeYe-

Mind you though: thermostats doesn't always fail with a wide-open valve for there shall always some thermostats that fail w/o opening. So far I have serviced 5 thermostats (one on my teacher's Corolla wagon with over 186000kms when it failed) that failed w/o opening.....
 
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