Overheating

[snarisi@verizon.net]

I've had my 92 seville for about 6 months w/ out a single problem. Then, last week I took a 5 minute drive to the store. When I came out I discovered that I had a coolant leak. I turned the car on to discover that my coolant temp was 246 degrees F. I let the car cool down and drove back home. When I got there I could not figure out where the leak was located. My first idea was the thermostat, so I replaced it w/ an new oem thermostat. Drove the car a few times and everything seemed to be ok, except, at idle the tempt would rise to about 225-230 before the fan turns on. I figured maybe this is normal so i let it be. Then, this weekend I had to make a 5 hour trek to West Virginia. No problems, temp rarely past 210 degrees, until I reached my destination. I sat idle and watched my the temp rise above 240 once again. So I quickly popped my hood to discover that the leak wasn't exactly a leak. My antifreeze was boiling out of the top of the resivoir. I have a few ideas of what may be going on which I'll throw out there, but any advice would be greatly appreciated.

1. Old/Bad coolant or water in coolant - I have no idea when the last time the coolant system was flushed and the the coolant replaced. I think this may be at least part of the problem because the temp never past 250 degrees and I understand that antifreeze should not boil above somewhere around 260 degrees.

2. Bad radiator fan sensor/relay/etc. - The fan does not turn on at idle until at least 225 degrees, however I have not a clue whether this is normal or not.

[adallak]

Fans kick off at 225. It is normal. Sounds like your coolant concentration is off.

[Scotty]

Its normal for the FAN to turn on around 222 degrees if I am not mistaken, but I don't think that is your problem. I would check these things:

1) Check that the coolant to water has a 50/50 mix, up to 70% coolant concentration is allowable (but 50% is preferrable) but less than 50% coolant is bad as it allows the coolant to boil at too low a BOILING temperature. If it is higher than 50% start bringing it down by adding some distilled water. Too high a concentration can shorten the life of the water pump seal.

2) Check the cap to make sure that the poppet valve is 1) not stuck, 2) not hanging loose, it should spring back up when it is operating correct. When the engine cools the contracting of the coolant and vacuum created draws coolant in from the resouvior. If the cap looks old buy a new one but MAKE sure its the correct type with the poppet valve that springs up, and don't buy a cheapo. An OEM cap is best IMHO. The types that have the handle on them I take off and see how far I can throw them....

3) If you don't know when your thermostat was replaced, replace it, don't hem and haw about it, just replace it its cheap and an easy job to do, make sure you buy and replace the rubber seal its sold separately in most cases.....

4) if all else fails drain your system and refill with clean green coolant and put in 6 coolant supplement tablets (VERY IMPORTANT).... Do a search for COOLANT SUPPLEMENT. NOW, what I would do is run clear water throught the radiator ONLY, ONLY if I thought it was clogged, but taking off the hoses and capping the outlet filling it a bunch of times with water and then releasing the lower cap...and by blowing high pressure water into the filler and the upper radiator hose inlet. DO NOT flush the engine, you put straight water in the block and its a PIA to get the 50/50 mix right again... We don't believe that the PRESTONE type flushes are necessary like we did in the old days, just drain and refill with fresh coolant...

5) Check to make sure that BOTH fans come ON and when the temp is 230 they are CRANKING at full speed... I had a fan in my 91 go bad and it spun VERY slowly and smelled like the windings were burned when I took it out..

6) Check your serpentine belt and tensioner for wear and looseness, but not likely the problem

7) If it still overheats (which by now it should be fixed), pressurize the cooling system and see if it holds pressure. The radiator end caps are plastic and in time they develop stress cracks and leak pressure, as you know if the pressure is dropped it lowers the boiling point.

8) look over your water pump grab the pulley and see if you can rock it, look at the weep hole to see if any coolant is present. While the car is running look at the water pump pulley to see that its steady and not rocking or noisy. The water pump IMHO self destructs with virtually NO warning when it goes so the water pump is not likely your problem and if the seal leaks it washes the grease out of the bearing quickly and the bearing blows up quickly. This is another reason to keep the coolant fresh and the concentration at 50/50, higher concentrations can hurt the seal.

I think, but I am not sure, that your FANS are coming on a LITTLE bit to late at 225 degrees if you are SURE about that, they should be coming on at 222, please check that and could someone else confirm this thought, I am too busy to consult the manual now. AND, the FANS should come one FULL when the AC is on, IF you have disabled the AC and don't run with AC your FANS behave differently and this is noticible in the SUMMER with perceived higher temps, BECAUSE with the AC ON the fans are on 100% of the time with the AC OFF the fans come on when the TEMP reaches 222 degrees so the car TENDS to appear ride a bit hotter W/O the AC on, once I fixed my AC my in-traffic TEMPS were cooler (and that was COOL, pun intended!)...

Good Luck, report back your findings soldier! Mike

[Oldgamer]

I agree with Scotty, just want to add my 0.2.

You already changed thermostat, so don't bother to change this one now. And I reccomend to make coolant change at first, cause you don't even know when it was changed. I don't mean that is a cause of overheatting, just making accent how important this is.

[Scotty]

OH I did not see that you replaced the stat, thanks Oldgamer, I blew right by that....