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Cooling fans not working?

Tiny
JDWIMSETT
  • MEMBER
  • 1997 CHEVROLET CAVALIER
  • 250,000 MILES
Seems like if I drive awhile, stop and then drive again it will overheat.

e.G. Drove 45 min to work this morning and it was fine. Drove 30 min fine on the way home, stopped to get gas, then left for the final 15 min home and it overheated. Its done this a few time. It was also spitting and sputtering before it overheated, but only when the engine was loaded (downshift to climb a hill.)Its been doing this for awhile.

I've replaced:
Thermostat
Fan relay (Fan is spinning when engine is hot)
Radiator
Waterpump
Radiator cap

I checked and didn't see any collapsed hoses, but I didn't check until the car cooled off.

I don't think its a bad head gasket as I pulled the fuel pump relay and turned it over while watching the coolant resivor and didn't see bubbles.

This all started after I drained the old coolant flushed and replaced it with non dex-cool product.

Any suggestions?

Thanks!
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Tuesday, July 12th, 2011 AT 5:15 PM

13 Replies

Tiny
SATURNTECH9
  • MECHANIC
  • 30,869 POSTS
So do you have a temp gun?What temp is the cooling coming on at?Are both the upper and lower radiator hoses getting hot?Do you have a air compressor if you do blow the a/c condenser and radiator fins out all the sand dirt debris etc also check them for bags etc. Also do you have any trouble codes in the cars computer?
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Tuesday, July 12th, 2011 AT 5:46 PM
Tiny
JDWIMSETT
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  • 7 POSTS
I don't have a temp gun so I can't answer that question, and I don't know what you mean by "bags." I can tell you the radiator is less than a week old and has only been driven 20 miles at the most.

There are no codes in the computer and both hoses are getting hot.
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Tuesday, July 12th, 2011 AT 5:50 PM
Tiny
SATURNTECH9
  • MECHANIC
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By bags I mean like the ones you get at the store when you buy something people run them over and then get trapped in the radiator and a/c condensor fins not allowing enough air flow thru. Also if you have a air compressor I would blow out the a/c condensor fins that will help it to run cooler also because thr air comes thru that before it goes thru the radiator fins. We should really have a temp gun when diagnosing a overheating problem we can see what temp the fan comes it might becoming on at the wrong temp. We can can see when the thermostat opens if coolant is properly flowing. Also to check for blown head gasket you would use a chemical tester you add a chemical in the tube and run the car and watch for a color change. They rent those at auto zone you just have to buy the chemical for about 8. The first thing I grab when I have a car that is overheating is my temp gun so I can see whats going on with it. Also what is the 8th digit of your vin number.
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Tuesday, July 12th, 2011 AT 6:04 PM
Tiny
JDWIMSETT
  • MEMBER
  • 7 POSTS
O ok. There are no bags stuck anywhere.

I can try to borrow a laser temp gun from work. Do you just look at the hose before and after the thermostat to verify its open and in the reservoir to verify the coolant temp when the fans kick on?

The 8th digit is a 4
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Tuesday, July 12th, 2011 AT 6:27 PM
Tiny
SATURNTECH9
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I would measure engine temp at the thermostat housing on the engine to see what temp the radiator cooling fan comes on at. As far as seeing what temp the thermostat opens at when the upper and lower hoses reach pretty close to the same temp the thermostat is open. The radiator cooling fan should come on at 223 degrees ferinhiet.
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Tuesday, July 12th, 2011 AT 8:35 PM
Tiny
JDWIMSETT
  • MEMBER
  • 7 POSTS
I took some measurements with an IR thermostat. Here is what I got.

Cool Engine:
Lower hose before thermostat - 106
Lower hose after thermostat - 98.6
Upper Hose - 98.9
Coolant - 99.6

Warm engine (Fan starts spinning)

Lower hose before thermostat - 200.3
Lower hose after thermostat - 186
Upper Hose - 185.1
Coolant - 195

I measured the Lower hose before thermostat on the hose up to the heater tube.
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+1
Tuesday, July 12th, 2011 AT 9:19 PM
Tiny
SATURNTECH9
  • MECHANIC
  • 30,869 POSTS
Those numbers are good so we just need to know what temp the fan comes on at?Also why do you think its overheating?Is it boiling over the cap?Also did you bleed the cooling system when you refilled the system?I posted how you do that. The fill instructions I posted says your car uses dexcool.
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Tuesday, July 12th, 2011 AT 10:09 PM
Tiny
JDWIMSETT
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I'm not currently running dexcool because I believe that is what cause this to begin with. I also don't think that running the green stuff would cause the car to overheat. Maybe I am wrong though.

I believe its overheating because the gauge sits fine for most of the trip then next its pinned at the H and my check gauge light is on. Also, i've had the ac compressor shut off which I read somewhere is a safety when the car is hot and recently it has started sputtering when the gauge is at H. It did spill over once, the very first time it overheated.

I don't see the water outlet bleeder valve. This is a base model, not the LS, I'm not sure if that makes any difference. What I do see is the fitting that goes to the vent hose.

The heater tube valve snapped off the last time I filled the system (after I replaced the water pump.) So I can't use that anymore. I did use it after I replaced everything else individually though. The only thing I do now to try to get the air out is keep the radiator above the engine when i'm filling the system and have it cycling.
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Tuesday, July 12th, 2011 AT 10:24 PM
Tiny
SATURNTECH9
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I have never heard of the factory dexcool causing the car to overheat. The bleeding instructions I posted are for your car as you can see there is two styles listed you just have to find your style and use that one. Air will cause overheating if something for bleeding is broken I would fix that and bleed it like the instructions show.I would also see what temp the fan comes on at. After we do all this next would be to do a chemical head gasket tester to rule that out.
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Wednesday, July 13th, 2011 AT 12:09 AM
Tiny
JDWIMSETT
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  • 7 POSTS
I'm sorry, I wasn't saying the dexcool caused the car to over heat. I meant the owner before me didn't change the dexcool or mixed glycol with dexcool and coated the inside of the cooling system with slime.

How can I see what temp the fans come on at? When the fans came on today, I opened the cap and took a measurement with the IT temp gun @ 195f.
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Wednesday, July 13th, 2011 AT 1:23 AM
Tiny
SATURNTECH9
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I would check the engine temp to see when the fan comes on right where the upper radiator hose hooks on the head on the head itself not the hose. Have you blown the a/c condensor fins out yet?
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Wednesday, July 13th, 2011 AT 2:04 AM
Tiny
JDWIMSETT
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No. I'll be doing that tomorrow.

You want the temp of the head? It's supposed to turn on at 223?
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Wednesday, July 13th, 2011 AT 2:08 AM
Tiny
SATURNTECH9
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Yes on the head and yes 223 the fan comes on.
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Wednesday, July 13th, 2011 AT 3:34 AM

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