1989 Chevrolet Other engine overheating

Tiny
ANNA BARRENTINE
  • MEMBER
  • 1989 CHEVROLET
  • 5.7L
  • V8
  • RWD
  • AUTOMATIC
  • 189,000 MILES
I have a 1989 Chevrolet 350 that keeps running hot.I have replaced the thermostat, water pump, checked the radiator and replaced the heater coil. When driving and it starts to run hot you can open the hood and the temperature goes back to normal. What could be the problem?
Tuesday, June 30th, 2015 AT 10:36 AM

25 Replies

Tiny
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  • MECHANIC
  • 3,711 POSTS
Hello,

Have you check the Fan Clutch?

With vehicle cold and not running spin fan - should spin easily - now start vehicle run till normal operating temp, shut engine off, Carefully spin fan again should be tight or harder to spin. If spins easily like vehicle when Cold replace fan clutch.
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Tuesday, June 30th, 2015 AT 11:13 AM
Tiny
ANNA BARRENTINE
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When vehicle is cold the fan will not go but a quarter of a turn, should it turn freely without my hand on it.
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Tuesday, June 30th, 2015 AT 11:26 AM
Tiny
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No it should just turn easily by hand
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Tuesday, June 30th, 2015 AT 11:31 AM
Tiny
ANNA BARRENTINE
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It is very stiff so does that mean it is the fan clutch needs to be replaced.
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Tuesday, June 30th, 2015 AT 11:34 AM
Tiny
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Is that with vehicle hot or cold.

If hot then no - When cold should be able to turn by hand easily, as it heats up it begins to tighten up to create more air flow so will be harder to turn by hand.

Ok, you said you checked the Radiator how did you check it?

If you can run your finger along the fins if they disintegrate or break up then would replace radiator.
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Tuesday, June 30th, 2015 AT 11:45 AM
Tiny
ANNA BARRENTINE
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Flushed it out and it has a good flow to it.
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Tuesday, June 30th, 2015 AT 11:48 AM
Tiny
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That was with the vehicle cold on the fan we checking on it when it is hot.
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Tuesday, June 30th, 2015 AT 11:49 AM
Tiny
ANNA BARRENTINE
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What is the normal operating temperature for a Chevrolet 350 V8 5.7 L?
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Tuesday, June 30th, 2015 AT 11:54 AM
Tiny
ANNA BARRENTINE
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Ok with the vehicle is hot the fan turn easily for a few turns then it tightens back up like when it is cold. Also when you first start the truck the fan runs really fast then starts to slow down some.
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Tuesday, June 30th, 2015 AT 12:04 PM
Tiny
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I believe it around 180 - 195

Even if you have good flow in radiator it the Cooling Fins aren't doing there job it will over heat.
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Tuesday, June 30th, 2015 AT 12:14 PM
Tiny
ANNA BARRENTINE
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Ok how will I know if the fins are doing there job.
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Tuesday, June 30th, 2015 AT 12:24 PM
Tiny
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With vehicle cold run your finger down different areas of the fins on the radiator. If they brake up easily or disintegrate then they are not doing there job.

Also, you said you changed the Water Pump did the overheating start after the replacement?
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Tuesday, June 30th, 2015 AT 12:30 PM
Tiny
ANNA BARRENTINE
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It started before I changed the water pump. I took the fan clutch off and it has a broken spoke on it. So do you think that could be it. I checked the radiator again and there are not any brake up or disintegrating.
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Tuesday, June 30th, 2015 AT 12:59 PM
Tiny
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Since it is broken I would replace it. It could be the cause but not sure.

Another thought is that there is an air pocket in the engine causing a hot spot which will cause it to overheat.

The way I usually attempt to get it out is to jack up the front of the vehicle so that the bubble will start to work its way out. Then run it with the cap on loose till gets heats up if has a gauge run till not quite in red, then let cool down refill with water if needed. You will know once bubble is gone, temp will go back to normal. This could take a few hours. It once took me 3 hours to get it out.
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Tuesday, June 30th, 2015 AT 1:16 PM
Tiny
ANNA BARRENTINE
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We are going to change the fan clutch out and then I will let you know what I find out. If that fixes it or not.
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Tuesday, June 30th, 2015 AT 1:22 PM
Tiny
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OK
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Tuesday, June 30th, 2015 AT 2:04 PM
Tiny
ANNA BARRENTINE
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Changing out the fan did not work. When you are sitting idle it does not run hot. When you go down the road as long as you stay below 55 miles per hour it does not run hot. When you get up to 70 it starts to run hot.
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Tuesday, June 30th, 2015 AT 4:22 PM
Tiny
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OK, did you change the Fan Clutch or the Fan, pics below are the Fan Clutch may not look exactly like the one on there.
Images (Click to make bigger)
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Thumb
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Tuesday, June 30th, 2015 AT 5:12 PM
Tiny
ANNA BARRENTINE
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Sorry I said fan but it was the fan clutch.
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Tuesday, June 30th, 2015 AT 5:17 PM
Tiny
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OK, do you know what temp thermostat you put in also did you replace the Radiator Cap.
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Tuesday, June 30th, 2015 AT 5:20 PM

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