Fluccuating tempature

Tiny
JJ58551
  • MEMBER
  • 1989 FORD BRONCO
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 118,000 MILES
Ok, I have an 89 bronco2 2.9L v6 automatis 4x4. I had a problem with the tempature fluccuating. We changed out the motor, thinking the head or head gasket was bad. We did everything else and this was the last option. Got it done and it runs great but still the temp. Is doing the same thing. What could this possibly be? Everything has been changed. Could this be the guage its self? Im just stumped and so is everyone ive talked to. Please help does anyone have any idea?
Thursday, March 31st, 2011 AT 9:56 PM

7 Replies

Tiny
WRENCHTECH
  • MECHANIC
  • 20,761 POSTS
That's usually caused by air pockets in the cooling system. Are you sure that you have all the air bled out?
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Thursday, March 31st, 2011 AT 10:30 PM
Tiny
JJ58551
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Im pretty sure? How would you bleed it out? It also seems to do it more when the heat is on and when you slow down for a stop, but it does drop back down after you stop. And I did change the heater core, and everything else. The tempature never stays up long at all.
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Friday, April 1st, 2011 AT 12:47 PM
Tiny
WRENCHTECH
  • MECHANIC
  • 20,761 POSTS
We generally use a vacuum filler to get all the air out but sometimes it will migrate to the radiator on it's own. The the coolant level when dead cold. You could have a leaking head gasket getting combustion gas into the cooling system too. They have chemical tests to check for that.

Here is a good video about that.

http://www.youtube.com/watch?v=oYQHkWVULn8
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Friday, April 1st, 2011 AT 12:55 PM
Tiny
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  • 33 POSTS
The temp now is much better. I just drove it around town and the temp still fuctuated just a little bit. Like I said it it is much better. I had a heater core hose that was leaking, and we got that fixed, but it was stil doing it. Now the temp is much better. Could the air pockets be working there way out, now that the leak has been fixed for a couple of days?
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Friday, April 1st, 2011 AT 2:11 PM
Tiny
WRENCHTECH
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Time will tell.
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Friday, April 1st, 2011 AT 2:13 PM
Tiny
JJ58551
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  • 33 POSTS
Thanks for help wrench tech. In finally figured out that I spent 1600 for nothing. The tempature gauge was wrong. It is getting surges from somewhere. The heads are fine. It runs perfect temp during the day, it only does when the lights are on, or when I roll my windows up or down. Ive never seen anything like it. All test confirmed that my tempature guage is a lier. What do you all think about that?
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Thursday, April 7th, 2011 AT 9:14 PM
Tiny
WRENCHTECH
  • MECHANIC
  • 20,761 POSTS
There must be a bad engine ground somewhere.
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Thursday, April 7th, 2011 AT 10:31 PM

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