2001 Jeep Laredo heat

Tiny
SCOOTIE
  • MEMBER
  • 2001 JEEP LAREDO
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 86,000 MILES
My water pump was leaking so I replaced it and also the thermostat(195degree). At idle the temp will be normal and the heat is very good. Once you start driving the temp goes down to approx 145 and the heater blows very cool. If you stop for awhile the temp goes back up and there is warm heat again. What could be the problem? Thanks for any help.
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Monday, March 15th, 2010 AT 5:29 PM

6 Replies

Tiny
BEEF99
  • MEMBER
Did you have this problem before you changed you pump and t-stat? I am assuming you did not. This would indicate that it is something that you may have done by accident. Try looking at your t-stat and make sure that you installed it correctly because they can be put in backwards on some models and this could cause your t-stat not to operate properly and make it stay open, also, if you did not buy a quality t-stat, you could have a defective one(this is more common than you may think). If the t-stat stays open while driving, the engine will cool and not maintain proper temperature along with a small drop in fuel mileage because you engine senses that it is colder and releases more fuel. Try to look at your t-stat and replace it with another if you did not put it in backwards. If this does not help, let us know.
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Monday, March 15th, 2010 AT 9:50 PM
Tiny
SCOOTIE
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Thank you for such a quick reply.I did not have this problem before I changed everything.I did have a problem with not much heat but I flushed out the heater core and it seemed to be better after that. Then I started to not have much heat again, but then the pump was leaking so I changed that and the t-stat. Even before that the temp never dropped ever since I owned it. I will check the t-stat and flush the heater core out again. Do you think the heater core is pluged up and how would that affect the system as I did flush it once? Thank you.
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Monday, March 15th, 2010 AT 10:21 PM
Tiny
BEEF99
  • MEMBER
If your heater core was plugged, yes it could cause you to loose heat for you inside heater system. BUT if you had a plugged heater core, it would not cause your engine to operate cooler than normal. Also, it is a possibility that your temp. Sending unit is bad. The one on your t-stat housing is the one that controls your guage and the one the is in your manifold controls you computer. If I remember right they are between $25-$35 at the store. Flushing your engine will not cause you engine to operate under normal operating temps either. You either have a fan that is stuck on adn won't shut off, t-stat sticking open, or a temp sensor or guage that is reading bad readings. My guess is that it has something to do with what you were working on physically because there was no issue before.
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Tuesday, March 16th, 2010 AT 7:41 AM
Tiny
BEEF99
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Using a high impedence, digitial ohmmeter, check the resistence of the sensor across the sensor terminals. The resistence should measure 3400-1600 ohms at 70-100degr Far, with the resistence below 1000 ohms, if the engine is warm. If the resistence is out of range, replace the sensor. Using the ohmmeter, connect one lead to the sensor connector terminal, and the other lead to the sensor wiring harness connector terminals 15 and 32. If there is an indication of an open circuit, repair the wiring harness.
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Tuesday, March 16th, 2010 AT 10:30 AM
Tiny
BEEF99
  • MEMBER
Degrees in farenheit

212degr.=185 ohms
160=450ohms
100=1600ohms
70=3400ohms
40=7500ohms
20degr=13,500ohms
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Tuesday, March 16th, 2010 AT 10:32 AM
Tiny
SCOOTIE
  • MEMBER
Thanks again for your quick response. I changed the t-stat and flushed out the heater core since I had the hoses off. Its been two days now and the temp is where it should be and staying there. The heat is blowing like it should be. I am asuming I probably got a bad t-stat. Nothing like doing it twice. Also it was not in backwards so that was good. I will keep you posted. Thanks again.
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Wednesday, March 17th, 2010 AT 9:52 PM

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