1999 Ford Explorer runs cold during colder months.

Tiny
PELINACA1
  • MEMBER
  • 1999 FORD EXPLORER
I own a 1999 Ford Explorer with the 4.0L 6 cylinder engine. The problem I am having is that when the temperature outside drops the truck never warms up. The needle stays below the cold line (below the lowest part of the normal operating range and frequently below the line next to cold). I do get heat within a normal amount of time (not the hottest in the world but sufficient to keep us toasty during really cold days) but the gauge keeps reading low. I can be driving for hours and it still reads cold. During warmer months the truck runs at the proper temperature and the needle is dead center in the normal operating range. Also, I sat in the driveway the other day and idled the truck at about 2000 RPM's for about 20 minutes to get the temperature to at least enter the lowest portion of the normal operating range but as soon as I turned on the heat the needle started dropping like a balloon loosing air and within about a minute at the most it was right back to below the normal range and was back below the line next to cold. Recently the check engine light has come on and when I connected my OBD II diagnostic tool it came back that the fuel was running in closed loop mode due to insufficient coolant temperature. Although I was having this problem prior it is worth noting that I recently had the coolant changed as the vehicle has 92,000 miles on it and it was getting close to the recommend interval in the owners manual. I originally thought perhaps the thermostat was the culprit but then I got to thinking that it should still warm up eventually just perhaps a lot longer. Am I wrong on that point? The truck is otherwise running fine and has no other symptoms or derivability issues. Any help would be greatly appreciated.
Sincerely,
Confused in Mastic
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Thursday, January 25th, 2007 AT 4:44 AM

5 Replies

Tiny
BRUCE HUNT
  • EXPERT
Does the engine surge such as go up and down in rpm? If so does it do it all the time, only when car is cold, or only when engine is warm? Another, question, has there been any maintenance on the intake manifold?
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Wednesday, November 22nd, 2006 AT 7:59 PM
Tiny
JAZZ
  • MEMBER
The rpm surges while idle cold. And this just started.I have not been driving the car. The first time it did it the car had been moving for at least 15 minutes. When I got it home it did it again. That when I decided to change my coolant and thermostat. Because after arriving home the reservoir was empty. The intake manifold was remove to better access the thermostat housing because the bolt broke. The intake manifold gasket was changed. I then flush the system put coolant in the system. Its still did it. I wait overnight to see if the engine would suck the coolant up, and it did. I added coolant to level off the system. I drove the car that day for an hour no problem. The dealership had mention that my upper hose needed to be changed. So I did that now the problem is back. When I tried to drive around the block the car started to run hot then went back down to normal and stayed there. When I filled up the antifreeze I let the car run with the radiator cap off and the heat temp control on full, but its blowing cold air. Could air in the system cause all these problems. Thanks again for you timely response.

Regards,
Jazz
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Thursday, November 23rd, 2006 AT 4:01 PM
Tiny
BRUCE HUNT
  • EXPERT
Here you go. First off, the car surges because air in the cooling system confuses the computer because it does not sense the temp of the engine correctly. So, use the bleeder on the system to release the air. The system is a closed system and should not have air pockets in it. Secondly, if this does not fix the problem, think about this if you did the intake repair yourself and ask if you are 100% sure that the old gasket was completely removed. Any fragment could cause the engine to suck in air around it and again this confuses the computer as more air is present and the engine will surge.
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Thursday, November 23rd, 2006 AT 9:31 PM
Tiny
JAZZ
  • MEMBER
Thanks for all your help I tried bleeding the air I drove the carabout 60 miles no surging on the clold start or hot start. Thanks for all your help
Regards,
jazz
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Saturday, November 25th, 2006 AT 4:01 PM
Tiny
SERVICE WRITER
  • EXPERT
It sure sounds like the thermostat. Sounds like it's stuck open. The truck won't heat up well enough as you drive around because of the increase airflow from moving. My guess is your gas milage is suffering too from this.
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Thursday, January 25th, 2007 AT 5:37 AM

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