Engine temp getting down between 140-150F on highway. Why??
Thread Starter
Burning Brakes
Joined: Nov 2003
Posts: 935
Likes: 2
From: Beverly, NJ
Engine temp getting down between 140-150F on highway. Why??
I had my chip tuned along with a 180F thermostat so the engine runs a little cooler. It worked great for quite a while. But now lately, the engine coolant temp gets down to around 142F on the highway, which is the lowest I have ever seen it get. I know the computer has got to be going into open loop at that temp (maybe I am wrong), but is there somewhere I can start looking that might be a possible problem? Anyone else have this problem. As far as idling or normal driving, the temp stays between 170-195F usually. Thanks!
Drifting
Joined: Jan 2002
Posts: 1,261
Likes: 4
From: Middle River MD
Originally Posted by Pete K
Your thermostat may have stuck wide open. I suggest changing it. Usually they slam shut at some point. Overheating then happens.
Mine does the exact same thing...I'll be pulling/testing the thermostat.
Team Owner
Joined: Jan 2003
Posts: 20,306
Likes: 242
From: Summerland B.C. Canada
Originally Posted by Pete K
Your thermostat may have stuck wide open. I suggest changing it. Usually they slam shut at some point. Overheating then happens.
Mine goes closed loop at about 135 so there is a good chance your still in closed loop. 
Drifting
Joined: Jan 2002
Posts: 1,261
Likes: 4
From: Middle River MD
I'm assuming that closed loop is occurring when my convertor locks up.?
It locks up right around 125 on the gauge, which I believe is more like 130.
When I had a scanner hooked up the ecm was seeing +5deg more than the gauge was showing.
It locks up right around 125 on the gauge, which I believe is more like 130.
When I had a scanner hooked up the ecm was seeing +5deg more than the gauge was showing.
Le Mans Master
Joined: Jan 2002
Posts: 9,036
Likes: 13
From: Edmonton AB
Originally Posted by Pete K
Your thermostat may have stuck wide open. I suggest changing it.
But under the circumstances reported, the thermostat is my primary
suspect, too.
The coolant level is up, right?
Try posting in C4 Scan & Tune to determine if or when coolant temp
signals open loop. HeeHaw89, ditto for the interaction between C/L
and the converter locking up.
.
Le Mans Master
Joined: Jan 2003
Posts: 8,596
Likes: 19
From: Portland Oregon
Originally Posted by darkman5001
I had my chip tuned along with a 180F thermostat so the engine runs a little cooler. It worked great for quite a while. But now lately, the engine coolant temp gets down to around 142F on the highway, which is the lowest I have ever seen it get. I know the computer has got to be going into open loop at that temp (maybe I am wrong), but is there somewhere I can start looking that might be a possible problem? Anyone else have this problem. As far as idling or normal driving, the temp stays between 170-195F usually. Thanks!
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by Pete K
Your thermostat may have stuck wide open. I suggest changing it. Usually they slam shut at some point. Overheating then happens.
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Racer
Joined: Nov 2005
Posts: 456
Likes: 3
From: Sumner Texas
Replace the thermostat with a fail open type such as the MotorRad.
It is VERY unhealthy for your engine to have low temperature especially in the winter time. It leads to lots of gunk and acids in the crankcase because the moisture is not boiled out of the oil.
I would also change oil when I change the thermostat.
Good luck,
It is VERY unhealthy for your engine to have low temperature especially in the winter time. It leads to lots of gunk and acids in the crankcase because the moisture is not boiled out of the oil.
I would also change oil when I change the thermostat.
Good luck,
Team Owner
Joined: Sep 2001
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From: Athens AL
C7 of the Year - Unmodified Finalist 2021
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I suspect the coolant temp sensor, even with a stat malfunction the coolant should not be able to maintain those temperatures.
Burning Brakes
Joined: Jun 2002
Posts: 1,159
Likes: 0
From: royal palm beach florida
Originally Posted by vader86
I suspect the coolant temp sensor, even with a stat malfunction the coolant should not be able to maintain those temperatures.
Drifting
Joined: May 2003
Posts: 1,730
Likes: 1
From: Charlotte NC
St. Jude Donor '05
Originally Posted by vader86
I suspect the coolant temp sensor, even with a stat malfunction the coolant should not be able to maintain those temperatures.
I aggree, it would have to be damn cold out to support that
Race Director
Joined: May 2001
Posts: 14,165
Likes: 9
Originally Posted by Alvin
I aggree, it would have to be damn cold out to support that
Certainly wouldn't hurt to check. What's a thermostat cost, $5?
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by vader86
I suspect the coolant temp sensor, even with a stat malfunction the coolant should not be able to maintain those temperatures.
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Pro
Joined: May 2002
Posts: 635
Likes: 6
From: New Jersey
Darkman,
Is your cooling fan on all the time while you are driving? My vette will go down to 155-165 while on the highway this time of the year but on the street it runs normal and I live in Jersey also.
Randy
Is your cooling fan on all the time while you are driving? My vette will go down to 155-165 while on the highway this time of the year but on the street it runs normal and I live in Jersey also.
Randy
Race Director
Joined: May 2001
Posts: 14,165
Likes: 9
Originally Posted by CFI-EFI
I sometimes wonder how low it could go.
Now if I let the car idle for a long time it would actually heat up, but the instant there was any airflow across the radiator it would go right back to ice cold.
The radiators on most cars are actually, for lack of a better term, "over efficient" and perfectly capable of plunging the operating temperature well below the ideal point, hence the reason for a thermostat in the first place.
A friend of mine had an LT1 that the thermostat stuck open on. I drove that car from his house to mine one night when it was about 12 degrees out. I drove 5 miles at highway speeds and when I got to my house I popped the hood and was able to place my hand right on the intake. Not only was it not hot, it was still ice cold.
Drifting
Joined: Jan 2002
Posts: 1,261
Likes: 4
From: Middle River MD
As a follow up to my post #3 above, I pulled my thermostat tonight and it was stuck open. Not all the way, but it was definately open.
I threw it in boiling water and it opened wide but after pulling it out it stayed open maybe1/3 of the way, just as it was when I pulled it out of the car.
Also if you are still unsure of your temp gauge accuracy, compare it to your oil temp reading. They are usually fairly close, with the oil running a little hotter.
I threw it in boiling water and it opened wide but after pulling it out it stayed open maybe1/3 of the way, just as it was when I pulled it out of the car.
Also if you are still unsure of your temp gauge accuracy, compare it to your oil temp reading. They are usually fairly close, with the oil running a little hotter.
