Car running cool while driving?

Sniper82

Lifer
Feb 6, 2000
16,517
0
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96 Geo Prizm with 1.6 runs to cool while driving. I barely get any heat. While idle though temps rise to normal and heat works great.

Is this normal for this small engine? Its been doing this for a long time and had been since I got it used about 15k miles ago. IDK why I didn't ask about it before. Probably because I rarely drive it in cold weather I guess.
 

DeviousTrap

Diamond Member
Jul 19, 2002
4,841
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Your thermostat is stuck open. Should be a $10 part + new coolant and an easy DIY if you don't mind working on it yourself.
 
Feb 19, 2001
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happens to me too.. i mean not cool. i get heat, but i get 20x more heat when im on city driving...

i'll ask the guy to keep an eye open when i go to my oil change later
 

Bignate603

Lifer
Sep 5, 2000
13,897
1
0
happens to me too.. i mean not cool. i get heat, but i get 20x more heat when im on city driving...

i'll ask the guy to keep an eye open when i go to my oil change later

If its a stuck thermostat he won't be able to tell that at all during an oil change. You can only check that by removal. Unless they stuck the thermostat in some place that is hard to reach anyone with an hour or so and a set of wrenches can do it. It's probably one of the easiest things you can do yourself. The hardest part IMO is cleaning off the sealant.
 

x-alki

Golden Member
Jun 2, 2007
1,353
1
81
Have you checked your coolant level? If it's low it could cause that problem. Another possibility is the radiator could be plugged and is restricting the flow of the coolant. Some years ago I had a vehicle that had a bunch of crap in the rad. It would heat at idle but cool down when I drove it.

Probably just the thermostat. Some are a bitch to change and some arent. Good Luck
 

bruceb

Diamond Member
Aug 20, 2004
8,874
111
106
Agree. Replace the thermostat. Use on made by Stant .. they are the best. And while you are at it, you may as well flush the cooling system, new antifreeze (use a premix of 50/50), new radiator cap and hoses. It is a 13 year old car and even if it has been done once or twice, it due for another change.
 

Sniper82

Lifer
Feb 6, 2000
16,517
0
76
well the thermostat fixed it thx all. But I am wondering its done this since I had the car(2 years ago and 15k later) no telling how long before I got it. Whats the long term damage for running it like this? Just bad gas mileage/no heat?
 

StageLeft

No Lifer
Sep 29, 2000
70,150
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well the thermostat fixed it thx all. But I am wondering its done this since I had the car(2 years ago and 15k later) no telling how long before I got it. Whats the long term damage for running it like this? Just bad gas mileage/no heat?
I recall something to do with acid buildup or something if an engine is run elow operating temp. For a while it's not a big deal, long-term I don't know. Probably you'll never notice but that would depend on how long this went on for, too.

I've had your problem in two cars and thermostat stuck open was the cause both times.
 

Vette73

Lifer
Jul 5, 2000
21,503
8
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Change your radiator cap as well. You can do it yourself. Just go to Advance/AZ or order from rockauto.com

I just changed the one in my dads truck to being to cool. Also did the Rad. cap. Of course it has over 210k on it with very little work. So he is not to upset with the little work it needs. Of course the dealer did not want for him to try and trade it in. :)
 

BUTCH1

Lifer
Jul 15, 2000
20,433
1,769
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A stuck open thermostat would delay the car warming up to operating temp but it should eventually get there, possible clogged heater core?. I would start as already suggested with a thermostat change and complete flush and oh, dear god don't let Fleabag see this thread...
 

Vette73

Lifer
Jul 5, 2000
21,503
8
0
A stuck open thermostat would delay the car warming up to operating temp but it should eventually get there, possible clogged heater core?. I would start as already suggested with a thermostat change and complete flush and oh, dear god don't let Fleabag see this thread...


No A open Therm can make the car run cooler all the time. Some cars have smaller Rad's/weak Rad caps/other issues that can cause them to run warmer.

My truck and as above my dads truck ran cool enough to see the Temp gauge not rise as high as it should. Even when both of them had a good 1500pds of rock in the bed the temp did not get high enough.
 

Bignate603

Lifer
Sep 5, 2000
13,897
1
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No A open Therm can make the car run cooler all the time. Some cars have smaller Rad's/weak Rad caps/other issues that can cause them to run warmer.

My truck and as above my dads truck ran cool enough to see the Temp gauge not rise as high as it should. Even when both of them had a good 1500pds of rock in the bed the temp did not get high enough.

It will probably warm up to operating temperatures idling there in normal air temperatures due very low air flow over the radiator. The electrical fan wouldn't kick on until the car is warmed up so it would allow the temp to rise. However, when you're driving around you'll get airflow over the radiator which will help drop the temp.

Trucks made for hauling tend to have oversized cooling systems to deal with things like dragging a large loaded trailer up a steep grade in 110* temperatures. I could easily imagine that the oversized radiator may have had significantly more convection, possibly enough to keep it from getting up to operating temps even just sitting there idling.
 
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BUTCH1

Lifer
Jul 15, 2000
20,433
1,769
126
No A open Therm can make the car run cooler all the time. Some cars have smaller Rad's/weak Rad caps/other issues that can cause them to run warmer.

My truck and as above my dads truck ran cool enough to see the Temp gauge not rise as high as it should. Even when both of them had a good 1500pds of rock in the bed the temp did not get high enough.

No, once the coolant reaches the temp the therm is rated for it's going to open anyway. Temp gauge might be right where it's supposed to be for that particular vehicle, I doubt a manufacturer would design a cooling system with so much overcapacity it never got to proper operating temp, that would bring a bunch of huge problems if that happened..
 

thedarkwolf

Diamond Member
Oct 13, 1999
9,000
110
106
No, once the coolant reaches the temp the therm is rated for it's going to open anyway. Temp gauge might be right where it's supposed to be for that particular vehicle, I doubt a manufacturer would design a cooling system with so much overcapacity it never got to proper operating temp, that would bring a bunch of huge problems if that happened..

Dude you are wrong wrong wrong wrong!!!!!
The thermostat opens when it reaches the set temp but guess what it does when the temp goes back down. yeah that is right it closes again in order to regulate the temperature. All cars have more cooling capacity than they need when the weather is cold so that they have enough when the weather is really hot.
 

LTC8K6

Lifer
Mar 10, 2004
28,520
1,575
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The thermostat opens and closes within a band around it's temperature rating. Both the thermostat and the cooling fan circuit regulate the coolant temperature. All thermostats vary their opening while the engine is running.

In fact one of the features of a Stant SuperStat is the reduction of the amount of cycling that conventional thermostats do.
 

BUTCH1

Lifer
Jul 15, 2000
20,433
1,769
126
Dude you are wrong wrong wrong wrong!!!!!
The thermostat opens when it reaches the set temp but guess what it does when the temp goes back down. yeah that is right it closes again in order to regulate the temperature. All cars have more cooling capacity than they need when the weather is cold so that they have enough when the weather is really hot.

Yep, I was wrong on this, 'stats do "cycle" in response to varying conditions. I guess if you live in certain climes (I live in FL) it probably stays open once it does open. I was reading the litaruature for the "SuperStat" and it's a real improvement or conventional 'stats, now I want one!!.
 
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LOUISSSSS

Diamond Member
Dec 5, 2005
8,771
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if ur coolant temps rise while doing slow city driving, it may be that ur radiator fan isn't turning on or isn't spinning fast enough. If thats the problem, continue to try and isolate it from there, is it the relay/fuse, power, improper grounding of fan power cable, etc
 

Bignate603

Lifer
Sep 5, 2000
13,897
1
0
if ur coolant temps rise while doing slow city driving, it may be that ur radiator fan isn't turning on or isn't spinning fast enough. If thats the problem, continue to try and isolate it from there, is it the relay/fuse, power, improper grounding of fan power cable, etc

That would make sense if his car was going over normal operating temps at idle but falling to normal temps at speed. That's not what's happening.
 

skyking

Lifer
Nov 21, 2001
22,009
4,775
146
Just did this with my camry, it was a cold drive across the mountains with it stuck!
To test a 'stat, put it in a pan of water on the stove and watch it open as the water comes to boil. If you have a good thermometer you can see the set point.