2G 97 GST Runs hot, but only when driving around.

[Jewelz]

Apologies if this should go somewhere else. I did a search but seem to be having the opposite issue as most people.

My car runs hot when I'm driving around, and by hot , I mean the gauge show in the middle of midway and Hot, see attached photo. My fans are working, I've burped the rad. When I'm idling the temp goes back to midway, fans cycle on and off just like normal. As soon as I start driving the temp starts to climb as shown in the photo.

Any ideas? I haven't done a coolant flush yet, but thought it might be something more serious.

Many thanks in advance!

You must be logged in to view this image or video.

 

[pauleyman]

At least replace the thermostat and rad cap. Have you done anything to diagnose it? Pressure check? Replace anything?

 

[Jewelz]

Thanks for your reply Pauleyman!

I haven't replaced either. I'll start with that along with a flush.

A few days ago, I did replace my stock air intake box with a generic eBay Cone style filter and MAF adapter. Not sure why that would cause any engine temp issues...

 

[Jewelz]

I should add that the temp weirdly goes up and down in relation to speed (highway speeds). The faster I go the hotter it gets, and then when I slow down, the temp strangely comes down too, not to normal, but it does come down more than when I'm faster.

 

[chrysler kid]

So here's the run down

When was the water pump replaced?
When was the thermostat replaced?
When was the radiator cap replaced?
Is it low on antifreeze?

You should do a cooling system pressure test to verify there are no minor leaks causing an overheat

Standard shotgun parts etiquette says replace the thermostat. If you want to verify the thermostat is the problem, put the old one in a pot of boiling water and see if it opens or is stuck closed. Typically I will cut a coke can top off and then fill with water and then hold a torch to the coke can too boil the water

Replace the radiator cap, $12 for peace of mind

If the water pump hasnt been replaced in the last 60k miles you need to replace it now

 

[Jewelz]

Thanks for the input Chrysler Kid!

To your first 4 questions, I bought this GST last month from a guy who bought it off someone 2 years ago. The guy I bought it from didn't do anything and the guy before him said he replaced the timing belt about 20K miles ago, not sure if the water pump was also replaced. No idea on the thermo or the cap. But I plan to do them next along with a flush, I'm hoping the shop will run the pressure test when they do the flush. The antifreeze reservoir is full.

Don't really want to replace the water pump/timing belt. I will if it will give me peace of mind if I can't figure it out.

 

[pauleyman]

You're hoping? Instruct them to do so.

 

[Jewelz]

Roger that!

 

[luv2rallye]

First definitely replace that rad cap!!! Then the thermostat and do a flush (flush when thermostat is out and flush it both ways - forward and reverse {top down and bottom up - ie. back flush}). After removing thermostat you can see if you still have the problem to rule it out. After that another possibility is the radiator may just be worn out and needs replacing if it's old - (IMHO your symptoms also fit this).

 

[99dsmer4g63]

I would hook up a scanner and verify the gauge is even reading accurately.

After I would run a leak down test.

I would make sure the motor is healthy enough to warrant a $12 thermostat.


Good luck, Daniel

 

[jesse12345]

Also make sure the shop that does any work to your car knows what they are doing. Especially if you have them do the water pump.

 

[Jewelz]

Thanks all for your input!

I will change the rad cap tomorrow, and report back. If that doesn’t work, then I’ll move onto the thermostat and flush. I won’t be doing that until the spring as I’ll be putting the car away for the winter in the next couple of weeks. So I’ll start off fresh in the new year!

Cheers everyone!

 

[Jewelz]

Okay, so before I replace the rad cap, I've noticed another thing. Temp stays high When idling now, not as hot as when I'm at highway speeds, but hotter than normal. However, when I'm parked and idling, as soon as I turn my defrost on, the temp starts to drop down to normal. Switch it off and it starts to climb again...

 

[chrysler kid]

Okay, so before I replace the rad cap, I've noticed another thing. Temp stays high When idling now, not as hot as when I'm at highway speeds, but hotter than normal. However, when I'm parked and idling, as soon as I turn my defrost on, the temp starts to drop down to normal. Switch it off and it starts to climb again...

It could be anything, you need to verify several things

1. There are no cooling system leaks
2. The radiator fan is working when the car starts to get hot. If the radiator fan is not working that will cause the car to over heat
3. If the radiator fan is working, and there are no coolant leaks, then we have to assume the thermostat is not opening to release the hot coolant to the radiator. Replaced the thermostat
4. If the thermostat does not remedy the over heating then you will need to have a block test done to verify that the head gasket is blown


You seem to be new to fixing cars, these older cars arent anything you can be chill about. Your typical mechanic/lube shop may tell you that you need a head gasket and want to charge you $1800 for a repair that could be an $18 thermostat. These cars are tricky and most shops wont do the job correctly

Stop driving the car if it is overheating. You could blow the headgasket, or it could already have a blown head gasket

 

[97egl]

Okay, so before I replace the rad cap, I've noticed another thing. Temp stays high When idling now, not as hot as when I'm at highway speeds, but hotter than normal. However, when I'm parked and idling, as soon as I turn my defrost on, the temp starts to drop down to normal. Switch it off and it starts to climb again...

This almost sounds like there is an electrical issue. The defrost should not effect the temp gauge.

This is just a hypothesis but if the voltage regulator was going out and the alternator is supplying too much voltage it would make the temp gauge climb at higher rpms on the highway due to more voltage and turning on the defrost draws a lot of amps so it would make sense that turning the defrost on would bring voltage down. Does the gas gauge climb and drop with the temp gauge?

 

[Jewelz]

It could be anything, you need to verify several things

1. There are no cooling system leaks
2. The radiator fan is working when the car starts to get hot. If the radiator fan is not working that will cause the car to over heat
3. If the radiator fan is working, and there are no coolant leaks, then we have to assume the thermostat is not opening to release the hot coolant to the radiator. Replaced the thermostat
4. If the thermostat does not remedy the over heating then you will need to have a block test done to verify that the head gasket is blown


You seem to be new to fixing cars, these older cars arent anything you can be chill about. Your typical mechanic/lube shop may tell you that you need a head gasket and want to charge you $1800 for a repair that could be an $18 thermostat. These cars are tricky and most shops wont do the job correctly

Stop driving the car if it is overheating. You could blow the headgasket, or it could already have a blown head gasket

1 and 2 I can confirm. I'll replace the rad cap and the thermostat first and report back. And you are correct to assume that I'm new to fixing cars. I do appreciate all your help!

 

[Jewelz]

This almost sounds like there is an electrical issue. The defrost should not effect the temp gauge.

This is just a hypothesis but if the voltage regulator was going out and the alternator is supplying too much voltage it would make the temp gauge climb at higher rpms on the highway due to more voltage and turning on the defrost draws a lot of amps so it would make sense that turning the defrost on would bring voltage down. Does the gas gauge climb and drop with the temp gauge?

The gas gauge does not move, just the temp.

Would turning on the defrost draw air from inside the engine which in turn would make the engine draw in the surrounding cold air from outside the engine bay, which would then lower the temp? Makes sense in my head, !

I'm hoping that its just the thermostat not opening fully and that's why its running hot. My guess is that the faster I go, the hotter the engine gets, and because the thermostat doesn't open fully, its not efficient at cooling. Fingers crossed!

 

[97egl]

The gas gauge does not move, just the temp.

Would turning on the defrost draw air from inside the engine which in turn would make the engine draw in the surrounding cold air from outside the engine bay, which would then lower the temp? Makes sense in my head, !

I'm hoping that its just the thermostat not opening fully and that's why its running hot. My guess is that the faster I go, the hotter the engine gets, and because the thermostat doesn't open fully, its not efficient at cooling. Fingers crossed!

You are correct. I am an idiot and assumed you were referencing the rear defroster. The front windshield defrost uses the engine coolant for heat and would lower the temperature. Ignore me and follow what others are saying.

 

[Jewelz]

You are correct. I am an idiot and assumed you were referencing the rear defroster. The front windshield defrost uses the engine coolant for heat and would lower the temperature. Ignore me and follow what others are saying.

Lol. No worries, we all have a brain fart every once and a while!