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Old 02-21-2017   #1
cschurman
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Talking 1991 gta

I have a 1991 GTA that has been having an overheating issue. It only overheats when it isn't moving. If I am driving down the highway I usually don't have any issues with it overheating.

I have had this car for almost 10 years now. I bought it when I was 14, it had front end damage and I redid that along with the interior of the car.

My question is, what is a problem like this typically linked to? Is it the relay, the temp sensor....Not really sure. I currently don't have the space to work on the car much so it sits in my storage unit a majority of the time. I have tossed the idea of just hardwiring my fans to a toggle switch, how difficult is this task?

2nd question, the car has about 130,000 miles on it, and the motor is in huge need of a rebuilt. What kind of rebuild should I do with this? The 700R4 transmission was rebuilt about 5 years ago and a shift kit and a corvette servo was installed in it. What would a stock rebuild for this engine run me cost wise? What would a rebuild beefing the motor up with some more performance parts run me? and how much gain could I get performance wise, I don't want to do anything too crazy that the rebuilt tranny couldn't handle.


I have been tossing back and forth what I want to do with this car for quite some time. Just looking for some ideas from others and what they have done with their cars.

Thanks in advance!
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Old 02-22-2017   #2
DynoDave
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Re: 1991 gta

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Originally Posted by cschurman View Post
It only overheats when it isn't moving.
Just so we are all starting on the same page, can you define overheating? Is it puking coolant into the overflow tank and on the ground?

Or are you just seeing a higher reading on the temp gage than you are comfortable with?

Moving, ram air from under the car feeds the radiator. At idle, the electric fans. Is you fan kicking on? Does it then kick off after the engine cools down some?

Just trying to figure out what conditions you may have, and what may or may not be normal. These cars do normally run hot by design, and hotter than what a lot of "old car" enthusiasts are used to.
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Old 02-22-2017   #3
JonBlake
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Re: 1991 gta

I got a buddy who owns a 3rd gen and he was having this same issue. When the car wasn't moving he also had a problem with the overheating. Turned out that the car didn't have the correct thermostat installed.

Another issue he had was...these cars came new with a plastic skirt that runs in front of the underside of the car which forces air flow into the rad. but that only works when the car is moving. The one on his car was missing cause he bought the car used (rode hard and put away wet by many previous owners) and it wasn't on there when he got it. After making one out of sheet metal, it kept pretty cool.

All those problems add up to a lot of engine heat. He was having issues both as it was sitting idle and moving. After getting the correct thermostat and fabricating that sheet metal skirt in the front, his car stays fairly cool now.

Jon
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Old 02-22-2017   #4
JonBlake
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Re: 1991 gta

Well like everything else, the cost to rebuild really depends on what shop you get the work done at, what parts they put into it, and last but not least, how you have them rebuild it/for what application.

Jon
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Old 02-22-2017   #5
cschurman
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Re: 1991 gta

Quote:
Originally Posted by DynoDave View Post
Just so we are all starting on the same page, can you define overheating? Is it puking coolant into the overflow tank and on the ground?

Or are you just seeing a higher reading on the temp gage than you are comfortable with?

Moving, ram air from under the car feeds the radiator. At idle, the electric fans. Is you fan kicking on? Does it then kick off after the engine cools down some?

Just trying to figure out what conditions you may have, and what may or may not be normal. These cars do normally run hot by design, and hotter than what a lot of "old car" enthusiasts are used to.
Well the temp gauge in the dash doesn't give me a reading. Since I have owned it this has never worked, even when the fans were properly operating. Now the fans won't come on at all. The air dam on the underside of the car is in place, and I knew these cars were designed to run a little hotter than many other vehicles. My fan motors are operational, last night I pulled them and tested them and the both spun and didn't have any odd noises coming from them as they spun. What sensors need to be checked and change, and where are they located?

The wiring in this car is a nightmare. When I first bought it somebody had half-a$$ attempted to fix wiring and it was horrible. For example, when I turned on a turn signal my headlights both when up and down with the flash of the turn signals. It was a mess!

As far as a rebuild, I would try and do a majority of the work myself, I am fairly knowledgable with engines and what not. I wouldn't be rebuilding the car to take out to the dragstrip and race for slips, I would be building it to be a reliable car that I could drive on occasion. But I would like it to have the power that it deserves. The transmission rebuild should be able to handle a fair amount shouldn't it? What kind of power can I expect to get out of it?
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Old 02-23-2017   #6
merc3065
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Re: 1991 gta

Sounds like a few issues.
Temp sensor sender is on the driver's side head, check that there is a brass fitting and a grey single wire going to it.

Fan temp sensor sender is on the passenger side head. Check that there is a brass fitting and a white/grey wire going to it.

Once you checked those, then move onto the fan relay.
Only 1 fan will kick on at around 220F.
The 2nd fan will kick on only with the A/C on at 245F

The engines are designed to run hot for emissions purposes.
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Old 02-23-2017   #7
cschurman
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Re: 1991 gta

Quote:
Originally Posted by merc3065 View Post
Sounds like a few issues.
Temp sensor sender is on the driver's side head, check that there is a brass fitting and a grey single wire going to it.

Fan temp sensor sender is on the passenger side head. Check that there is a brass fitting and a white/grey wire going to it.

Once you checked those, then move onto the fan relay.
Only 1 fan will kick on at around 220F.
The 2nd fan will kick on only with the A/C on at 245F

The engines are designed to run hot for emissions purposes.
Awesome thank you!! Are both of these sensors something that is fairly easy to pull out from the top side of the engine? I don't have very much space to work on the car, no flat area to get the car jacked up to get to it from the underside. I have a temp sensor sender that I bought a while back to change and never got to it. I hope they are easy to get to from the top side of the engine.
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Old 02-23-2017   #8
merc3065
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Re: 1991 gta

They sort of are...
Pass side head is between the 6 and 8 exhaust ports.
Driver's side head is between the 1 and 3 exhaust ports.
With all the factory emissions stuff it is a bit of a pain to get at.

I would also recommend that you check the fans themselves and make sure that they still spool up. There should be a way to apply power to the fans to check that they are still working, I just can't remember the voltage or which pins are what.
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Old 02-23-2017   #9
merc3065
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Re: 1991 gta


There's a fan switch with the connector.

Here's the relay switch
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Old 02-24-2017   #10
cschurman
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Re: 1991 gta

great! thanks for your help! I have already put power to both fans and they are operational
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Old 04-21-2017   #11
EfronDon
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Re: 1991 gta

Quote:
Originally Posted by JonBlake View Post
Well like everything else, the cost to rebuild really depends on what shop you get the work done at, what parts they put into it, and last but not least, how you have them rebuild it/for what application.

Jon
Exactly. So many variable to consider.
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