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Old 05-28-2018   #1
ned707
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Join Date: Mar 2010
Posts: 74


Help with coolant system

I just brought my 90 GTA out of storage. After cranking a few times she fired up and idled perfectly. Let it idle for a while, the radiator fan came on, then after about 33 minutes I noticed the temperature gauge was reading high... i looked closer and realized that the temperature needle was pointing JUST BEFORE the red-line zone on the temp gauge. I quickly shut the engine down. I really hope I didn't cook the block. Any ideas whether I did or didn't?

Right after shutting down the engine I start hear this sort of periodic swooshing or churning of hot liquid sound coming from the coolant reservoir and or radiator and hoses... hard to pin point the sound exactly. Then steam starts to rise from the radiator (just a puff of steam really). Suddenly I realize green coolant is drizzling out from under the radiator area. I could see coolant dripping on the radiator near the upper passenger end. It was hard to pinpoint where the coolant was leaking from, or why. The coolant reservoir was full. I suppose dirt could have built up in the radiator cap, preventing it from venting?

Any ideas what could be happening to my coolant system?

Could it be something like the water pump isn't working so isn't circulating coolant properly? Or is this impossible?

Could it be a stuck thermostat?

Oddly enough this happened to my motorcycle a while ago. I started it up after it sat for a while... it idled for a while... then overheated and started spewing hot coolant.

What is going on here?

Thanks

Last edited by ned707; 05-28-2018 at 05:20 PM.
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Old 05-29-2018   #2
89-5.7GTA
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Location: Rocky River Ohio
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GTA Year: 1989
GTA Engine: 350 TPI Automatic
Re: Help with coolant system

Usually when the water pump goes it usually leaks coolant from the pump as the seal goes bad. I'm not sure I understand about the coolant you are seeing, but obviously leaking from somewhere. Once cooled down, what was the coolant level in the radiator? Once you find and resolve the leak I'd replace the thermostat, its the easiest and least expensive part to replace, and, especially if its never been done before it is good insurance.

I bought my car with a known bad water pump, and a new one in the box came with the car. I was able to drive it home, though, and it promptly puked out most of the coolant in my driveway when I arrived. I replaced the pump and put in a 180 degree fail safe thermostat and have had no problems the last 9 years. The fail safe thermo is supposed to fail in the open position. I don't know if that really works because it hasn't failed me yet.
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Old 05-29-2018   #3
ned707
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Re: Help with coolant system

I didn't get a chance to check the rad level. It may be some time before I can unfortunately. It seems likely based on a post I read that the t-stat got stuck closed (either fully or partially) and when the engine was warm/hot and pressure got high enough in coolant system it sprung a leak.

Would you happen to have any pointers on changing the t-stat? Anything I need to remove?

Sure would be nice if t-stats always fail open!
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Old 05-30-2018   #4
89-5.7GTA
Tony
 
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Location: Rocky River Ohio
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GTA Year: 1989
GTA Engine: 350 TPI Automatic
Re: Help with coolant system

As I remember, the T-stat replacement was pretty straight forward. I think the stock T-stat is 195 degrees. I put in a 180 and made no other mods (to ecm or fan switch). Runs well and does not overheat on the hottest days.
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Old 06-08-2018   #5
CanuckDreamz
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Re: Help with coolant system

Four years, two kids, finally get back on the forums for some time with the garage queen...

First post I see:

"Help with coolant system"

Yup! Haven't missed a beat here!
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Old 06-08-2018   #6
CanuckDreamz
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Re: Help with coolant system

To answer your questions, OP, coolant system tear-down is doable for an amateur.

Was the first thing I did with mine (lower temp tstat swap, plus decided to drill-out also). I haven't done enough testing with it to recommend the drill-out or not.

Mine will still overheat at idle, and I don't know if there has ever been a solution proffered outside of heavy bucks on rad/pump upgrades. Need the airflow.

You should be ok. All the information that I needed to do my teardown, I found here and at 3rdgen.
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