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Old 05-15-2018, 05:16 PM   #1  
PaulZR1
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Default overheating

While highway driving the car seems to stay fine at 180, upon exiting into stop and go traffic, the car then starts to get hot to the redline at 260. What can I do to get the car to keep cool in the proper operating temperature ?
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Old 05-15-2018, 05:32 PM   #2  
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First place I would start is to verify fans work. An easy way I've found to check is to crank car & turn on air conditioning. With hood opened, carefully verify fans spin. We can go from there.

Ted
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Old 05-15-2018, 07:50 PM   #3  
billschroeder5842
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Make sure you have good air flow. The area in between the radiator and condenser is notorious for collecting debris. You will need to inspect, then pop off the shroud before you vacuum, water flush and dig out leaves, bugs papers bags or cigarette butts.

If you have an debris issue, the cleaning will make a huge difference

Here is what I found "in the in between"
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Old 05-16-2018, 11:38 AM   #4  
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Could also be a partially stuck thermostat.
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Old 05-16-2018, 12:38 PM   #5  
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Well, in ANY CASE, you don't ever want to let the all aluminum LT5 get close to 260.

According to Marc Haibeck, the difference in the greater expansion rate of aluminum with temp vs. the steel head bolts results in the head gasket getting crushed - namely the metal compression seal ring around the cylinder. Once the heat is reduced, the aluminum retracts, but the gasket will not rebound and a coolant leak will develop.

Replacing a head gasket means the engine has to come out because re-timing the cams can't be done practically with the engine in the car.

too that the radiator eventually gets full of dirt and grass clippings (discharged by lawnmower to the side of the road). I replaced my broken rad with a stock one that Pete removed from a car someone was having him install a new 4-row radiator into.

Before installing the used rad, I flushed it (or course), but boy what a surprise I got when I pressure washed the cooling fins. There musta been a quart of mud and sand that was forced out of that core! No wonder someone thought they needed a new radiator.
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Old 05-16-2018, 02:28 PM   #6  
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Thank you all so much for your quick replies. I've already replaced the old thermostat with a new one (this past Tues). I'll try the pressure washing. Thanks again guys.
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Old 05-16-2018, 07:58 PM   #7  
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Quote:
Originally Posted by PaulZR1 View Post
Thank you all so much for your quick replies. I've already replaced the old thermostat with a new one (this past Tues). I'll try the pressure washing. Thanks again guys.

Just to remind you, what Paul said, "pressure washed before installing."

You cannot effectively pressure wash or blow compressed air through the radiator while it is installed. You must remove it to do the job.
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Old Yesterday, 11:35 AM   #8  
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Quote:
Originally Posted by A26B View Post
Just to remind you, what Paul said, "pressure washed before installing."

You cannot effectively pressure wash or blow compressed air through the radiator while it is installed. You must remove it to do the job.
Jerry is correct--you need to remove it to clean it. In my '93 I had overheating problems. Took it to my local ZR-1 dealer mechanic at the time, had the radiator removed and it was roughly 40% blocked with debris. Once it was hosed out it ran fine for as long as I owned it. Back in the late '90s when I had it done it cost about $300 to have it done. Afterward I installed a 1/4" mesh screen over the bottom feeder air intake opening to prevent further leaf pickup in the fall. A good modification todo. BTW, I would be careful using a pressure washer on a radiator--they are powerful and can damage the fins. I would use a regular hose perhaps with a nozzle to get all the water in you will need. --Bob

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Old Yesterday, 11:51 AM   #9  
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After you clean everything and flush system well, If you decide you neede a 160* thermostat let me know, I make them upon request.
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Old Yesterday, 03:43 PM   #10  
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Did the oP ever confirm his actual coolant temps w/the digital display? Or did he see the "idiot light" analog gauge heading toward 260 and panic?




Quote:
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Keep the RPM above 2,000 rpm at all stops.
No way this is necessary. Not on a properly running car. No way.
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Old Today, 12:03 AM   #11  
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Originally Posted by Dynomite View Post
OK.......but if outside air temperature is 100 deg F or higher ???
And you are sitting letting the LT5 run at 750 rpm......for a few minutes......
Yeah? So?

GM didn't design the car so you'd have to sit and hold the throttle at stops. That's ridiculous. The ZR-1 had to go through the same validation as all the other GM products...that means testing in Death Valley, Davis Dam and other places where the temp soars above 100˚F. Car should be able to sit idling all day long in 100+ temps. If it can't there is something that needs attention; cleaning, flushing, fans...whatever.

But in this OP's case, I think the first priority is to determine how he came up with "the car then starts to get hot to the redline at 260". B/c if he's looking at the analog gauge, he very likely has no issue at all.
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Old Today, 12:10 AM   #12  
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Yup, gotta go off the digital coolant reading
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Old Today, 09:26 AM   #13  
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One of the best things you can do is get a custom prom. I never see temps over 205 even in heavy traffic on a hot day.


This for the 91 you did not list your year but the links are on Marc's site

http://zr1specialist.com/HAT%20Web/p...on%20BFXBG.htm
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