LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

94 z28

Old 05-14-2019, 03:34 AM
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94 z28

So ive had a recent issue with my otherwise perfect running z28. I started to overheat. I. In a new climate. Sacramento. And it gets hot here. But my car has always maintained 180 like clockwork. So i took off my shroud and found a plastic bag stuck in one of my fans. I removed it and all was well. Topped off all my fluids and same. All was great. But now, sitting in traffic, it will run up over 200 and almost hit red!!! My gf drove it the other day and it almost boiled over... (my fault) but i drove 1.5hrs to work today and found that if i run the a.c. it stays in normal temp range? I was gna replace thermostat this weekend but this sounds like more of an elec issue.... thoughts??? Thank you in advance.
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Old 05-14-2019, 07:37 PM
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Re: 94 z28

Welcome to !

I'll move this to an appropriate tech forum. "Site Help..... “ is for problems with the operation of the site - uploading pictures, making a signature, etc..

How badly did it overheat with the plastic bag blocking the radiator? Risk is a blown head gasket, and increased overheating. Is the PCM program stock, or has it been reprogrammed? GM designed the engine to run at ~210F to maximize fuel efficiency and minimize emissions. The fans are programmed accordingly - first fan on at 226F, second fan on at 235F (early 94’s); or both fans on low speed at 226F and both fans on high speed at 235F (late 94’s). The 1st fan (or both on low) comes on when the A/C is turned on.

Is the SES light on? There are codes for the coolant temp sensor in the water pump housing, and for the fan relays. Best thing to do is put a real time scanner on it to see what temp the coolant temp sensor is sending to the PCM. Scan9495 (free download) software allows you to look at the status of the fans, along with all the sensor readings and PCM parameters.
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Old 05-14-2019, 09:25 PM
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Re: 94 z28

If the bag was actually caught up in the fan, is that fan still working?
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