I might have a overheating issue

1989 GMC C1500

5,000 MILES • 3 CYL

JONATHAN57818

MEMBER
4 POSTS

I have a 1989 GMC Sierra with 5.7l rebuilt. I might have a overheating issue, the temperate raises to about 230 when I start it up and drive , then it drops to 190, at first I thought the gauge wasn't reading correctly but I came to a conclusion it could be the radioator cap I have a 18 pound cap right now. Should I put a lower psi cap?

Jan 26, 2016 at 6:31 AM

SQM

✓Experienced Mechanic
6,383 POSTS

Hello,

The recommended radiator cap is 15 PSI for this truck.

https://www.2carpros.com/articles/symptoms-of-an-overheating-engine

The cap could be the culprit. Keep in mind that many times when it only overheats while stationary it is due to the cooling fan not working properly. As the fan does not flow sufficient air through the radiator. But as the vehicle start to move the air flow brings down the temperature.
This could be due to a bad fan clutch.

https://www.2carpros.com/articles/fan-clutch-symptoms

I have attached diagrams for your reference.

Please let me know if you have any questions.
Thank you.

Images (Click to enlarge)