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SBC 350 Overheats

4452 Views 86 Replies 12 Participants Last post by  Joe White
I've been battling an overheating issue for quite some time. Now I do understand it is 100+ degrees out right now, but I'd like to believe the engine should still be able to cool itself off.

I've got a big three core aluminum radiator, with dual electric puller fans, and smaller electric pusher fan. Running a 195 thermostat at the moment, was running a 180 (no change). There is ac in the truck, but the overheating problem still exists with the ac off. I am able to open the hood and let it idle and it will cool down to around 210. Doesn't seem to matter if I idle or drive around, if anything heats up faster when driving around.

The trucks radiator appears to keep up for the first 3 or so openings of the thermostat, keeping close to 195. But after than it seems to overpower the radiator, and the fans are just blasting 200 degree heat constantly.

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heats up faster when driving
you've answered your own question right there. Every vehicle, with any engine combo should be able to completley remove all cooling fans and be able to drive above 45 mph and have zero cooling issues. this is due to the forced air being pushed through the radiator.
On my v8 swap i had a climbing temp issue above 65mph. I had the V6 rad and the intrepid fans. II removed the interepid fans and went for a blast down my local highway. What i ended up finding is i had an air pocket underneath my engine bay where the hot air leaving the rad would turn and go back into the radiator. I brought a few pieces of carboard and sheetmetal with me and put various 'airducts' taped to my truck under the bumper and on the sides of the rad until i found the issue. I could then drive from 55 to 105mph without any issues.

GM has put air dams under vehicles for a while. 3rd gen camaros (think KITT) have a very necessary air dam under the core support that if not there, will over heat. Just that one simple piece causes that much issues. thats where i got the idea for the duct work under my truck .

Also, all the red arrow hot airs are just going right past your rad..
remove the pusher fan its not needed.
check your puller fan specs, they might not be good fans.

make sure the fans are sealed to the rad

and block off or redirect all air (red arrors) that are escaping around the rad. youcan easily bed a piece of sheetmetal and direct the air through the bumper towards the radiator

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Did some research
have you tried a second temp gauge? just to make sure youre not chasing the dragon?
way back at some post of mine in this thread i mentioned you should be able to remove your fans completely and go drive. anything above 40mph your truck should not over heat, in fact should be perfect. I have a freeway very close to me and i jump on the highway and take a 30 mile cruise to test vehicles before i give them back.
When i had a temp creeping issue on my hombre, i figured it out to be too much air circulation. Meaning, hot air was escaping and being pulled back in the rad above 60mph. there was a bubble being formed under the truck causing this.
under 60 mph no issue, above 60 it would creep up and get up to 230 before i had to slow to 60 to get the temp to cme down.
I still will bet money its your airflow.
OR, you have an internal issue with your engine. wrong head gaskets, or something more intnerla to your water jackets.
It's getting cooler outside, you shouldn't be having any getting hot issues at all
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just bounces off the engine and deflects it towards the front of the truck
try removing your hood and go for a drive. That should help out the diagnosis. No hood, plenty of places for hot air to go and not bounce back.
I might be out of options.
i wish we were closer, id love to figure out what is going on with your truck. Im starting to think something is fishy with the engine. Like wrong headgaskets or something.
Removing the hood should've had a huge impact as it creates a very negative area and literally pulls all the air out of the engine compartment up and over the car.
with it still over heating that means either your rad is internally plugged, or, you need to pull the engine and do a tear down and inspection, as something isn't right.
there appears to be no exhaust gas in the cooling system.
you dont have a 'blown' head gasket, you probably have the wrong head gasket. meaning, its blocking/restricting water flow. Every test will be 100% perfect, thats not the issue, you physically will have to remove the heads to see if the gasket is on backwards, or you have the wrong style for your head/block combo
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