Over heating 97 12v

WILD_PHIL

WILD_PHIL

New member
Well I used the search and didn't find any information pertaining to my issue. My truck will sometimes over heat at 70mph. If I back it down to 60mph until it cools down its fine the rest of the time and I can run it back up. When I'm pulling my camper it pretty much stays on the last line right before over heating. From my search I have gathered that I need to check all the hoses and do a bubble test. While pulling I noticed it will kinda cool down going up hill. Running around 30psi of boost. I picked this truck up a few months ago from a kid that had no idea what the truck had done to it. I haven't really looked at it. I know it has some blow by but not enough to worry about. It's sitting on 37x13.50s and turning 2500rpms at 70mph. I doubt that has anything to do with it but thought I'd mention it. I know the pump has been tweaked and it has a 3 piece manifold on it. Other than that I'm not sure. I haven't played with it much yet. So I come to the Cummins guru's in search of answers. Please let me know what other information is needed to help narrow this down.

Missing my 6.4.
 
First place i would check is the fan clutch, second would be a plugged radiator or sticking thermostat


I like to go fast
 
I forgot another thread had mentioned he sprayed his radiator out and fixed the problem. I will be working on it this weekend. I will spray it Friday.

Missing my 6.4.
 
Gotta remember those radiators were designed to cool 160hp worth of heat. My 95 will get hot at the top of hills if I tow heavy.
 
stock bumper? i have an homemade that blocks some of the rad, it will get warmer then usual when hauling heavy
 
If you replace a thermostat, stick with the cummins stat. Can you hear the fan kicking in and out? I bet the stat is sticking!
 
I would try some Water Wetter if you could find some, no telling what kind of debris is floating around in the cooling system.
 
Stock bumper. I was thinking of swapping the t Stat out also but I've read a few post of guys having no luck. I'm a big fan checking the simple (cheap) stuff first. When you check the hoses should you warm it up or check em cold? I'm thinking hot so there's pressure in the hoses. The few times I have been under the hood with it running the fan has been on the whole time.

Missing my 6.4.
 
The fan should have a temperature sensitive clutch on the front of it. When the air flowing through the radiator gets to a certain temp the clutch will lockup and drive the fan harder. When the clutch locks it really makes the fan howl. If you don't hear any extra noise then your fan clutch could be the culprit.
 
I don't think I have ever heard it. I'm driving it to work on Friday. I guess when it gets hot if I pull over and don't hear that fan howling it will be a good indicator that the fan clutch is out? Suggestions on where to buy a new one? Or does it not matter?

Missing my 6.4.
 
It's not something your gunna hear "kick on". It is a viscous drive clutch, meaning there is a silicone based fluid that is temperature sensitive inside the aluminum piece that your fan is bolted to. As heat from the radiator heats that aluminum piece up the fluid reacts by becoming thicker and in turn drives the fan closer to the fan pulleys speed. When the truck is cool the fan should turn freely with the engine off, once it gets hot going down the highway, pull over shut the truck off and try to turn the fan by hand by the blades, if it turns easily replace the fan clutch, you should feel resistance, that's what makes it speed the fan up. Hope this helps.


I like to go fast
 
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