Engine overheating

[1987 GMC Jimmy]

Yeah, I’m against the cooler stat, also. Get you a little Preston’s flush kit from Walmart and backflush your cooling system. It’ll tee into your garden hose at one of the heater hoses (can’t remember if inlet or outlet at the moment). As far as a cleaning agent goes, I’ve heard of Borax, never having tried it, but I’ve used the Prestone flush liquid and CLR/Zep. I liked the former better because it did get some stuff out with the expedited flush, and it didn’t feel like I had to be painstakingly thorough to neutralize the pH in my cooling system. If the system was even somewhat maintained, just the water pressure should do the trick.

I’d like to see where this and the shroud get you. I don’t think it’ll bring you home, but it’ll help when you isolate your culprit. Check the weep holes for leakage on your water pump, and you can listen to it with a long screwdriver or a mechanic’s stethoscope. If it passes these tests, the only thing left is the impeller being eaten away by hard water. I’ve been lucky with water pumps, but if you’re flushing, you can pull a rad hose and check the volume on it just running it with water in the system for a few seconds. I have a $17 Valucraft unit on my Jimmy, which has worked fine. Would probably spring for something better in the future, though. And I have a NAPA unit on my car, which has been problem free. Those are generally have a middle to upper-middle price point.

If you’re worried about a clutch, there are some archaic ways to test that like grabbing the fan or sticking a magazine in there, but I wouldn’t do that personally, and it doesn’t sound like that’s your problem. And forgive me if this was covered already, but I’d verify your temp reading with an infrared thermometer to make sure you’re not spinning your wheels based on what the gauge is saying.

 

[75gmck25]

I will also give you a solution that has been very effective in cooling my k25:
- OEM 7 blade metal fan and stock shroud
- 50% antifreeze mixture
- Champion aluminum 3 row radiator
- Hayden Severe duty fan clutch
- Stewart high flow 195 degree thermostat
- Stewart Stage One high flow water pump

With this combination I can run 65 mph on the highway or I can leave the truck idling in the driveway in the summer with the A/C on, and it always reads about 185-190 degrees. All the pieces and parts are readily available and relatively inexpensive.

Bruce

 

[Snoots]

I will also give you a solution that has been very effective in cooling my k25:
- OEM 7 blade metal fan and stock shroud
- 50% antifreeze mixture
- Champion aluminum 3 row radiator
- Hayden Severe duty fan clutch
- Stewart high flow 195 degree thermostat
- Stewart Stage One high flow water pump

With this combination I can run 65 mph on the highway or I can leave the truck idling in the driveway in the summer with the A/C on, and it always reads about 185-190 degrees. All the pieces and parts are readily available and relatively inexpensive.

Bruce

X2!

Or, a FlowKooler water pump.

 

[trukman1]

Make sure you don't have an air pocket trapped in your cooling system.

Sent from my SM-N975U1 using Tapatalk

Good suggestion. One thing I'd like to point out as a long shot, I had a 454 with a 4 core radiator and had constant issues with over heating. I checked everything I could think of then it hit me...timing. I reset the timing and the problem went away.

Engine Masters did a show on cooling and essentially said the fan shroud didn't help (I know I'll catch a lot of flak over that one but you can Google it. They had better cooling on their test engine w/o the shroud, IIRC.) Also, fan distance from radiator is important.

Good luck!

 

[DoubleDingo]

Yeah I disagree on the shroud because I can feel my shirt being pulled into the grill when a shroud is installed, and not without a shroud. Maybe for nothing but highway driving lacking a shroud is okay, but I'll stick with having shrouds on my rigs both for better air flow and for safety.

 

[Shorty81]

Yeah I disagree on the shroud because I can feel my shirt being pulled into the grill when a shroud is installed, and not without a shroud. Maybe for nothing but highway driving lacking a shroud is okay, but I'll stick with having shrouds on my rigs both for better air flow and for safety.

X2

 

[peats]

get the fan shroud in place as it was engineered by GM. go from there

 

[Rick Dobbins]

The thermostat is just the MINIMUM temp the engine will run. Has nothing to do with overheating.

Now, have you looked at the oil? Is it milky? Could be a blown head gasket.

2nd: That plow is blocking your airflow at speed.

3rd: (Most likely( The radiator is full of crud. I had one once that would run cool all day until I was under a load. Pulled the radiator (even tho I had flow thru it- and looking into it the top vanes looked perfect!) and the radiator shop told me it was blocked halfway down completely with crud. Put a new radiator in and fixed the problem.

4th: Water pump belt is slipping. So when you're at speed, flow is not what it should be.

GOOD LUCK!

 

[73c20jim]

The thermostat is just the MINIMUM temp the engine will run. Has nothing to do with overheating.

I am truly amazed with the amount of car people who don't understand this.

 

[Buff71]

Also did you consider that the plow may be blocking airflow to your radiator? It could all be an airflow issue.

Jester took the words out of my mouth. I have a k20 with a plow. If it is 50 degrees plus outside, I kick the plow off because the truck will overheat. I am sure that by now you have tried quite a few remedies. If you havent kicked the plow off, definitely do that and take the truck for a spin.