I couldn't find a K10 section, but I have "acquired" a 1984 K10 with a 350. I don't know what has been done to the engine, but I need help. My 18 yr old had added headers, holley carb and this thing screams BUT the faster you drive, the more it overheats. There does not appear to be water in the oil. Ive changed the thermostat out to 190 degrees and gentle driving it runs about 200 degrees. I have added a new temp sensor(that fits into the thermo housing) so I know the temp is accurate. I just got through flushing it and currently running the "Peak" radiator cleaner through it. It just doesn't make sense. Usually when you slow down, things overheat, but this is totally opposite. The water that has drained and boiled out is extremely rusty. One parts store guy said maybe the water pump impeller has rusted out and its not moving a lot of water. Another one said fan clutch.....this was a farm trk so it didn't get drove too much for a while....any suggestions?

Thanks
David

 

Make sure you have enough blades on the fan. I had an issue with my C10 not having the correct fan so not enough air was moving. Also make sure you have a fan shroud, I really don't like them but they do work. Another thing could well be your radiator is getting jammed up with calcium deposits, replacing it works.

 

I second the guy at the parts store. Rusty coolant + high RPM overheating screams waterpump impeller to me. I'd go ahead and pull the thing and take a look. Couldn't hurt. Careful not to break bolts though!

 

Had a truck once that did that, lower hose would collapse under rpm...