1966 Chevy C10 running a 77 250 inline 6. Overheated yesterday morning. Tested thermostat (boiling water method) and it appears to open okay. Pulled the valve cover and checked the oil in there as well as in the dipstick and doesn't seem to have any coolant in it. Coolant was leaking, however, and seemed to be coming from where the upper radiator hose goes INTO the thermostat housing (?). Thinking I need to test my water pump next BUT how do you test a water pump? I don't have access to any of those fancy vacuum/guage testy things they always want to sell you at the parts store. Any help greatly appreciated! Lon
To test the water pump for wear remove the belt and grap the fan and move around from side-to-side, up-n-down, back-n-forth, and all-around. If there is ANY free play at all, replace it, it's probably shot. I tested mine in that manner, but found nothing. I replaced it anyway because I had already replaced all hoses, thermostat and added a fan shroud with no result to overheat problem. Water pumps are pretty cheap and most chain auto parts stores will give you a life-time warrenty. ( ask first) Lesson; Just because it feels ok and is not leaking, dosn't mean it isn't bad. Turns out it was the FACTORY water pump with 150,000 miles on it. After replacement I took the old one apart and discovered that although the bearings were still good, the impeller had rotted away to half it's normal size. DV
You could have a clogged radiator. It may look OK as you peek at the top with the radiator cap off, but it may be clogged at the bottom.
Update: I replaced the upper & lower radiator hoses, thermostat (and housing gasket), and radiator pressure cap. I flushed the radiator and refilled it w/ coolant. Started everything up today and let her idle to operating temperature. Everything seemed fine. I went ahead and left my Mom's (where I'd left her the past few days) and drove home. The needle started climbing again and went just into the H zone (not near as far buried as the needle was the other day) BUT none of the other symptons I experienced on Tuesday. Tuesday the engine was knocking, it was sluggish, and steam was coming from under the hood. Today the needle showed H BUT no knocking, sounded/ran smoothly, and no steam. I pulled into my driveway, still idling, popped the hood and everythign looked/sounded just fine. Then I shut her off and that's when the hissing began... steam began flowing up from near where the lower radiator hose connects into the radiator. This was confusing... why did this NOT start until after I shut the engine off??? I'm still up-in-the-air as to cause of my problems. I'm guessing since it's still getting hot that I probably AM going to ahve to replace the water pump. ??? Lon
Lon When you shut off the engine it actually gets hotter because coolant flow has stopped. This happens to all gas engine vehicles and is normal but yours is running so hot that it is reaching pressure above the cap pressure and the hot water turns to steam at when the pressure is reduced. You could try this to see if the radiator is clogged. As the truck warms up feel the outside of the radiator core with your hand, you are looking for cooler areas which indicate a clogged section. If you find a cool section the radiator has to come out to be boiled out. At this point, regardless of the radiator I would suspect the pump is not moving enought coolant fast enough to keep it cool. Hope this helps Vic
One thing you may not want to overlook is your timing. This caused my 1965 Chevy to overheat. I adjusted the timing and all was better. Good luck.
Thanks, everyone, for the replies. Ack, I'm so stupid. Before leaving my Mom's house I had filled the radiator to what I THOUGHT was full. WRONG. Sunday I opened the radiator cap and ran the engine for about 15 minutes. I kept adding water/antifreeze until the radiator was ACTUALLY full. The needle never rose above the 1/2 mark. Then I put the cap back on and ran her for another 15 minutes and again it never rose above 1/2 way. Then I took it for a little test drive out past BTK's house and then into the country. Took her Hazzard-Style down some back country roads and everything seemed to be fine. Last couple days I've driven her to work and about the fist 3-4 minutes she runs real rough and then all of a sudden BAM clear as a bell. Not sure what's going on there. Could that possibly have something to do w/ the timing like you suggested? Lon
"about the fist 3-4 minutes she runs real rough and then all of a sudden BAM clear as a bell" Sounds like a choke adjustment...
Hmm... it's a manual choke. I pull the knob as I start it but then I usually push it back in right away. That's how I've always driven her and it's always been fine. Should I not be so quick to push the knob back in? Lon
>Hmm... it's a manual choke. I pull the knob as I start it >but then I usually push it back in right away. That's how >I've always driven her and it's always been fine. Should I >not be so quick to push the knob back in? > >Lon Try just moving it halfway until it warms up... DV
