98 Silverado Overheating

noob1982 · October 31, 2010

My 98 Silverado w/ 213K on it started showing some heat issues this past week. I came out of a store and noticed there was some cooling leaking on the drivers side in front of the wheel. I thought the side jacket had a leak, but couldn't see where it was coming from. I checked the coolant and it looked okay. I took off driving watching the gauge. I noticed the gauge was climbing to 210 and dropping to 190 over and over. when I was idling it seemed to stay around 190. I thought it was a fan clutch so I replaced it and at the same time replaced the temp sending unit (drivers side block above exhaust manifold). The fan clutch did and still does run while idling and continues to run when the RPMs are up. After doing this the temp gauge climbed to 210 and kept going. I pulled over at 230 so it could cool down. Then i thought the thermostat was junk so I replaced it. The symptoms are the same. Some history on this truck is I had some parts replaced last fall just for preventative maintenance. They were: water pump, radiator (it was leaking), thermostat, and all hoses. So, about 1 year ago everything was new.

Currently the situation is: thermostat, fan clutch, and temp sensor are new. The top radiator hose is hot and feels like there is pressure on it when the truck is running. The bottom hose is cold to touch. There is no coolant leaking, and I have not had it flushed since I bought it at 203k. When I drained the coolant to replace the thermostat I did not notice junk in it that would indicate a flush is needed. I am leaning towards a water pump, but since the pressure is on top hose it seems like it would be fine. nothing out of the weep holes on the pump though.

I don't want to throw parts at it, and don't have a lot of money to have it worked on. Any suggestions are appreciated.

txab · October 31, 2010

When you say "junk", might it have clogged your new radiator, resulting in restricted flow. Something to think about. Make sure your coolant level is full. Did you properly bleed any trapped air form the system after replacing parts/coolant? If not, you might have an air pocket causing some of your problem

jim brock · October 31, 2010

If your coolant level is not dropping then it would indicate a flow problem or restriction somewhere. What happened to the coolant leak mentioned in opening statements? Did it go away? Was any shrouding material removed from around the fan when these PM services were performed? The lower radiator hose may be cool but also make sure it is not collapsing. Check your freeze plugs if you can for any signs of deterioration/leakage. The coolant leaking from freeze plugs as system pressure builds can result in overheating but you will not necessarily see any coolant on the ground. (It evaporates with engine heat). Hope you get it figured out. Good luck...