1997 Lumina overheating

SCOTT PINNEY

MEMBER
1997 CHEVROLET LUMINA
3.1L
V6
FWD
AUTOMATIC
120,000 MILES

I purchased this car yesterday for my high school daughter to drive. The car has approximately 120,000 miles. I looked under car and there was no fluid marks on pavement. I took the car for a test drive and parked it back in same place. I left the car sit for a couple hours while I went and looked at another car. When I returned to purchase the vehicle, I looked under car again and there were no fluid marks on pavement. We purchased the car while we were visiting family. We had approximately 4 1/2 hour drive home. The car ran great with now problems for about three hours when traveling home then the Low Coolant light came on. I told my daughter that we needed to pull into the next town (approximately eight miles) to get coolant. The light went of after driving about a mile. We still pulled into next town to purchase 50/50 coolant. It was dark so not real accurate but level of coolant in reservoir was about where should be and was cold to touch. I took of radiator cap after car had set for a while. I added about 1/3 gallon of coolant to fill radiator. We then proceeded to travel home. We drove about one more hour and the temperature all of a sudden went up and "HOT" light came on. I had my daughter pull car over on an approach this time since car was hot. The coolant reservoir was full to top this time with coolant being cool to the touch. We let car sit for a while and then I took radiator cap off and filled with about 1/2 gallon of coolant. We then drive the additional fifteen miles home with no more problems. When got home and had some light available, I let car idle in driveway. The fans would kick on as temperature increased and would kick off as temperature gauge cooled. I let car set overnight. When I checked the next morning, the coolant level in reservoir was in correct range. I started the car and let it run for a while, I then squeezed the top radiator hose. I could squeeze hose almost flat. I could feel pressure and water movement, but there wasn't much pressure. How much pressure should be generated on the top hose from water pump? Is the water pump the likely culprit or would you recommend trying something else?
Thank you
Scott

1 Reply

CARADIODOC

MECHANIC
33,873 POSTS

The water pump does not develop any pressure. Its only purpose is to push the coolant around the system. The pressure comes from the expansion of the coolant as it heats up. It goes into the reservoir so the level there will go up, then, when the coolant cools down, it contracts and is drawn back into the engine, and the level in the reservoir goes back down.

The fact you are having to add coolant with no visible leaks suggests a cylinder head gasket is leaking. Your mechanic can perform a quick chemical test to verify that. The test involves drawing air from the radiator, (reservoir on GM cars), through a glass cylinder with two chambers partially-filled with a special dark blue liquid. If combustion gases are leaking into the cooling system, the liquid will turn bright yellow.