Car runs hot

Asked by Dec 11, 2017 at 09:23 PM about the 1999 Chevrolet Lumina

Question type: Maintenance & Repair

I recently replaced the thermostat on my 99 chevy
lumina because the temp gauge would jump
randomly from hot to cold.  After replacing it for
about a day and a half the problem was fixed and
car ran at normal temp.  Now its back to running
from hot to cold however its not getting as hot as it
was prior to installing new thermostat.  What could
be causing this problem and what do you suggest i
do to fix it?

8 Answers


is the coolant low , after being topped off ? . look under the oil fill cap what do you see ? what does the exhaust look like ?


First , are the fans coming on when it gets hot ?

Well the oil looked ok just low because have oil change coming up soon. The exhaust looked normal too. Now i forgot to mention that the heater blows cool air and gets hot sometimes.

And yes the fans come on as well


intermittent heat sounds like low coolant or air pocket in the system , what did the bottom of the cap look like ? a compression test will tell you if the head gasket is blown , which is what I think has happened

The bottom of the cap looked normal. I'm guessing you need special equipment to do the compression test right?

Also is replacing a head gasket expensive?


more importantly is the car worth it , is it rotting out underneath ? If the head gasket is gone or going it'll show [signs] lose of gas mileage , disappearing coolant , compression tester is pretty cheap , If it's been good to you there may be one thing after another to go wrong

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