Cadillac Repair: 1994 sls seville, head gasket problems, coolant level

Question
replaced the water pump 8 months ago. Car just started to overheat again. Could it possibly be the water pump again or an air pocket in the cooling system?

Answer
Hi Herb,

     Not sure what engine you have so I will answer as best I can.

     The first place to start is to check the coolant level in the radiator with the engine cold and add as necessary. Put the radiator cap on and warm the engine up to operating temperature. The Sevilles should have a temp gauge that you can watch so if the temp. gets to 230 degrees F and the fans still don't turn on then you would need to find out why. Maybe the thermostat is sticking closed. Also make sure nothing is placed in front, between or behind the rad. and condenser that would block air flow through it.

    If the stat opens and the fans turn on but you still overheat then there is definitely a problem and it might be a problem with the head gaskets. Both the 4.9L and 4.6 Northstar have head gasket problems that develop when the threads where the bolts are in the block pull out. What happens then is the temp gauge will warm up normal...then go hot or overheat area and drop down to normal again all in a matter of 10 minuets. What I do in that case is to drain the antifreeze down when the engine has cooled off so that when the thermostat is taken out the anti freeze is 1/2" from the top. Remove the serp. belt and then start and run the engine. What you are doing is watching for bubbles and what side they come from. That way you know what head gasket to really look for problems on when removing both heads to replace both gaskets. I'm not sure if this method would work with the Northstar because of where the thermostat is but I know it works with the 4.9L.

       I don't feel that the waterpump is your problem at this point unless it was leaking. Bill