Hello, I recently got my water pump, alternator and a couple of other things replaced on my car from Tom Bell Chevy dealership. Before I got all of that replaced my car wasn’t overheating but after driving it for possibly less then two weeks it’s been showing as it’s overheating. The mechanic is saying air is getting into the system and it might be a head gasket problem does that sound right or was it something he could have possibly caused? My car never had a overheating problem but now it does are they just trying to get more money out of me? This is what the dash looks like but it goes into the red zone. Also the mechanic replaced the thermostat so that shouldn’t be the problem.

 

Any advice helps thank you

 

If they didn’t correctly bleed the air out of the LT1’s “reverse flow” (heads get cooled first) cooling system, it can overheat.

Air can also enter the system if the overflow line from the radiator fill neck to the reservoir is cracked, preventing the vacuum in the radiator from pulling coolant back from the reservoir as the system cools down. With the radiator completely cooled down, take the radiator cap off and see if the radiator is full to the very top. If it isn’t, good chance the hose or the metal pipe it connects to under the battery has a leak in it (or the radiator itself).

A pressure cap that doesn’t hold 18 PSI can cause overheating, when the coolant boils.

Do both fans run on low speed when the A/C is turned on, or when the coolant temp reaches 226°F? Do both fans move to high speed when the coolant temp reaches 235°F (pretty much the hashmark just to the left of the needle in your picture)?

There are two coolant temp sensors - one in the driver side head for the gauge, the other in the water pump housing for the PCM (which controls the fans). Shoebox has a test procedure for the sensors and circuits - see item #20 on this page - note there are several very useful articles on the cooling system operation and problems:

4th Gen LT1 F-Body Tech Aids

 

PS: the thermostat has to be on specifically for the LT1. Can't use a generic SBC t'stat.

http://shbox.com/1/tstat.jpg

And Yes, a blown head gasket can cause overheating.... and overheating can cause a blown head gasket.