2001 deville northstar

[james.18959]

Hi, i had a small crack on my coolant reserve tank, i bought sealant to get by till i found a good used reserve tank, i found one for $25, i installed it everything seemed fine till i took off down the street, the Engine Hot & AC Off light came on & the temp gauge went all the way up... Note, before i changed the coolant tank i had zero problems, drove 100 miles a everyday for 4 days in a row...one mechanic said to try changing the thermostat.... Another mechanic over the phone (without even seeing the car) said it was the head gasket HELP!

 

[USAFRet]

Not sure what "help" we out here can give you.
Someone needs to lay hands on this and find the actual problem.

Might be the coolant tank, might be a head gasket, might be a cracked block.