2005 grand am overheating
my 2005 grand am is overheating according to the temp gauge. the gauge will go up to 130 and the high temp light will come on but only stays on for approximately 5-10 seconds then the gauge goes back down to 90. it hovers between 90 and 100 degrees but doesnt exceed that. we have replaced the intake gaskets, thermastat, we have added a can of head gasket fix but it continues with the temperature going up then coming back down. our mechanic is stumped and is questioning the head gaskets to be replaced which is quite costly. any suggestions?