I have a 91 lumina eurosport, 222,000 miles, with 3.1 engine. I recently had some engine work done and had intake manifold gasket replaced. The engine now runs noticeably hotter than before repair at both idle and at speed. At idle the temperature gauge continually goes almost to red area before fan kicks in and brings temperature down then fan kicks off and temperature rises again. At speed I am running noticeably hotter to. I have no external coolant leaks and do not appear to be losing any coolant. My thermostat appears to working ok and never had any engine overheating problems until recent intake manifold gasket repair. Any ideas what could be causing this condition?
Try bleeding the cooling system see below don't work follow the next suggestion.
1. Always bleed air from cooling system after replacing coolant. Set heater for maximum heat. Remove radiator cap. Loosen drain plug and remove drain bolt (if equipped) from engine block. Drain coolant reservoir. Fill coolant reservoir to MAX mark with 50/50 water-coolant mixture. Loosen bleed bolt and fill radiator up to base of filler neck. Close bleed bolt when coolant flows out without bubbles. Tighten bleed bolt. With radiator cap removed, start and operate engine to normal operating temperature. Add coolant if necessary and check for leaks.
Block and Pressure test
2. Have it block and pressure tested-do the block first to pinpoint a combustion leaking into the cooling system or a gas analyzer to sniff for hydrocarbons at the radiator fill neck.
Pressure test: do not do a pressure test if there's leakage at the headgasket this might cause coolant into the cylinders and lock it up or bend a connecting rod if cranked thereafter. The headgasket should be repaired before doing the pressure test.
If the block and pressure test passes check the following: Thermostat, Pressure test the Rad. Cap, Clogged radiator, Fan clutch, Radiator electrical fan, collaspe hoses, water pump.