Why does it keep overheating?

JUNKPATROL

MEMBER
BUICK LESABRE

I bought this car second hand and they were troubleshooting an overheating problem. They had already replaced the radiator, thermostat, pressure cap and starter. They claimed the water pump needed replacing. I have since replaced the water pump and headgaskets along with taking the heads to the machine shop and having then tested and machined in hopes of solving this problem. Yet even after all this it can only drive 5-10 minutes before boiling the 1/2 & 1/2 coolant inside the overfow. A mechanic noticed that the cap and right side of the radiator are cool and the left and hose are hot and tight with pressurized fluid. After overheating, it can take up to 20 minutes for the coolant to flow naturally back through the radiator. I have had it flow checked and pressure tested. Finally, I took the thermostat out completely and the gauge continues to rise and fall at it's own pace and seems to be unaffected by turning the heat on or off. Also without change in driving or traffic it seems to reach the red and fall back with a mind of it's own, yet I know when it will overheat by the temperature of the heat in the car, the inside heater throws cold air just before overheating again. The fan seems fine but may be turning on late. What else can be done? After reading many forum Q&A I am wondering what to do next. Another pressure cap? A freeze plug? A temperature sensor? A radiator chemical flush? Intake manifold gasket? Another pressure test for a leak that has not been found? I really want to drive this car with a thremostat before winter. HELP

Monday, September 3rd, 2007 AT 1:05 PM

5 Replies

RASMATAZ

MECHANIC
75,992 POSTS

White smoke coming out of the tailpipe? Could also be air lock in the cooling system

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Tuesday, September 4th, 2007 AT 3:10 PM

JUNKPATROL

MEMBER
4 POSTS

White smoke coming out of the tailpipe? Could also be air lock in the cooling system[/quote:97f34732f9]
no whit smoke but everyone says it could be an air bubble. Now after a new radiator cap and a new thermostat gasket. It only overheats occasionally but is still losing fluid due to the fluxuation of temperature and I know when it will get to hot by the cold air blowing from the heater. When the interior heat is hot the gauge is normal. I think the fluid is exiting from the overflow bottle o the ground when hot, therefore unable to enter back into the system. Any answers?

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Sunday, September 9th, 2007 AT 9:36 PM

RASMATAZ

MECHANIC
75,992 POSTS

The problem here I don't even have a description of the vehicle. Could try bleeding the air out. See below

BLEEDING COOLING SYSTEM:

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
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.

If it continues try checking below

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.

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Sunday, September 9th, 2007 AT 9:57 PM

JUNKPATROL