2001 Mitsubishi Montero over heating

2001 MITSUBISHI MONTERO
122,000 MILES • 6 CYL • AWD • AUTOMATIC
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EDDIE FORTNER
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2001 montero starting over heating. I replaced the thermostat but got same result. I removed the thermostat and it quit running hot for a couple months. Now when I crank up and run it will register on the temp guage half way to just above half hot. The guage will sometimes bounce up to 3/4's and back to half. Whenever I stop with the engine running the temp doesn't rise or fall. Whenever I shut the engine off and turn the engine back on in 1 to 20 minutes the guage is pegged out hot. After it runs for approx 3 to 5 minutes the temp guage comes back down to half way.
I put another thermostat in and within 5 minutes of running it pegged out hot. I could here the water boiling and tell by the tightness in the hoses that it was very hot. I unscrewed the vent bolts above the therm and on the top hose side it released lots of pressure but no water. I was able to remove the radiator cap and it boiled over. When i removed the therm it was still open so it was working correctly.
Any ideas?
Jul 18, 2009 at 1:09 PM
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KHLOW2008
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Hi Eddie,

The engine is definitely overheating and seems there are air in the system. Did you bleed the system after replacement of the thermostat?

When engine is cold, remove the radiator cap and check the coolant level. If it is low, loosesn the bleeder bolt on top of thermostat housing and fill coolant till no bubbles overflows. Tighten bolt and top up at radiator cap. Turn on heater to maximum and start engine without the radiator cap.
When coolant level drops, top it up and continue running till the level stays constant.

If the coolant in radiator is not moving when thermostat has opened, the problem could be a faulty water pump.

If the level maintains after some time and you keep getting air bubbles, the most likely problem would be a bad head gasket.

If level remains constant and no bubbles are noted, close radiator cap and restest. Top up reserve tank if necessary. If it is overflowing most of the time, either the head gasket or radiator cap is bad.
Jul 19, 2009 at 1:33 AM
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ANTUF
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Hello Eddie, I have the same problem and would like to know if you solved it. Please reply.Thanks
Jan 29, 2011 at 7:23 AM
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KHLOW2008
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Antuf,

Have you done all those that I have advised?
Feb 3, 2011 at 12:37 PM
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ANTUF
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Hi, thanks for the reply. The car is in the garage at the moment fitting new nozzles. I shall try out your suggestions and get back to you asap. They are having a problem at the moment. The computer is reporting a faulty "main sensor" on the injector pump and it is causing high revs. Dunno what that is but this is Kenya and we have to live with our mechanics who do not possess the required training. It was okay when I bought it there.
Feb 5, 2011 at 6:15 AM
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KHLOW2008
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If the Check Engine Light is indicating, get the trouble codes and let me know what it is.

High revs could be due to a faulty or stuck Idle Solenpoid Control Valve or lack of coolant in system.
Feb 6, 2011 at 6:05 PM
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ANTUF
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Hi,Got the car back from the garage after replacing the the nozzles and serviced the injector pump. It is running really fine now but still have the problem of the resovoir filling up.I removed the thermostat which gave me better results but the car heats up as soon as I switch off the engine. There is absolutly no smoke and no moisture in the exhaust pipe, no bubbles or oil in the Rad.The garage mechanics came up with the conclusion that it might be the cylinder head gasket. Please HELP.
Feb 11, 2011 at 10:13 AM
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KHLOW2008
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If you have not replaced the radiator cap, replace it and retest.

If pressure still builds up, you have a possible fault with the head gasket.

Feb 11, 2011 at 1:47 PM
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