1996 Jeep Grand Cherokee Boiling water in reservoir

Tiny
CHRISBL
  • MEMBER
  • 1996 JEEP CHEROKEE
My Jeep does not overheat but after running the A/C for a short time the water in the reservoir boils and spews out. I have replaced the thermostat and the water pump. What else could be my problem?
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Monday, August 7th, 2006 AT 6:28 PM

10 Replies

Tiny
MIKEYBDMAN
  • MEMBER
I would suspect the fan clutch. Here is a test you can perform.

To check the clutch fan, disconnect the bimetal spring and rotate 90 counterclockwise. This disables the temperature-controlled, free-wheeling feature and the clutch performs like a conventional fan. If this cures the overheating condition, replace the clutch fan.
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Monday, August 7th, 2006 AT 6:53 PM
Tiny
CHRISBL
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The Jeep actually doesn't overheat. It just boils water in the reservoir. Would you still suggest the fan clutch?
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Monday, August 7th, 2006 AT 7:44 PM
Tiny
MIKEYBDMAN
  • MEMBER
This is odd. What does your water temperature gauge read? It should regulate the water temerature at 195 degrees, and the water that transfers to your resevoir is after it goes thru the radiator. So, either it is overheating and boiling the water, or you have something pressurizing the fluid.
It makes sense that normally the system can handle a load and keep the engine cool, but with the extra load of the airconditioning compressor, and the added temperature of the air crossing the condensor, it is just a little more than your system can handle. If your water temperature gauge is bad, you might not know how high your temp is really going.
Knowing that water boils at 212 degrees, and even higher with radiator fluid mixed in, then I think you are getting hotter than you think.
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Monday, August 7th, 2006 AT 8:19 PM
Tiny
CHRISBL
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It never gets above 215 or so. Usually stays around 210.

My gage acts like it should. It is cold when I start the engine then warms up to about 215 and then backs down to about 210.
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Monday, August 7th, 2006 AT 8:22 PM
Tiny
MIKEYBDMAN
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Ok, if your temp overshoots like you stated, that is usually an indication of air in your heads. Might have a leak in the head gasket. This could explain the bubling water if the compression of a cylinder is over pressurizing your radiator. That can push fluid out of the resevoir. To check this, you will need to do a compression check on all 6 cylinders. If you have one or two that are a lot lower than the others, I would suspect a leaking head gasket, or possibly a cracked head. I am going to post the D/O of the cooling system. Maybe something will set off a light in your situation.

PURPOSE
Cooling System - Circulates coolant through the engine to remove heat developed by combustion.

Water Pump - Circulates coolant through entire system, block, head, thermostat, radiator, and heater core.

Thermostat - Allows for a rapid engine warm-up and maintains a minimum operating temperature.

NOTE: A normally operating thermostat does not control the upper limit for coolant temperature. The maximum temperature is controlled by the amount of air flow drawn across the radiator.

Cooling Fan - Provides airflow across the radiator to remove heat from the coolant.

Fan Clutch - Controls the upper limit for coolant temperature. The clutch engages to prevent the coolant from reaching its boiling point.

Fan Shroud - Forces air from the cooling fan to be drawn directly across the radiator.

CAUTION: Operation of the engine without the fan shroud significantly reduces the cooling ability of the engine.

Radiator - Transfers heat from the coolant to the air passing across it. The cooling ability of the radiator is directly dependent on the amount of air flowing across it and the amount of coolant flowing though it.

TEMPERATURE CONTROL
Cold Engine
With a cold engine the thermostat is closed, forcing coolant to re-circulate through the engine block and head assembly. This results in a rapid warm up of the coolant.

When the coolant temperature reaches the thermostat set point, the thermostat will begin to open, allowing coolant to flow through the radiator.

NOTE: The upper radiator hose will remain cold until the thermostat begins to open, at this point it will rapidly warm up. This is a quick and easy indication of when the thermostat opens.

Warm Engine
With the thermostat open, the cooling system temperature will now be dependent on the amount of air flow across the radiator.

The amount of air flow is dependent upon:

- Driving speed.
- Cooling fan clutch engagement.

Under normal conditions, driving the vehicle in excess of 25 mph will provide enough air flow across the radiator to sufficiently cool the engine.

Under severe conditions, such as climbing a steep hill, the coolant temperature may rise enough to fully engage the fan clutch, thus adding additional air flow across the radiator.

During stop and go driving, the fan clutch will engage to provide sufficient air flow across the radiator.
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Monday, August 7th, 2006 AT 8:35 PM
Tiny
CHRISBL
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Hmm. This is making me think the fan clutch because this happens after stop and go traffic. Also when I was testing it out today I let it sit running for a while then with the A/C for a while. Everything was fine while running but as soon as I cut it off the reservoir began to fill and bubble.
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Monday, August 7th, 2006 AT 8:41 PM
Tiny
MIKEYBDMAN
  • MEMBER
If you decide to replace the fan clutch, usually auto zone will lend you any special tools if needed to replace it. Chevy's are bad about needing tools for things like that.
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Monday, August 7th, 2006 AT 8:46 PM
Tiny
CHRISBL
  • MEMBER
I think that'll be my next step.I'd much rather do that than worry about a blown head gasket. Thanks for your help!
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Monday, August 7th, 2006 AT 8:48 PM
Tiny
CHRISBL
  • MEMBER
Just something else I noticed:

I let the jeep run yesterday for about 30 minutes and 15 of those minutes with the A/C on. Everything was fine while running, but as soon as I turned the car off the reservoir filled way past full and almost boiled. As it cooled the reservoir went back down.
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Tuesday, August 8th, 2006 AT 8:36 AM
Tiny
GIANTSCALERCGUY
  • MEMBER
Mine has done that in the past. Added "Fix Leak" by Barrs and hasn't done it in 2 years
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Monday, June 29th, 2009 AT 11:48 AM

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