Head gasket or cracked head?
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Joined: Apr 2018
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Model: Cherokee(SJ)
Head gasket or cracked head?
so i replaced the thermostat and water pump on the jeep filled everything up let it cycle and Bubble and all that good stuff, I filled the resovor up as well. Now I have almost no coolant in the resovor two days after doing all this and what’s left in the resovor while the motor is running will bubble also when I’m coasting or sitting still the heat will get real cool until I get back on the gas. Is this more a cracked head or blown head gasket? No coolant in the oil and zero leaks
CF Veteran
Joined: Oct 2018
Posts: 1,577
Likes: 279
From: United Kingdom
Year: 1995 RHD
Model: Cherokee (XJ)
Engine: 4.0l
Is there white smoke coming out of the exhaust (more than just exhaust fumes)? If not then from your description, water is not leaving the system which would not be a cracked head or gasket. Are you sure that the system is fully bled? The heater core could be trapping air.
Other than that, you may find fault in the pump or thermostat not letting enough coolant flow around.
The best way to actually test your theory though would be to use a leak down tester as that will indicate any cylinder pressure loss and where it's going. If water can get to the cylinders via the gasket or a crack, air will go the opposite way when testing and should show as bubbles in the radiator fill port.
Other than that, you may find fault in the pump or thermostat not letting enough coolant flow around.
The best way to actually test your theory though would be to use a leak down tester as that will indicate any cylinder pressure loss and where it's going. If water can get to the cylinders via the gasket or a crack, air will go the opposite way when testing and should show as bubbles in the radiator fill port.
CF Veteran
Joined: Nov 2017
Posts: 3,700
Likes: 238
From: Groton, MA
Year: 1995
Model: Cherokee(XJ)
Engine: I6 4.0L
I'm going to guess that you probably just had some trapped air that has now worked it's way out of the system. Fill it up again and keep a close eye on it. It wouldn't hurt to do the leakdown test just to be certain, of course.
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