Overheating
Thread Starter
Newbie
Joined: Aug 2019
Posts: 14
Likes: 1
Model: Cherokee (XJ)
So with a rapid heat up within the first few minutes of starting the vehicle, that can usually be a sign of a bad thermostat, one that is closed.
Is the top radiator hose (coming from the thermostat housing) to the radiator, hot when the gauge is reading 210? It should be hot to the touch (like you should not be able to hold it for more than a second) and if you wrap your hand around it and squeeze it should be hard to squeeze. If the hose is cooler when it is showing that temperature on the gauge, you may want to look at replacing the thermostat, really easy to do. If you do ending up getting a new one, try and get a Mopar or factory part from the dealership. Maybe a little pricier but the thermostats at the auto parts stores are not reliable (in my opinion).
Air in the system could be a culprit, but typically within a few warming and cooling cycles, the air should naturally work it's way out. The cooling system is designed to release pressure (or air) out the highest part of the cooling system (the radiator cap). Others have already said this but to make sure there is no air in the cooling system, turn your heater control in the vehicle to Hot (like you are turning on the heater). Take the radiator cap off of the radiator and fill with coolant to near the top. Start the vehicle. When you do this you want to get the vehicle up to operating temperature or when the thermostat begins to open (close to when your gauge hits 210), or when you feel the top radiator hose get hot. Once this happens, turn the vehicle off, replace the radiator cap, make sure that coolant in the reservoir (the plastic container) is the appropriate mark. That would get any air out of the system. Here is the thing though, if you are doing this and you are not feeling the top radiator hose getting hot at all, the thermostat would be the first thing to replace.
Is the top radiator hose (coming from the thermostat housing) to the radiator, hot when the gauge is reading 210? It should be hot to the touch (like you should not be able to hold it for more than a second) and if you wrap your hand around it and squeeze it should be hard to squeeze. If the hose is cooler when it is showing that temperature on the gauge, you may want to look at replacing the thermostat, really easy to do. If you do ending up getting a new one, try and get a Mopar or factory part from the dealership. Maybe a little pricier but the thermostats at the auto parts stores are not reliable (in my opinion).
Air in the system could be a culprit, but typically within a few warming and cooling cycles, the air should naturally work it's way out. The cooling system is designed to release pressure (or air) out the highest part of the cooling system (the radiator cap). Others have already said this but to make sure there is no air in the cooling system, turn your heater control in the vehicle to Hot (like you are turning on the heater). Take the radiator cap off of the radiator and fill with coolant to near the top. Start the vehicle. When you do this you want to get the vehicle up to operating temperature or when the thermostat begins to open (close to when your gauge hits 210), or when you feel the top radiator hose get hot. Once this happens, turn the vehicle off, replace the radiator cap, make sure that coolant in the reservoir (the plastic container) is the appropriate mark. That would get any air out of the system. Here is the thing though, if you are doing this and you are not feeling the top radiator hose getting hot at all, the thermostat would be the first thing to replace.
The top radiator hose gets hot and is always easy to squeeze. I just replaced the thermostat like I mentioned but new parts can always be faulty too. Also last night it was rainy but I went out and just started it and sat in it and it took 25 minutes to run hot. I don’t get it
Senior Member
Joined: Nov 2017
Posts: 535
Likes: 101
From: Northern Indiana
Year: 2000, 1991
Model: Cherokee (XJ)
Engine: 4.0
Top hose being easy to squeze when hot might indicate that the radiator cap is not sealing to allow pressure to build up or that there is air in the system. With the system pressurized the boiling point of the coolant is increased. Major auto parts stores have a rental cooling system pressure tester and also includes a radiator cap pressure tester. Or get a new high quality radiator cap and see if it makes a difference.
Seasoned Member
Joined: Aug 2019
Posts: 255
Likes: 58
From: Pasco,WA
Year: 2001
Model: Grand Cherokee (WJ)
Engine: 4.7L
Top hose being easy to squeeze when hot might indicate that the radiator cap is not sealing to allow pressure to build up or that there is air in the system. With the system pressurized the boiling point of the coolant is increased. Major auto parts stores have a rental cooling system pressure tester and also includes a radiator cap pressure tester. Or get a new high quality radiator cap and see if it makes a difference.
Thread Starter
Newbie
Joined: Aug 2019
Posts: 14
Likes: 1
Model: Cherokee (XJ)
Top hose being easy to squeze when hot might indicate that the radiator cap is not sealing to allow pressure to build up or that there is air in the system. With the system pressurized the boiling point of the coolant is increased. Major auto parts stores have a rental cooling system pressure tester and also includes a radiator cap pressure tester. Or get a new high quality radiator cap and see if it makes a difference.
Senior Member
Joined: Nov 2017
Posts: 535
Likes: 101
From: Northern Indiana
Year: 2000, 1991
Model: Cherokee (XJ)
Engine: 4.0
Senior Member
Joined: Sep 2018
Posts: 802
Likes: 140
From: NJ
Year: 1992
Model: Cherokee (XJ)
Engine: 4.0
Couple of quick questions:
How long have you owned the truck, and how many owners has it had (if you know)?
You said it has overheated before? When has it overheated, at random times or does it overheat at certain points?
What I am wondering is if the vehicle may have had some stop leak added to the coolant system by a previous owner that is clogging the system, even though the radiator may be brand new.
I assume someone else did the work, would you be able to ask them what the condition of the coolant and such was when they did the work?
How many times have you driven it since you replaced the radiator and thermostat.?
How long have you owned the truck, and how many owners has it had (if you know)?
You said it has overheated before? When has it overheated, at random times or does it overheat at certain points?
What I am wondering is if the vehicle may have had some stop leak added to the coolant system by a previous owner that is clogging the system, even though the radiator may be brand new.
I assume someone else did the work, would you be able to ask them what the condition of the coolant and such was when they did the work?
How many times have you driven it since you replaced the radiator and thermostat.?
Thread Starter
Newbie
Joined: Aug 2019
Posts: 14
Likes: 1
Model: Cherokee (XJ)
Thread Starter
Newbie
Joined: Aug 2019
Posts: 14
Likes: 1
Model: Cherokee (XJ)
Seasoned Member
Joined: Aug 2019
Posts: 255
Likes: 58
From: Pasco,WA
Year: 2001
Model: Grand Cherokee (WJ)
Engine: 4.7L
Here's a link to help you in your diagnosis. #2 deals with the water pump.
https://axleaddict.com/auto-repair/D...r-Pump-Failure
https://axleaddict.com/auto-repair/D...r-Pump-Failure
Old fart with a wrench
Joined: Nov 2010
Posts: 14,398
Likes: 740
From: Manlius, east of Syracuse, NY
Year: 2000 XJ Sport & WJ Laredo
Model: Grand Cherokee (WJ)
Engine: 4.0L
People, are we forgetting this has the 0331 head on it?
The easiest way I've found to bleed all the air out of the system on a refill is to remove the temp sensor, fill it up until coolant flows out of the sensor hole, reinstall the sensor and continue filling. After warmup, you may only need an additional quart, put the cap on, then fill the reservoir.
The easiest way I've found to bleed all the air out of the system on a refill is to remove the temp sensor, fill it up until coolant flows out of the sensor hole, reinstall the sensor and continue filling. After warmup, you may only need an additional quart, put the cap on, then fill the reservoir.
Last edited by dave1123; Sep 18, 2019 at 10:04 AM.
Senior Member
Joined: Nov 2017
Posts: 535
Likes: 101
From: Northern Indiana
Year: 2000, 1991
Model: Cherokee (XJ)
Engine: 4.0
[QUOTE=dave1123;3573838]People, are we forgetting this has the 0331 head on it?
After cooling system work the initial and easy step seems to be to eliminate potential air in the system. (Good tip Dave on removing the temp sensor to help purge air) I expect that a very rapid rise in indicated cooling system temperature is potentially a result of air in the system (sensor being exposed to steam instead of coolant) where a more gradual rise after being driven some distance is the result of a cooling system problem, head issue or other internal engine problems. (has anyone seen any data on this?)
Yes, unfortunately as Dave referred to, 2000 and 2001 4.0 engines have a head casting that is prone to cracking, especially if overheated. A cracked head and/or a bad head gasket typically allows combustion gas to enter the cooling system and results in overheating. A do-it-yourself combustion gas test using a parts store rental combustion gas tester (also referred to as block tester) and purchase of the test fluid will help eliminate or confirm a likely bad head gasket or cracked head. An oil analysis by an oil test lab such as Blackstone Labs (www.blackstone-labs.com) will identify even a very small amount of antifreeze in the oil, an almost certain sign of a potential head/head gasket failure.
After cooling system work the initial and easy step seems to be to eliminate potential air in the system. (Good tip Dave on removing the temp sensor to help purge air) I expect that a very rapid rise in indicated cooling system temperature is potentially a result of air in the system (sensor being exposed to steam instead of coolant) where a more gradual rise after being driven some distance is the result of a cooling system problem, head issue or other internal engine problems. (has anyone seen any data on this?)
Yes, unfortunately as Dave referred to, 2000 and 2001 4.0 engines have a head casting that is prone to cracking, especially if overheated. A cracked head and/or a bad head gasket typically allows combustion gas to enter the cooling system and results in overheating. A do-it-yourself combustion gas test using a parts store rental combustion gas tester (also referred to as block tester) and purchase of the test fluid will help eliminate or confirm a likely bad head gasket or cracked head. An oil analysis by an oil test lab such as Blackstone Labs (www.blackstone-labs.com) will identify even a very small amount of antifreeze in the oil, an almost certain sign of a potential head/head gasket failure.
Last edited by third coast; Sep 18, 2019 at 10:45 AM.
Senior Member
Joined: Nov 2017
Posts: 535
Likes: 101
From: Northern Indiana
Year: 2000, 1991
Model: Cherokee (XJ)
Engine: 4.0
As an FYI to this thread starter, a head problem is not an inexpensive or simple repair, especially when not being mechanically inclined on engine repair work or without proper tools. Also depending on how long the problem has been going on and how much overheating has been experienced significant engine wear and damage may have been done.