I need help... Overheating problem

[Thepepenator]

:dunno:

I have a 99 xj that is that is my daily driver for the moment as i finish my 87 MJ but shes giving me problems.

It had been overheating for a bit so i took off the thermostat, changed the radiator, installed a 12inch electric fan in front of the radiator sucking in air from the outside in, changed the AC fan, put a new fan clutch and a new fan. All of that kinda did the trick. I am driving and the temperature is slightly under 210, as soon as I stop in traffic or stoplight the temperature goes up over 210.

What could be the problem? It doesnt leak coolant. 

 

is my water pump going bad? Is it a bigger problem than that?   

 

Thanks  :banana:  . :MJ 1: .

[ParadiseMJ]

Still sounds like a fan clutch to me.  Not enough air flow over the radiator at slower, stopped speed

 

Water pump might be an issue if this was happening at speed.  Are you sure that fan isn't just interfering with the mechanical fan and e-fan...if I have this straight, you have 3 fans.  One in front of the radiator, and two behind the radiator??

[DirtyComanche]

You took out the thermostat?

 

Because otherwise it sounds 'normal.'  Your gauge probably reads wrong.  Unless sitting still and idling it just gets hotter and hotter.

 

But I would have done the water pump, or at least pulled it off and looked at it, before adding a pusher fan.  Try revving it up while you're stopped (in park/out of gear) and see if the temperature comes down at higher RPM, if so that's a classic sign that the water pump is on its way out or potentially obstructed.

[Thepepenator]

Still sounds like a fan clutch to me. Not enough air flow over the radiator at slower, stopped speed

 

Water pump might be an issue if this was happening at speed. Are you sure that fan isn't just interfering with the mechanical fan and e-fan...if I have this straight, you have 3 fans. One in front of the radiator, and two behind the radiator??

 

Exactly. 1 outside and 2 inside. I put the fan after it was heating up. It helped a little bit

[Thepepenator]

You took out the thermostat?

 

Because otherwise it sounds 'normal.' Your gauge probably reads wrong. Unless sitting still and idling it just gets hotter and hotter.

 

But I would have done the water pump, or at least pulled it off and looked at it, before adding a pusher fan. Try revving it up while you're stopped (in park/out of gear) and see if the temperature comes down at higher RPM, if so that's a classic sign that the water pump is on its way out or potentially obstructed.

It might be reading wrong but it even smells hot. But as soon as I take off it starts cooling again.

I'll try revving it. See if that helps.

Thank you

[daking]

A lot of people will remove the thermostat and "think"? it will result in better cooling. But the fact is it will cause more harm. You want the Thermostat (or at least a resistor plate) to slow the water. The Thermostat helps to keep the water pressure higher in the engine block. The higher pressure of the coolant will absorb the heat better off the iron block. A thermostat will also slow the flow of coolant, allowing to stay in the engine long enough to absorb the heat. And more importantly, keep the coolant in the radiator longer to disparate the heat. You want the water leaving the radiator to be less then ~20 Degrees cooler then when it was put in. Total system PSI is important too. The higher the PSI, the hotter you can run coolant before it boils ( makes bubbles, as air is a bad absorber of heat). The higher PSI also forces the liquid against the metal, for better transfer of heat. Don't go crazy, ~16PSI cap is fine. I've seen guys run very low PSI caps, and overheat. Also a common mistake is using too much coolant. Rule of thumb is 50/50. However, many mistakenly think, " 50% is good, so 100% antifreeze MUST be better". That is NOT the case.  But, pure water and some soap will cool much better. Issues is, no corrosion protection, and ZERO freeze protection. I have run pure water in the summer months. 

[Thepepenator]

A lot of people will remove the thermostat and "think"? it will result in better cooling. But the fact is it will cause more harm. You want the Thermostat (or at least a resistor plate) to slow the water. The Thermostat helps to keep the water pressure higher in the engine block. The higher pressure of the coolant will absorb the heat better off the iron block. A thermostat will also slow the flow of coolant, allowing to stay in the engine long enough to absorb the heat. And more importantly, keep the coolant in the radiator longer to disparate the heat. You want the water leaving the radiator to be less then ~20 Degrees cooler then when it was put in. Total system PSI is important too. The higher the PSI, the hotter you can run coolant before it boils ( makes bubbles, as air is a bad absorber of heat). The higher PSI also forces the liquid against the metal, for better transfer of heat. Don't go crazy, ~16PSI cap is fine. I've seen guys run very low PSI caps, and overheat. Also a common mistake is using too much coolant. Rule of thumb is 50/50. However, many mistakenly think, " 50% is good, so 100% antifreeze MUST be better". That is NOT the case. But, pure water and some soap will cool much better. Issues is, no corrosion protection, and ZERO freeze protection. I have run pure water in the summer months.

I use nothing but the 50/50 sold at any store.

But thank you for this! I will put the thermostat back on before working on the water pump. Just some buddies and my dad suggested that it works better without the thermostat and I have it a shot.

[Zebvance]

 

A lot of people will remove the thermostat and "think"? it will result in better cooling. But the fact is it will cause more harm. You want the Thermostat (or at least a resistor plate) to slow the water. The Thermostat helps to keep the water pressure higher in the engine block. The higher pressure of the coolant will absorb the heat better off the iron block. A thermostat will also slow the flow of coolant, allowing to stay in the engine long enough to absorb the heat. And more importantly, keep the coolant in the radiator longer to disparate the heat. You want the water leaving the radiator to be less then ~20 Degrees cooler then when it was put in. Total system PSI is important too. The higher the PSI, the hotter you can run coolant before it boils ( makes bubbles, as air is a bad absorber of heat). The higher PSI also forces the liquid against the metal, for better transfer of heat. Don't go crazy, ~16PSI cap is fine. I've seen guys run very low PSI caps, and overheat. Also a common mistake is using too much coolant. Rule of thumb is 50/50. However, many mistakenly think, " 50% is good, so 100% antifreeze MUST be better". That is NOT the case. But, pure water and some soap will cool much better. Issues is, no corrosion protection, and ZERO freeze protection. I have run pure water in the summer months.

I use nothing but the 50/50 sold at any store.

But thank you for this! I will put the thermostat back on before working on the water pump. Just some buddies and my dad suggested that it works better without the thermostat and I have it a shot.

 

 

 

AMC/Jeep payed engineers a lot of money to design a cooling system that works the most efficiently it can. Just like every manufacturer also, A thermostat was designed to help the cooling system. Car manufactures don't like wasting money, they are trying to cut cost in every way they can to stay competitive in a market saturated with to many competitors. They are not going to waste one dime on putting something in a car that does not need to be if they can help it. The thermostat in a car is just as important as the radiator and water pump. Put a new one back in there and one rated to the temp that it came from the factory with. I believe it was 190.   Also, How many miles is on the engine and is it the 4 or 6 cylinder. Has it been showing any signs of head gasket failure? Loosing coolant, sweet smell in the exhaust, not running smooth?

[Thepepenator]

 

 

 

A lot of people will remove the thermostat and "think"? it will result in better cooling. But the fact is it will cause more harm. You want the Thermostat (or at least a resistor plate) to slow the water. The Thermostat helps to keep the water pressure higher in the engine block. The higher pressure of the coolant will absorb the heat better off the iron block. A thermostat will also slow the flow of coolant, allowing to stay in the engine long enough to absorb the heat. And more importantly, keep the coolant in the radiator longer to disparate the heat. You want the water leaving the radiator to be less then ~20 Degrees cooler then when it was put in. Total system PSI is important too. The higher the PSI, the hotter you can run coolant before it boils ( makes bubbles, as air is a bad absorber of heat). The higher PSI also forces the liquid against the metal, for better transfer of heat. Don't go crazy, ~16PSI cap is fine. I've seen guys run very low PSI caps, and overheat. Also a common mistake is using too much coolant. Rule of thumb is 50/50. However, many mistakenly think, " 50% is good, so 100% antifreeze MUST be better". That is NOT the case. But, pure water and some soap will cool much better. Issues is, no corrosion protection, and ZERO freeze protection. I have run pure water in the summer months.

I use nothing but the 50/50 sold at any store.

But thank you for this! I will put the thermostat back on before working on the water pump. Just some buddies and my dad suggested that it works better without the thermostat and I have it a shot.

 

AMC/Jeep payed engineers a lot of money to design a cooling system that works the most efficiently it can. Just like every manufacturer also, A thermostat was designed to help the cooling system. Car manufactures don't like wasting money, they are trying to cut cost in every way they can to stay competitive in a market saturated with to many competitors. They are not going to waste one dime on putting something in a car that does not need to be if they can help it. The thermostat in a car is just as important as the radiator and water pump. Put a new one back in there and one rated to the temp that it came from the factory with. I believe it was 190. Also, How many miles is on the engine and is it the 4 or 6 cylinder. Has it been showing any signs of head gasket failure? Loosing coolant, sweet smell in the exhaust, not running smooth?

 

Yeah, that makes sense. I'll be putting one on this weekend. It's a 4.0 4x4 It hasn't been doing that. It runs very smooth. It has 140k miles on it. Someone had told me that the filter might be affecting it but I have a K&N Intake I just added last month so it's pretty new

[DirtyComanche]

A plugged cat can also make it run hot, if you have one and it's been in there a long time.   One of those things that people don't think about because it is not at all related to the cooling system.  Normally you get low power associated with that though.

 

Is it an oiled air filter?  I would not recommend running one if it is, but that's not related to your cooling problem.

[yxmj]

Check /change the water pump before any other "fixes.

An easy check is to remove the heater hose that comes right off the pump by the upper rad hose...use that hose (or another spare chunk) and run it from the pump into a milk jug or other container...if you have no thermostat when you start it you will get a strong stream off the pump....a weak stream....a trickle...or no flow will tell you for sure....

 

I have 3 XJ's of the same era an 2 of them have gone therough new pumps inside of 4 years...

 

Just MHO

. :MJ 1: .

[SBpunk]

http://www.jeepsunlimited.com/forums/showthread.php?364431-All-XJ-MJ-overheating-issues-explained-NOOB-s-welcomeOk...there seem to be too many threads with "my xj is overheating" or "yet another overheating thread" or "it only overheats when..." and I am going to try to answer them all and maybe we can get this to become a sticky or maybe posted somewhere.

All cherokees from the factory have a cooling system which is designed to remove heat from the engine and transfer it away. Coolant being pumped by a water pump flows through cooling jackets/passages in the head and block of the engine. It flows around exhaust and intake ports and around the cylinders. From there it goes to the radiator which had hundreds of small fins to increase surface area and that allows as much air as possible to take heat away from the coolant and the cycle repeats istelf over and over.

Chrysler opted for a mechanical clutch style cooling fan to draw air over the radiator to cool at idle and slow speeds. Some models depending on options also have an electric fan for optional A/C or towing package which turns on with a/c (on 2000 and 2001 xjs it turns on with a/c only when pressure in the lines goes past 300 psi) or when coolant temperature exceeds between 218-224 degrees F.

When working correctly and all parts are maintained, this setup works great.

Here are some reasons your cherokee would overheat (240+f) at idle but not at 30+mph:
Fan clutch worn out
Old coolant
Aux. electric fan not turning on
blocked radiator or coolant passages
Low fluid level
Low engine oil level
Water pump impeller wearing causing low flow at slow speeds
clogged radiator fins or air blockage to radiator
Damaged fan shroud
Retards who upgrade engines and leave stock cooling system


If your cherokee overheats on the highway 240+F:

Clogged passages
Stuck closed thermostat
Towing a heavy load up a grade on a hot day w or w/o ac on (temp. overheat)
contaminated coolant
bad waterpump
clogged radiator fins
blocked airflow
brakes sticking/ebrake on

If you overheat on the highway and NOT at slower speeds / idle:

partial blocked passages not flowing enough for highway engine demand but flows enough at idle.
Radiator blocked or fins clogged for same reason above
Brakes sticking
Overloading


Also, xj's have tight engine compartments and they will run 220ish in the summer with a/c on or off and that is NORMAL for xj's. Other vehicles have different coolant temps that they are designed to run well at so don't do too much comparing such as " my Taco runs 210 even though I beat it half way to hell) Thats great...I only like taco from taco bell and the one she gives me...but anyway

Another thing to note...fan clutches run about 40bux new depending where you go. With personal issues there is no TRUE way to test a clutch because they fail soo many ways (trust me). Next time your engine is getting very hot, open the hood and feel the air the fan is pulling...rev er up some and if its not hurricane force, then replace that clutch. With the new body style xj's they upgraded the E-fan to a higher flow rate...so that might be an option for upgrades.
Please add on if you have anything extra.
Thanks for the sticky!

 

[Thepepenator]

A plugged cat can also make it run hot, if you have one and it's been in there a long time.   One of those things that people don't think about because it is not at all related to the cooling system.  Normally you get low power associated with that though.

 

Is it an oiled air filter?  I would not recommend running one if it is, but that's not related to your cooling problem.

no, its not an oiled air filter.  

[Thepepenator]

Check /change the water pump before any other "fixes.

An easy check is to remove the heater hose that comes right off the pump by the upper rad hose...use that hose (or another spare chunk) and run it from the pump into a milk jug or other container...if you have no thermostat when you start it you will get a strong stream off the pump....a weak stream....a trickle...or no flow will tell you for sure....

 

I have 3 XJ's of the same era an 2 of them have gone therough new pumps inside of 4 years...

 

Just MHO

. :MJ 1: .

thank you!!  ill check it out 

[Thepepenator]

http://www.jeepsunlimited.com/forums/showthread.php?364431-All-XJ-MJ-overheating-issues-explained-NOOB-s-welcomeOk...there seem to be too many threads with "my xj is overheating" or "yet another overheating thread" or "it only overheats when..." and I am going to try to answer them all and maybe we can get this to become a sticky or maybe posted somewhere.

 

All cherokees from the factory have a cooling system which is designed to remove heat from the engine and transfer it away. Coolant being pumped by a water pump flows through cooling jackets/passages in the head and block of the engine. It flows around exhaust and intake ports and around the cylinders. From there it goes to the radiator which had hundreds of small fins to increase surface area and that allows as much air as possible to take heat away from the coolant and the cycle repeats istelf over and over.

 

Chrysler opted for a mechanical clutch style cooling fan to draw air over the radiator to cool at idle and slow speeds. Some models depending on options also have an electric fan for optional A/C or towing package which turns on with a/c (on 2000 and 2001 xjs it turns on with a/c only when pressure in the lines goes past 300 psi) or when coolant temperature exceeds between 218-224 degrees F.

 

When working correctly and all parts are maintained, this setup works great.

 

Here are some reasons your cherokee would overheat (240+f) at idle but not at 30+mph:

Fan clutch worn out

Old coolant

Aux. electric fan not turning on

blocked radiator or coolant passages

Low fluid level

Low engine oil level

Water pump impeller wearing causing low flow at slow speeds

clogged radiator fins or air blockage to radiator

Damaged fan shroud

Retards who upgrade engines and leave stock cooling system

 

 

If your cherokee overheats on the highway 240+F:

 

Clogged passages

Stuck closed thermostat

Towing a heavy load up a grade on a hot day w or w/o ac on (temp. overheat)

contaminated coolant

bad waterpump

clogged radiator fins

blocked airflow

brakes sticking/ebrake on

 

If you overheat on the highway and NOT at slower speeds / idle:

 

partial blocked passages not flowing enough for highway engine demand but flows enough at idle.

Radiator blocked or fins clogged for same reason above

Brakes sticking

Overloading

 

 

Also, xj's have tight engine compartments and they will run 220ish in the summer with a/c on or off and that is NORMAL for xj's. Other vehicles have different coolant temps that they are designed to run well at so don't do too much comparing such as " my Taco runs 210 even though I beat it half way to hell) Thats great...I only like taco from taco bell and the one she gives me...but anyway

 

Another thing to note...fan clutches run about 40bux new depending where you go. With personal issues there is no TRUE way to test a clutch because they fail soo many ways (trust me). Next time your engine is getting very hot, open the hood and feel the air the fan is pulling...rev er up some and if its not hurricane force, then replace that clutch. With the new body style xj's they upgraded the E-fan to a higher flow rate...so that might be an option for upgrades.

Please add on if you have anything extra.

Thanks for the sticky!

 

 

thank you! 

[coathanger37]

Just to add to all the confusion. If it overheats under load but not at idle. Possible blown head gasket or if you really unlucky a cracked cylinder wall (I had it happen several years ago).