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4.0 cooling problem?

N

NVRwheels

NAXJA Forum User
Location
Cary, NC
Okay so I just put a fairly new engine (73K) in my XJ. I have put 160 miles on it and the engine runs GREAT. But today after takin it on the highway for 15 minutes I pulled off and parked and when I got out coolant was pooring out the overflow bottle.

Now the engine seemed hot but I have no way of telling b/c i have the damn idiot gauges still from my old engine and the sensor don't work b/c the new engine had good gauges.

So could this be an overheating issue or something with the radiator not circulating the coolant or what?
thanks,
Jake
 
Assuming the cooling system is in good condition (ie. clean coolant, radiator has good coolant flow thru it) there are a few things to check for proper operation.... Thermostat, electric fan, clutch fan and water pump....

Once the engine cools down... you need to ensure there is coolant flowing thru the radiator once the thermostat starts opening....

What year XJ do you own...? <1991 or >1991
Does it have an open cooling system or the closed one?
 
ehall said:
the most likely cause is that you filled the overflow bottle all the way to the top and it spilling out when the coolant expands

what year is the vehicle/engine
Click to expand...

THat would make sense, I filled the radiator with coolant and then when the thermostat opened it sucked it into the block then I topped of the coolant in rad. and filled overflow to top.

its a 1996 XJ 1996 4.0 out of another XJ

I would be able to tell what temp. it is but I can't the damn dash over the steering wheel to put the new cluster I picked up today in.
 
CharlesS said:
Assuming the cooling system is in good condition (ie. clean coolant, radiator has good coolant flow thru it) there are a few things to check for proper operation.... Thermostat, electric fan, clutch fan and water pump....

Once the engine cools down... you need to ensure there is coolant flowing thru the radiator once the thermostat starts opening....

What year XJ do you own...? <1991 or >1991
Does it have an open cooling system or the closed one?
Click to expand...

Well I got a new cluster in and it is definitely running hot. The engine only has 73k and I know the thermostat is good and am pretty sure the water pump is to. Both fans work great. The only thing from the old motor is the radiator so thats why im leaning toward that. If i start the jeep with the cap off all that happens is the coolant just sits in the radiator and doesn't flow, same with when the xjs off. I will flush it tonight and see what comes out.
 
well if coolant was coming out the overflow then it was coming out the radiator cap so hot fluids were definitely go into the radiator

do you have the right relief cap on the radiator? there are plain old caps and then there are relief caps, the latter are 2x the price but are needed for this vehicle
 
Are you sure that you've gotten the air bubble out of the head? There is a space in the head above the thermostat. If the sensor is in an air bubble, and not immersed in coolant, you'll get an abnormally high reading.

Several years ago, when I replaced the head on my 94 4.0l, it took almost 300 miles of highway running before my temp gauge finally settled down. It'd read high, then low (when it got splashed,) high, low, lather, rinse, repeat.

There are a couple of ways that you can try and get rid of that pesky bubble. One of them is to raise the rear of the XJ so that the temp sensor hole at the rear of the head is now higher than the front of the block, and fill in through that hole.
 
ehall said:
well if coolant was coming out the overflow then it was coming out the radiator cap so hot fluids were definitely go into the radiator

do you have the right relief cap on the radiator? there are plain old caps and then there are relief caps, the latter are 2x the price but are needed for this vehicle
Click to expand...

No idea what my rad cap is its just the one that came with the jeep how can I tell?


ChiXJeff said:
Are you sure that you've gotten the air bubble out of the head? There is a space in the head above the thermostat. If the sensor is in an air bubble, and not immersed in coolant, you'll get an abnormally high reading.

Several years ago, when I replaced the head on my 94 4.0l, it took almost 300 miles of highway running before my temp gauge finally settled down. It'd read high, then low (when it got splashed,) high, low, lather, rinse, repeat.

There are a couple of ways that you can try and get rid of that pesky bubble. One of them is to raise the rear of the XJ so that the temp sensor hole at the rear of the head is now higher than the front of the block, and fill in through that hole.
Click to expand...

Well I just put coolant in regularly, I put coolant in radiator, started jeep, thermostat opened and sucked coolant in, topped off coolant and then the resivor.

Anyone else?
 
When you say you are topping off the reservoir, are you filling to the full line or to the lid? If to the lid, you're too full!

The easiest thing to check and overlook is the radiator cap itself. When it is not working correctly the pressure of the system gets all funky. The purpose of the cap is to raise the boiling point of water. Ours is a 16lb cap, and raises the boiling point from 212F to around 260F. So therefor if your cap is bad, it lowers the boiling point possibly back down to 212 which is where the 4.0 wants to be. I'm pretty sure that if you're spewing out the reservoir, then your thermostat is opening. The next thing is the water pump. One thing that happens fairly often is in aftermarket pumps they aren't always reverse rotation, which is needed for a serpentine belt setup. Is the pump on there aftermarket or the original (if it's the original from 96 and only has 76kish miles then I'd almost bet on crusty impellers)? But nothing beats a good old pressure test for a cooling system.
 
Arkansas91XJ said:
When you say you are topping off the reservoir, are you filling to the full line or to the lid? If to the lid, you're too full!

The easiest thing to check and overlook is the radiator cap itself. When it is not working correctly the pressure of the system gets all funky. The purpose of the cap is to raise the boiling point of water. Ours is a 16lb cap, and raises the boiling point from 212F to around 260F. So therefor if your cap is bad, it lowers the boiling point possibly back down to 212 which is where the 4.0 wants to be. I'm pretty sure that if you're spewing out the reservoir, then your thermostat is opening. The next thing is the water pump. One thing that happens fairly often is in aftermarket pumps they aren't always reverse rotation, which is needed for a serpentine belt setup. Is the pump on there aftermarket or the original (if it's the original from 96 and only has 76kish miles then I'd almost bet on crusty impellers)? But nothing beats a good old pressure test for a cooling system.
Click to expand...

As far as I know its the original water pump, how would I be able to test if its the rad. cap?
also how do you do a pressure test for a cooling system?
thanks,
Jake
 
go to autozone and ask for the cooling system pressure test kit. all it is is a hand held pump that pressurizes the system that allows air to escape from any leaks or small holes in the system.
 
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