Running Warm Idling....

I know I know another cooling issue thread hasta I searched

When driving at low RPMs and sitting at an idle it will run warm. If I throw into neutral and rev it up a few times it will drop down to around 225.

Heres the deal. I wanted to replace the fan clutch because I was told it was bad out on the trail one day. It was running right at 210* but I had my doubts about it after it overheated on me in the desert while in some soft sand.

I installed the new fan clutch and while I was at it I put in a new Tstat (195*). This is when I started having this issue. I thought it may be air in the cooling system. I "burped" it even though its a '96 and shouldn't require it. Still no good. Took it in and had the cooling system cleaned and flushed. Same problem. The new fan clutch seems to spin more freely than the old one when it is at operating temp.

At this point I am thinking it may be the water pump or a bad fan clutch.

Just wanted to hear some opinions.

Thank you.

1996 4.0L NP231

How old is your water pump? A shop "flush" is usually a drain and fill. Unless they ran a flush and drain and filled it many times. Possibly your cooling system can still be plugged or still dirty. And or a weak water pump.

As far as I know the water pump is original Havent had the Jeep that long so there is no real way I could tell.

The shop put it on a machine to do the cleaning and flushing.

when you burped the cooling system did you remove the temp sender in the back of the block? I had a similar issue and it was a small air bubble at the temp sender.
also you may want to remove your rad and run water through it backwards to remove possible debris

hope that helps

The temp sender is actually at the tstat housing. The previous owner had a T connector at the temp sensor hole with both in the T. I removed the T and drilled and tapped a hole in the housing for the sender.

K.Hess said:

when you burped the cooling system did you remove the temp sender in the back of the block? I had a similar issue and it was a small air bubble at the temp sender.
also you may want to remove your rad and run water through it backwards to remove possible debris

hope that helps

Click to expand...

Even 225 is way too hot.

Could be wear on the water pump impeller, thus less flow, also some age old plugging of the radiator tubes, combined it results in less cooling. Also the new clutch may not be any good, weak. I gave up on stock clutches, and upgraded to the ZJ clutch.

Is the E-fan turning on? IF so it is turning on at the right temp? Some people hot wire the e-fan with a dash switch, overides the computer control. Check for an exhaust leak blowing on the side of the engine block. Check the belt tension on serp belt.

Is it all stock, if not what mods, lift?

E-fan is hard wired already. I will check tension on the belt tomorrow.
4.5" lift 33 12.50s

Ecomike said:

Even 225 is way too hot.

Could be wear on the water pump impeller, thus less flow, also some age old plugging of the radiator tubes, combined it results in less cooling. Also the new clutch may not be any good, weak. I gave up on stock clutches, and upgraded to the ZJ clutch.

Is the E-fan turning on? IF so it is turning on at the right temp? Some people hot wire the e-fan with a dash switch, overides the computer control. Check for an exhaust leak blowing on the side of the engine block. Check the belt tension on serp belt.

Is it all stock, if not what mods, lift?

Click to expand...

I have heard of issues caused by lifts, and poor air flow, causing a recycling of hot air back to the front of the vehicle at idle, especially ones where the fan and cowl system were modified like yours. So that might be adding to other weaknesses. If I had to pick which one to do first, I would replace the radiator with an upgrade, but it is easier to do both water pump and radiator at the same time. Do not buy a rebuilt or a cheap brand water pump, we have all bad luck with them. Is this with AC and overheating with AC on?

Also, check for trash in the radiator or condenser fins, blocking air flow.

This issue was present before lift.

It does have AC but it doesn't work. Never turn it on. Think about going with an OBA system instead of AC. Its not a DD so AC isn't super important.

Ecomike said:

I have heard of issues caused by lifts, and poor air flow, causing a recycling of hot air back to the front of the vehicle at idle, especially ones where the fan and cowl system were modified like yours. So that might be adding to other weaknesses. If I had to pick which one to do first, I would replace the radiator with an upgrade, but it is easier to do both water pump and radiator at the same time. Do not buy a rebuilt or a cheap brand water pump, we have all bad luck with them. Is this with AC and overheating with AC on?

Also, check for trash in the radiator or condenser fins, blocking air flow.

Click to expand...

Sounds like the aux fan isn't running. @ 225, that aux fan should have cooled things down already.

Airflow though the radiator will cool the system sufficiently when at speed. But at low speeds, the mechanical fan, and the aux fan are both required to keep things cool.

The fan should be reasonably easy to turn when cold, and harder to turn when hot. You said you replaced the clutch fan? New or Used?

Also, the AUX fan should be automatically controlled by the PCM, and some folks bypass it when on the trail due to the added heat and no airflow. IMO the OEM fan works best for air flow and fit.

-Ron

edit: A/C doesn't work? Hmmm... Clogged A/C condenser fins? That used to be a big problem with A/C equipped cars that took a rock though the grill. There is oil in the Freon and it attracts dust like nobody's business.

Replace fan clutch with a new. It has just as much resistance warm as it does cold. The electric fan is hard wired and is working. I may put the old one back on and see if it helps.

WB9YZU said:

Sounds like the aux fan isn't running. @ 225, that aux fan should have cooled things down already.

Airflow though the radiator will cool the system sufficiently when at speed. But at low speeds, the mechanical fan, and the aux fan are both required to keep things cool.

The fan should be reasonably easy to turn when cold, and harder to turn when hot. You said you replaced the clutch fan? New or Used?

Also, the AUX fan should be automatically controlled by the PCM, and some folks bypass it when on the trail due to the added heat and no airflow. IMO the OEM fan works best for air flow and fit.

-Ron

edit: A/C doesn't work? Hmmm... Clogged A/C condenser fins? That used to be a big problem with A/C equipped cars that took a rock though the grill. There is oil in the Freon and it attracts dust like nobody's business.

Click to expand...

The aftermarket XJ fan clutches are junk it seems. I upgraded the ZJ (Grand Cherokee) clutch it made a big difference on mine.

The ZJ rotates at higher % of full speed than the XJ does, and the aftermarket ones don't seem to work as well as they should. I try an oem thermostat at the same time based on your posts.

Put the old clutch back on this morning and still acted the same.

OK, now try running it with no thermostat (less restriction, less pressure drop), to get a little more flow pressure. If it still runs hot, I would go for a new radiator myself next. If it runs cooler, I would replace the water pump, and put in an OEM thermostat at the same time.

Keep in mind both fan clutches may not bee good enough. But if the coolant flow is too slow, the clutch won't any difference, good or bad, and will not get hot enough to lock all the way up even if it is new.

I used to put my questionable clutches over a gas stove top flame, or in boiling water to test the lock up!!!!