Hi, the engine in my 93 4.0L did run hot, i changed the termostat since the old one didnt open, but its still hot, not as hot as before, but hot (110c). today i removed the waterpump to check, but thats all fine. I then tok out the termostat and now its running at 70c, strange. I have boiled both termostat and the old one didnt open much but the new one did open full at around 90c. I will run some days without termostat to see how its working, but could there be some pressure in the system that prevents the termostat from opening?

It tok me 4 hours to take out the waterpump, take out the termostat, clean and flush the cooling system and put it all in place again, and this is my first time ever removing a waterpump. Its a nice car to work with :-)

 

235f is hot, although 220f is not "that" hot. The 4.0l typically run 210 to 215. They can also be a pain to burp all of the air out of the system. If the air is still in the system it will run hotter.

Ron

 

Do NOT run without the t-stat, keep a 195 degree t-stat in there.

 

But my problem is that when i have a 190F t-stat in there the engine get realy hot. I'm 100% sure that its open at 190-195F but the engine still get up to 230-235F before it goes down to 215-220F, without t-stat its around 160F. I have used radiator cleaner and flushed the system and i will run some days without t-stat.

Is there some trick to get all the air out of the system if thats the problem? When i replaced the temperatur sender (back on the engine) it didnt flush much water out of the hole, i could see the water. Could there have been a air pocket where the sender was and that i got that away when flushing and refill the system?

 

Stupid question, did u have teh thermostat in right? Spring end in the head?

 

he he, yes, its not possible to not insert it right :-)

 

I was running hot as well.. 220-230. The coolant levels were fine and the coolant looked brand new. I was going to replace the tstat and water pump all at once but then I decided to test the fan clutch. That was my problem. Swapped a new one in and have not been above 210 since. Might be worth looking at.

 

What the condition of your clutch fan its it has no resistance its shot and to bleed it run the truck with the rad. cap off till no more air bubbles come out

 

Here is a rundown:

1. Make sure you have the proper mix of coolant and water
2. Make sure to get any air pockets out.
3. Make sure you have no obstructions on your radiator.
4. Make sure your fan shroud is in good shape.
5. Test the fan clutch.
6. Check the water pump and water pump belt.
7. Check/Replace the Coolant Temp Sensor or CTS. It's on the T-Stat housing. Check its electrical connection.
8. Check your oil, make sure it is at the right level.
9. Make sure your air filter is clean.

The coolant temp sensor part number is SU326 at AutoZone. It is a Duralast part. This part number is for a '93 4.0L which is also what I have. My other Jeep, '93 XJ 4.0L kept over heating even after a T-stat change, coolant change and CTS change. In the end it was the water pump.

 

you have a restriction possible the bottom of the radiator internally the hotter the T-dtat the longer coolant sits in the radiator but you don't have rad compacity to cool it/ no T-stat sends it faster

 

I have to drive my Jag up on ramps to get the front as high as possible to get the last air bubbles out of it. Maybe that idea will help you.

The V-12 has 2 bypass T-stats to help warm up the engine quicker. Because of that, it runs even hotter when the T-stats are removed!

 

updates:
Changed the radiator since it was a litle leak in it
Changed the fan clutch
changed the termostat to a 82celsius
Changed the temperatur sensor, but i got the first one wrong from jeep4x4center since it show to low ohm, i think the supplier have made them wrong since it follow the ohm table from older cherokees.
Changed the temperatur sender since the gauge didnt work
Flushed the system 3 times.

The temperatur gauge still show hot, but if i use a ohm meter i read that the temperatur is arround 85 on the temperatur sensor and if i use a oven cooking temperatur the water in the radiator is arraound 85. I havent tested the temperatur sender, but could it be that the sender also have wrong resistance? Is there different types (ohm) temperatur senders like there is different types of temperatur sensors?

 

Most likely just your gauge but make sure you don't have a HA t-stat...I've had that happen to me before.

 

Updates:
boiled my temperature sender and its correct, about 115ohm at 100celsius. I did then take a 115ohm resistor and tested the gauge and thats correct to (100 celsius). When i took out the temperature sender it did came coolant out of the hole, not much, and if i touched the radiator hose it came more coolant out.
After i put it back in i took it for a litle ride and after 5min its 110celsius. I then parked the car and let it run on idle, the fan didnt run very fast, but thats because the coolant isnt 110celsius, its arround 85 if i measure the ohm on the temperatur sensor (in thermostate house), i can touche the radiator hose and the heater hose and its not as hot as it should have been if the water is 110celsius.
After 20min on idle it got a little bit hotter (not the gouge, thats on 110celsius) and the fan started to run at full speed (same speed as the waterpump) and did that for a litle while, then it slowed down. But the water in the radiator isnt very hot, i can hold my hand on the radiator.
Could it be some air trapped in there some place arround the temperatur sender that make it hotter than it should be?
The pressure in the cooling system is okey, if i try to press the upper radiator hose i feel its hard to press and the level in the reservoar rise, the first times after flushing and refill the hose was softer because of air inside and it burped in the reservoar.
I parked the car in a steep slope with the front up and let the engine run to and opened the thermostate to release air.
The good thing is that i cant get it over 110 celsius :-)