I keep getting mixed answers on this. I flushed the radiator and add new fluid. But it seems my engine is still overheating (P.S. what is recommend amount of engine oil do I put in a 4.0L?)

BUT I keep getting mixed answer saying I should just run without a mechanical thermostat and I was also told if I run without one I risk cracking my block. So which one is true?

 

The t-stat is there for a reason - quick engine warm-up. It only controls MINIMUM engine temp. If flushing hasn't worked u probably need to replace the rad, fan clutch and water pump. 6 qts of motor oil with a new filter. Oil level should be between the 2 marks on the dip stick.

 

I second the replace the radiator.
I wouldn't worry with the water pump if its not leaking.
There is times when a engine will run hotter without a thermostat than with one. The coolant flows to fast through the engine to absorb the heat.

I've found the XJ radiator is boarder line large enough as it is, add in a few years of scale and corrosion build up and it doesn't take long to overheat in any kind of pull situation.

 

and if you get a new rad, get a 3 row

 

i had that same problem and now that i fixed it my jeep runs at about 160*driving and 170-180*idle and i live in Mesa,AZ. what kind of cooling system do you have, are you a renix or newer

 

LISTEN to this guy bud he'll give you the right answers and no bullshxx.

 

What did u do to "fix it" and get those low coolant temps in AZ??????????

 

I dont think I would want to run that cool. could'nt that cause some sludge build up? I am sure it would cause bad MPG.

 

I'm questioning that it actually runs that cool.

 

160* is too low of an operating temp for this engine, it is designed to run at 210*.

A two row radiator would be sufficient to keep everything cool. A three row rad requires fans that move a lot of air. The thicker core of a three row actually impedes air flow and can do more harm then good if not paired with strong e-fans.

 

160* is too low of an operating temp for this engine, it is designed to run at 210*.

A two row radiator would be sufficient to keep everything cool. A three row rad requires fans that move a lot of air. The thicker core of a three row actually impedes air flow and can do more harm then good if not paired with strong e-fans.

 

Me thinks it was designed for the factory gauge to indicate 210F.

 

running without thermostat will cause the engine to in what is called open loop meaning the cumputer will run it rich thinginig it not warmed up trust me when i bought my 92 xj it had no t-stat had to replace radiator and have d-carbonized

 

This is 100% incorrect. Running without the Tstat during the winter could cause this to happen. But during a hot summer day. Just the opposite will happen. You WILL over heat. Like stated above, the factory radiator is crappy to say the least. The 4.0 is designed to run at 210 (stupid if you ask me). I would replace the radiator, and if you have the older closed loop style system then do yourself a favor and upgrade to the open loop system. And get a 2 row radiator at the minimum. If it were me I would look at a getting a double pass aluminum radiator and just making the hoses work.

 

lots of good advice so far, but I like to add my 2cents also lol, if you end up pulling the rad for replacement, do a good flush, and you may want to look into a new pump/thermostat/hoses.

you can bet the rest of the system isn't in much different condition than the bad part, and if you have the rad out already it makes all that other fun stuff easy to get to.

just some food for thought, also it gives you peace of mind, and in most cases replacing a bad part (at least in my experience) stresses the next worn part in the system....and you end up doing it anyways. It costs more, but imho is better down the road.