• NAXJA is having its 18th annual March Membership Drive!!!
    Everyone who joins or renews during March will be entered into a drawing!
    More Information - Join/Renew
  • Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

Time for another overheating thread

omwtwys

NAXJA Forum User
Location
ventura ca
Looking for some suggestions on what to do next. My 88xj i6 overheats irregularly. It has been upgraded to the open coming system. The first time in recent history that it over heated it was being driven at 55mph on a highway for about two hours. I replaced the thermostat, flushed the coolant and refilled properly. I let it idle on my driveway for 1 hour with no problem so I thought everything was good. I drove it for a couple of days, then the coolant began spewing out of the overflow tank as I was parking after an hour drive.

System was re filled properly, no coolant in the oil and no white smoke from the exhaust pipe. Coolant level doesn't drop. Fan clutch seems to be working properly, no kinks in the hoses. Only things I can think of are faulty water pump or clogged radiator. Anything else I should be looking at?
Thank you
 
You should be looking at everything.

Overheating can be caused by anything that decreases the cooling system’s ability to absorb, transport, and dissipate heat, such as a low coolant level, loss of coolant (through internal or external leaks), poor heat conductivity inside the engine because of accumulated mineral deposits in the water jackets or radiator, a defective thermostat that doesn’t open, poor airflow through the radiator, a slipping mechanical fan clutch, an inoperative electric cooling fan, a collapsed lower radiator hose, an eroded or loose water pump impeller, leaky frost plugs, or even a defective radiator cap.

The cooling system is a group of related parts that depend on proper function from each of its component parts to keep the engine cool. Service the cooling system and replace any under-performing or suspected weak parts. Any component part of the cooling system that is not fully doing its job will stress the others, and your engine will overheat. Temperature creep on the 4x4 trails, at idle, or in stop-n-go traffic, points to a weak or failing mechanical fan clutch or worn out water pump fins.

The most important maintenance item is to flush and refill the coolant periodically. Coolant should be replaced every 36,000 miles, or every two to three years. Anti-freeze has a number of additives that are designed to prevent corrosion in the cooling system, but they have a limited life span. The corrosion causes scale that eventually builds up and begins to clog the thin flat tubes in the radiator and heater core, causing the engine to eventually overheat.

-Inspect/test or replace the mechanical fan clutch. A worn fan clutch will allow temperature creep at stoplights, in heavy traffic, and on the 4x4 trails. A fan clutch that “looks” OK is not the same as working OK.
-Inspect the electric cooling fan and the fan relay. Apply 12 volts and make sure the fan runs. Exchange the cooling fan relay with one of the others similar relays. Confirm that the e-fan starts when engine temps reach 215-218*. Repair or replace the fan or relay as needed.
-Inspect/test or replace the coolant temperature sensor that activates the e-fan.
-Replace the water pump. The pumping fins can deteriorate over time and the pump will not flow enough coolant to keep the temps under control.
-Inspect/replace the radiator hoses. Make sure the coiled wire is installed in the lower hose.
-Inspect all of the freeze plugs in the block and the ones on the backside of the head for rust holes and coolant leakage.
-Use a chemical flushing/cleaning solution to remove mineral buildup or rust, flush with clean water, and then drain and fill the radiator with a fresh 50/50 coolant and water mix. With neglected cooling system you may have to flush several times.
-Inspect the radiator for mud/bugs/grass clogging the outside and mineral deposits clogging the inside. Clean or replace as needed.
-Replace the thermostat with a genuine Jeep 195* thermostat. Cheap thermostats are cheap for a reason.
-Replace the radiator cap if your Jeep has one. An old worn out radiator cap will allow not hold system pressure which can cause boil overs and/or allow the coolant flash over into to steam. You will likely see the coolant temps suddenly jump from 210* to the Red Zone and back to 210* if your radiator cap is weak.


If you have covered all the points listed above and still have overheating issues, inspect and test the head for cracks and head gasket for leaks. Exhaust gasses entering the coolant can raise the temperature of the coolant or cause steam pockets in the coolant that will temporarily block the flow of coolant.


Read more about cooling systems here –
www.offroaders.com/tech/engine-overheating.htm
www.carparts.com/classroom/coolingsystem.htm



.
standard.jpg
 
How do you know this? "Coolant level doesn't drop"

I'd pull and replace the overflow hose to the coolant overflow bottle and replace the cap with a tested cap next.

Replace the fan clutch, use OEM or get a ZJ fan clutch

Also, I had your problem for years, turned out the exhaust manifold flange donut was bad and only leaked under load on the freeway long enough to over heat the oil and oil pan that worked its (heat) way into the coolant slowly on a long drive. temps peaked when I got off the freeway.
 
has a fresh radiator cap.

I ran it without the cap ant the coolant had a bubble popping up about every 5 seconds? Does it look like a head gasket leak?

thanks
 
Rent a block tester kit (free rent, just a security deposit) and buy the test fluid, and test for exhaust gasses in the radiator cap outlet.

has a fresh radiator cap.

I ran it without the cap ant the coolant had a bubble popping up about every 5 seconds? Does it look like a head gasket leak?

thanks
 
If you suspect a head gasket leak, purchase a leak test kit for combustion byproducts in coolant.
 
How did you do the open conversion?
If it was with the use of the radiator fill hose adapter it can cause the symptoms you are experiencing if its installed to close to the block or to below the top of the radiator.
 
Back
Top