Another cooling question..

I hate to do this, and fwiw I've done plenty of reading..

Recently on hot days (100*, and at 4500' of elevation) I've been nudging up past 210, almost to 230 on one occasion. The interesting thing is that this is not affected whether cruising on the highway or sitting at a stop light in town, also ac on and off didn't seem to make a difference.

When the outdoor temps are lower (90*) it's been fine. The only exception has been driving up a canyon at 6+% grade where I've seen it nudge just up to 215 or so. Additionally, on the way down the same canyon, engine braking in 3rd and 2nd the engine temps actually dropped to 200.

Did a coolant flush a couple years ago, as well as the water pump. Otherwise afaik everything is original. I can feel the metal support in the lower rad hose so I presume that's fine. The coolant still looks good but I will flush it.

Other than a coolant flush where would one start? I don't have any intention of 'upgrading' anything, other than perhaps going to a 2 or 3 row rad.

99 XJ, 4.0, AW4, 33's, regeared with 4.10's. I've spent plenty of time crawling with high outdoor temps and never had the temp go above 210 before recently.

Thanks!

The genuine Jeep 2 row Heavy Duty radiator is all you will need unless you live and work in Death Valley.

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 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.

-Use a flushing/cleaning solution to remover mineral buildup or rust, 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 boil overs and/or allow the coolant flash over into to steam. You will see the coolant temps suddenly jump from 210* to the Red Zone and back to 210* if your radiator cap is weak.
-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.

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

What always bothers me about post's related to cooling problem's is that the op never say's how many miles are on the vehicle, especially the engine.
So how many miles are on it?, regardless of tire size, gearing and what you flushed it with.

I find that after 3-4 years I usually need to tighten some hose clamps just a 1/2 turn or more as they start to loose the prefect seal (the rubber extrudes, and flattens). But they do not leak visible fluid, you just see a trace of dried fluid at the hose to nipple seal area. It shows up as a slow fluid level drop in the bottle over time, or as a mild increase in peak temps on the hottest days.

Yours may be a mild film forming on the radiator tube guts and/or dirt on the outside of the radiator. Is the E-fan cutting on at the right temp, and is the dash gauge reading right?

Transpoquick said:

What always bothers me about post's related to cooling problem's is that the op never say's how many miles are on the vehicle, especially the engine.
So how many miles are on it?, regardless of tire size, gearing and what you flushed it with.

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Mine is an 87 with 288,600 miles on it (engine and body) and it runs nice and cool even with the AC on max, in 90% humidity on 105 F days in Houston, in stop and go traffic for hours. Miles are irrelevant.

Ecomike said:

Mine is an 87 with 288,600 miles on it (engine and body) and it runs nice and cool even with the AC on max, in 90% humidity on 105 F days in Houston, in stop and go traffic for hours. Miles are irrelevant.

Click to expand...

I disagree w/ miles are irrelevant, but the other part of the post is.

Radiator might be at its limit for heat transfer. Mine stopped working on hot days after the winch bumper went in front of it.