230 degrees

My son purchased a 1995 XJ yesterday that while on the test drive was fine. Owner was original and had service records and reciepts.

After purchasing the vehicle, he noticed that the coolant temps on the dash gauge where running about 230 degrees. We pulled off the freeway and sat for 10-15 minutes and the vehicle cooled to normal temps. We even called the guy back and he said never had a problem with it. I was immediatly suspect of a head gasket as I had a Grand Cherokee that only overheated at highway speeds but would cool down at street speeds. This is not the case as he was out driving around today on surface streets at 45mph with the same results.

According to the repair records the water pump was replaced in 2010 as was the radiator prior to that, with what he explained as a three row brass cooler.

Is it possible for a T-stat to cause this type of scenario? it is hard for me to tell if coolant is circulating because the filler neck is not directly over the tank.

I did notice a lot of bubbles/foam when i took the cap off which made think head gasket or could a cavitating water pump do the same?

Baffled and need to address soon before his mother sends me to dog house.

The gauge in my '95 is incorrect. it reads 15* high. The gauge is no longer available so I had to install an aftermarket

As mentioned, check the temperature gauge. Mine also reads a bit high.

However, the biggest thing that resolved my cooling issue (besides a new radiator, motor, water pump, alternator, thermostat, fans, etc) was changing the fan clutch. They are hard to check to verify proper operation, but can cause issues with a load, almost regardless of the speed. If the fan clutch isn't audibly howling (amount of howl depends on fan type), then I'd consider replacing it.

David Bricker / SYR

As mentioned, the first thing you must do is verify. Get a point and shoot laser thermometer (widely available and cheap now, a great tool to have) and point it directly at the thermostat housing of a hot engine.

Then you'll know. Don't want to be chasing a ghost.

You can also check if the electric fan is coming on at this supposed 230 degrees. I'm not positive but I *think* your '95 has separate gauge sender & computer sensor. If so, you can check the gauge against the computer : the computer will turn the fan on when it sees 220 degrees.

I don't see any indication mentioned of a head gasket problem. Just because it got hot does not point immediately to a head gasket. As you mentioned (and others) since the radiator is 5 yrs old and it overheated on the freeway at speed I'd be looking at coolant (level, condition, circulation) issues.

4-5 yrs. on a water pump and/or radiator could be a long time if not recently flushed/filled/checked. 4-5 yrs could also be a short time if properly maintained and it sounds like the guy kept records and such. I had a 3 row on my XJ that was clogged after about 5 yrs. 3 rows are not necessarily better (smaller channels).

Do some more diagnoses, fans, pump, coolant, heater core, etc. Change the oil, see if there is any goop in there. Then go rent a block test kit to rule out a head gasket or cracked head which would be last ditch as far as I'm concerned, especially on a 95.

start the troubleshooting with simple stuff..... look at the radiator / AC condensor. is it packed with bugs or dirt? accesory belt condition and tension?
fan clutch wont contribute to over heating if the vehicle is in motion under normal driving, plenty of airflow for a normal system.
if the radiator is really a decent brass unit, it's worth pulling and having it cleaned profesionally if a good system flush ease your pain.
pull off the upper radiator hose and inspect the inside of it. often times a seller will fill a cooling system with stop-leak to try to keep the vehicle from coming back. inside the hose will tell you if anything was added.

Thanks guys, all really good suggestions and all seem to be consistent. We will start checking piece by piece this weekend and I will post our results.

I agree with David bricker. Clutch fan. They are really hard to tell when they are going out. They cost about $35.You may also want to think about down the line hood louvers.they really work.it dropped the temp of my engine bay by 40 degrees. My hood would get so hot that I had to use a shop rag to open it. On really hot days you could actually see the heat go out the louvers

PSoffe said:

Thanks guys, all really good suggestions and all seem to be consistent. We will start checking piece by piece this weekend and I will post our results.

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Update?

I have a 95 and just changed the clutch fan! I replaced it with a ZJ of the same year but 4.0. Compare the two clutches at the auto part store and you will see that for $20.00 more the ZJ part even looks like it will last longer. It's heavier and bigger in diameter! When you install it, don't stand in front of the grille cause you could get suck thru it (just kidding). Listen to what I'm saying and you will be happy!

run the heater on full hot when its overheating, and if there is hot air coming out, then your coolant system is functioning (ie: tstat is open). Could be a sticking t-stat, but would be more suspect of the fan and / or head gasket. The head gasket could be easy to test for with a little kit from an auto parts store.

My 96 XJ would reach the 220-230 mark during the summer if it idled for a long period of time in stop and go traffic. The previous owner had it checked by a mechanic and he said that the problem was the gauge. I've noticed that even though the electric fan would turn on at 220 degrees the clutch fan was barely moving any air even when the engine was revved. Replaced the fan clutch and the over heating went away completely.

So here is where we are at with the cooling system.
Replaced the T-Stat with a 195 and flushed the coolings system, Lots of sludge in the bottom of the recovery bottle and really murky coolant. Replaced with 50/50 coolant. Temps never got over 200. Appx. two weeks of commuting at hiway speeds everything was fine and then the temp spiked one afternoon and pinned the temp gauge started running rough. Came home on the hook! Pulled the t-stat and tested it worked fine (it was a failsafe and was locked in the full open position) replaced with a non failsafe type, flushed the system again everything clear, replaced lower hose as it was pretty oil soaked from the steering box and feared it may be collapsing under high rpms. By the way there was no spring in the lower hose and called several shops to see if one existed, no luck. Drove no change, replaced the fan clutch and viola! everything normal until today. Took it out for a run around town hit the freeway and the temp climbed to 220, after a a 5 mile return trip parked in driveway and let idle and temp came down after about 15 minutes. Aux fan is working.

So guess the next step is checking for a bad head gasket. I have seen no indication in the oil or at the tailpipe of any evidence of a blown head gasket i guess its time to by a hydrometer and test the coolant.

:smsoap:

Thoughts?:

Did you actually confirm actual temp vs gauge? What are your ambient temps when driving? When was the last time trans was serviced?
If auto, the "cooler" is in the side of the radiator,if running warm/hot could possibly affect coolant temp. System bled properly? Not sure if 95 still has coolant sender in the back of the head, but a common place for air to sit.

220-230 seems a bit high, but not that bad. The temp gauge on my '96 has 210 right in the middle and it's been my experience that this is where you want it at on pretty much all vehicles. Cooler does not always equal better, and in fact can be just as bad as overheating. For what it's worth, a 50/50 mixture of coolant boils at 218 F and a 16 PSI radiator cap should increase that boiling point to 268 F.

It is an A/T , haven't serviced it since we purchase a few months ago. Ambient temps have been in the mid 80's to low 100's. Yesterday was mid 80's. There is a temp sending unit of some kind on the side of the T- housing. We had originally purchased a infra red thermometer and where getting readings very close to the factory dash gauge and readings where consistent with different test locations. Seeing variances from the inlet side to outlet side of Rad. Also driveway has a 4-5 deree angle to it so everything running up hill for system bleed.

You said it was full of sludge, did you take it to a Radiator shop to get it and the block flushed right? The junk we buy at the store won't clean a radiator as good as they can. I stopped wasting my money on that years ago.

I would consider replacing the radiator and water pump as well as putting a spring in the return line and getting a IR gun to verify temperature.

CompleteCherokee said:

run the heater on full hot when its overheating, and if there is hot air coming out, then your coolant system is functioning (ie: tstat is open). C

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The heater core has a t-stat bypass. The heater will work even if the t-stat is closed.