XjCivic1993

My 95 cherokee xj will get up to the white line right before the red starts before 260. It goes down if i turn the heat on but idk what it could be. The thermostat, water pump, radiator, hoses, and heater control valve have all been replaced and its not losing coolant.

NewbJeep

Are you driving highway or sitting when this happens?

XjCivic1993

Driving about 45 max in traffic. My brother drove it 2 years ago on the highway and it got hot so he turned the heat on. Hes in germany now so it has been sitting since then

NewbJeep

I'm betting something is clogged. When was that stuff replaced and was a flush done before replacing? Sometimes stuff gets knocked loose and with those temps at that speed, the coolant isn't flowing.

XjCivic1993

Man i have no idea. I asked him if he flushed the coolant but he couldent remember but im sure he did.

nakosd

Another important thing is that the larger cooling cavities such as the heater core and the cylinder head can produce rust (very quickly in fact) if you have ever had to run it on water, even for a short time before refilling it with coolant. The internal surfaces in the head and the heater core will eventually start to scale from corrosion, and in the worst case scenario can be completely covered in rust.

A rust coated cylinder head will not conduct heat as well as a clean one, which means the coolant can't do its job quickly enough, and the engine will run hotter.

I know this because I had to replace the cracked 0331 head on my 2000 XJ a few years and ago, and had to resort to running it on water for over a week to get to work before I could do the teardown, and when I pulled the water pump off I could see the entire internal surface of the cylinder head coated in rust. And I did in fact notice a significant improvement in my jeep's cooling capability after installing the new head. Idling at a packed stoplight in 100 degree weather the temp gage would quickly rise to the final white line, and after the head was replaced I could idle in the same conditions pretty much indefinitely as the electronic fan was able to keep the temp down.

So even after replacing every other component, this brown stuff can eventually detach and get sucked into the cooling stream and begin to clog the radiator. Also important to note that the mechanical fan clutch is prone to failure, and I'm sure it can still help cooling even when cruising at 45 mph.

One easy way to check for rust in the system is to just take the radiator cap off and if you see any sort of mud or sediment collecting in the neck or sticking to it, then its likely that a component in the system has or had rust.

XjCivic1993

I just flished the coolant and put a new cap on the radiator and shes running hood now!

'90Cherokee

First verify that it's actually running 230 with another gauge, I use an infrared thermometer on the thermostat housing. If it is actually running 220 then it's likely a bad thermostat.

'90Cherokee

I've had mine get pretty hot, almost into the red. I was off-roading on a very hot day with the A/C on pulling a long slow climb and found that the fans just couldn't pull enough air to keep it cool. A/C off helped and when we'd stop I put in N and raise the revs which also helped. On that trip I found out that even a new fan clutch allows a lot of slippage. Another guy was overheating repeatedly so I used wire to lock the fan to the clutch and that kept him from overheating, and the fan was very much louder further proving that it was spinning faster.

As for numbers, I wouldn't worry at 220. At 230 I wouldn't want to put a big load on it, anything over that I wouldn't want any load on it. And since you'll be towing you'll want a trans temp gauge to know if it needs a cooler. As long as the converter stays locked it shouldn't get too hot. Manually downshifting on hills will help keep it locked, when you roll into the gas and it has to downshift it unlocks the converter first, then down shifts if it needs more. I wired in a switch to be able to lock mine manually as well as another switch so I could manually select 2nd gear. Engine braking is much improved with the converter locked so there are a couple bonuses.

chris white

I'm not one to tell anyone that they are wrong when I'm no expert, but I drive '98 ZJ with a 4.0. It's my first jeep and I have had it just over a year. I put a 165 tstat in mine and while driving around town and long drives it maintains temp at about 175, the only time it heats up is if I sit idle with the a/c on and even then it only reaches 200withe the exception of when the exhaust manifold was cracked and after I replaced the manifold with a header a bolt loosened and the flu GE leaked around the gasket. But other than that it has always held a low temp around 170. Although I. The winter the heater doesn't get as hot but I'm OK with that because I handle the cold really well anyway. With the 165 tstat, performance header, Flowmaster 44 running a 2.5" pipe , K&N air filter with a ram air system I made myself, 3" lift and 255/70/R17 I get 18 mpg in town and 24 mpg on hwy.

'90Cherokee

I'd be surprised if your 165 stat doesn't trigger a fault code. 18/24 MPG seems impossible; how are you arriving at those numbers?

EEVEE

mine with ac on then shutting down and turning back on hits around 220 225 but 230 is the max if it doesnt go down or it starts rising pull over and let it sit i usually i let the fans do the work of cooling it down. but mine is a 99 so if yours is older the older electric fan may keep it sitting there as my friends did that and didnt actually cool it down. i been looking at a coolant additive when i flush mine to keep it cooler quicker its an ocd thing to see it that high lol. plus triggers ptsd of my friends jeep overheated on the side of the high way with traffic going 80 mph. scary stuff if you have giant trucks flying past you.

'90Cherokee

A '99 getting that hot isn't normal. Unless this only happens under extreme conditions something's wrong with it.

jordan96xj

If running at speed on the highway you notice that the vehicle is overheating (> 230f) do not just immediately pull over and stop (unless you have no other choice). Remove the demand from the motor by either coasting or shifting into neutral, and coast as long and as fast as possible to a stop. The goal is to keep as much air moving over the motor as long as possible before stopping.

EEVEE

it was under extreme conditions as constant shutting off starting up and off like i said only when it turns back on it hits that temp plus it was a very hot day in florida that day at around 98 to 99 degrees and sun beating on it but it cooled right down it was on the last white line at times but also i havent flushed my radiator yet im sure theres some rust and such inside hindering performance. but with idling it never overheats