High altitude, and I can't stop overheating at speed!

[fsupaintball]

People in this thread have been helpful, but I'm wondering if my rocky mountain bros would be of greater assistance here. I'm sure I'm not the only one who has had this problem in Colorado.

Anyway, I overheat at high speed going uphill on the highway when it's 70 degrees or warmer outside. It's bad; straight to the red in just a few minutes while I'm running the heater and sweating my ass off. If it's very flat highway or low speeds I don't have much of a problem; gets a little warm but usually not awful.

About the jeep:
1996 Cherokee XJ, 4.0 inline 6, 185k miles
3-4" lift, 31" tires, steel wheels, and 4.10 gears in the diffs
Bored out throttle body, spacer, 97+ style intake manifold, K&N filter for stock airbox, Borla exhaust
Various other crap like amps/stereo, foglights, H4 headlights. Doubt that's related.

I feel like I've replaced everything in the cooling system.

Things I have already tried:
-Replaced radiator with aluminum 2-row (coolant does NOT leak)
-Replaced water pump, twice
-Replaced thermostat, twice
-Replaced coolant
-Replaced fan clutch
-Replaced cracked and leaky Thorley exhaust manifold, and changed the donut seal.
-Installed 16lb radiator cap (though I don't understand the purpose of that)
-Garden hose block flush
-Tried water wetter
-BG44k'd fuel to clean injectors
-Angrily pointed an IR temperature gun at it in a threatening manner, which then reported "Yeah, it's ****in hot"
-Weeping when nothing else worked


More info:
-I'm sure that the larger tires and diff gearing contribute to running harder at -higher RPMs, making things run hotter. Still, this is excessive.
-I have no coolant leaks
-Aux fan kicks in properly.
-It IS getting way too hot; it's not just a temp gauge thing.
-I can see the temperature drop when the thermostat opens up the first time, but it'll eventually creep up past the point of no return.
-Compression tests come back good. No crap found during spark plug change.
-I trimmed the mech fan's shroud a little at the bottom so it fits with the new radiator, but not a ton.


Seriously, every time I change something I think "Surely THIS will fix the problem!" And then the jeep says "F you buddy, it won't make a DAMN bit of difference!"

All the new gear has improved cooling at low speeds/idling but it's just as bad as ever at speed on any incline. As soon as I stop and let it sit with the heater going it'll start to cool down a bit. If I go downhill and goose it it'll usually cool down REAL fast.

 

[karstic]

Going to watch this thread. I have similar ossues in my 92.

 

[WB9YZU]

Is the ""At Speed" a problem?

I found that realizing that you can't do posted speed is a big part of mountain driving. You have 2 big things you are trying to cool, the engine an the transmission.

Are you trying to go up hill in D or are you shifting to 3?

I see you replaced the Clutch Fan.
Make sure fan housings are intact. These make a difference.

Think about adding a transmission cooler. Mount the cooler on the lower radiator brace where the winch used to go.

If there anything obstructing the grille?
Is the A/C condenser (The condenser is the aluminum radiator before the radiator) Clean? If they leak or get mud in them, you won't get airflow to the radiator.

I see someone suggested you replace the Catalytic Converter. Did you do that yet, and what was the result?

What about the bend in the upper pipe, has the bend become more restrictive?

 

[SolarBell]

I would also add to do a good chemical flush on your cooling system, not just a water flush. I wouldn't be surprised if there was still a ton of gunk still stuck in the block.

 

[fsupaintball]

A couple other minor details - automatic transmission, NP242 transfer case

Is the ""At Speed" a problem?

I found that realizing that you can't do posted speed is a big part of mountain driving. You have 2 big things you are trying to cool, the engine an the transmission.

Yeah, it is. It's my daily driver. And I'm pretty sure it does it whether I'm going 75 or 55 on the same incline.

Are you trying to go up hill in D or are you shifting to 3?

I downshift to 3rd for the biggest incline. But I still have the issue on slighter inclines where I'm generally staying in 4th.

If there anything obstructing the grille?
Is the A/C condenser (The condenser is the aluminum radiator before the radiator) Clean? If they leak or get mud in them, you won't get airflow to the radiator.

I think it looked pretty clean when I swapped out the radiator. I don't have a transmission cooler; maybe I should install one.

I see someone suggested you replace the Catalytic Converter. Did you do that yet, and what was the result?

No, I haven't. I'm not having any of the other issues that they mentioned typically go along with Cat problems though - power and RPMs are good and consistent.

What about the bend in the upper pipe, has the bend become more restrictive?

I don't think so. I'll compare to my buddy's stock jeep.

I would also add to do a good chemical flush on your cooling system, not just a water flush. I wouldn't be surprised if there was still a ton of gunk still stuck in the block.

Seemed to be flowing OK when I flushed and not a lot of crap came out, but maybe I'll check into that...

 

[adrenalinepirate]

When I do my flush I use distilled water and prestone flush. I think it was less tan 3 gallons and followed the instructions on the bottle. Also flushing it this way you can clean your heater core. When I do this I use an air line to blow the heater core junk out. Is the radiator fluid changing color?

 

[fsupaintball]

Nah, the fluid looks OK.

 

[jimgrms]

is the t/stat the correct range ,as in the specs

 

[fsupaintball]

What, like is it reporting temperature correctly? Yes.

 

[rockfrog]

Like the correct temperature thermostat. I think 195 is stock, is the t-stat colder than that?

 

[fsupaintball]

Oh, tstat, not tsensor. Yeah, it's stock. Like I said, I can see it drop temp when it opens the first time, so it appears to be working properly.

 

[fsupaintball]

Someone kindly PM'd me about this link - sounds damn familiar. They even had a 2-row Radiator Barn radiator, like mine.

Apparently installing a new, genuine, bone stock MOPAR radiator solved their issue. I'm considering it.

 

[adrenalinepirate]

I would even put a 180*f t stat. I yave been running that for ten years on all my jeeps.

 

[Digger87xj]

I'll be of no help, but wanted to express my sympathies. I have had two cherokees in a row that I could not fix to overheating problems with.

My current one, a 95, has has 4 different reman engines,
3 different brand radiators,
trans cooler delete,
engine oil cooler,
water pumps,
fan clutches,
electric fans,
head gaskets,
different injectors,
sensors,
hood vents,
no hood,
hood scoop,
different ECU,
the list is endless.

bottom line.. same as you, nothing I did worked. Some things did change how fast or slow it took to get too hot, but ultimately there was no smoking gun.

running 4:56 gears and 35s, I always wondered if gearing down to 4:88 would help but I know several jeeps with my same set-up that don't run the slightest bit hot.

Instead I did a V8 swap thinking the 4.0 was over-worked, and now it skipped right over overworked to over horsepowered, and am still fighting up-hill cooling problems. A $500 Becool radiator is next in line, along with a GMB high flow water pump; when the funds will allow.


Good luck. I really really mean that. I hope you can fix it.

 

[Digger87xj]

Read the thread you referenced; I did not try a factory radiator but it sounds encouraging.
My jeep had a performance radiator 3 row copper/brass in it when I got it... had it rodded, no change so I bought a CBR 3 row.. ran hotter.

So I sold that and bought a plastic/alum vista-pro from O'Reilly's .. this one cooled the best, but was still getting too hot.

Still not happy I bought a champion 3 core all alum. ran hotter so I put the plastic tank one back in until I swapped engines.


sigh

 

[yamamaharay]

Following this too, mine does the same exept im on 35's w 4.56's .I have replaced everything,even spaced the hood and added vents. Big hills on the highway booooo all I do is stare at my temp gauge all the time and that sucks!!!!!!!!

 

[stockli]

Try pulling your ac condenser out of there and see if it helps. Mine runs a tad warm when it's real hot out and I am almost positive it's because my condenser fins are trashed after 250k miles

 

[Led]

I hard pin the fan clutch on all my xj/mj 's and they never go over 210 on the passes.

 

[old_man]

Pull the plugs and show them. If you know a shop with an exhaust gas analyzer. My bet is that you are running lean.

 

[Gunter]

also, perhaps prior owner did it and was not aware. xj an Tj's have water pump that spins in different directions. if prior owner did it and you did same as he did, you could have wrong waterpump going in wrong direction.the direction and impeller are different.
have you tried hood on vs hood off?
maybe a scoop can let air in to cool and heat out better?
02 sensor? could be telling comp to run lean? Old Man is right, an analyzer can tell you what it is doing.fuel pressure regulator may contribute to less fuel and the possible lean condition. weak fuel pump too. easy to check with fuel pressure gauge .