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having overheating issues. 94

I don't see anywhere that you said what tire size and gears you have?
 
Get a standard (gates is my preference) water pump on your rig. Your high flow pump works at idle right? Spin it at 2k rpm and it is to much. What do you have to lose? Along with others here I crawl my rig in 100 degree weather for hours on a stock cooling system with no issues. I would also return the tstat housing to oem as well. If the parts don't works Napa will probably gladly take them back if you discuss your issue before hand.

The increase pressure and volume can cause strange things to happen. Cavitation and turbulence lead to terrible flow and fluid with tiny air bubbles... Remember the water ports are small and not straight. This just adds to turbulence in the system.

Sent from my SM-G950U using Tapatalk
 
How's your catalytic converter?

My old 94 had a similar overheating issue that still would pop up intermittently even with every cooling part replaced.

Ended up being a clogged cat.
 
Been reading this with interest. I used to have the same problems as you. My 95 XJ 4.0 has a lot of accessories and comes in at over 2T. I have 4.56, 33" AW4, Derale tranny cooler, aftermarket fully ceramic coated headers, ALL new cooling system, Run Cool vents etc.. I did have triple electric fans. No matter what i did, under stress, the Jeep would run hot. And i mean getting into the red. Beach driving was really bad. I had restrictors as per Go Jeep, i tried this, that and the other...


I have a winch in the front end so air is restricted.


The ONLY thing that worked for me.. and i mean worked (I never see the temps go just a whisker over half way), was to remove the triple electrics, reinstall the original aux fan that comes on with the aircon, and fit a ZJ clutch fan. The ZJ clutch fan is the miracle cure. It spins faster and harder than a standard XJ fan. Fits the XJ perfectly (remember, the ZJ has a 4.0 as well). It has a bigger clutch and pulls an incredible amount of air. Sounds loud and makes your Jeep sound like a truck. I have recommended this upgrade to several people with your problem and they have all come back with a big grin and a thumbs up. Hope this helps as for less than $40 its worth a crack...
 
i have replaced the thermostat this week and been driving it. better, AC on in 65 degree weather and it will still get hot(230) but much later in the drive. No AC temps are stable at 195-200.
yes it's a 195 stat.
 
Replaced possibly suspect flowkool water pump with gates replacement. No change. It takes 20 plus min for it to cool down idling with good open. Flushed radiator today and will pull a block plug and check for sediment build up.
 
No dice on pulling block plugs and checking, can't get them out. Did flush the radaitor and block as best i could got some crud out but nothing major(some sediment and magnetic junk but coolant was still green). no luck. still wants to over heat. Whats average temp drop across the radiator on these things. begining to wonder if i'm having a tune up related issues( lean running) Please help.

Chris.
 
Here is another unusual suggestion. Check the exhaust to header connector and make sure that is tight and sealed. Your O2 sensor is down stream of that joint and if it is leaking the Jeep TCU may think the fuel mixture is off. I installed a RussP new stroker last summer, and it nearly killed me trying to keep it from overheating. I swapped radiators (multiple version including CSF HD, Mishimoto, and generic). Multiple water pumps, (Hayden, Mopar, Flowcooler, and ZJ versions). I put in various combinations of thermostats and tranny cooler positions. I swapped out the electric fan to mopar, add override switches, and made sure my shroud was perfect. The only things that made this manageable was putting in hood vents and an aux fan to pull air out of the engine compartment which helped. Finally, I tightened the exhaust collector joint to the Banks header really tight and things settled down. YMMV. Arizona is the ultimate heat test proving ground in the summer.
 
I think the collector is the place to watch. Leaks in header probably just push exhaust gas out of the system. At the collector you can get a Bernoulli effect and draw air into the exhaust with the right sized leak.
 
I'm not sure I understand the mechanism of a header leak causing overheating. Sucking outside air into the exhaust would trick the O2 sensor into thinking you're running lean and add more fuel, which generally makes it run cooler. The extra fuel isn't great for the cat, though. Now if the O2 sensor isn't working right, that could cause you to run lean.
 
Trans temp seems awfully high, could be extra drag in the tranny working the engine harder and dumping excess heat into the cooling. Still would suspect the cat at this point too, I know its newer but trying it with a cat bypass would be inexpensive and quick. Also you replaced that cat because of high nox? Geo metros were phased out because of tightening emissions because their extremely lean burning 3cyl put out very high nox. So you may also still be looking at running way too lean.
 
running lean has been a though. cooling system is functioning at idle. and there is no reason it should not be. current collector is very small leak, i can't get a down pipe to seal correctly to the header due to the angle it's at.
o2 sensors are cheep relitivly.
 
My understanding is that Jeep engineered the 4.0 to run slightly lean to help with NOx emissions, fuel efficiency, and “engine heating”. My guess is that running slightly rich actually increases the fuel air mixture on the jeep to stoic which increases heat output. It may be that the leak can throw off the O2 sensor input to ECU and add to the heat budget of a very delicate cooling system in the best of times. Just adding a theory based on my experiences. I am adding a wide beam sensor above my stock O2 sensor and this will allow me some testing opportunities.

Look at this video and see if it tracks.


https://www.youtube.com/watch?v=vcgmEKhCFTs
 
To the OP, I know what your next step should be. My story, 1998 XJ.

Aug 2019, hot (RH) side rad tank splits on way home from work. Antelope Valley of Mojave, 100f day, temp goes into the red, 4.0 stuttering, thought I'd nuked it before could get to place for AAA tow. My experience with plastic tanks is that the crimp seal between tank and heat exchanger starts leaking giving warning of an issue, you can nurse it home. This rad had a 4 inch split in tank, Jeep is dead right now. Thought about times in Death Valley, middle of nowhere Nevada, etc. and how bad this could have been.

Bought an all welded aluminum rad from reputable source to kill this worry. Installed new NAPA wp, stat, stat housing, hoses. On 1st drive to work it gets hot at the 20 minute mark. Scenario repeats. Did a lot of troubleshooting without success. With a new cooling system and how hot I had got the motor, assumed I cooked the head gasket.

Pulled the head and took the 0630 to local machine shop for crack evaluation, resurface and valve job. Reinstalled. The Jeep ran great but would still get hot when it should not. To the point it's not practical when the weather gets over 70f.

Checked hose ports to see if I left shop towel in, no dice. Checked for lower hose for collapsing at RPM, all good. Pulled wp to check for correct reverse rotation orientation. Pulled and water boiled a few 195f stats. cleaned AC condensor fins. Vacuum gauge checked the intake, good. Replaced fan clutch. Checked exhaust joints, no leaks. Ran Jeep after warm in dark to check header, no glow.

Thought maybe block is cracked and coolant is getting impinged by combustion gas (I know, no steam in exhaust, getting out there...). Got Jeep hot and pulled plugs, valve cover and rocker arms. Installed plug adapter / compressor, when regulator gets to 20 psi the piston goes to BDC and exposes whole cylinder wall and head. Install spill free funnel and increase to 140 psi, if there's a crack then bubbles will be crazy. Repeat for all cylinders. Nothing - nada.

Three weeks ago spent an afternoon and fixed my Jeep. Now, in daily driving it never gets close to 210. Went to Panamint valley this past weekend, 90's, would only hit 210 when going less than 5mph going on long uphill grades, then the AC fan kicks on and it's cool. Ran the hwys at 70 with the AC on and loaded down, half a hash mark below 210 (high 190's?).

What I did was pull the all-aluminum Mishimoto radiator and replace with the "heavy duty cooling" Mopar 52080104AC, nothing else was changed. My experience only and not a slam on that maker, my particular unit seems to be defective (clogged tubes during mfg process?). Back to plastic side tanks but whatever, hopefully last 15 years before a chance of tank split....

Sorry for the many words.
 
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