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  #1  
Old July 10th, 2020, 15:10
whatwave whatwave is offline
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Sudden overheating, at a loss what to do next

I've been having this issue where my XJ stays around 210 creeps to 220 then suddenly jumps up to full overheating. The engine bay gets too hot to touch. It already toasted a head gasket and now I'm not trying to screw around with it.

I've installed an entirely new cooling system (t-stat, water pump, fan clutch, griffin radiator) but the problem persists. I really don't think there's any air in the cooling system. I haven't replaced anything related to the electric fan but I've seen it running prior to overheating.

Up until now I've had to have my indie do the work because my apartment building has become sincerely uncool about doing work in the garage. But I think it's got to be in my own hands now and building rules be damned.

Can anyone offer some opinions on what it could be or what I can do?

Also, I know there are a ton of threads on this but I actually haven't been able to find one where someone fixes the problem. I'll be sticking with this and updating when it gets sorted.
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  #2  
Old July 10th, 2020, 20:07
Unclewolverine Unclewolverine is offline
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Re: Sudden overheating, at a loss what to do next

good luck. Make sure you have the stant super stat. When I upgraded to the full aluminum rad the Napa premium stat i had in mine made it constantly cycle from hot to cold. Never saw a resolution on the last thread I saw with this exact same problem.

Updates people!
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  #3  
Old July 10th, 2020, 20:26
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4x4JeePmaNthINg 4x4JeePmaNthINg is offline
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Re: Sudden overheating, at a loss what to do next

its been very hot lately, ive been a tad over 210 when really cruising.

what year is your jeep?

What happens when your vehicle overheats?
Have you shot the thermostat with a temperature gun?
what kind of water pump are you running?
have you tested for the head gasket lately, overheating can cause more issues?
Do you have a proper mix ratio of coolant/water?

Its summer time you can dump all coolant and run water if you like, even a deep clean may be a good idea until everything flushes clean. If a previous owner was "smart" enough to dump snake oil into the engine, cooling passages could be blocked.
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  #4  
Old July 10th, 2020, 20:31
SV-BDN SV-BDN is offline
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Re: Sudden overheating, at a loss what to do next

I've been working through some overheating issues myself lately, with all the high temps we've been getting in southern CO.

I have done the following and its helped somewhat:
New 160f high flow thermostat (for now, planning to put in a 180f soon as the system is sorted) - this has been the biggest temporary help
new higher flow water pump
new xj fan clutch (removed and replaced with dual e-fan setup (8 blade and taurus))
upgraded from my stock 5 blade e-fan ('93 XJ) to a 8 junkyard 8 blade e-fan ('95-'96 XJ)
both e-fans are temporarily on a manual switch, will be wiring to a temp switch soon.

My temp was at about 180f today driving in to work in this 100f heat, going about 75mph most of the way with both e-fans running. I do notice that my temps will spike when I go from highway speeds to lower speeds (45mph or less) but the e-fans are working for now.

A few things I plan to do still, which I hope will help, but will have to report back:
Upgrade thermostat housing for a high-flow variant
Adding a coolant filter (increase system volume, filter coolant)
Adding a second heater core on the return line from the factory heater core (increase system volume, cool coolant returning to the engine from the heater core)
Adding an oil cooler (increase oil volume, cool oil)
Replacing stock radiator with a thoroughly cleaned stock radiator (after filter install, might upgrade, but probably stay with 2 core)
Install hood lifters or hood vents for better airflow (last on my list right now, might not go this route)

I have a week off coming up, hoping to make some headway on this list. Has anyone tried any of these options before?

My XJ is a 1993 Sport 5-spd w/ upcountry package (maybe? Has a LSD rear diff, and factory skid plates) that is mostly stock. I have done an AC delete and relocated the alternator up, installed a '99+ intake, fan clutch delete and dual e-fans on a manual switch.
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  #5  
Old July 11th, 2020, 17:36
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Re: Sudden overheating, at a loss what to do next

Quote:
Originally Posted by whatwave View Post
I've been having this issue where my XJ stays around 210 creeps to 220 then suddenly jumps up to full overheating .....
These symptoms describe a cooling system that is not holding the specified 16 lbs pressure. The pressurized cooling system raises the boiling point of water, loss of pressure allows the water to instantly flash to steam.

Typically you would replace the radiator cap and solve the problem. If all your cooling system parts are fresh, and the symptoms persist, you should look at the frost plugs for leakage and to the head gasket for leaking super heated exhaust gases to the coolant.

The stock XJ Cherokee cooling system is not ideal, but with a heavy duty radiator, and regular cooling system preventative maintenance it can handle just about anything except Death Valley in the summertime. No other specialty parts should be required.
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  #6  
Old July 12th, 2020, 07:26
Unclewolverine Unclewolverine is offline
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Re: Sudden overheating, at a loss what to do next

X2 I run mail all day in mine with ac running in upper 90s with 80-90% humidity with no problems. I have a cheap all aluminum rad from Amazon and I'm only running an 8 pound cap because I'm worried that the heater core cant take the full pressure. Stock components with a 195 stant superstat.
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  #7  
Old July 12th, 2020, 09:18
JonnyCat63 JonnyCat63 is offline
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Re: Sudden overheating, at a loss what to do next

After years of owning XJ's, I'm going to finally weigh in on cooling issues. These are my experiences and opinions, and I'm not intending to ruffle any feathers, so I'm not calling anyone out on their expertise. There are far many better and smarter mechanics on this and other forums than me.

The fact of the matter is, that XJ's seem to have inherent cooling issues. There's too much evidence of that to deny it. I've probably read every thread, post, article on the Internet about XJ cooling problems. I've talked with radiator shops and a number of other people about these issues, as well.

I've come to the conclusion that no one really knows what the Eff the problem is with XJ's. Period. One fix works for one person, but not another. Some people, (myself included) do some repairs and it works, while others, (myself included) try a number of things and just put up with the problem. Seems to me hit or miss. I suspect the root problem to some of these problems is a clogged passage somewhere due to corrosion. That's the only thing I can think of. Could also be head gasket issues that people can't diagnose properly. Regardless, no one has ever said that "culprit Z" is the issue and you need to fix that and the cooling issues are fixed. It's always try this, that, and the other thing, usually with mixed results. Here's my experiences with 4 XJ's that I still currently own.

On my 97, 160,000 miles, you couldn't get that thing to overheat if you tried. Have an American Eagle 2 row aluminum radiator, but everything else is stock. Stays just below 210 all day long even in the So Cal desert. Mostly a trail rig, but I can drive it all day long on the street or highway, short or long trips, doesn't matter.

99 2 door, 200,000 miles (current build). Had some overheating issues early on. Looked like PO neglected the cooling system. Changed out the radiator to a Mopar heavy duty, Hesco water pump, new stat, hoses, etc. Old radiator was clogged, but everything else looked okay, just old and dirty. Flushed the system and now she runs cool as could be.

My sons stock 99, 140,000 miles, his daily driver, has mild cooling issues, but nothing too major. Looks like PO used some stop leak. We've been flushing out the system, but I will probably change out the radiator and other components as part of regular maintenance.

My 95 trail rig, 81,000 miles, has been the typical XJ cooling headache. Started with temp creep on the highway, and in town. So after putting on the lift kit, lockers, gears, 31's, I decided to attack the cooling system. I ended up changing everything, and I do mean everything. I tried every fix that I read about or was recommended to me. I tried 3 different radiators, CSF, stock, and one other. I finally had the biggest, stupidest radiator custom made to get the most fluid capacity. Re-routed the trans to it's own cooler. Tried Hesco and stock water pump, high flow T-Stat housing, deleted the heater control valve, new muffler and cat, ZJ fan clutch and stock fan clutch. I've checked for exhaust manifold cracks. Checked the radiator fluid, checked the compression, checked for fluid in the oil, blah, blah, blah. No culprit anywhere that I could find. So I just put up with it. I just cycle my fan override switch on the trails, and that keeps the temps where I want them. That's how I choose to manage the problem for now.

That's been my experience with XJ's. I can't figure it out, and frankly, doesn't seem like anyone else has. Seems like your cooling system works, or it doesn't. All the dozens of vehicles I've owned over the years have never had a cooling issue. If they did, it was an obvious fix, and I've owned a variety of vehicles.

So my advice, throw some parts at it, do what you have to do to make it work for you. I've even read where people have done engine re-builds over this issue. But I have no evidence of anyone saying "this" is the root problem. Yes it can sometimes be obvious and changing a few parts work, or it can be a major headache. Everyone seems to have different results. It's just baffling how so many people can have these problems without a clear solution. I'm at a loss to figure it out.

JMHO
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  #8  
Old July 12th, 2020, 09:42
whatwave whatwave is offline
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Re: Sudden overheating, at a loss what to do next

Wow. Really great info guys. And I see why other threads are so inconclusive.

I'm going to throw some parts at it and see what I can do. I'll report back once I have something satisfactory to add.
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  #9  
Old July 12th, 2020, 09:43
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Tim_MN Tim_MN is offline
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Re: Sudden overheating, at a loss what to do next

The root cause is typically lack of regular preventative maintenance. The XJ cooling system is slightly undersized, but properly maintained it does the job.

To fix cooling system problems, one has to have a correct diagnosis. Throwing random parts at an undiagnosed problem often ends up with ineffective results. There is no one single faulty part causing XX% of cooling problems.

I do not consider a complete overhaul for a poorly functioning cooling system, with all parts replaced, as excessive.
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Quote:
Originally Posted by bimmerjeeper

People are dumbfounded when I tell them I know how to change the spark plugs on a car.

Last edited by Tim_MN; July 26th, 2020 at 10:57.
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  #10  
Old July 13th, 2020, 09:29
whatwave whatwave is offline
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Re: Sudden overheating, at a loss what to do next

Just realized this isn't in my signature.or anything

1997 4.0, 127k miles, Lightly modded
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  #11  
Old July 13th, 2020, 10:24
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old_man old_man is offline
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Re: Sudden overheating, at a loss what to do next

I have seen the lower hose collapse when hot and at high flow situations. The original hose had a "spring" inside to keep this from happening. I hear they are hard to find anymore.

Do not raise the back of the hood to get better airflow. It actually makes things worse. Go with a hood vent if you are going that direction.

I pull a trailer so I added an external transmission cooler. It seemed to help.

Make sure your fan clutch is good and you have a shroud around your fan. You should also have an aux fan. Add a manual switch so you can run it before it gets hot.
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  #12  
Old July 13th, 2020, 20:34
Unclewolverine Unclewolverine is offline
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Re: Sudden overheating, at a loss what to do next

Agreed about the raising the back of the hood! I tried it in my 01 and it helped greatly when I was going box to box in town but once I got on the highway it acted like cowl induction and reduced airflow, increased temp. Would work on a slow speed/trail only rig, but not on anything that sees more than 20 mph.
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  #13  
Old July 14th, 2020, 14:46
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techno1154 techno1154 is offline
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Re: Sudden overheating, at a loss what to do next

Quote:
Originally Posted by old_man View Post
I have seen the lower hose collapse when hot and at high flow situations. The original hose had a "spring" inside to keep this from happening. I hear they are hard to find anymore.

Do not raise the back of the hood to get better airflow. It actually makes things worse. Go with a hood vent if you are going that direction.

I pull a trailer so I added an external transmission cooler. It seemed to help.

Make sure your fan clutch is good and you have a shroud around your fan. You should also have an aux fan. Add a manual switch so you can run it before it gets hot.
And where would you place the hood vents? I have seen some placed forward, just behind the radiator. Jeep OEM hood vents come to mind. Others are at the back of the hood.
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  #14  
Old July 14th, 2020, 15:05
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Re: Sudden overheating, at a loss what to do next

Hood vents help with keeping the engine cooler, they do not solve overheating issues.

The front corners of the hood is the most effective place for hood vents, but since low speeds are when the underhood temperatures rise the most, anywhere they will fit will help. Locating hood vents is somewhat limited due to the inner hood reinforcements on the underside.

There are tons of old hood vent threads to dig thru. >>> https://www.naxja.org/forum/showthread.php?t=1066309



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Quote:
Originally Posted by bimmerjeeper

People are dumbfounded when I tell them I know how to change the spark plugs on a car.

Last edited by Tim_MN; July 14th, 2020 at 15:14.
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  #15  
Old July 14th, 2020, 17:03
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devildog0 devildog0 is offline
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Re: Sudden overheating, at a loss what to do next

Just so you know I've seen parts be bad right out of the box. I got a brand new OEM Mopar radiator cap. The return plunger was bad out of the box. Allowed coolant to bypass the cap into the overflow bottle. Same things for thermostats. I've had them fail out of the box in both directions stuck closed and open.

Resist the urge to run lower than stock thermostats. Running an engine too cool is almost as bad as running it too hot. You get worse fuel mileage and significantly increased cylinder bore wear.

When it overheats as you describe does it only do it at speed, or at idle/low speed?
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