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  #1  
Old June 22nd, 2017, 09:39
SBpunk SBpunk is offline
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Running out of ideas on overheating

1992 Jeep 4.0 AX15 NP242 with around 2k miles on rebuild. Started having issues after the rebuild that've gotten progressively worse. Running at 230 with A/C on in 90 degree weather. Would probably go higher but I shut it down and flip on the heat. I just need somewhere else to look. Here's the stuff I've done already:

Rebuilt Motor running 5w40 T6 oil
New CSF 3 core radiator (put water through it before install just to double check flow)
2 195 degree thermostats and now a 180
New Thermostat Housing
On 3rd water pump with no signs of failure on the previous two when pulled
New radiator hoses
Deleted the heater valve and running straight to the heater core
50/50 coolant (added coolant specific UV dye to ensure no leaks)
New Mopar coolant sensor (ran a couple others but no change)
Exhaust is brand new and no leaks
A/C condenser was cleaned
ZJ cutch fan
Later model electric fan on a switch running constantly
New belt and pulleys
I have an aux temp gauge I'm going to hook up this weekend to double check against my stock gauge

The only things I can think of is maybe my coolant overflow is blocked (not sure how to test/clear it) and my A/C compressor clutch is old but operational. I thought maybe it was causing drag not letting the water pump flow 100% but it'll hit close to 230 even without the A/C. I've had the system pressure tested at a shop no dice. Leak down and pressure test on the cylinders after the rebuild. Any idea's or guidance would be appreciated. I know enough to do most the work myself with the exception of rebuilding the motor/trans. I've pulled AX15s to do clutch work in the past and completely rebuilt my 242 before installing so not completely mechanically stupid hahaha. Thanks again.
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  #2  
Old June 22nd, 2017, 10:16
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old_man old_man is offline
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Re: Running out of ideas on overheating

What is your idle speed? You could have a vacuum leak causing it to run lean.
Are you running a radiator shroud?
Do a spark plug reading to make sure you aren't running too lean.

First off gauges are notorious for being off. Having said that, 230 on a 90 degree day with the AC on isn't abnormal. As long as you are not loosing coolant I wouldn't worry. I would go ahead and run it and see where the temp levels off. If it does before you puke antifreeze, I would be wondering about your gauge accuracy.
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  #3  
Old June 22nd, 2017, 10:48
SBpunk SBpunk is offline
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Re: Running out of ideas on overheating

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Originally Posted by old_man View Post
What is your idle speed? You could have a vacuum leak causing it to run lean.
Are you running a radiator shroud?
Do a spark plug reading to make sure you aren't running too lean.

First off gauges are notorious for being off. Having said that, 230 on a 90 degree day with the AC on isn't abnormal. As long as you are not loosing coolant I wouldn't worry. I would go ahead and run it and see where the temp levels off. If it does before you puke antifreeze, I would be wondering about your gauge accuracy.
Idle speed is just above 700/750. Radiator shroud is still there but haven't checked the spark plugs since the rebuild. I'll shut it off at 230 because it'll keep climbing (I'm assuming scared to try). I'll check with the forums and see how I go about testing to see if I'm running too lean on fuel. If I can't do it I'll find a shop.
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Old June 22nd, 2017, 12:17
nicpaige nicpaige is offline
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Re: Running out of ideas on overheating

Mine will run 220-225 with AC on in hot temps but it stays there. I noticed mine averages about 5-7 degrees hotter since I installed the winch. You can invest in an a/f data logger or gauge to monitor your a/f readings throughout the day. Does it happen at idle as well or only under load?

Last edited by nicpaige; June 22nd, 2017 at 12:22.
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  #5  
Old June 22nd, 2017, 12:35
SBpunk SBpunk is offline
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Re: Running out of ideas on overheating

Idle and underload. City or highway driving. Just drove 4 miles without the efan to double check it wasn't just the AC and it went to 220 before I shut it down. Fan doesn't kick on automatically but I have it switched so I can control it.
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  #6  
Old June 22nd, 2017, 19:34
Vernicious Vernicious is offline
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Re: Running out of ideas on overheating

What kind of pump are you running? I'm assuming a high flow. If so this is probably the cause. The cooling system is designed to leave your coolant in the radiator long enough to cool it down. If you "upgraded" to a high flow the coolant doesn't have time to cool down prior to going back into the engine. Just a thought.
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Old June 22nd, 2017, 19:37
SBpunk SBpunk is offline
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Re: Running out of ideas on overheating

Nope just a plain ole Napa pump
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  #8  
Old June 22nd, 2017, 22:09
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David_Bricker David_Bricker is offline
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Re: Running out of ideas on overheating

As old_man mentioned, if you're not blowing coolant out of the overflow, you really aren't "overheating". Maybe warmer than you like, not you aren't putting the engine in jeopardy. An engine could run 260 without damage for a fairly extended period of time. Would I like it, no. But at 230, you have nothing to worry about.

The factory gauge in mine will show 210 for extended idle periods. If I push the engine, particularly low speed, off road, light throttle conditions, the factory gauge will read 260. I installed an auxiliary gauge, with the sender in the upper radiator hose. At extended idle, it reads 180-190 with a 195 degree thermostat (ONLY thing you should use). In the low speed stuff, it reads 200-220. So, yes, the factory gauge is not the best indicator of true temperature.

On the other hand, if you are boiling over, then either the pressure cap is defective, or you are truly overheating.

Also consider some Water wetter. It can help. Since you're in OK, you likely experience freezing conditions at some point in the year. Therefore, 50/50 mix is best. In my case, I run 75% water, 25% anti-freeze. Water is a better conductor of heat. Granted, anti-freeze also raises the boiling point of the coolant, but in my case, I was working on keeping temps down as much as possible.

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  #9  
Old June 22nd, 2017, 22:33
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Green Mesa XJ Green Mesa XJ is offline
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Running out of ideas on overheating

I dunno. Seems pretty hot to me, our XJ of the same era don't get near that hot.
Could be a crappy gauge, and in away it's not too hot really but it's not what I'd consider good either.

If your not losing radiator fluid, I'd think about the o2 sensor or something that could make it run lean.
You might test the overflow line by squirting so compressed air through the line. I'd unplug it from the radiator then see if the bottle bubbles.

Other thought I've have is perhaps something is wrong with the rebuild, bad headgasket? Clogged water ports? All of that seems unlikely.


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  #10  
Old June 22nd, 2017, 23:06
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lazyxj lazyxj is offline
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Re: Running out of ideas on overheating

Sometime the A/C condenser gets so gummed up that no matter what you try to clean it, it is still partially plugged up.
Had this issue on a friend's XJ, its cooling system was all new, with a Mopar HD radiator, and it still ran hot. Replacing the condenser cured it.
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  #11  
Old June 23rd, 2017, 02:05
Eerielayne Eerielayne is offline
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Re: Running out of ideas on overheating

Quote:
Originally Posted by SBpunk View Post
Started having issues after the rebuild that've gotten progressively worse.
When you say progressively worse what do you mean? It's been running progressively hotter? Also is this under all driving conditions or specifically highway/city driving

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  #12  
Old June 23rd, 2017, 05:52
SBpunk SBpunk is offline
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Re: Running out of ideas on overheating

David_Bricker - I get what you're saying and I'm most likely going to swap back over to a 195 thermostat. I had planned on putting in an high flow pump and thermostat housing but at this point I don't think its the problem. Prior to the rebuild it ran at 195 no matter what I did. A/C blasting 100 degree weather etc. The hottest I've let it get was the tick right before the red before shutting it down and running the aux fan to help it cool off. I'm guessing venting the hood would help but that's going to be a last ditch effort before I just blow up the thing with some military grade explosives....

Green_Mesa_XJ - Definitely crossed my mind. I thought the guy rebuilding it was squared away from what people told me but since I've gotten it back it seems worse than before. It almost sounds like my lifters are smacking my valve cover when I run it at idle. The compression test and leak down were good but still sounds like something wasn't installed right or the wrong parts were used. Pulling the head and just replacing it with a rebuilt from Clearwater (think that's the company) has crossed my mind a few times.

Lazyxj - Yeah I'm kind of pissed I didn't replace it when I put in a new to me compressor (R12). I didn't know much about A/C when I did it and honestly didn't even know the condenser was up in front of the radiator. Took a pic and had to ask over facebook. Definitely on the list since if the compressor is the issue I might just convert to R134a.

Eerielayne - Running back from OKC to my town (1.5 hrs) it was running around 210-215ish on the highway. When the temp started picking up a bit it would shoot up to 220 before I could make it from my house to work (around 6 miles @35-45mph only 3 stop lights). When I got the A/C going again the damn thing would come close to overheating and didn't matter if it was highway or city. Stopped using the A/C and it would get up to 230 within 10 miles driving around in low 90s outside temp.
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Old June 23rd, 2017, 06:20
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90xj06 90xj06 is offline
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Re: Running out of ideas on overheating

i know on my renix i get air stuck in the back of the head by the dash temperature sensor. the dash gauge will show over 210 but the ecu reading is 195 ish. or maybe that temp sender is faulty.
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Old June 23rd, 2017, 06:20
nicpaige nicpaige is offline
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Re: Running out of ideas on overheating

I would verify that temp with an analog gauge for sure, that may put your mind at ease.
Pull a few plugs and see of they look lean. See if anyone you know has a wideband o2 sensor you can hook up to check your a/f ratio. Have you verified the timing is correct, maybe pull a few degrees out?
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Old June 23rd, 2017, 06:33
SBpunk SBpunk is offline
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Re: Running out of ideas on overheating

Quote:
Originally Posted by nicpaige View Post
I would verify that temp with an analog gauge for sure, that may put your mind at ease.
Pull a few plugs and see of they look lean. See if anyone you know has a wideband o2 sensor you can hook up to check your a/f ratio. Have you verified the timing is correct, maybe pull a few degrees out?
The computer controls the timing on the HO I thought? I've replaced the distributor (idle issue since I've had it) and it would only go in one way. The "retaining" clip thing was on there but when we looked through the service manuals there was nothing about it when performing maintenance on the distributor. I have a new mopar O2 sensor coming in to replace the Bosch I installed just because it was 25 bucks shipped from a buddy. I have a gauge sitting in my passenger seat I need to look into how to hook it up without pulling my sensor again. Not trying to fight these stupid air bubbles again.
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