Phantom overheating - JeepForum.com
 
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post #1 of 12 Old 04-22-2017, 02:54 PM Thread Starter
earljeeper1
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1999 XJ Cherokee 
 
Join Date: Apr 2017
Location: Tucson
Posts: 12
Xj Phantom overheating

Hi folks, new to forum, appreciate your help with strange heating warnings driving me nuts.

Have both dash gauge and Ultragauge showing overheating on '99 XJ; been going on for awhile. Ultragauge shows temp rising above 215 degrees within 15 mins. of driving, and gets to alarm range at highway speeds within 20-25 minutes. Dash gauge never rises slowly; stays down at 215 most of the time, then pegs to 250 degrees all of a sudden, and stays there. Alarms all over the place. Lighted odometer blacks out when this occurs. If I turn on the cabin heater and back off on speed, the dash gauge drops down to 215 within a couple minutes and the gauge warning disappears, Ultragauge temp drops but stays around 230-245 degrees.

Checked with infrared sensor gun when gauges have shown warnings, which seems to suggest all is well. Upper radiator hose at about 190, lower radiator hose about 180. Metal near coolant temperature sensor a bit higher, 200 range. Engine block on passenger side shows around 210-215, cylinder head area around 185. I've tried getting a read on the manifold side of engine, and that reading bounces around all over but shows as high as 300 degrees, so that's an outlier, not sure I'm getting good read there. No boil-overs.

I know I have some dash gauge issues: occasionally voltage gauge reads incorrectly at zero, then will be fine next time I start it. A bit more frequently, the oil pressure gauge will read at zero, but if I push and hold trip odometer it usually corrects itself. All other gauges seem to function fine. When I do the gauge check (holding odometer button and turning ignition without starting), all lights and gauges respond properly.

Clearly there are some gauge issues, but I think there's something wrong at the signal/sending side that won't be addressed just by pulling the dash and working on the contacts, though I plan to do that. Wiring? I haven't torn into electrical... Or is it possibly really overheating somehow? Manuals not very helpful on electrical.

Additional info:

- On third coolant temp sensor, I think these have all been functional.
- New radiator, hoses, performance water pump, gasket, coolant done by a shop.
- 2 year old accessory fan.
- All fans run, radiator fan clutch shows no sign of play, doesn't spin loosely with manual push.
- No particular signs of head gasket being blown, doesn't shoot coolant out of open radiator cap, no bubbles in coolant, no apparent coolant loss. Most recent oil change at Walmart, no reports of coolant in oil.
- No particular signs of heater core problems, no leaking on floorboard, no humidity, no leaking of any kind in driveway.
- Had some white smoke coming out of tail pipe, found leaks in manifold, so personally replaced with Banks header, Monster exhaust, and Flowmaster catalytic, and I replaced all motor mts. Pipes welded by good exhaust shop. No smoke. Engine runs smooth.
- No engine warning lights.
- Belt seems to be in good tightness range, it's pretty new.
- Do have AC, this does lead to faster gauge indications of heating. Don't use it much.
- Never any issues at idle, and gauges read reasonable temps.
- Auto transmission.
- I have a snorkel, 4" diameter Spectre hoses, 5" OD Spectre inline filter enclosure with cone filter.
- Ultragauge shows intake manifold temps of about 110 to 118, sometimes 120, 122.
- No sign of brakes dragging.
- Had major engine problems with original engine blown (bad cylinders, oil leaking through engine), replaced with rebuilt at good shop about 3-4 years back couple years after buying the Cherokee. Don't want to blow another one.

Anyone had something like this? Advice appreciated.

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post #2 of 12 Old 04-22-2017, 03:00 PM
delesandwich
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Join Date: Apr 2017
Posts: 17
Quote:
Originally Posted by earljeeper1 View Post
Hi folks, new to forum, appreciate your help with strange heating warnings driving me nuts.

Have both dash gauge and Ultragauge showing overheating on '99 XJ; been going on for awhile. Ultragauge shows temp rising above 215 degrees within 15 mins. of driving, and gets to alarm range at highway speeds within 20-25 minutes. Dash gauge never rises slowly; stays down at 215 most of the time, then pegs to 250 degrees all of a sudden, and stays there. Alarms all over the place. Lighted odometer blacks out when this occurs. If I turn on the cabin heater and back off on speed, the dash gauge drops down to 215 within a couple minutes and the gauge warning disappears, Ultragauge temp drops but stays around 230-245 degrees.

Checked with infrared sensor gun when gauges have shown warnings, which seems to suggest all is well. Upper radiator hose at about 190, lower radiator hose about 180. Metal near coolant temperature sensor a bit higher, 200 range. Engine block on passenger side shows around 210-215, cylinder head area around 185. I've tried getting a read on the manifold side of engine, and that reading bounces around all over but shows as high as 300 degrees, so that's an outlier, not sure I'm getting good read there. No boil-overs.

I know I have some dash gauge issues: occasionally voltage gauge reads incorrectly at zero, then will be fine next time I start it. A bit more frequently, the oil pressure gauge will read at zero, but if I push and hold trip odometer it usually corrects itself. All other gauges seem to function fine. When I do the gauge check (holding odometer button and turning ignition without starting), all lights and gauges respond properly.

Clearly there are some gauge issues, but I think there's something wrong at the signal/sending side that won't be addressed just by pulling the dash and working on the contacts, though I plan to do that. Wiring? I haven't torn into electrical... Or is it possibly really overheating somehow? Manuals not very helpful on electrical.

Additional info:

- On third coolant temp sensor, I think these have all been functional.
- New radiator, hoses, performance water pump, gasket, coolant done by a shop.
- 2 year old accessory fan.
- All fans run, radiator fan clutch shows no sign of play, doesn't spin loosely with manual push.
- No particular signs of head gasket being blown, doesn't shoot coolant out of open radiator cap, no bubbles in coolant, no apparent coolant loss. Most recent oil change at Walmart, no reports of coolant in oil.
- No particular signs of heater core problems, no leaking on floorboard, no humidity, no leaking of any kind in driveway.
- Had some white smoke coming out of tail pipe, found leaks in manifold, so personally replaced with Banks header, Monster exhaust, and Flowmaster catalytic, and I replaced all motor mts. Pipes welded by good exhaust shop. No smoke. Engine runs smooth.
- No engine warning lights.
- Belt seems to be in good tightness range, it's pretty new.
- Do have AC, this does lead to faster gauge indications of heating. Don't use it much.
- Never any issues at idle, and gauges read reasonable temps.
- Auto transmission.
- I have a snorkel, 4" diameter Spectre hoses, 5" OD Spectre inline filter enclosure with cone filter.
- Ultragauge shows intake manifold temps of about 110 to 118, sometimes 120, 122.
- No sign of brakes dragging.
- Had major engine problems with original engine blown (bad cylinders, oil leaking through engine), replaced with rebuilt at good shop about 3-4 years back couple years after buying the Cherokee. Don't want to blow another one.

Anyone had something like this? Advice appreciated.
Stuck thermostat?

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post #3 of 12 Old 04-22-2017, 03:56 PM Thread Starter
earljeeper1
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Join Date: Apr 2017
Location: Tucson
Posts: 12
Thanks, possible, but new thermostat put in last summer also, sorry I forgot to mention... seems unlikely...
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post #4 of 12 Old 04-22-2017, 05:26 PM
delesandwich
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Quote:
Originally Posted by earljeeper1 View Post
Thanks, possible, but new thermostat put in last summer also, sorry I forgot to mention... seems unlikely...
What do the coolant passages look like inside the head? Was RTV used on the head gasket or thermostat housing?

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post #5 of 12 Old 04-22-2017, 07:42 PM Thread Starter
earljeeper1
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Location: Tucson
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I haven't looked inside the head.. can't answer that...
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post #6 of 12 Old 04-22-2017, 07:56 PM
delesandwich
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It might have some pretty significant corrosion depending on what is ran in it. I just replaced the head on mine which had the notorious 0331 casting. After looking into it i could peel chunks of rust out. It's possible you could have a clogged or blocked passage.

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post #7 of 12 Old 04-23-2017, 09:48 AM
oIIIIIooIIIIIo
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Join Date: May 2013
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Posts: 83
Over heating is a common problem on XJ/MJ so is bad readings, if you put a second sender in the only way to do this is to tee it outside the bock. Trouble with this is the sender is under the exhaust manifold. In the 2003 wrangler they used two senders! One is in the block and that one goes to the gauge in the dash. The second one is in the thermostat housing.That one goes to the computer. There was also two different systems used, an open and a closed system.?The closed system has a plastic tank on the firewall. These tend to leak.
The sender they use is the cheapest piece of junk there is.


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post #8 of 12 Old 04-23-2017, 09:53 AM
oIIIIIooIIIIIo
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Posts: 83
The engineers use the varisters because they are simple and cheep. Thermocouples work 1000x better but the circuitry is more complicated.


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post #9 of 12 Old 04-23-2017, 12:59 PM Thread Starter
earljeeper1
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Join Date: Apr 2017
Location: Tucson
Posts: 12
Pretty sure the 99 doesn't use the sender in the block, nothing in manual... Do you know differently? Thanks.
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post #10 of 12 Old 04-23-2017, 02:31 PM Thread Starter
earljeeper1
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1999 XJ Cherokee 
 
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Location: Tucson
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You are CORRECT, sir, there is a sender back there. I was confusing that with the sensor on the other side of block at rear that older cherokees used. Apparently this is the sender to the dash gauge, so following that up, super helpful. Any tips on testing it?
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post #11 of 12 Old 04-23-2017, 02:52 PM Thread Starter
earljeeper1
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Location: Tucson
Posts: 12
Nope, nope, just an engine block ground back there...
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post #12 of 12 Old 04-24-2017, 01:57 PM Thread Starter
earljeeper1
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1999 XJ Cherokee 
 
Join Date: Apr 2017
Location: Tucson
Posts: 12
I think I'll go ahead and put in a second sender to a second gauge, t-ing off the coolant temp sensor junction per this method. Sound reasonable to folks?

https://www.jeepforum.com/forum/f11/a...method-990168/ Seems like it would conclusively answer the heat level vs potential gauge/electrical issue. Will pull gauges today, check contacts.

Thanks all.
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