03 KJ Overheating after 30 minutes of driving. (Fixed)

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randyre

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Short version ... For those that don't feel like reading a novel scroll to the bottom for the final fix, but I think you might find the story and the troubleshooting steps intriguing.


Long version, here goes.

So been a KJ owner for about three years, but only lurked on here and thought I would give back with writing about my overheating experience and the final fix.

So, problem started when the AC clutch locked up and took out the serpentine belt. Ordered a new clutch and went to work. Could not for the life of me get the old clutch off, so after a few days of trying everything under the sun the Jeep sat next to the house.

Fast forward to about a year ago and I really needed another vehicle and so I started working on the Jeep again, finally got out the grinder and went to town on the old AC clutch and got it off, but in the process buggered up the threads for the retaining bolt, as well as the spline a bit too. After beating the new clutch on realized it wasn't going anywhere so put her back together and started driving it around town and it was fine, so start to drive back and for to work about 40 miles each way.

By now you're probably asking, where's the overheating? Get to it already! So here goes. On the third day it overheated on the way to work. Everything blowing out the expansion tank. Let it cool and drove some more until I could get to some water, and boy was she hot (good for Women, bad for vehicles). Opened the bleed screw to pour in water and just blew out steam for the first gallon. Anyhow, checked everything the next morning and on the way home from work she overheated again. This time water was pouring out the water pump and had to have it towed the rest of the way home.

So, onto the water pump replacement, new pump installed, belt installed, and everything topped off. Went for a drive around town and seemed fixed.

On the way to work guess what... She overheated again. repeat and rinse for about three days, finally decide to park it again for almost a year. Then last month decided I need a winter vehicle again, so on to the repair. Replaced thermostat, flushed entire cooling system and went for another drive around town, and she seemed fixed, but alas it was folly. On the way to work she overheated again, and again on the way home. By this time, I was carrying 3-4 gallons of water with me just in case.

So went through it again at home and couldn't see anything wrong with it but did notice the tensioner was bad and moving a lot so decided to replace it. Put it all back together and started it and after it warmed up a bit decided to top off the coolant and when I went to open the bleed screw and it blew off and water was shooting out of it al the way to the hood. Then I thought, could the water pump be turning the wrong way? No that's not really possible, is it? My KJ has had the radiator support replaced so has no stickers on it, so went online for a belt diagram and just in case anyone was wondering, yes you can put the belt on in a way that it routs properly, as in flats on flats and ribs on ribs, and you can get the water pump to run the wrong direction.

So, I say to myself, Duh, water pump running wrong way, maybe doesn't let thermostat heat up or water is circulated wrong direction, so "FIXED" right? Wrong... next day it overheated again on the way to work. Then I started thinking what else can it be? then I realized it overheats at almost the exact same place every time, so what can it be? Head gasket? Oh man, I hope not.
So got a head gasket coolant test kit and it tested fine, not a drop of exhaust in the coolant.

I finally hooked up my ODB2 dongle and app so I could monitor temps, seems that it runs at 100-201 for a long time, then it bumps up to 203 for a bit and then 206 for a few minutes, then started climing through 210 and about then my heat starts blowing cold and that's followed by 220-226 and I start seeing steam. So, my next thought is water pump impellor slipping, or some other high speed cavitation problem, so the next day I drove it home again, this time at 45mph as I've never had it overheat while idling or while just running around town.

Guess what.... Nope not it, still overheated, but well before the same place it usually overheated, so I think, AHA, its time related not speed or miles. What else can it be?

Still stumped I looked at what I've Replaced:
Water Pump, Hoses, Thermostat and flushed the system three different times.

So last thing I can think of is the radiator, even though water flows through it pretty well, I figure there's no way thats it, but I've tried everything else so what do I have to loose but more money and time.

So new radiator comes in, flushed the system, boil tested both the new and old thermostat (they both functioned correctly) and decided to install a metal impellor water pump even though after removing the old one it seemed to be doing OK, but was worried the excessive heat had reduced the life of the bearing and seal. Refilled again with proper coolant and ran it again, this time let it sit running for almost two hours. Stayed at 199-201 forever, then started climbing again past 203, 206, 210... I thought great here we go again. Then it hit 217 and I decided to turn on the AC to get the fan to come on and the temp dropped again to 201. Hmm, bad fan? So let it climb again, 217, 220, 226....bang, fan came on by itself, temp back to 201. Scratch head and decide to let it sit for another 20-30 minutes and temp rises, fan comes on, temp goes back down multiple times just as it should. Take it for an hour-long drive, watching the ODB2 temps and it stays between 199 and 203. Pull into a parking lot and let it idle, temps eventually climb to 226 and fan comes on and back to normal. Drive it home and for the last 4 days it's been perfect. Re-ran the head gasket leak test and it's got no contamination.

So finally. FIXED. I'm guessing that the radiator, although flowing was not flowing well enough. But in the long run, I now had a nearly new cooling system. And it wasn't really too hard to replace the radiator so no harm no foul.


Thanks for the long read, and I hope this helps someone else.

Randy
 

wilton

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Did you end up replacing the fan? I had one that would work intermittently. Once I found it was the cause of my overheating I replaced it. I only ran it for a few months until I collected all the HD cooling parts. Now it just sits on a shelf in my garage. It's yours if you want/need it.
 

blackhawk

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That's a long Odyssey. That's why I always try to find original Mopar parts. But it's a hard labor nowadays.
 

CheddarGau

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Short version ... For those that don't feel like reading a novel scroll to the bottom for the final fix, but I think you might find the story and the troubleshooting steps intriguing.


Long version, here goes.

So been a KJ owner for about three years, but only lurked on here and thought I would give back with writing about my overheating experience and the final fix.

So, problem started when the AC clutch locked up and took out the serpentine belt. Ordered a new clutch and went to work. Could not for the life of me get the old clutch off, so after a few days of trying everything under the sun the Jeep sat next to the house.

Fast forward to about a year ago and I really needed another vehicle and so I started working on the Jeep again, finally got out the grinder and went to town on the old AC clutch and got it off, but in the process buggered up the threads for the retaining bolt, as well as the spline a bit too. After beating the new clutch on realized it wasn't going anywhere so put her back together and started driving it around town and it was fine, so start to drive back and for to work about 40 miles each way.

By now you're probably asking, where's the overheating? Get to it already! So here goes. On the third day it overheated on the way to work. Everything blowing out the expansion tank. Let it cool and drove some more until I could get to some water, and boy was she hot (good for Women, bad for vehicles). Opened the bleed screw to pour in water and just blew out steam for the first gallon. Anyhow, checked everything the next morning and on the way home from work she overheated again. This time water was pouring out the water pump and had to have it towed the rest of the way home.

So, onto the water pump replacement, new pump installed, belt installed, and everything topped off. Went for a drive around town and seemed fixed.

On the way to work guess what... She overheated again. repeat and rinse for about three days, finally decide to park it again for almost a year. Then last month decided I need a winter vehicle again, so on to the repair. Replaced thermostat, flushed entire cooling system and went for another drive around town, and she seemed fixed, but alas it was folly. On the way to work she overheated again, and again on the way home. By this time, I was carrying 3-4 gallons of water with me just in case.

So went through it again at home and couldn't see anything wrong with it but did notice the tensioner was bad and moving a lot so decided to replace it. Put it all back together and started it and after it warmed up a bit decided to top off the coolant and when I went to open the bleed screw and it blew off and water was shooting out of it al the way to the hood. Then I thought, could the water pump be turning the wrong way? No that's not really possible, is it? My KJ has had the radiator support replaced so has no stickers on it, so went online for a belt diagram and just in case anyone was wondering, yes you can put the belt on in a way that it routs properly, as in flats on flats and ribs on ribs, and you can get the water pump to run the wrong direction.

So, I say to myself, Duh, water pump running wrong way, maybe doesn't let thermostat heat up or water is circulated wrong direction, so "FIXED" right? Wrong... next day it overheated again on the way to work. Then I started thinking what else can it be? then I realized it overheats at almost the exact same place every time, so what can it be? Head gasket? Oh man, I hope not.
So got a head gasket coolant test kit and it tested fine, not a drop of exhaust in the coolant.

I finally hooked up my ODB2 dongle and app so I could monitor temps, seems that it runs at 100-201 for a long time, then it bumps up to 203 for a bit and then 206 for a few minutes, then started climing through 210 and about then my heat starts blowing cold and that's followed by 220-226 and I start seeing steam. So, my next thought is water pump impellor slipping, or some other high speed cavitation problem, so the next day I drove it home again, this time at 45mph as I've never had it overheat while idling or while just running around town.

Guess what.... Nope not it, still overheated, but well before the same place it usually overheated, so I think, AHA, its time related not speed or miles. What else can it be?

Still stumped I looked at what I've Replaced:
Water Pump, Hoses, Thermostat and flushed the system three different times.

So last thing I can think of is the radiator, even though water flows through it pretty well, I figure there's no way thats it, but I've tried everything else so what do I have to loose but more money and time.

So new radiator comes in, flushed the system, boil tested both the new and old thermostat (they both functioned correctly) and decided to install a metal impellor water pump even though after removing the old one it seemed to be doing OK, but was worried the excessive heat had reduced the life of the bearing and seal. Refilled again with proper coolant and ran it again, this time let it sit running for almost two hours. Stayed at 199-201 forever, then started climbing again past 203, 206, 210... I thought great here we go again. Then it hit 217 and I decided to turn on the AC to get the fan to come on and the temp dropped again to 201. Hmm, bad fan? So let it climb again, 217, 220, 226....bang, fan came on by itself, temp back to 201. Scratch head and decide to let it sit for another 20-30 minutes and temp rises, fan comes on, temp goes back down multiple times just as it should. Take it for an hour-long drive, watching the ODB2 temps and it stays between 199 and 203. Pull into a parking lot and let it idle, temps eventually climb to 226 and fan comes on and back to normal. Drive it home and for the last 4 days it's been perfect. Re-ran the head gasket leak test and it's got no contamination.

So finally. FIXED. I'm guessing that the radiator, although flowing was not flowing well enough. But in the long run, I now had a nearly new cooling system. And it wasn't really too hard to replace the radiator so no harm no foul.


Thanks for the long read, and I hope this helps someone else.

Randy
Good work. If the rad was clogged, the heater core may also be partially clogged. I would back flush the heater core and see what comes out. Replacing a rad is easy, but no one wants to do a heater core.

Also I'm a fan of putting in the clutch fan and shroud(with different electric fan) just in case the electric fan ever fails. You essentially get the HD cooling for your engine.
 

randyre

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Did you end up replacing the fan? I had one that would work intermittently. Once I found it was the cause of my overheating I replaced it. I only ran it for a few months until I collected all the HD cooling parts. Now it just sits on a shelf in my garage. It's yours if you want/need it.
Didn't replace the fan as I never found it to not work, in fact turning on the AC to get the fan to come on early is probably what kept me from blowing a head gasket.
 

randyre

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Good work. If the rad was clogged, the heater core may also be partially clogged. I would back flush the heater core and see what comes out. Replacing a rad is easy, but no one wants to do a heater core.

Also I'm a fan of putting in the clutch fan and shroud(with different electric fan) just in case the electric fan ever fails. You essentially get the HD cooling for your engine.
Thanks, I did flush the entire system three times, including back-flushing the heater core, but even the radiator was showing water moving through it, just seems that it either wasn't flowing through all the fins, therefore not cooling enough, or backing up when under pressure, as it seemed to have good flow, but since the upper hoses and tank became pressurized, and the bottom hose didn't I figure it was blocking itself when under heat and pressure, but with a garden hose it was just fine.

I may look into the HD fan arrangement, but really never have liked mechanical fans all that much.
 

CheddarGau

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Thanks, I did flush the entire system three times, including back-flushing the heater core, but even the radiator was showing water moving through it, just seems that it either wasn't flowing through all the fins, therefore not cooling enough, or backing up when under pressure, as it seemed to have good flow, but since the upper hoses and tank became pressurized, and the bottom hose didn't I figure it was blocking itself when under heat and pressure, but with a garden hose it was just fine.

I may look into the HD fan arrangement, but really never have liked mechanical fans all that much.
It's a 2 fan system. 1 mechanical and 1 electric.

For the back flushing, I change directions every 10 seconds, it works well, but a heater core is much smaller than a rad, so it's a lot easier to see progress. Radiators are cheap enough to just replace and call it a day.
 

randyre

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Just a quick update, System is still working, no overheating with almost 600 miles since the new Rad. Still looking for the HD parts, but no luck in any of the local wrecking yards.
 

CheddarGau

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Just a quick update, System is still working, no overheating with almost 600 miles since the new Rad. Still looking for the HD parts, but no luck in any of the local wrecking yards.
I bought mine new. The only one that really cost a lot was the fan blade itself. Everything else I could order for reasonable prices. I did a mix of local parts suppliers and rock auto. Electric fan/shroud I went local since it would be easier to warranty if the electric fan packed it in. Also at some point Chrysler went to a 2 stage electric fan vs a single stage. You will need to check how many pins your electric fan connector has, or match it to the connector, since they are different and won't fit each other.
 

JeepJeepster

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226F is a bit high for the fan to kick on. Before I added the HD fan, my electric fan always kicked on at 217F. Ive never seen my engine above 217F, Ive never seen it above 204F with the HD cooling.

Ive got to wonder if the fan has lost its low speed.
 

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