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Posted: 5/19/2005 1:46:30 PM EDT
...but before it did, my engine was running very erratically.
As if it had a miss...and kept dying...but the engine was NOT overheating! Does anyone know IF a water pump going out on a Jeep Grand Cherokee with the 4.0 in-line-six engine could possibly make the engine run erratically WHEN the motor is not overheated? And why would it do so? So, what think ye, hive mind? Eric The(ShadeTreeMechanic)Hun 
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Posted: 5/19/2005 1:47:34 PM EDT
[#1]
That's a pisser
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Posted: 5/19/2005 1:49:27 PM EDT
[#2]
only if the water pump was leaking, and water got into the distributor, which is unlikely.......
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Posted: 5/19/2005 1:54:17 PM EDT
[#3]
I was thinking that maybe the bearing going out in the water pump might cause enough friction as to slow down the engine to some degree, and make it appear that it was missing.
Hmmm, I just want to figure out if there is something else I need to be checking in addition to the water pump. Thanks. Eric The(Bumfuzzled)Hun
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Posted: 5/19/2005 1:55:14 PM EDT
[#4]
Had a GC with a 4.0 also, water pump went out, got a new one at autozone, had it going again in no time. It was running rough before, overheating and what not, but did fine after. Thats a bulllet proof motor, maybe something electrical?
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Posted: 5/19/2005 1:56:00 PM EDT
[#5]
That's all I could come up with ETH, but it seems pretty thin to me. |
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Posted: 5/19/2005 1:56:58 PM EDT
[#6]
over heating how? If the pump were going and not circulating fluid, it is unlikely your gauge was reading correctly. I would not rely on that as an indication that the jeep did not overheat at all.
Also, lower flow may have made it seem like it was cooling ok, but you may have had hot spots in the low flow area's of the engine. Also you don't mention what year it is. There are coolent temp sensors independent of the gauge that may have caused a computer problem. |
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Posted: 5/19/2005 1:57:09 PM EDT
[#7]
Sorry man..............my skills are limited to changing the oil and not much more.
Will be interesting to see how it runs after replacing the water pump. vmax84 |
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Posted: 5/19/2005 1:57:28 PM EDT
[#8]
Please, Dear God, no! Not something electrical ! That's always a real beotch! Eric The(KnowsEnoughAboutElectricalMattersAsToKnowHeKnowsNothing)Hun
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Posted: 5/19/2005 1:58:04 PM EDT
[#9]
The bearing set was seizing slightly...same thing happened on my 98' TJ.
You will be fine once you get it replaced... |
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Posted: 5/19/2005 1:59:47 PM EDT
[#10]
Wow, this seems to make quite a bit of sense. Hope your engine isn't damaged. vmax84 |
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Posted: 5/19/2005 2:02:44 PM EDT
[#11]
Like moving from the typical 200 degree F into the halfway mark to the red line. But it only did that right at the end. I shut the motor down before it stayed there for more than a minute.
The engine appearearances suggested that it was hotter than normal.
True. Would that have tripped some computer response to make the engine run erratically?
1997, with about 125,000 miles on it. So, the water pump failure, which was original, is no surprise. What about those coolant temp sensors? Eric The(StillBumfuzzled)Hun
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Posted: 5/19/2005 2:04:12 PM EDT
[#12]
Your motor didn't overheat? Or the water temperature sensor didn't overheat? I'm betting the latter.
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Posted: 5/19/2005 2:05:32 PM EDT
[#13]
I surely hope that is precisely what it was! The water pump has been 'going out' for a couple of days, now! Water has been leaking from the weep hole. Not enough to have to worry about a massive loss of coolant, but it did show me that there was definitely a problem with the water pump. Yesterday and today, I could actually hear the 'whine' of the water pump when the engine was running. Eric The(Oh,Well,RollingUpMySleeves!)Hun
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Posted: 5/19/2005 2:06:00 PM EDT
[#14]
It doesn't have an overheating safety trip that turns off cylinders does it?
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Posted: 5/19/2005 2:07:24 PM EDT
[#15]
If its new enough it could have been the ECM retarding timing and ignition to keep the temperatures down.
The newer makes can do that to keep a serious problem from becoming an engine breaker |
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Posted: 5/19/2005 2:10:09 PM EDT
[#16]
I have a 2001 Cherokee; 4.0 6 cyl.
The coolant temperature sensor (ECT), does more than just monitor the coolant temp, it communicates with the computer module to control other engine components that could easily result in your engine running erratically. From the factory service manual... OPERATION At key-on, the Powertrain Control Module (PCM) sends out a regulated 5 volt signal to the ECT sensor. The PCM then monitors the signal as it passes through the ECT sensor to the sensor ground (sensor return). When the engine is cold, the PCM will operate in Open Loop cycle. It will demand slightly richer air-fuel mixtures and higher idle speeds. This is done until normal operating temperatures are reached. The PCM uses inputs from the ECT sensor for the following calculations: † For engine coolant temperature gauge operation through CCD or PCI (J1850) communications † Injector pulse-width † Spark-advance curves † ASD relay shut-down times † Idle Air Control (IAC) motor key-on steps † Pulse-width prime-shot during cranking † O2 sensor closed loop times † Purge solenoid on/off times † EGR solenoid on/off times (if equipped) † Leak Detection Pump operation (if equipped) † Radiator fan relay on/off times (if equipped) † Target idle speed |
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Posted: 5/19/2005 2:11:01 PM EDT
[#17]
Yeah, the engine 'overheated' just a bit. The temperature guage showed about 235 degrees F, which is about halfway between normal operating temp and severe (red line) overheating.
Well, I don't know about that, one way or the other. The guage showed 235 degrees F, and I think that was likely the actual temp of the engine at the time. I'll just replace the water pump, the serpentine belt, and both radiator hoses and see if the 'erratic' running continues! Thanks for your response! Eric The(EverHopeful)Hun
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Posted: 5/19/2005 2:12:48 PM EDT
[#18]
Great question! Does it? Eric The(InquiringHunsWantToKnow)Hun
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Posted: 5/19/2005 2:14:27 PM EDT
[#19]
My 98 Cherokee overheated badly on me a couple times due to a persistent problem with my radiator.
That was when I had about 185,000 miles on it. I now have 212,000. Once you get it running again, check your oil to make sure no water is mixing with it. If there is, the oil will look like chocolate milk, and you have a blown head gasket. There is a chance that you could end up with oil in your radiator, but that is kinda remote. Other than that, I think you will be fine. The 4.0 six is one tough engine. I would like to buy a couple of wrecks and fix up the engines just for me to use. |
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Posted: 5/19/2005 2:14:28 PM EDT
[#20]
Yes, indeed. A prayer would be in order. Eric The(DearLord...)Hun
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Posted: 5/19/2005 2:15:27 PM EDT
[#21]
Shadetree Mechanic Advice:
Use a high quality replacement water pump when changing it out..........let's not do this twice. Practice is fun in certain things  ..............but this ain't one of them.Maybe it did send a couple codes to the computer when it started to overheat. Can you disconnect the battery for a few minutes to "reset" the computer? A little knowledge in the wrong hands is dangerous. vmax84 |
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Posted: 5/19/2005 2:16:41 PM EDT
[#22]
Did the electric fan kick in? It should when the temp reaches around 225. |
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Posted: 5/19/2005 2:19:16 PM EDT
[#23]
Disclaimer:
Even though it may sound like it, or I might even pretend, I am NOT a mechanic. I am not kidding on this. I may have frequented a Red Roof Inn from time to time, but fixing engines was never discussed or even remotely thought about. vmax84 
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Posted: 5/19/2005 2:30:11 PM EDT
[#24]
Quoted:
This year model Jeep only has the physical fan that's attached to the water pump. But having been involved with motor vehicles since an early age, I would say that the engine 'seemed' to me to be around 225 to 235 degrees F. Not seriously 'overheated', but well on its way there. Eric The(Ouch!Doesn'tTakeMeLongToTestARadiatorCap!)Hun
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Posted: 5/19/2005 3:56:35 PM EDT
[#25]
My guess is you have a serpetine belt? If so, the pump may have affected belt which turns the alternator which in turn would probably affect the electrical which would in turn affect the ignition which would make it miss?
Geez, sounds like the old story about "for the want of a nail"?  |
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Posted: 5/19/2005 3:59:36 PM EDT
[#26]
My guess it that the temp guauge is also bad.
If the engine is not overheating then the water pump would have no other affect on the car other then circulating coolant, no parts from the pump can enter the engine. SO I am guessing the jeep WAS over heating but the guage was reading incorrectly and now the damage is already done inside the motor. Sgat1r5 |
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Posted: 5/19/2005 4:06:59 PM EDT
[#27]
Bingo! That or spray from the "weep" hole, tho I seriously doubt that. Low level most likely, 4.0 is a great motor, hope it did not get so hot as to warp the head tho.  I'd probably run a pressure check on the cooling system when replaced, also check the consistancy of the oil make sure it looks like oil.
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Posted: 5/19/2005 4:07:53 PM EDT
[#28]
lol, it's a Jeep...IMO Chrysler is the King of Electrical Problems... I started getting burnt out taillights in my Jeep...one bulb went out...I replaced it, and 5 seconds later a different bulb burned out...replaced that one, and 5 seconds later another bulb burned out...replaced that one and, well, you get the picture  My GC was doing the same thing, running really rough and erratic, I replaced the water pump and the freeze plugs (3 had rust holes!) and the engine hasn't given me any problems since (5.2l V8)...if only I could say the same for the tranny and suspension 
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Posted: 5/19/2005 4:14:20 PM EDT
[#29]
ETH, It's good practice to go ahead and replace the thermostat while you are replacing the pump, belt, and hoses. Save yourself some headache and do it now. good luck! |
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Posted: 5/19/2005 4:23:55 PM EDT
[#30]
Be glad more didn't happen. My water ump went bad seized and wrapped the belt around a pulley. That in turn yanked the fan into the hood and radiator. Damaged the alternator pullley , fan shroud ,tensioner pulley and snapped the water pump arms so the w/p was loose underr the hood. $700 later all was fixed. Try to fix the w/p then see how it runs. A belt would be good to replace at the same time. Good luck.
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Posted: 5/19/2005 5:24:30 PM EDT
[#31]
Sorry I was in a bit of a rush and didn't get to finish everything I wanted to say.
If you killed it like you said, I doubt you did any damage. I meant to finish saying that the coolant sensor would probably have tripped something in the computer and thus you lost power and the engine acted funny. I would definatly replace the thermostat while you have stuff apart, and look into the fan clutch while you are at it. Most of that comes off anyway when you replace the pump. |
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Posted: 5/19/2005 5:58:16 PM EDT
[#32]
Quoted:
Great idea! There's only two bolts holding it on, the price is under $10.00, and it's original, so it's got 125,000 miles on it, as well! Thanks!
Thanks, again! I'll let y'all know what happens tomorrow afternoon! I'm spending the evening (and night) with the ex-Miz Hun at the moment! Eric The(Va-Va-Voom!)Hun
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Posted: 5/19/2005 6:00:39 PM EDT
[#33]
Absolutely! Stories like yours are precisely what I was trying to avoid! What sort of noise was the water pump making before it seized? A high-pitched 'mechanical' whining? Eric The(Huh?)Hun
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Posted: 5/19/2005 7:10:25 PM EDT
[#34]
Newer cars tend to be ultra-intolerant of any kind of overheating situation. I am praying that you didn't blow the headgasket; now may be the time for an authoritative leak-down test to see if you get any losses. Check the coolant/oil for signs of "inappropriate mixing" (really, I'm not a bigot, I just play one on TV), and if you haven't gotten the system broken open yet, do a pressure test on the cooling system, although the pressure may just bleed at the weep hole.
If you've blown a head gasket, you better break out that crisp new Mastercard, and hold onto your hat!
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Posted: 5/19/2005 7:31:33 PM EDT
[#35]
If my 4.0 liter inline-six Jeep motor blows a head gasket at a mere 235 degrees F., then it is not the engine that I have come to know and love over the last two decades!
Trust me, it never got any hotter than that, even if the temp gauge wasn't working. I grew up in West Texas where car radiators boiling over on 115 degree Summer days was the norm. Nope. I will disconnect the battery to reset any defaults, but I doubt that even that will be necessary. Hopefully. Eric The(AndWithCars,AllYouCanDoIsHope)Hun
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Posted: 5/19/2005 7:36:39 PM EDT
[#36]
ETH,
regardless of where one lives todays modern engines should never overheat unless there is a problem. Most engines are designed to operate at around 200 degrees. I agree that you should replace the thermostat as part of the job. Sgtar15 |
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Posted: 5/19/2005 7:39:15 PM EDT
[#37]
Hey, pardner....I imagine that you'll be OK once you get the water pump changed.
These guys are the arfcom of Jeeps: NAXJA 4.0 Litres of any given year are the same between XJ's and YJ's. 
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Posted: 5/19/2005 7:39:54 PM EDT
[#38]
A water pump going out is just such a problem!
Mine did, as well, until today!
I concur! It's less than $10.00 and will be in front of my face for about an hour tomorrow afternoon! Thanks! Eric The(WrenchSpinning)Hun
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Posted: 5/19/2005 7:40:00 PM EDT
[#39]
1997 4.0L Jeeps usually don't hurt the head even if they overheat. Your trusty mount could have been on the verge of vapor lock. I think the fuel injector for the #3 cylinder can act up when things get too warm. 4.0Ls can be a bit of a pain to get all the air out of the system once the coolant has been drained. To try and avoid "hot spots" when restarting I recommend you remove the coolant sensor <should be on the cylinder head towards the firewall on the passenger side> and add coolant until it flows out of the hole. Then reinstall the sensor and top off the coolant in both the radiator and the overflow reservoir. Other than that the job should be pretty straightforward. Change the pump and thermostat and see how she behaves. Don't worry about any electronics until you've got the known mechanical problem solved. I bet she'll be fine.
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Posted: 5/19/2005 7:43:06 PM EDT
[#40]
Much grass, Amigo! I have that Preston Radiator flush valve on the heater hose return line (or is it the intake hose line?), so getting any air out of the system and topping it off with coolant shouldn't be a problem. Again, hopefully . Eric The(AlwaysHopeful)Hun
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Posted: 5/19/2005 7:50:10 PM EDT
[#41]
If you want to know how serious it got, then you need to pull and inspect the plugs.
One or more holes could have run hot enough to fry the plug, detonate, or melt an electrode. You need to have a look -- and replace them to be on the safe side. |
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Posted: 5/19/2005 7:54:45 PM EDT
[#42]
btw...according to the Jeep repair manual I have this repair requires a MINIMUM of 12 beers to complete.
Sgat1r5 |
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Posted: 5/20/2005 1:08:38 PM EDT
[#43]
I thought that was preliminary groundwork?????
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Posted: 5/20/2005 1:16:20 PM EDT
[#44]
God is punishing you for something.
What have you done wrong lately?
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Posted: 5/20/2005 1:22:13 PM EDT
[#45]
Truely great manuals. vmax84 |
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Posted: 5/20/2005 1:22:58 PM EDT
[#46]
Oh, Honey, if it was God punishing me for doing something wrong lately, the motor would have fallen out of the vehicle onto the Interstate! It's just a water pump, so it's likely just a coolant system demon tormenting my soul!  Eric The(ThankfulIt'sNotAnElectronicSystemDemon)Hun
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Posted: 5/20/2005 2:13:36 PM EDT
[#47]
Hun. be sure to check the trouble codes before running it again. You don't need a code reader to do this. Just follow the instructions on the following link. www.allpar.com/fix/codes.html. This will give you a better indication of any other possible problems.
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Posted: 5/20/2005 5:02:52 PM EDT
[#48]
So.....is it fixed now?
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Posted: 5/21/2005 3:02:00 PM EDT
[#49]
Indeed it is! Fine as wine! Running perfectly! I've been driving it pretty hard today in all the heat, and not a bit of overheating! The engine actually idles better than it has in months! Thanks to everyone who helped with advice and pointers in this thread! I appreciate everything y'all did. Of course, it would have been better if y'all had actually done the work for me yesterday! It was fricking 100 Degrees F in Wylie, while I was workling on the Jeep! Thanks, again, y'all! Eric The(Grateful)Hun
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Posted: 5/21/2005 3:20:37 PM EDT
[#50]
excellent!
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