Posted: 3/15/2009 6:17:03 PM EDT
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Anybody care to stay up late with me? I've got a fun couple of problems I get to fix. A customer (my wife - she pays me by slobbing my knob) has brought me a 98 Jeep Cherokee 4.0L with the following problems: 1. The rear hatch doesn't stay open. She's using a broom handle to hold it open when she brings groceries in, which cuts into knob slobbing time. New struts have been aquired. 2. Two months ago, the engine overheated. Root cause of coolant loss unknown. It was filled with coolant again and it's been fine ever since. However, ever since then, gas mileage has dropped significantly (used to get 300 miles to a tank, and now it's about 200). Idle is a tad rough. No additional coolant loss has been observed, and the oil looks clean. Despite this, I suspect that the head gasket may have blown. Customer is stressed, and it's affecting knob slobbing performance. There are no DTC's. 3. The latch mechanism on the rear hatch is reported to be intermittently working. Apparently, the hatch will not consistently open. Sometimes, if the customer pushes very hard on the hatch and blasphemes the virgin Mary, the latching mechanism will free itself and allow the hatch to open. Geek mechanic with a perpetually hard dick in need of relief has a shit load of tools at his disposal, and intends to perform a compression test, followed by a leakdown test. Geek mechanic lives in the middle of bumfuck Ohio, and was not able to locate another block test kit (to check for combusion gasses in the coolant) on short notice, and wishes that he was more organized during the move, 4 years ago. Geek now has a heated shop on the property, and a case of beer. I'll try and take pictures. |
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sounds like your head gasket may be pinched, may have overheated your IAT sensor as well which can cause a reduction in milage, but if its not far enough out of range, it wont trip the CEL.. you may want to check your plugs. also yank your IAC valve and clean it. may want to check your pcv valve.
seeing your other posts about mechanics/mechanic work, you've proally already thought of this stuff, but I thought I would make mention |
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A minor blown head gasket won't set a DTC.
I would suggest pulling the plugs. If you have a coolant leak into the cylinder you'll have one or more plugs steam cleaned. I also suggest a compression test and if you have the equipment a leak down test. This will give you an idea of the engine health. In respect for your wife I won't be asking if your planning on sharing payment... 
Don't suppose the geek happens to be able to look at the data stream by any chance? |
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Quoted: Don't suppose the geek happens to be able to look at the data stream by any chance? Geek lives up to his name, and can monitor the data stream of any sensor as reported by the PCM, and geek - still living up to his name - owns a Digital Storage Oscilloscope, and can monitor sensor voltages directly. |
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gotta go to bed early tonight (already earned my knob slobbering)
but tag for results since my 98 Cherokee mileage has been teh suck lately. My rear door did that too - IIRC you gotta just pull the back panel off and adjust something. (great help I know) The rear hatch struts on mine never work when it's cold. Wait until that Neutral Safety Switch starts getting fussy. That's some fun stuff. I'm too cheap to replace it and too dumb and lazy to rebuild it so I short pins 3 and 5 to bypass and then it starts.
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Quoted: Take the radiator cap off and with the engine cold crank it and watch to see if you get any bubbles in the radiator. No need, as I'll be performing a leakdown test (right after I finish this cold drink). Shop air will pressurize the cylinder, and any leaks (exhaust, intake, into the water jacket, etc) will be audible - and visible, in the event of a coolant leak. |
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Quoted:
Anybody care to stay up late with me? I've got a fun couple of problems I get to fix. A customer (my wife - she pays me by slobbing my knob) has brought me a 98 Jeep Cherokee 4.0L I got exactly that far before deciding this was going to be too involved and painful to even read. |
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Quoted: Fan of hybrids, I take it? Quoted: Anybody care to stay up late with me? I've got a fun couple of problems I get to fix. A customer (my wife - she pays me by slobbing my knob) has brought me a 98 Jeep Cherokee 4.0L I got exactly that far before deciding this was going to be too involved and painful to even read.  |
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Take the radiator cap off and with the engine cold crank it and watch to see if you get any bubbles in the radiator. No need, as I'll be performing a leakdown test (right after I finish this cold drink). Shop air will pressurize the cylinder, and any leaks (exhaust, intake, into the water jacket, etc) will be audible - and visible, in the event of a coolant leak. Not without letting off the rocker arms. |
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1. drink beer.
2. smack tailgate with mallet. 3. drink more beer. 4. cuss at tailgate. 5. drink more beer. 6. get your ass back to the computer where you belong and fix the now playing tab in subnet radio. 7. drink more beer. 8. come up with some sort of excuse for the car, then get knob slobbed? 
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Quoted: Not without letting off the rocker arms. What? That's got nothing to do with anything. The piston is brought to TDC, compression stroke with 80-90psi of shop air applied. If either the intake or exhaust valve are leaking, I'll hear it. If there's a break in the head gasket allowing combustion gasses to permeate the water jacket, I'll hear (and see) it. |
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Quoted: sounds like your head gasket may be pinched, may have overheated your IAT sensor as well which can cause a reduction in milage, but if its not far enough out of range, it wont trip the CEL.. you may want to check your plugs. also yank your IAC valve and clean it. may want to check your pcv valve. seeing your other posts about mechanics/mechanic work, you've proally already thought of this stuff, but I thought I would make mention I hope you meant ECT sensor, as IAT has NOTHING to do with coolant or even oil. (assuming we're talking about the same acronyms here) |
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I know AutoZone has combustion gasses in coolant kits for loan. And I know Napa sells them....
Being that you only lost coolant that one time, I don't think it would be a head gasket. Wouldn't it continue to leak if it was? Is you radiator cap still good? Heater core maybe? Yank out the radiator and see if the radiator is the culprit? I don't know, just throwing stuff out there. If you were in bumfuck Okla we'd have a good time drinking beer and maybe even fixing cars! I blew a headgasket in my truck. Finally got the motor torn down and the passenger side head removed. I did a compression check and figured out it was on that side.. ordering new parts tomorrow. |
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Not without letting off the rocker arms. What? That's got nothing to do with anything. The piston is brought to TDC, compression stroke with 80-90psi of shop air applied. If either the intake or exhaust valve are leaking, I'll hear it. If there's a break in the head gasket allowing combustion gasses to permeate the water jacket, I'll hear (and see) it. Nevermind. good luck 
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Quoted: it took this long to say solution=sell jeep and buy toyota? One of my best friend's is a Toyota dealer mechanic (has been for 20+ years). He's not exactly Maytag repairman bored... Shit happens, dude. Talk to a mechanic that works at an indepentant shop that services everything. Blind brand loyalty is stupid. |
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In my experiance, calling it 'knob slobbering' and talking about it with strangers on the interweb is a good way to lose that privilage.
And I have nothing to contribute - so I will just rub it in how cool my mechanic is. ;o) http://www.ar15.com/forums/topic.html?b=1&f=5&t=845174 |
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Check thermostat. They can be sticky. Check in hot water. If it doesn't open fully...replace. They can leak grease, then become "sticky" and can "repair" themselves by sucking in water to replace the lost grease, then they appear to work again.
The grease is seperated from the wax with a membrane. They work on expansion of wax when it melts.. |
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it took this long to say solution=sell jeep and buy toyota? One of my best friend's is a Toyota dealer mechanic (has been for 20+ years). He's not exactly Maytag repairman bored... Shit happens, dude. Talk to a mechanic that works at an indepentant shop that services everything. Blind brand loyalty is stupid.  Incidentally...I bought the wife a new car yesterday...and I must say..so far I'm impressed...................this is coming from a Chevy guy....................
I bought a 08 Nissan Versa
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Quoted: In my experiance, calling it 'knob slobbering' and talking about it with strangers on the interweb is a good way to lose that privilage. And I have nothing to contribute - so I will just rub it in how cool my mechanic is. ;o) http://www.ar15.com/forums/topic.html?b=1&f=5&t=845174 My wife is reading this thread right now, and has been laughing her ass off. We're a fun couple. |
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Quoted:
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In my experiance, calling it 'knob slobbering' and talking about it with strangers on the interweb is a good way to lose that privilage. And I have nothing to contribute - so I will just rub it in how cool my mechanic is. ;o) http://www.ar15.com/forums/topic.html?b=1&f=5&t=845174 My wife is reading this thread right now, and has been laughing her ass off. We're a fun couple.
awesome. Do you swing? |
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Quoted: I don't know if I trust her judgment she married SubnetQuoted: Quoted: In my experiance, calling it 'knob slobbering' and talking about it with strangers on the interweb is a good way to lose that privilage. And I have nothing to contribute - so I will just rub it in how cool my mechanic is. ;o) http://www.ar15.com/forums/topic.html?b=1&f=5&t=845174 My wife is reading this thread right now, and has been laughing her ass off. We're a fun couple. awesome. Do you swing? |
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Quoted:
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it took this long to say solution=sell jeep and buy toyota? One of my best friend's is a Toyota dealer mechanic (has been for 20+ years). He's not exactly Maytag repairman bored... Shit happens, dude. Talk to a mechanic that works at an indepentant shop that services everything. Blind brand loyalty is stupid. I know, and ive said bad things about toyota in the past too, such as, my truck half rusted away. I wasnt being serious. |
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Okay, I needed to finish my cold drink, but I also needed to bring the vehicle up to operating temperature. The customer is on her way to the store to buy a carton of smokes, and a case of beer. I figure by the time she gets back, the vehicle should be ready for compression testing (nice and toasty). My cold drink is finished, so now I'm just waiting for the customer to hurry the fuck up. You gotta keep the pimp hand strong. |
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4.0 liter Jeep, ran hot, root cause of coolant loss unknown, yeah, I'd say it's going out the tailpipe.
You could try pulling the upstream O2 and seeing if it has a green/whitish tint from coolant, but the leak down test will tell you for sure. A leak down tester is God's gift to basic engine diagnosis. |
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A friend of mine had a focus he lost all of the coolant out of and over heated.
After we got it fixed, it didn't ran as well or as strong. The computer put the engine in a reduced running mode to prevent as much damage as it could when over heating and didn't self reset (I think he said his rpms were limited too). You may be battling something similar with your poor milage. As for why you lost coolant in the first place? Good luck. I had a T-Bird lose a LOT of coolant one summer and it never lost a drop again after that (this of course was after the tradition head gasket replacement on the 3.8L engine). Good luck. |
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A leak down tester is God's gift to basic engine diagnosis. Yes it is. And don't kill me, but mine is a Harbor Freight special. 
I want to hate it, and I know I'm supposed to, but the fucker really works. I'm kinda ashamed to admit it, but I didn't even own one until about a month ago. I used hoses from my compression tester and a pair of vice grips clamped on an air hose as a regulator valve to pump the cylinder full of air. It worked fine for changing valve springs, and although I didn't have a leak down gauge, it accomplished what I needed to see what was leaking from where and how badly.
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