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 Re: 89 cherokee 4.0 running bad (newbie)
[Re: BigJim]
#750272
09/11/06 04:04 AM
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Joined: Sep 2005
Posts: 692
Rock Warrior
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Ok dude think of it thisaway!!! The compression has more POWER than the coolant pressure.. If you have a headgasket leak into the engine the compression goes OUT INTO the coolant and you get spewing all over the place! FORGET about a headgasket failure!! Ok BJ I must disagree a little here. Now I do agree while running the pressure in the cylinder is absolutely higher than coolant pressure, but when the engine is not running the pressure in the cooling system is higher than the pressure in the cylinder. I had 79 Honda Accord that had a leaking head gasket in cyl #2 and as long as I drove the car every day it would keep running, but if I let it sit for more than about 3 days enough coolant would leak into the cylinder that the engine would not turn over and I would have to pull the plug and crank it over to let the water out before it would start. The really quick tell tail if there is a coolant head gasket leak, when he starts the jeep does it puff ôwhite smokeö (steam) out the tail pipe for the first minute or so, what does the coolant in the radiator look like, and what does the oil look like. Eventually it will get to the point where there is oil in the water and water in the oil if the head gasket is leaking. Now all that being said, to me it does not really sound like this guy has any of these problems. It sounds to me like his jeep needs a tune up. Sean Maybe so Sean... But while you were driving, it was puking it's guts out! Headgasket to cylinder leaks fill the coolant passages and radiator with compressed gasses.. after a few minutes or miles the puking starts and the radiator empties itself.. and overheating is quick under these circumstances. <img src="/forums/images/graemlins/smile.gif" alt="" /> I did get a big grin over you draining the cylinder before starting... Thats pretty hard headed. Big Jim <img src="/forums/images/graemlins/pfft.gif" alt="" /> In all honesty, I dove the car for a good year, ~10,000 miles like this. I was poor and in college and didnt have time to fix it. I only had to fill the radiator about every week or so. When it actually did go the head gasket was completely gone between 2 and 3 and the waterjacket, but for whatever miricle, it was still in tact around the oil passages. Sean
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Re: 89 cherokee 4.0 running bad (newbie)
[Re: snowrodeo]
#750273
09/11/06 05:24 AM
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Joined: Mar 2004
Posts: 2,398
Body Damage is Cool
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Running bad all the time, losing coolant, strange deposit on #1 plug. Hmmmmm No it's not a common "Jeep thing" but strange things happen to all makes. I'm thinking a cracked head could leak coolant into the intake valve area, above the valve, so the engine could indeed "suck coolant". cracks open and close some with temp changes and properties would change as the crack grew with time. The O2 sensor should not affect the way the engine runs cold, it's out of the loop so to speak. I would talk about the fuel system but that would have nothing to do with coolant loss. If what is said is true, coolant loss with no external leaks, I'll guess cracked head. <img src="/forums/images/graemlins/notooth.gif" alt="" />
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Re: 89 cherokee 4.0 running bad (newbie)
[Re: JeePete]
#750274
09/11/06 03:15 PM
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Joined: Sep 2005
Posts: 692
Rock Warrior
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Running bad all the time, losing coolant, strange deposit on #1 plug. Hmmmmm No it's not a common "Jeep thing" but strange things happen to all makes. I'm thinking a cracked head could leak coolant into the intake valve area, above the valve, so the engine could indeed "suck coolant". cracks open and close some with temp changes and properties would change as the crack grew with time. The O2 sensor should not affect the way the engine runs cold, it's out of the loop so to speak. I would talk about the fuel system but that would have nothing to do with coolant loss. If what is said is true, coolant loss with no external leaks, I'll guess cracked head. <img src="/forums/images/graemlins/notooth.gif" alt="" /> These all have cast iron heads right? I mean I know its not impossible, but it just seems unlikely that one cracked. Question though, why would an O2 sensor be out of the loop when the engine is cold? And have things changed because on my 99 I can watch the output of the O2 sensor with a scan tool and my laptop, and I can also watch the status of the fuel system, and the only time it says it runs in open loop is at wide open throttle, and under decel with the throttle closed.
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 Re: 89 cherokee 4.0 running bad (newbie)
[Re: Bigbird79]
#750275
09/11/06 03:34 PM
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Joined: Oct 2003
Posts: 7,768
Web Wheeler
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why would an O2 sensor be out of the loop when the engine is cold? If it is left in the loop it will lean out the mixture when the engine is cold and needs the extra fuel to run.. The computer keeps the mixture a bit rich..just like the choke on a carb.. until temp is reached and then the 02 is brought into the loop to keep the milage up. Big Jim <img src="/forums/images/graemlins/pfft.gif" alt="" />
professional bovine relocation specialist
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Re: 89 cherokee 4.0 running bad (newbie)
[Re: Bigbird79]
#750276
09/11/06 04:43 PM
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Joined: Mar 2004
Posts: 2,398
Body Damage is Cool
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These all have cast iron heads right? I mean I know its not impossible, but it just seems unlikely that one cracked. It's also unlikely an engine would lose coolant without an external leak but not impossible. Stranger things have happened. I don't think cracked cast iron heads are especially rare. But I'm just guessing at something that may account for all the symptoms described. It's my understanding, while the O2 sensor is functioning while the engine is cold and you can monitor it, the computer does not use it's output until the engine warms up. As BJ said, it would not run well cold on the computers Normal temp program. OBD-II systems may be different, but we're dealing with OBD-I here. BTW, I don't think anyone mentioned checking for troublecodes yet. That should be step #1 when diagnosing a Jeep with OBD. <img src="/forums/images/graemlins/cheers.gif" alt="" />
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Re: 89 cherokee 4.0 running bad (newbie)
[Re: JeePete]
#750277
09/11/06 05:14 PM
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Joined: Sep 2005
Posts: 692
Rock Warrior
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Good points, I didnt think about the fuel system trying to duplicate a choke function. That makes perfect sense. Hey I learned something today, that means I can stop thinking now. <img src="/forums/images/graemlins/lol.gif" alt="" />) As for checking any trouble codes, I kinda figured that went with out saying, but you're right we should have mentioned that too. <img src="/forums/images/graemlins/cheers.gif" alt="" />
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Re: 89 cherokee 4.0 running bad (newbie)
[Re: BigJim]
#750278
09/11/06 11:49 PM
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Joined: Jun 2004
Posts: 1,063
Body Damage is Cool
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I see no reason whatever to clean what don't need cleaning inside the engine. I would be scared as hell of chunks of crap floating around and into my pump! We know what the inside of a 200K engine looks like... I think they should be left alone. Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" /> well it depends on who owns the 200k engine. if it was well maintained it shouldnt have any build up. <img src="/forums/images/graemlins/smile.gif" alt="" />.you can hook a snap -on scanner to the jeep and get a read out on the o2 as well as the tps and other things. that is how i found out my o2 sensor was bad. as far ad the low coolant,I am still trying to find a leak in mine. it isnt coming from any hoses,waterpump,radiator or anything .and it isnt being dumped into the engine or the floorboard.
out of all the jeeps in this town the d**n gremlin had to invade mine
I've done so much,with so little for so long i can practicly do anything with nothing
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Re: 89 cherokee 4.0 running bad (newbie)
[Re: cuervo25]
#750279
09/12/06 09:29 AM
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Joined: Apr 2002
Posts: 290
OP
Mudrunner
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hey thanks guys, you've given me some directions here. i didn't think of checking for codes because no CEL has come on. it could just be an O2 problem, although the gunk on the one plug has me confused. someone told me the valve seals may be shot, i suppose that could show up as gunk on the plug. i have done plugs/cap/rotor to no effect. i will let you know what i find. <img src="/forums/images/graemlins/patriot.gif" alt="" />
97Rodeo Rancho9ks/Aisins/3.2L SOHC/M1 only
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Proper Prior Planning Prevents P*ss-Poor Performance--Maj. R.T.Spooner USMC(Ret.)
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Re: 89 cherokee 4.0 running bad (newbie)
[Re: snowrodeo]
#750280
09/12/06 02:13 PM
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Joined: Mar 2004
Posts: 2,398
Body Damage is Cool
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Bad 02 sensors don't cause coolant loss but I'm sure you know that. Check the new plug(s) for fouling. Good luck <img src="/forums/images/graemlins/cheers.gif" alt="" />
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