Blown head gasket on an '01 Cherokee

90Pioneer · Sep 16, 2004

Neighbor today was giving me a ride to Portland to pick up my other Jeep today. Portland is about a 3 hour drive from where I live. Anyway, about 2.5 hours into the drive, she notices some smoke coming out the back of her rig. I have her pull over at the nearest place so I can take a look at things.

Oil was dripping down, from about where the rear main seal is located. It was then blowing back onto the exhaust, and that is what was causing the smoke. I took a gander into her recovery bottle, and it was full of oil. Popped the cap on the radiator and it was also full of oil. However no coolant appeared to be in the oil itself, just oil in the coolant.

No over heating, and to both of our knowledge, it has not in the past 8k miles she's had it.

Needless to say, the Jeep was towed.

It's a 2001 Cherokee Classic AW4 4.0L with 64k miles. Is this common? Why could it have blown so earily in the XJs life? She just purchased it about 8k miles ago.

Comments/ideas? What other possible damage may have resulted from this?

CharlesS · Sep 16, 2004

The reason why you find oil in the coolant is oil system pressure (20-55 psi)IS higher than the cooling system pressure (12-16 psi).
As for why the head gasket blew could be due to several problems.... Cooling system not keeping the engine cool (warped head), or defective gasket.
Since it is a 01 and she has had the Jeep only 8K miles... the repairs should be under warranty.....

Charles

90Pioneer · Sep 17, 2004

The Jeep has 64k miles on it, she's only had it the last 8k.

I guess the mechanic told her that her transmission was over full, and the fluid heated up, and then spewed out onto the exhaust, causing the smoke. The mechanic also said the coolant was discolored from a bottle of stop leak that may have been poured in.

For one, I am 100% positive it was engine oil that was leaking back onto the exhaust, and it was oil in the coolant, not stop leak. I don't even see how stop leak could cause the coolant to look identical to coolant with oil in it. The tranny was over full, I checked it. But this Jeep makes the 3 hour drive weekly, and I'm sure it would have already spewed out on one of the prior trips. Not only this, I checked her coolant level about a week and a half ago. It was bright green, just as it should be. And the coolant has not been touched since she bought it, about 8 months ago.

I think the mechanic is on crack. What do you guys think?

jeepguy97 · Sep 17, 2004

He's been hittin the reefer.

Eagle · Sep 17, 2004

I think you need to consider what he said very carefully.

The head gasket seals the interface between the head and the block. There are no pressurized oil passeges between the head and the block. Oil gets to the head and rocker arm assemblies through the valve lifters (in the block) and then up through the hollow pushrods. The oil in the valve chamber then drains back down into the block at ambient pressure, not at the 40 or 50 pounds of pressure that the oil pump sends to the bearings.

It is exceedingly unlikely that a blown headgasket would or could result in massive quantities of oil escaping into the coolant, since the coolant IS under pressure at the head/block interface.

miked106 · Sep 17, 2004

90Pioneer said:
Neighbor today was giving me a ride to Portland to pick up my other Jeep today. Portland is about a 3 hour drive from where I live. Anyway, about 2.5 hours into the drive, she notices some smoke coming out the back of her rig. I have her pull over at the nearest place so I can take a look at things.

Oil was dripping down, from about where the rear main seal is located. It was then blowing back onto the exhaust, and that is what was causing the smoke. I took a gander into her recovery bottle, and it was full of oil. Popped the cap on the radiator and it was also full of oil. However no coolant appeared to be in the oil itself, just oil in the coolant.

No over heating, and to both of our knowledge, it has not in the past 8k miles she's had it.

Needless to say, the Jeep was towed.

It's a 2001 Cherokee Classic AW4 4.0L with 64k miles. Is this common? Why could it have blown so earily in the XJs life? She just purchased it about 8k miles ago.

Comments/ideas? What other possible damage may have resulted from this?

Not sure about it being common, but i blew my head gasket on my 2001 back in April this year. I had just bought it and it had about 103000 miles on it(it was a sales vehicle for someone) anyways i put about 1,000 on it before it happened. Sure pi.ss.ed me off. These motors should be good for well over 200K miles.

90Pioneer · Sep 17, 2004

Eagle said:
I think you need to consider what he said very carefully.

The head gasket seals the interface between the head and the block. There are no pressurized oil passeges between the head and the block. Oil gets to the head and rocker arm assemblies through the valve lifters (in the block) and then up through the hollow pushrods. The oil in the valve chamber then drains back down into the block at ambient pressure, not at the 40 or 50 pounds of pressure that the oil pump sends to the bearings.

It is exceedingly unlikely that a blown headgasket would or could result in massive quantities of oil escaping into the coolant, since the coolant IS under pressure at the head/block interface.

I never said there was massive quantities of oil in the coolant, just that there was oil in the coolant. I have no doubt about it. I also saw oil dripping out while the Jeep was idling after we pulled over. I am 100% sure it was oil which was dripping. I checked the oil and it was still full, so there was not a whole lot of oil that leaked.

Lets say that I am entirely wrong about everything I've said. Is it even possible that Stop Leak could have made the coolant look like it has oil in it? If so, it must have been poured in over eight months ago, and not turned this way until now. I looked at the coolant a week and a half ago, and it was just as it should be. Is this even possible?

What could account for the oil which appeared to be dripping from the rear of the head?

Eagle · Sep 17, 2004

The usual cause of oil dripping from the back of the head is the valve cover gasket. If the oil is dripping from the back of the engine but you're not certain it's coming from as high up as the head, it could be the rear main seal, or it could be oil from the oil filter adapater housing that has blown back along the side of the block.

It is exceedingly unlikely that a blown head gasket will result in oil getting into the coolant. The opposite is what usually happens. However ... I assume that this is an automatic. The tranny fluid runs through an internal cooler in the radiator. Is it possible that what you saw was tranny fluid rather than engine oil? If so, a failing radiator may be the culpri.

However, neither a leak between the coolant and the tranny fluid in the radiator nor a blown head gasket would account for sufficient oil to be dripping down the exterior of the engine to cause a smoke screen. Having "been there and done that," I'd say that sounds like a rear main seal. It happened to me on the XJ I drove to Montana last year. The rear main seal had been okay around town, but the CCV system wasn't up to snuff and once I got on the Interstate for extended cruising, pressure built in the crankcase and it started pushing massive amounts of oil past the rear main seal.

90Pioneer · Sep 18, 2004

Eagle said:
The usual cause of oil dripping from the back of the head is the valve cover gasket. If the oil is dripping from the back of the engine but you're not certain it's coming from as high up as the head, it could be the rear main seal, or it could be oil from the oil filter adapater housing that has blown back along the side of the block.

It is exceedingly unlikely that a blown head gasket will result in oil getting into the coolant. The opposite is what usually happens. However ... I assume that this is an automatic. The tranny fluid runs through an internal cooler in the radiator. Is it possible that what you saw was tranny fluid rather than engine oil? If so, a failing radiator may be the culpri.

However, neither a leak between the coolant and the tranny fluid in the radiator nor a blown head gasket would account for sufficient oil to be dripping down the exterior of the engine to cause a smoke screen. Having "been there and done that," I'd say that sounds like a rear main seal. It happened to me on the XJ I drove to Montana last year. The rear main seal had been okay around town, but the CCV system wasn't up to snuff and once I got on the Interstate for extended cruising, pressure built in the crankcase and it started pushing massive amounts of oil past the rear main seal.

Then what could account for oil in the coolant?

Dr. Dyno · Sep 18, 2004

90Pioneer said:
Neighbor today was giving me a ride to Portland to pick up my other Jeep today. Portland is about a 3 hour drive from where I live. Anyway, about 2.5 hours into the drive, she notices some smoke coming out the back of her rig. I have her pull over at the nearest place so I can take a look at things.

Oil was dripping down, from about where the rear main seal is located. It was then blowing back onto the exhaust, and that is what was causing the smoke. I took a gander into her recovery bottle, and it was full of oil. Popped the cap on the radiator and it was also full of oil. However no coolant appeared to be in the oil itself, just oil in the coolant.

No over heating, and to both of our knowledge, it has not in the past 8k miles she's had it.

Needless to say, the Jeep was towed.

It's a 2001 Cherokee Classic AW4 4.0L with 64k miles. Is this common? Why could it have blown so earily in the XJs life? She just purchased it about 8k miles ago.

Comments/ideas? What other possible damage may have resulted from this?

It does sound like you have an oil leak from the rear main seal but it's difficult to be sure. A leak from the back of the valve cover can mimic this condition so put your hand behind the head and see if it feels dry or oily. If the oil is coming from the rear main seal, you'll see it drip from the bellhousing.
The oil in coolant is more difficult to account for. Like Eagle said, it's highly unlikely but not impossible for oil to track into the coolant if the head gasket's blown. Usually it's the other way round. The coolant pressure will be 14-16psi (depending on the pressure rating on the radiator cap) while the oil pressure in the oil galleries is next to zero because that's the route by which oil returns to the sump.

However ... I assume that this is an automatic. The tranny fluid runs through an internal cooler in the radiator. Is it possible that what you saw was tranny fluid rather than engine oil? If so, a failing radiator may be the culprit.

That's probably the most plausible explanation for oil appearing in the coolant recovery bottle. Check your tranny fluid and see if it looks like milkshake.

Blown head gasket on an '01 Cherokee

90Pioneer

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CharlesS

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jeepguy97

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Eagle

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miked106

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90Pioneer

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Eagle

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