Steam cleaning your 4.0
Newbie
Joined: Dec 2016
Posts: 4
Likes: 0
Model: Cherokee
Why is it better to get the carbon buildup out?
What good thing results?
What happens if you just leave the carbon in there?
PHM
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What good thing results?
What happens if you just leave the carbon in there?
PHM
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I've done a seafoam treatment but pulled the vac line off the booster. boy did that sucker smoke for a bit after the shut-down and restart. #mesquitorepellent.
I'd also like to add that the 4.0L is prone to carbon build up. If you've never done a top-end cleaning, than it's highly recommended especially higher mileage engines. To prolong carbon buildup in the future, take your XJ for a high RPM run down the highway time to time.
EDIT* notice I said high RPM run... I feel the need to correct that and mention that this does not mean high speed! Simply wind out first or second gears. You can keep the RPM's high by keeping her out of OD too.
I'd also like to add that the 4.0L is prone to carbon build up. If you've never done a top-end cleaning, than it's highly recommended especially higher mileage engines. To prolong carbon buildup in the future, take your XJ for a high RPM run down the highway time to time.
EDIT* notice I said high RPM run... I feel the need to correct that and mention that this does not mean high speed! Simply wind out first or second gears. You can keep the RPM's high by keeping her out of OD too.
No, I don't lick fish.
Joined: Mar 2011
Posts: 11,169
Likes: 26
From: Northern Kentucky
Year: 1999
Model: Cherokee (XJ)
Engine: 4.0
Carbon buildup, especially around the valve seats, can cause valves to stick, and can also cause stem seals to wear prematurely if carbon builds up on the stems themselves.
Newbie
Joined: Nov 2010
Posts: 23
Likes: 0
From: Dexter Oregon
Year: 1990
Model: Cherokee
Engine: 4.0L
Great post. Forgot about this we used to do this in the late 70's to our muscle cars to clean the carbon out of the combustion chambers. Then we added water injection on cars helped with detonation due to higher compression and also helped with mileage.
Thanks again
Thanks again
Senior Member
Joined: Mar 2016
Posts: 707
Likes: 20
From: AV Kalifornia
Year: 1996
Model: Grand Cherokee
Engine: 4.0
I think steam cleaning my engine might have messed up the Cadillac converter. about 6 months later I had to get a smog inspection and it failed do the Cadillac converter. It could just be a coincidence but prior to that it had no problems passing smog.
CF Veteran
Joined: Aug 2019
Posts: 1,601
Likes: 226
From: East Tennessee
Year: 1996
Model: Cherokee (XJ)
Engine: 242 cui
CF Veteran
Joined: Jun 2016
Posts: 1,011
Likes: 20
From: CO
Year: 99
Model: Cherokee (XJ)
Engine: 4.0
ide think spray in from the throttle boddy would evenly distribute the water a bit more perhaps?
anyone tried both?
Newbie
Joined: Jan 2023
Posts: 1
Likes: 0
Forgot about this trick and remember seeing a mechanic do it to quiet a noisy valve train back in the 90's.
Did this yesterday on my GF's 99 Laredo 4.0 with 239K on the odometer. I thought the engine was on the way out as it was noisy at idle (like a diesel), had a significant series of misfires at idle and would stumble/lurch trying to get to highway speed. Used a quarter under the throttle to get it to 2800 RPM and slowly ran about 28 ounces of water through. Amazing results! Top end is now quiet, misfires are gone and the engine has strong acceleration from stop to highway speeds. I've always driven imports and have heard this engine is a beast - suffice to say I'm impressed with how it runs with this many miles on the odometer.
I might do it again and I realize the results may not be as significant the second time around, and may do this on my V6 Accord with 60k. Next up replacing her clock spring (air bag light when turning to the left) and oil pressure sending unit (pressure drops at idle when warm).
-Eric
Did this yesterday on my GF's 99 Laredo 4.0 with 239K on the odometer. I thought the engine was on the way out as it was noisy at idle (like a diesel), had a significant series of misfires at idle and would stumble/lurch trying to get to highway speed. Used a quarter under the throttle to get it to 2800 RPM and slowly ran about 28 ounces of water through. Amazing results! Top end is now quiet, misfires are gone and the engine has strong acceleration from stop to highway speeds. I've always driven imports and have heard this engine is a beast - suffice to say I'm impressed with how it runs with this many miles on the odometer.
I might do it again and I realize the results may not be as significant the second time around, and may do this on my V6 Accord with 60k. Next up replacing her clock spring (air bag light when turning to the left) and oil pressure sending unit (pressure drops at idle when warm).
-Eric
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