Does excessive blow-by mean complete rebuild?
08-23-2018, 09:57 PM
#1
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Year: 1994
Model: Cherokee (XJ)
Engine: 4.l
Does excessive blow-by mean complete rebuild?
94 xj 152k miles been fighting excessive blow by. Replaces PVC, CCV, hoses even tried some oil treatment that is supposed to help seal piston rings which will probably make it worse. Still, when driving at highway speed with some stress on the motor I get oil into my air filter, oil seeps from the oil cap, and oil out of of the seat of my oil dip stick tube.
Beaides this issue I have no other problems or leaks. Engine feels and sounds strong. Runs great and has plenty of power. Even compression is good and close across all cylinders.
What are my options? is it it worth it and posisble to change piston rings without full engine rebuild?
There is a 94 4.0 from a rolled xj local on Craigslist for $150 should i buy that and chance it’s good? Should I buy an ATK reman. engine and swap?
I need to keep clay down as much as possible but also want to ensure I make he right moves and don’t end up regretting the decision and end up spending more money in the near future?
What y’all think?
Beaides this issue I have no other problems or leaks. Engine feels and sounds strong. Runs great and has plenty of power. Even compression is good and close across all cylinders.
What are my options? is it it worth it and posisble to change piston rings without full engine rebuild?
There is a 94 4.0 from a rolled xj local on Craigslist for $150 should i buy that and chance it’s good? Should I buy an ATK reman. engine and swap?
I need to keep clay down as much as possible but also want to ensure I make he right moves and don’t end up regretting the decision and end up spending more money in the near future?
What y’all think?
08-24-2018, 07:45 AM
#3
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Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
If you shine a light into the oil filler, how sludgy is the engine?
How much oil do you consume between changes?
Done a dry, then wet compression test?
How much oil do you consume between changes?
Done a dry, then wet compression test?
08-24-2018, 08:29 AM
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Year: 1994
Model: Cherokee (XJ)
Engine: 4.l
I did a dry test
115
125
125
110
120
125
i stoped with the dry test thinking my results were good but after reading the past few days I guess if the wet test results go up that would indicated bad piston rings. How much of an increase would I expect to see?
115
125
125
110
120
125
i stoped with the dry test thinking my results were good but after reading the past few days I guess if the wet test results go up that would indicated bad piston rings. How much of an increase would I expect to see?
08-24-2018, 08:31 AM
#5
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Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Just do it and report back your results. I seriously doubt you have a ring issue.
Whaddya see inside the rocker cover?
Whaddya see inside the rocker cover?
08-24-2018, 03:59 PM
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Year: 1994
Model: Cherokee (XJ)
Engine: 4.l
I bought a new compression gauge set bc the one I used before was borrowed.
This go around here are my results
dry
1) 150
2) 150
3) 155
4) 150
5) 160
6) 155
wet
1) 145
2) 155
3) 150
4) 150
5) 155
6) 150
i would say that is good compression for this engine 153k miles. Sounds great, feels powerful even with stock gears, 4.5lift, 32in tires, JCR front and rear bumpers. No overheat issues
replaces CCV and PVC elbows and hoses. I still get oil into my air filter. Which I can work around by putting a catch can in.
My big mess of a problem is I get oil seeping heavily out of the matting surface of the oil dip stick tube. I tried replacing it with a Mopar part. I had to tap it in there to seat it and still get an oil leak. Tried sealing it with gasket sealer to no resolve either.
Whats next? Damn it. It’s bad enough to we’re I cannot drive far on highways and it will leak enough oil to start smoking heavily as it burns off the engine block.
This go around here are my results
dry
1) 150
2) 150
3) 155
4) 150
5) 160
6) 155
wet
1) 145
2) 155
3) 150
4) 150
5) 155
6) 150
i would say that is good compression for this engine 153k miles. Sounds great, feels powerful even with stock gears, 4.5lift, 32in tires, JCR front and rear bumpers. No overheat issues
replaces CCV and PVC elbows and hoses. I still get oil into my air filter. Which I can work around by putting a catch can in.
My big mess of a problem is I get oil seeping heavily out of the matting surface of the oil dip stick tube. I tried replacing it with a Mopar part. I had to tap it in there to seat it and still get an oil leak. Tried sealing it with gasket sealer to no resolve either.
Whats next? Damn it. It’s bad enough to we’re I cannot drive far on highways and it will leak enough oil to start smoking heavily as it burns off the engine block.
08-24-2018, 09:20 PM
#7
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Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
I bought a new compression gauge set bc the one I used before was borrowed.
This go around here are my results
dry
1) 150
2) 150
3) 155
4) 150
5) 160
6) 155
wet
1) 145
2) 155
3) 150
4) 150
5) 155
6) 150
i would say that is good compression for this engine 153k miles. Sounds great, feels powerful even with stock gears, 4.5lift, 32in tires, JCR front and rear bumpers. No overheat issues
replaces CCV and PVC elbows and hoses. I still get oil into my air filter. Which I can work around by putting a catch can in.
My big mess of a problem is I get oil seeping heavily out of the matting surface of the oil dip stick tube. I tried replacing it with a Mopar part. I had to tap it in there to seat it and still get an oil leak. Tried sealing it with gasket sealer to no resolve either.
Whats next? Damn it. It’s bad enough to we’re I cannot drive far on highways and it will leak enough oil to start smoking heavily as it burns off the engine block.
This go around here are my results
dry
1) 150
2) 150
3) 155
4) 150
5) 160
6) 155
wet
1) 145
2) 155
3) 150
4) 150
5) 155
6) 150
i would say that is good compression for this engine 153k miles. Sounds great, feels powerful even with stock gears, 4.5lift, 32in tires, JCR front and rear bumpers. No overheat issues
replaces CCV and PVC elbows and hoses. I still get oil into my air filter. Which I can work around by putting a catch can in.
My big mess of a problem is I get oil seeping heavily out of the matting surface of the oil dip stick tube. I tried replacing it with a Mopar part. I had to tap it in there to seat it and still get an oil leak. Tried sealing it with gasket sealer to no resolve either.
Whats next? Damn it. It’s bad enough to we’re I cannot drive far on highways and it will leak enough oil to start smoking heavily as it burns off the engine block.
This applies to the earlier 4.0s but I wonder if someone changed a valve cover at one point. Most early and even later Renix 4.0s could be bothered by excessive oil in the air cleaner box.
A fix from my old days as Service Manager at a Jeep dealership follows. Information was provided to me from a buddy at JeepTech during those days. I don’t believe it ever came out in a Technical Service Bulletin.
Remove the valve cover and turn it over. Next, remove the fluted tubes that are now facing you by removing three screws on each.
Chop 1 inch off each of them. Then, drill a half inch hole as shown in the photo. The flat side of the flute that’s closest to the edge of the valve cover.
Clean and de-burr/sand all rough edges nicely, clean with solvent, and reinstall. Don’t be concerned about the chintzy gaskets that will probably crumble into oblivion when you remove the fluted tubes. They can go back together without gaskets.
Here’s a handy video from my friend Brendan showing more detail.
Got a photo of your CCV stuff? You mention PCV, but they don't have one.
The vacuum fitting that pulls the vapors from the engine. Is it clogged not allowing it to work?
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08-24-2018, 10:05 PM
#8
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Year: 1994
Model: Cherokee (XJ)
Engine: 4.l
Thanks for the great info.
as far as PVC and CCV I am not sure and I have been trying to figure out what’s the deal. I have 1994 XJ original engine. The valve cover at the rear has a vent to the intake manifold it is identical to the forward vent to the air box. I thought the one at the rear was the PVC and had the small orffice and the vent at the front is the CCV and would be a large orffice that vents to the air box.
I cannot not find a clear picture, diagram or explanation. Maybe some help on what should be there either front or back with some part numbers would help as I find conflicting info for the 1994.
I really hope it’s just an easy fix of replacing a few external things bc this engine runs great it’s just sending oil everywhere at the moment.
i thank you all for th help I hope to figure this out soon.
as far as PVC and CCV I am not sure and I have been trying to figure out what’s the deal. I have 1994 XJ original engine. The valve cover at the rear has a vent to the intake manifold it is identical to the forward vent to the air box. I thought the one at the rear was the PVC and had the small orffice and the vent at the front is the CCV and would be a large orffice that vents to the air box.
I cannot not find a clear picture, diagram or explanation. Maybe some help on what should be there either front or back with some part numbers would help as I find conflicting info for the 1994.
I really hope it’s just an easy fix of replacing a few external things bc this engine runs great it’s just sending oil everywhere at the moment.
i thank you all for th help I hope to figure this out soon.
08-24-2018, 10:12 PM
#9
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Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Thanks for the great info.
as far as PVC and CCV I am not sure and I have been trying to figure out what’s the deal. I have 1994 XJ original engine. The valve cover at the rear has a vent to the intake manifold it is identical to the forward vent to the air box. I thought the one at the rear was the PVC and had the small orffice and the vent at the front is the CCV and would be a large orffice that vents to the air box.
I cannot not find a clear picture, diagram or explanation. Maybe some help on what should be there either front or back with some part numbers would help as I find conflicting info for the 1994.
I really hope it’s just an easy fix of replacing a few external things bc this engine runs great it’s just sending oil everywhere at the moment.
i thank you all for th help I hope to figure this out soon.
as far as PVC and CCV I am not sure and I have been trying to figure out what’s the deal. I have 1994 XJ original engine. The valve cover at the rear has a vent to the intake manifold it is identical to the forward vent to the air box. I thought the one at the rear was the PVC and had the small orffice and the vent at the front is the CCV and would be a large orffice that vents to the air box.
I cannot not find a clear picture, diagram or explanation. Maybe some help on what should be there either front or back with some part numbers would help as I find conflicting info for the 1994.
I really hope it’s just an easy fix of replacing a few external things bc this engine runs great it’s just sending oil everywhere at the moment.
i thank you all for th help I hope to figure this out soon.
Make sure the vacuum fitting threaded into the intake manifold is not plugged.
and, make sure you have the fixed orifice at the rear of the valve cover. Also, that the hard line isn't shoved way down into the grommet.
08-24-2018, 10:12 PM
#10
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08-24-2018, 10:20 PM
#11
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Year: 1994
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haha... i am still thinking of picking that up and just rebuilding it on the side to just do as another project. But yes I will entertain all options before just pulling and replacing.
thank you all for the sound advice and recommendations.
thank you all for the sound advice and recommendations.
08-24-2018, 10:23 PM
#12
CF Veteran
I agree, he was asking about a rebuilt engine vs a used one, and the used one would be a better option, but you don't need either one if yours is still good. However $150 isn't bad for a good 4.0, and it never hurts to have a spare engine if you have the room for it.
08-24-2018, 10:25 PM
#13
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Year: 1994
Model: Cherokee (XJ)
Engine: 4.l
so, I currently have a “fixed” small orffice valve on both the front and rear of the valve cover. Not sure that swapping in the appropriate CCV/PCV large orffice to the front to vent it to the air box will fix this but I sure hope it will. Just ordered both replacements and I will check back with results. Not optimistic but will hope for the best!
08-24-2018, 10:57 PM
#14
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Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
so, I currently have a “fixed” small orffice valve on both the front and rear of the valve cover. Not sure that swapping in the appropriate CCV/PCV large orffice to the front to vent it to the air box will fix this but I sure hope it will. Just ordered both replacements and I will check back with results. Not optimistic but will hope for the best!
Great.
08-24-2018, 11:10 PM
#15
CF Veteran
Couldn't this also be solved by just letting the crank case vent to the air and plugging the hole in the airbox and intake manifold?
Last edited by 00t444e; 08-24-2018 at 11:24 PM.