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Unread 05-01-2014, 02:10 PM   #1
Candymancan
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1998 ZJ 
 
Join Date: Aug 2010
Location: Virginia
Posts: 3,780
Are my Valve seals bad ?

So my 4.0 it has 210k miles on it. Original engine and tranny.. I have noticed the gas mileage is pretty.. eh 14mpg combined highway and city... Mostly city... usually it gets 16.. Also noticed the oil level is starting to drop.. Its always been at the mark I fill it when I change the oil. But now I have to add oil. I should note oil pressure is always 35-40psi.. I haven't checked the compression yet

Thought nothing of it until today when my mom started the Jeep and I was behind it.. I noticed a puff of blue smoke out the tailpipe then it went clear. Im guessing this means the valve seals are bad ? If so.. What all do I need to replace them tool and part wise and how hard of a Job is it to do ?

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Unread 05-01-2014, 03:08 PM   #2
AVR2
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1993 ZJ 
 
Join Date: Apr 2007
Location: UK
Posts: 2,182
If you get blue smoke on startup, and also at idle (but not during normal driving), then yes, it's most likely valve stem seals. I recently had this issue myself.

You can potentially change the seals with the head installed. You either feed compressed air into the cylinders to hold the valves up when you pop the locks off, or you fill the cylinders with nylon rope/paracord, which achieves the same result.

Because I don't have access to compressed air, I tried the rope trick, but it was impossible for me to pop the valve locks using a screw-type valve spring compressor - they were too well stuck. In the end I wound up pulling the head and getting a full valve job done at a local machine shop, and with your engine at 210k, that's probably the best idea for you as well.
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Unread 05-01-2014, 07:14 PM   #3
gearheadnick
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1997 ZJ 
 
Join Date: Mar 2012
Location: Tunkhannock, PA
Posts: 562
You should do the dry/wet compression test anyway. There's a chance the rings are going bad, but hopefully it's just the seals.
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Unread 05-02-2014, 07:37 AM   #4
zjosh93
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1993 ZJ 
 
Join Date: Aug 2010
Location: Austin
Posts: 1,079
The compression test wouldn't hurt. If you let it idle and it starts to smoke blue smoke that's a strong sign that the seals are bad. Plus, mine were pretty bad at 214k so you're in the ballpark for bad seals mileage-wise. I did them on the engine using the rope trick. 1/4" nylon rope from the hardware store. You want soft nylon that won't shed in your engine. Buy about 6 feet. Use the finger-on-the-spark-plug-hole method and watch the valves to make sure the cylinder is on the compression stroke (both valves closed). Push about 4 feet of rope into the engine. turn the crank by hand (take out all the spark plugs) until the piston gently hits the rope. Back the piston up and push it back into the rope a few times. This helps make sure the rope is jammed tight against the valves. Take a deep socket around 5/8" - 3/4" and place it on the retainer. Strike the top of the socket sharply with a small hammer. This breaks the keepers free from the valve and retainer. If you keep the socket on the retainer and don't let it hit the keepers or valve there is no danger of messing up the valve. If you do this right the keepers will pop right out and you won't need the valve spring compressor to remove them. Since you need the compressor to put them back in and it's easier if you just left the spring compressed from removing it I try to avoid popping out the keepers with the hammer. Use the compressor to compress the spring and remove the keepers. Pull the spring and retainer out with the compressor. Swap the seal. Install is reverse of removal. I'd clean the keepers and the keeper groove to make sure that they don't sit on old varnish and get loose. A dab of grease keeps the keepers in place while you loosen the compressor tool. The compressor can't do the last three or four valves though because of the firewall. I made a tool using a piece of 1" x 1/4" steel bent to contact the valve cover rail and let me use the rocker arm bolt to compress the spring. Tricky to use but it worked.

Buy new plugs since they will need to come out and burning oil fouls the plugs.
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Unread 05-03-2014, 07:41 AM   #5
OverlandZJ
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1998 ZJ 
 
Join Date: Oct 2012
Location: Bristol, Pa
Posts: 926
Quote:
Originally Posted by zjosh93 View Post
The compression test wouldn't hurt. If you let it idle and it starts to smoke blue smoke that's a strong sign that the seals are bad. Plus, mine were pretty bad at 214k so you're in the ballpark for bad seals mileage-wise. I did them on the engine using the rope trick. 1/4" nylon rope from the hardware store. You want soft nylon that won't shed in your engine. Buy about 6 feet. Use the finger-on-the-spark-plug-hole method and watch the valves to make sure the cylinder is on the compression stroke (both valves closed). Push about 4 feet of rope into the engine. turn the crank by hand (take out all the spark plugs) until the piston gently hits the rope. Back the piston up and push it back into the rope a few times. This helps make sure the rope is jammed tight against the valves. Take a deep socket around 5/8" - 3/4" and place it on the retainer. Strike the top of the socket sharply with a small hammer. This breaks the keepers free from the valve and retainer. If you keep the socket on the retainer and don't let it hit the keepers or valve there is no danger of messing up the valve. If you do this right the keepers will pop right out and you won't need the valve spring compressor to remove them. Since you need the compressor to put them back in and it's easier if you just left the spring compressed from removing it I try to avoid popping out the keepers with the hammer. Use the compressor to compress the spring and remove the keepers. Pull the spring and retainer out with the compressor. Swap the seal. Install is reverse of removal. I'd clean the keepers and the keeper groove to make sure that they don't sit on old varnish and get loose. A dab of grease keeps the keepers in place while you loosen the compressor tool. The compressor can't do the last three or four valves though because of the firewall. I made a tool using a piece of 1" x 1/4" steel bent to contact the valve cover rail and let me use the rocker arm bolt to compress the spring. Tricky to use but it worked.

Buy new plugs since they will need to come out and burning oil fouls the plugs.

Good post.. but i prefer filling the cylinder with air.

I hadnt used a spring compressor on a ZJ, and had issues on cyl 6 on an XJ. Was wondering if there was enough room under the "shelf".
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Unread 05-03-2014, 08:06 AM   #6
zjosh93
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1993 ZJ 
 
Join Date: Aug 2010
Location: Austin
Posts: 1,079
Air is fine and lots of people do it that way. It just makes me nervous because if you loose air pressure the valve drops and the air pressure tends to push the piston down. Drop the valve then and you are pulling the head to get it back. Just have to brace the crank though. I like being able to be rough with the valve and not worry.

I'll try to remember to snap a pic of my rear valve compressor tool today.
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