Pulled my plugs and! - Page 2 - JeepForum.com

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post #16 of 17 Old 01-16-2010, 10:57 AM
Running On Empty...
1973 CJ5 
Join Date: Aug 2007
Location: South West Indiana
Posts: 11,180
Originally Posted by donobrew View Post
So I pulled my plugs last night to take a look at them. What I saw was 5 of the 6 plugs were caked with ash/gray deposit on one side of the plug. The #6 plug looked “normal”.
I did some research on this and found out that either I’m using cheap gas, cheap oil and or I have an oil leak in the cylinders from worn valve guides or valve seals. I have notice that I add quart of oil right around the 3000 mile mark so when I’m down a quart I know its time for an oil change…

If it is worn valve guide/valve seals how difficult is that to replace?
Valve seals aren't hard to replace.

Valve seals go bad over time, with heat exposure, ect.
There is no set 'Mileage' that valve seals will give up,
And manufacturer is a big deal,
The 'Import' ones don't last long,
While the ones from places like 'Fel-Pro' last a good, long time.

There are two basic types of valve stem seals,
One is a teflon type material with metal band that mounts on top of the valve guide and wipes the valve stem as it cycles.
These take machining on the top of the valve guide to install, and sometimes take machining to clearance things (like valve retainers) to clearance for them.

The second type is an 'Umbrella' seal, and that is simply a 'Rubber' cup that fits on the valve stem/guide and no special machining is necessary to install.

Now, if you want to change the valve stem seals,
You can do that fairly easily yourself,
But you will need some specialized tools...
To be specific, you will need a valve spring compressor and you will need to learn how valve locks work in the valve spring retainer.

You will need to find TDC of Compression Stroke for the cylinder you want to work on so both valves are closed before you do anything.

This is easy to do, remove the spark plug from the cylinder you want to work on,

Then turn the engine over BY HAND until compression starts in the cylinder you want to do.

What I normally do is feed COTTON rope into the cylinder I'm working on,
Then turn the crank BY HAND until the piston pushes the cotton rope up against the valves.
This will allow you to work on/remove the valve springs without the danger of the valves dropping into the cylinder.

Once the rope is in the cylinder, and pushed up against the valves...
You can take the valve cover off and remove the rocker arms for the cylinder you want to work on.

That will give you access to the valve springs, which you use a valve spring compressor on to expose the valve locks in the valve spring retainer.
Remove the locks, valve spring retainer, and if you wish,
The valve spring,

Remove the old seal, replace with new valve stem seal,
Then put the spring, retainer and locks back on the valve,
Once the rocker arms go back on you are done with that cylinder.

Not much to it besides a lot of hand turning the engine and watching for the intake valve to close on the cylinder you want to work on...

Use COTTON rope because the fuel in the cylinders will melt may synthetics,
And don't forget to back the engine up a little before you try to take the rope out of the cylinder!
Most of the time, it's pinched in there pretty good, and just yanking on it isn't an option!

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post #17 of 17 Old 01-18-2010, 12:40 PM Thread Starter
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1985 CJ7 
Join Date: Jul 2008
Location: San Diego
Posts: 135
Ok, great thanks for the info...
Donobrew is offline  

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