Valve sticking?` - Ford Powerstroke Diesel Forum
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Old 06-24-2014, 08:25 PM
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Valve sticking?`

2006 6.0. Had the diesel tech at the Ford house hook up to diagnose what has been a persistent "miss" The motor stumbles under slight load and makes a weak popping sound out the tailpipe. I thought it was an injector issue - one or more of them not consistently firing. The tech said it is a sticking valve. It's been doing it for a while and doesn't seem to be getting worse.

My questions are: is there anyway to tell exactly which cylinder is having the problem? I'm wondering if it might be a floating valve - in other words a valve spring is giving out and isn't closing the valve consistently. If this is the case I might be able to replace a valve spring if I can figure out how to keep the valve close while using a spring compressor.

I'm trying to solve the problem without tearing the heads off yet. That's coming eventually but right now I can't pull the truck out of service for long.

Anybody have any ideas or experience with a sticking valve? I've used Wynn's in the crankcase and Seafoam in the gas tank and neither have had any effect.
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Old 06-25-2014, 03:25 AM
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There are a number of tests but none are 100% accurate.
You can remove a glow plug at a time and screw in a compression tester adapter. Check which cylinder builds compression and then drops off or is slow to build compression.

Visually check for a broken spring or other obvious damage.

You can install a dial indicator and check the valve travel on each cylinder as you rotate the motor by hand.

All are subjective tho to the experience level of the tester. What a really experienced tester may see, hear and feel will be different than what a novice will see, hear and feel.
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Old 06-25-2014, 07:40 PM
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Sounds like my best first option is a compression test. Never done one on a diesel and since there is no ignition wouldn't there be a risk of the cylinder firing? If so I imagine I have to use a remote on the starter and leave the key off. If I don't come up with anything that way I'll pull the valve covers off and check for damage and see if the lifters all feel equally stiff. Then if I can't figure it out that way I'll use my old dial guage with the magnetic base to check for valve travel.

If that doesn't get me answers I guess I'll have to yank the heads.
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Old 06-25-2014, 07:59 PM
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I don't mean to scare you but I recently had a sticking valve problem which in turn caused a rocker arm to crack and a pushrod to bend. So I would take a look at this issue sooner rather than later. You might still have to check the status of the pushrods anyway as a percaution. As far as testing for the sticking valve without taking the head off is beyond me.
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Old 06-25-2014, 08:50 PM
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Pull the FICM fuse should keep it from starting. Personally I prefer to roll by hand.
Same procedure you use for a gasser just a higher compression ratio.
Best to use a diesel tester not a gas engine gauge. Have blown up a few compression tester gauges over the years.
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Old 06-30-2014, 08:00 AM
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With the valve cover off I see the rocker arm pedestals are held down by head bolts. Is there anyway to replace a lifter WITHOUT taking out a head bolt (and subsequently having to pull the head)?
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Old 06-30-2014, 08:14 AM
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No way to change a lifter with the head on, they won't fit through the hole in the head and you can't get the lifter retainer out with the head on.
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