Valve sticking?` - Ford Powerstroke Diesel Forum
 
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post #1 of 7 Old 06-24-2014, 09:25 PM Thread Starter
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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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post #2 of 7 Old 06-25-2014, 04:25 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.


Lord I shall lead them to the water but I will not try to make them drink
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post #3 of 7 Old 06-25-2014, 08:40 PM Thread Starter
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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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post #4 of 7 Old 06-25-2014, 08:59 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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post #5 of 7 Old 06-25-2014, 09:50 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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post #6 of 7 Old 06-30-2014, 09:00 AM Thread Starter
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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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post #7 of 7 Old 06-30-2014, 09:14 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.

Diesel Equipment service manager lead technician
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