Valve stuck due to carbon buildup.

[Will Jacocks]

Got this A-4 from a guy in New Orleans, 600 bucks running. He said it won't pressure on #4 due to stuck valve. I got it home, pulled the valve cover plate and #4 exhaust is stuck open. Tried hitting it with lubricants and such, no luck. Can't even move it, was very tight. Pulled the head and found whole of all 4 cylinders just covered in carbon black soot. I am guessing the valve got covered so much it won't close anymore. Can't even push it down unless I tap it with a hammer. (Just to see if it moved, which it does very little at a time)

How do I go about working on carbon buildup in the valve to be able to get it out of there? I am beginning to think I'll have to pound it down, un lock it and pull it and replace both the valve and the guide. Any suggestions on freeing it without doing all that? Is there anything that can remove carbon buildup on the valve stem?

Thanks!

[sailhog]

Can you work some carb cleaner down the valve guide?

[Will Jacocks]

Didn't try carb cleaner. Mostly wd-40, all I pretty much and brake cleaner which I just shot a bit in there just to add something to the mix. Not really for carbon as it is for grease.

[edwardc]

People in the know here seem to speak highly of Marvel Mystery Oil and/or Automatic Transmission Fluid (ATF) for freeing stuck valves.

[hanleyclifford]

Also, add acetone to the ATF.

[Will Jacocks]

Picked up both mystery oil and carb cleaner, did a quick spray down with the carb cleaner. Will go back out in a bit and hit it with mystery oil. I don't want to get too much stuff down in the oil pan since the lower end appears to be in good condition and I would rather not have to tear into it at this time. I have some Dex ATF and some fingernail polish remover, will that work?

[hanleyclifford]

I believe the finger nail polish remover is acetone.

[Al Schober]

Will,
You've got the engine in the shop, right? The head is off, right? Forget the foo-foo juice and just remove the valves. Do the cleanup yourself, or send the valves out to a shop for cleaning and grinding.
Once they're clean (or back), I think you'll find they fit the guides nicely. Otherwise, you'll have to clean the guides. Rather than ream them, I think I'd go to your local gun shop a get a kit for cleaning a 38 - should fit the guides just about right. And the powder solvent should be a good cleaner. I don't think you need a concealed carry permit to buy a cleaning kit!
On reassembly, you may want to treat yourself to a set of new valve springs.

Al

[Will Jacocks]

Will,
You've got the engine in the shop, right? The head is off, right? Forget the foo-foo juice and just remove the valves. Do the cleanup yourself, or send the valves out to a shop for cleaning and grinding.
Once they're clean (or back), I think you'll find they fit the guides nicely. Otherwise, you'll have to clean the guides. Rather than ream them, I think I'd go to your local gun shop a get a kit for cleaning a 38 - should fit the guides just about right. And the powder solvent should be a good cleaner. I don't think you need a concealed carry permit to buy a cleaning kit!
On reassembly, you may want to treat yourself to a set of new valve springs.

Al

3 broken valve springs, yes the engine is in my garage. This is to maybe replace the one in the boat if we can't get that one spinning. (froze due to water in cabin, just haven't had a chance to dig into it big time.) I will order the springs and spring tool this week.

Is there something I should be aware of with ATF and fingernail polish remover?

Also, there is a leak on the starter side of the block, just below the head gasket. Is this a week spot? A little to the right if you are looking at it from that side. I will try to post a pic later this week.

[Al Schober]

Will,
Any chance that leak is coming from the cover plate that goes into the cooling passages? Standard fix for that leak is to replace the plate with a stainless one, and to install the plate with studs and nuts rather than bolts.

Al

[ILikeRust]

Is there something I should be aware of with ATF and fingernail polish remover?

Forget fingernail polish remover. Just go to Lowe's or Home Depot and buy a can of Acetone. Mix it 50/50 with ATF to get an extremely effective penetrating oil formulation.