Delivery valve internal leak as a cause of nailing? Yes? No? Maybe??? - Page 8 - PeachParts Mercedes-Benz Forum

RunningTooHot · #**106** 05-13-2017, 01:27 PM

Agreed that a metal-to-metal valve face takes a lot of abuse. Just as tetraethyl lead in gas helped prevent valve seat wear, the sulfur in diesel fuel acted similarly to lube & cushion parts in the fuel pump and injectors. With ULSD... well, you know. Lubricity enhancing agents are added, but I always treat the fuel with an extra shot of magic elixir. (PowerService mixed with some two-stroke oil.)

As far as dirt getting through the filter, I'd hazard a guess that wet fuel is the primary cause of wear, pitting, and corrosion. The metal is no doubt a very hard alloy, so infrequent encounters with relatively softer dirt particles is not likely going to account for the majority of any wear.

On a personal note, I saw in the service history files for my '98 that the PO's wife had mistakenly put gasoline in the car. I have to wonder if just that one isolated incident would have been enough to cause some wear on the DV's. Doesn't seem likely, but who knows.

Diseasel300 · #**107** 05-13-2017, 03:16 PM

I do often wonder about ULSD causing issues. The IP that was fitted to my car when I got it is the one it left the factory with. Car was parked in early 2007 before ULSD was really a "thing". The DV's in it are fine, despite the engine having >200K on it. The 3.5L IP I have fitted to it now is of unknown mileage, but so far I've replaced 2 worn delivery valves on it. Both causing nailing and rough running. I'm tempted to swap in the other 4 from the 3.0L IP next time I do any sort of real service "just because". I run 2SO in mine too. ~4Oz per fill up.

Diseasel300 · #**108** 05-16-2017, 09:28 PM

I swear I'm going to beat this thread to death...

I got curious about whether or not attempting a re-lap of the seating face would actually accomplish anything, so I took one of the extra DV's I have and decided to try it. I used honing oil as my lubricating, chucked up the "piston" part of the valve in a 7.2V drill and used Cerium Oxide as my abrasive. Cerium Oxide is used for polishing glass, it is a very mild abrasive and extremely fine, much finer than the usual valve lapping paste.

The results were fairly surprising. I did 3 valves, and all 3 showed a spectacular improvement in the seating faces and a very surprising improvement in the ease of movement of the plunger in the bore.

The photos below show one of the DV's I did before I touched it. The piston part is turned upside down for photographing. The beveled part of the seating face has a noticeable rough area (shows as a line) where it mates against the cylinder and a layer of hardened "stuff" further back towards the shaft. No idea what that stuff is, but it is present on ALL of my DV's, including the ones pulled out of the 3.5L pump and solvent doesn't take it off.

The beveled face of the cylinder isn't the happiest either. It has some rough areas, but isn't pitted yet.

Diseasel300 · #**109** 05-16-2017, 09:32 PM

And so here are the photos everyone actually wants to see. The "After" photos.

Notice how shiny and smooth the beveled face of the "piston" is. All that rough "stuff" is gone.

The cylinder part also cleaned up well. The rough areas are much smoother, to the point that they look bright and shiny in person. You can only see the imperfections on the camera from the flash.

I'm tempted to swap one of these DV's in and see if it nails. If I decide to try it, I'll definitely report back. Right now my engine is running well and no nailing, so I'm reluctant to fix what ain't broke.

As a sidenote, I'm now convinced that delivery valve parts are the hardest thing on earth to photograph clearly. The 4 photos posted over the previous 2 posts are the result of over TWO HUNDRED separate attempts with 3 different cameras. Please, for the love of God, don't ask me to take any more because I will politely refuse!

RunningTooHot · #**110** 05-17-2017, 03:20 AM

Hey Diseasel, could you take a few more shots from a different angle? Just kidding...

But seriously, that looks fantastic. Great idea on the Cerium. About how long did you spin it up for? Did it cut through pretty quick or take a while? (I assume that Bosch used a pretty hard alloy.)

I'd hate to encourage you to "fix what ain't broken" but it would be awesome to know how it turns out.

So, massaging & blueprinting DV's may be the next "big thing" for us, huh?

Maxbumpo · #**111** 05-17-2017, 07:40 AM

I predict a fail. Polishing the sealing surfaces: OK. Polishing the plunger/bore area: Fail. The plunger needs to move straight up and down, if you allow it too much side-to-side, it will allow the sealing surfaces to make contact off-the-flat, which means it won't seal as well as it would have originally. The tolerances here are REALLY fine...

Diseasel300 · #**112** 05-17-2017, 09:31 AM

The cerium oxide is an extremely fine abrasive, almost like fingerprinting dust. It is not aggressive, so it takes a LOT of work to get much done with it. Very little material comes off, it is more of a polish than anything.

I made sure the abrasive was NOT in the bore area, only under the sealing face. I dipped the piston in oil, then used a toothpick to lay on the abrasive where I wanted it.

Diseasel300 · #**113** 05-18-2017, 06:52 PM

So polishing the faces of the DV's works.

I took the 2 DVs from Cyls 4 and 6 that were causing such loud nailing and gave them a polishing session. Cleaned well and swapped them into 1 and 2. I had no nailing before the swap and have no nailing after the swap. I'm currently running straight pump #2 without any additives, so any nailing would be very obvious.

I'll keep driving it and give a status report after a few days worth of driving and some cold starts. Seems promising though and could explain quite a lot of nailing issues that seem so hard to resolve.

It is important to note that the DVs I used were the last thing replaced to eliminate irritating nailing. Injectors were tested, DV seals were redone 3x, ran diesel purge, adjusted timing, added 2-stroke oil to the fuel, tried cetane booster. Nothing worked. As the engine warmed up, it would start to nail and just get louder until the engine reached temperature at which point it was ridiculous. Swapping in different DV's killed the problem in both cylinders. Now those DV's that I pulled got polished and reinstalled in different cylinders that were NOT nailing and continue to NOT nail afterwards. Far from scientific, but certainly seems to suggest that polishing/lapping the sealing faces helps.

RunningTooHot · #**114** 05-19-2017, 12:47 AM

Awesome! Thank you for going out of your way to do that; I realize that it wasn't necessary since you've already solved your problem. But that knowledge will definitely be helpful to others in the future.

I'm looking forward to hearing how they hold up after some extended driving. That would be great if the Cerium treatment is all that's needed instead of having to procure new or used DV's.

OM617YOTA · #**115** 05-19-2017, 10:17 AM

Just wanted to pop in and thank everyone for starting and contributing to this thread. I've been chasing noises all over my engine for two years and was at wit's end. Now have another possible avenue that suits my symptoms better than other options I was pursuing. Will be pulling DV's this weekend.

Diseasel300 · #**116** 05-19-2017, 11:26 AM

Just a word of advice and caution to anyone willing to be guinea pigs with DV face polishing:

USE THESE INSTRUCTIONS AT YOUR OWN RISK!!! PLEASE BE CAREFUL AND DON'T TRY THIS ON YOUR ONLY MEANS OF TRANSPORTATION!!! EVERYTHING BEING DISCUSSED HERE IS THEORETICAL AND EXPERIMENTAL!

If you do wish to try polishing your DV sealing faces, use common sense and follow the instructions below:

1: Make sure you have your DV oriented correctly. If it has a groove on the barrel, it should be pointing down, away from the plunger part of the DV.

2: Before you do anything to the DV, clean it in solvent, such as lacquer thinner to remove any varnish or contaminants.

3: Dip the entire DV in a thin oil such as sewing machine oil, or even WD-40 as a lubricant.

4: Use Cerium Oxide as your abrasive. It is extremely fine (finer than makeup powder) and is a very "soft" abrasive.

5: Use a battery operated drill and fasten the tip of the plunger part of the DV that the spring attaches to in your drill chuck.

6: Use a toothpick dipped in oil to transfer some of the cerium oxide to the beveled face of the DV. Try not to get it anywhere else. Keep applying until you have a coating of the cerium oxide on the face.

7: Insert the plunger into the barrel and press the two pieces together firmly and run the drill at medium speed for ~15 seconds.

8: Pull the parts apart and clean in your solvent. Inspect the faces and look for a polished appearance. If they need more polishing, repeat 3-7 above until you're satisfied with the final appearance.

9: Use a toothpick dipped in cerium oxide to clean up the entire beveled face of the plunger. I held the drill up and ran the tip of the toothpick back and forth over mine. This will help get any other oxides off and give you a fully polished sealing face.

10: Clean both halves of the DV in CLEAN solvent. Dry and repeat in a new pot of CLEAN solvent. Use a tooth brush or a Q-tip to really scrub everything perfectly clean.

11: Dip the DV in thin oil and reassemble to check fit. It should move freely without dragging. Press the DV halves together and twist. It should not feel "rough".

Keep in mind this process and all of the anecdotes attached to it are theoretical and experimental. If you screw up your IP or break your only car, you have yourself to blame. Not I, Pelican Parts, or anyone else is responsible for you or your engine. As the fine print always claims - "Your results may vary"

barry12345 · #**117** 05-19-2017, 01:29 PM

Power lapping seems a safe approach. My only comment is if you find one with a leaking valve to seat issue. The others may not be in that great shape either.

Perhaps not bad enough to cause noticeable issues. The other delivery valves should actually clean up easier as they are not in as bad of a condition.

Kind of a general maintenance issue then in my mind. . Past repairing the really problematic one.

Anyways congratulations on the newest if not only delivery valve reconditioning approach. As the member cautions just use your head when doing it. Do your best at keeping the valve and seat in equal contact when lapping.

The risk is minor. If you some how manage to mess up. Just get another new or used delivery valve.

I live in a small area. Can you mention a source of the light abrasive you used?

I was impressed with the way you tackled this. I knew the valve was too small to reliably lap it on glass in combination with dealing with the seat as well separately. These two parts probably had been finished lapped against each other in production as well.

Original life cycle of the check valves is great with no valve rotators present as well. There are no specific water separators on these cars either. I wonder since there is probably always a little water in the fuel we buy.

The only water trap is the secondary fuel filter and I have always wondered why they recommended such frequent fuel filter changes.

Over the years the moisture adding a little surface corrosion to those seats and valve faces might be what is being polished out. When enough is present it creates a leakage situation.

Fifteen seconds with that abrasive is not going to cut hard metal very much if at all. Polishing or cleaning of softer corrosion is more probable. As that was loosened up it would mix with the new lapping compound perhaps.

Many more people will be doing this now. Perhaps someone could examine the valve face with a microscope. Post what the observe.

Diseasel300 · #**118** 05-19-2017, 01:39 PM

I bought my cerium oxide from Amazon. I originally used it with a power buffer to get rid of tree sap on my Honda's windshield after it got baked on and literally nothing would take it off. It will be sold as a glass polish. As a useful sidenote, it's also GREAT for removing hard-water spots from windows.

The reason I chose to use cerium oxide is because it is such a mild abrasive. Far less than the carbide and carborundum usually used in valve lapping compounds. The goal was to polish the faces and it did just that. One of the DV's I polished had noticeable pitting to the face. Apparently it wasn't very deep because it polished out.

Until we have some anecdotal evidence from a few other brave souls, it would be wise to hold off doing an entire rack of DV's until we can gather some data points.

RunningTooHot · #**119** 05-19-2017, 02:09 PM

Hey Diseasel - you may want to put a caveat somewhere in your post.

All kidding aside, thank you for the comprehensive instructions!

(Now I just wished that the DV's were as easily accessible on a 606 vs 603.)

barry12345 · #**120** 05-19-2017, 02:40 PM

Quote:

Originally Posted by Diseasel300

I bought my cerium oxide from Amazon. I originally used it with a power buffer to get rid of tree sap on my Honda's windshield after it got baked on and literally nothing would take it off. It will be sold as a glass polish. As a useful sidenote, it's also GREAT for removing hard-water spots from windows.

The reason I chose to use cerium oxide is because it is such a mild abrasive. Far less than the carbide and carborundum usually used in valve lapping compounds. The goal was to polish the faces and it did just that. One of the DV's I polished had noticeable pitting to the face. Apparently it wasn't very deep because it polished out.

Until we have some anecdotal evidence from a few other brave souls, it would be wise to hold off doing an entire rack of DV's until we can gather some data points.

Of course holding off on doing the whole rack of them. Until some overall experience is gained. Just something to consider now.

Why I considered it safe was for true lapping both surfaces have to be held parallel to each other. Usually requiring some form of valve guide to hold the relationship. You cannot achieve this with a hand held drill alone. Where cleaning up corrosion and other hard deposits is not nearly as demanding. What you established is far too important to ignore.

There will be failures if there is an obvious flow erosion channel across a seat or valve for example. Or the corrosion is massive. Common sense will have to be used. Personally I think your approach is going to work out well for many members.

I am old enough and experienced enough to recognise an approach that will usually probably work. A seat or valve warped from the heat for example is never going to occur. So I just suspect you have developed a real winner of a more constantly occurring problem all the time here.