OM603 Internal Valve Cover Breather Failure Solution - PeachParts Mercedes-Benz Forum

Squiggle Dog · #1 11-09-2019, 04:05 PM

It seems that most of the internal breather valves which are hidden away inside the baffling which is riveted in place under the valve covers of the OM603 engines are failing by now. Mercedes must not have intended the engines to last this long. Their solution is to buy a new valve cover (603-010-05-30) at $615.00.

When this check valve fails, the turbocharger will start to suck in oil from the engine and coat the intake manifold with oil. See this link for more information: https://www.coolcatcorp.com/Mercedes%20valve%20cover/Mercedes%20Valve%20Cover%20Breather.html

Diseasel300 came up with a great solution, which is to install a PCV valve from a 1999-2004 Volkswagen Golf or Jetta diesel: http://www.peachparts.com/shopforum/restoration-projects-long-term-builds/383293-diseasel-86-300sdl-11.html#160

Apparently you can tell if the internal check valve has failed by putting a hose up to the little hole on the right rear of the valve cover and draw a vacuum--if oil comes out, the diaphragm has failed. On both the valve covers I have here, the holes are wet with oil. I just did a head replacement on this car with the one from the Diseasel, the same one in the picture above. It came with the valve cover, and before the head swap, the previous valve cover on the car which I am working was allowing oil to get sucked into the turbo as well.

I decided to get a Volkswagen PCV valve. I was reading this thread here: http://www.peachparts.com/shopforum/diesel-discussion/395618-0m-603-971-cold-starts-right-up-then-8.html#107 and clicked on the link and purchased a similar PCV valve. Then I realized that the valve I purchased (part number 06A129101D) is a different one than what Diseasel300 used (028129101E) and is actually for a gasoline-powered 1.8 liter Audi and Volkswagen. Oops.

Part number 028129101E that Diseasel300 uses:

The 06A129101D part that I ordered:

You can see they are different in shape. The one Diseasel300 uses has an offset lower fitting, which keeps it away from the oil filler cap. It's centered on the one I ordered, so it might interfere with the oil filler cap, but I won't know for sure until I test fit it. It looks like it might be smaller, too. One benefit is that the fitting on the side could be pointed toward the original path of the breather tube.

But, I wonder if it's going to be compatible with the application, anyway, as the spring inside might be stronger or weaker than the one I was supposed to order (gas vs diesel and different engine sizes--maybe one closes to vacuum, while the other opens?). I don't really have a way of comparing its properties to the failed on in the valve cover.

Diseasel300 says his has worked fine for a while, so I might order one of them in case this one doesn't work out. But, I think the think I am most concerned with is if these two parts open and close at the same amount of vacuum. Maybe they are all the same in this way, and shape is the only difference?

I wish they made one that was a mirror imagine of the 028129101E part number so the fitting on the side would be pointing toward the original breather tube routing instead of away from it. I should probably order one of the other part number so I can compare them by hooking up a vacuum gauge and also seeing which fits the best.

Diseasel300 · #2 11-09-2019, 05:21 PM

I certainly can't take credit for the idea of using a VW puck, it's been mentioned many times on this forum, STD, and Benzworld, among others I'm sure. I got the idea to try it on my car from a post tjts1 made a couple years ago. It's worked well for my car(s) ever since. Nobody ever documented how to do it, and I had a couple of jury-rigged trial runs in my car before I settled on the way I documented. Still running that setup in the 350SD since it has the valve cover with the failed breather from the SDL. It really cuts down on the amount of oil in the intake snorkel.

Squiggle Dog · #3 11-11-2019, 10:53 PM

It seems that these pucks work differently than the conventional PCV valve. As I understand it, the purpose of a PCV valve is to release air pressure within the engine back into the intake. So, the valve is closed all of the time except when the pressure forces the valve open. Working this way, it also keeps flames and pressure from a backfire from going back into the engine.

However, if I understand it correctly, the valve inside the OM603 valve cover was designed to work in the opposite way; the valve is always open to allow pressure from within the engine to be vented into the intake, except when the turbocharger is drawing in air to the extent that it creates a vacuum which would suck oil out of the engine--in which case the valve would close until the vacuum decreases.

The Volkswagen puck should then be always open except when there is a certain amount of vacuum applied to it. I will have to see if the puck that I ordered (for a gasoline vehicle) works in the same manner. It's for a turbocharged vehicle, so I imagine it must.

I've seen some PCV valves which are smaller, but the valve might open instead of close when the turbocharger creates pulls a vacuum.

Diseasel300 · #4 11-11-2019, 11:18 PM

Typically a gasoline PCV valve closed due to high vacuum in the intake manifold of a gasoline engine to prevent a vacuum leak through the breather system. When the throttle plate opens, the spring in the PCV valve opens it back up so the crankcase gasses can enter the intake manifold and get burned.

The diesels are a bit different, there's not any appreciable vacuum in the manifold at idle, and because the engine is turbocharged, there's high pressure in there when the engine is turbo is spooled up. Simply dumping the crankcase vent into the turbo inlet without any sort of valve or oil separator will allow it to suck the vapor right out of the engine when the turbo spools up - the turbo draws a vacuum in the intake tube due to restrictions in the filter and incoming tube.

The breather puck has a spring loaded diaphragm in it. In normal situations, the valve is wide open to allow gas passage. When the end connected to the intake hose has vacuum applied to it, the diaphram closes and blocks off the valve. If the pressure in the crankcase rises, it will override the spring and open it up again to allow pressure to bleed into the intake hose. The puck I bought can easily be tested by giving a quick suck on the intake hose side, it will quickly shut the valve. It operates on very little pressure.

The 617's took a different approach, they used an oil separator in the air cleaner housing with a drain going back to the sump to separate oil from the blowby air stream. While there's not any "valve" to fail in that setup, it does require the oil separator and the return plumbing and doesn't do anything to prevent the crankcase from being drawn into vacuum when the turbo spools.

There's pros and cons to every approach. The idea to include a *RUBBER* diaphragm inside the metal valve cover with non-replaceable stakes is very much a *CON* in my book. Such a German thing to do. Because, you know, replacing the valve cover is such a *NORMAL* thing to do on anybody else's engines...

Another thing that sort of "completes the set" of swapping to the VW TDI breather puck is using their grommet as well. It has an elevated area that supports the breather puck. The puck will fit the OE MB grommet, but it will sit right down on the valve cover. VW part number is 028103500 and will fit the MB valve cover hole like it was made for it. They're available for under $5 shipped on eBay.

Squiggle Dog · #5 11-11-2019, 11:44 PM

Thanks for the explanation. So in the case of these pucks, they aren't simply a one-way valve, but can work in both directions (vacuum closes the valve but pressure inside the manifold forces it open again)? I'm not sure how that would work, but it seems that's what it would have to do.

If the puck I purchased fits and functions properly, the Volkswagen grommet will likely not be needed as the puck would rest on the Mercedes grommet.

However, if it doesn't work due to it interfering with the oil filler cap or the valve working in the wrong direction and I need to order the type you have, it appears I can order one with the grommet included. The fitting on the side of yours is lower than the bottom, so I can see how that would rest on the valve cover without the taller grommet.

Diseasel300 · #6 11-12-2019, 09:15 AM

Quote:

Originally Posted by Squiggle Dog

So in the case of these pucks, they aren't simply a one-way valve, but can work in both directions (vacuum closes the valve but pressure inside the manifold forces it open again)? I'm not sure how that would work, but it seems that's what it would have to do.

No. Vacuum in the intake snorkel (outlet side of the puck) closes the puck diaphragm. Rising pressure in the valve cover (inlet side of the puck) pushes it open again. When we're talking about pressure and vacuum, we're talking about very small amounts here, probably less than 1PSI.

Mxfrank · #7 11-12-2019, 10:37 AM

On any other car, this would be a part you periodically replace. But who is going to install a whole new valve cover? The only indication of a problem would be an oily mess on the turbo impeller or a trickle of oil at the tiny air bleed on the side of the valve cover. I bet a lot of turbos have been replaced when a failed breather is misinterpreted as a leaky turbo oil seal.

Squiggle Dog · #8 11-12-2019, 11:13 AM

Quote:

Originally Posted by Diseasel300

No. Vacuum in the intake snorkel (outlet side of the puck) closes the puck diaphragm. Rising pressure in the valve cover (inlet side of the puck) pushes it open again. When we're talking about pressure and vacuum, we're talking about very small amounts here, probably less than 1PSI.

I wish I could understand how this works. It seems that pressure inside the valve cover would force the diaphragm closed even harder. But, I wonder if the diaphragm has two parts to it--part of it which closes in vacuum, and then another part (maybe in the center of it) that opens under pressure at the inlet side.

But, whether it's pressure at the inlet side, or vacuum at the outlet side, the flow is always in one direction, so I'm not understanding how it's possible for it to open again from force in the same direction that closed it in the first place. I guess if that's what it does, I shouldn't question it, I just wish I understood how it works.

Maybe I'm thinking about it wrong as I'm picturing a valve inside of a pipe, where pressure on the inlet and vacuum on the outlet can do nothing but close it. Perhaps it's more like a diaphragm with the inlet and outlet on the same side of the diaphragm, rather than opposing sides of it. Therefore, the diaphragm could be closed by vacuum on the outlet as well as pushed back open by pressure in the inlet. I think this is probably likely.

Diseasel300 · #9 11-12-2019, 11:58 AM

You're overcomplicating the operation of the diaphragm inside the valve. It's extremely simple in operation. Picture a wine glass with a tube running up the center, a tube coming in from the side, and a balloon stretched over the top. The tube up the center of the glass is maybe 1/8" from the balloon. The gas from the crankcase comes in through the side pipe and exits through the center pipe. As long as the system is at atmospheric pressure, or if there is pressure in the crankcase, the balloon is kept away from the center pipe. Create a vacuum on the center pipe and the balloon is pulled towards the center pipe until it contacts and is then held there by the vacuum. If the vacuum is then released, or if the pressure in the crankcase rises enough to overcome the vacuum in the center tube, the balloon is pushed away and gas can then flow again. The operation of the PCV puck is exactly analogous to this description. There's no fancy valve, no special operation, no special anything at all. It's all atmospheric pressure acting on a rubber diaphragm! If you look carefully at the seam of the PCV puck, you'll see an opening where it references atmospheric pressure on the top side of the diaphragm, this is exactly the same function as the small hole in the side of the valve cover on the 603.

Squiggle Dog · #10 11-12-2019, 08:52 PM

Quote:

Originally Posted by Diseasel300

You're overcomplicating the operation of the diaphragm inside the valve. It's extremely simple in operation. Picture a wine glass with a tube running up the center, a tube coming in from the side, and a balloon stretched over the top. The tube up the center of the glass is maybe 1/8" from the balloon. The gas from the crankcase comes in through the side pipe and exits through the center pipe. As long as the system is at atmospheric pressure, or if there is pressure in the crankcase, the balloon is kept away from the center pipe. Create a vacuum on the center pipe and the balloon is pulled towards the center pipe until it contacts and is then held there by the vacuum. If the vacuum is then released, or if the pressure in the crankcase rises enough to overcome the vacuum in the center tube, the balloon is pushed away and gas can then flow again. The operation of the PCV puck is exactly analogous to this description. There's no fancy valve, no special operation, no special anything at all. It's all atmospheric pressure acting on a rubber diaphragm! If you look carefully at the seam of the PCV puck, you'll see an opening where it references atmospheric pressure on the top side of the diaphragm, this is exactly the same function as the small hole in the side of the valve cover on the 603.

So, in other words, the two tubes are on the same side of the diaphragm which therefore explains how pressure from one tube and vacuum from another tube can have an opposite effect on the diaphragm. Vacuum from one tube sucks down the diaphragm, and pressure from the other tube pushes it back up. It's not like the older PCV valves that have a straight or bent pipe with a valve inside that can only be closed by vacuum and also closed by pressure.

Sadly, the puck arrived today, and while it seems it would be even more ideal than the one you are using, the bottom tube is too thick to fit into the grommet. It's nearly the thickness of the hole for the grommet. Darn it!

Diseasel300 · #11 11-12-2019, 09:25 PM

Yes, you have the concept correct! Too bad about the hole being the wrong size! It's always something.

Squiggle Dog · #12 11-20-2019, 10:11 PM

This is how the 028103500 part number Volkswagen grommet fits on the valve cover--tall side up!

Here is how the 028129101E part number PCV valve looks on the valve cover. Unfortunately, it points in the wrong direction and can't be rotated without obscuring the oil filler cap. I tried to think of elegant ways to route the hose so it would be secure and wouldn't interfere with the belt tensioner access or removal of the fan. I even considered using 5/8" aluminum A/C tubing and bending it to shape and securing it to the front of the head using spacers and clamps.

But then I had a breakthrough! I figured out a way that I could use this 06A129101D part number breather valve after all.

Because the Volkswagen grommet is so tall, a large portion of it is on the outside of the valve cover, allowing it to expand without the valve cover restricting it. I found that if I cut off the flare at the bottom of the valve, the grommet would stretch enough for it to be inserted.

Squiggle Dog · #13 11-20-2019, 10:13 PM

I had an old breather tube on which the insulation had deteriorated, and a fairly new one.

I cut off the part that fits into the valve cover on the old breather tube. The tube is wider on this end due to the plastic fitting which was inserted, which also adds strength and makes the outer diameter of the tube closer to the fitting on the breather valve.

Then the insulation from the newer breather tube was slid over to connect the tube to the valve--which has the grommet attached to it. Due to adding the breather valve on the end, the tube was now too long, so I cut off about 1 1/2" from the bottom.

Then I slid on the grommet and lower piece of insulation.

I am very happy with the new breather arrangement. It looks original and does the job without getting in the way of other parts.

Maxbumpo · #14 11-21-2019, 01:32 PM

Squiggle Dog, that looks nice. I used the other version that Diseasal first brought to my attention, and facing the same issue of the valve opening pointing away from the tube the goes to the intake snorkel, I simply added a piece of rubber hose to lengthen it, looping around the oil fill cap. Cheap and not as pretty as your work, but gets the job done.

However, I have not noticed any reduction in oil usage in my engine, and I still find oil has been sucked out of the new valve.

Diseasel300 · #15 11-21-2019, 03:06 PM

Quote:

Originally Posted by Maxbumpo

However, I have not noticed any reduction in oil usage in my engine, and I still find oil has been sucked out of the new valve.

If your engine has blowby issues, the breather puck won't help since the crankcase pressure will always be pushing the diaphragm open when the engine is under load. Some oil will always make it through the valve, its purpose is not to stop oil vapor getting through, it's to minimize it.

My SDL's poor engine had the cylinder liners worn slick (I suspect it had WAY more than the 189K miles indicated on the odometer) and always used oil. Between rebuilding the leaking lift pump, valve guide seals, rebuilding the turbo, and installing the breather puck, it went from using a quart in 250-500 miles (depending on driving style) to a quart in 1500-2000 miles which still isn't great, but WAY better than what it was initially.