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Ordered this, will be here tomorrow. We shall see! I was going to do a good cover-off visual engine inspection anyway to look for anything obvious, vacuum hoses/connections/etc., so I'll knock that out while I replace this check valve then go from there.
in order to check the valve on your car without removing it, you can start the engine and pull the hose off the end of the valve and see if any air or oil mist is blowing out. It should only be sucking in. If you find it is broken, when you get the new parts just blow through them to make sure they are truly one way. The last pack of three I purchased were all good, but there have been reports of some receiving non-functioning parts.
in order to check the valve on your car without removing it, you can start the engine and pull the hose off the end of the valve and see if any air or oil mist is blowing out. It should only be sucking in. If you find it is broken, when you get the new parts just blow through them to make sure they are truly one way. The last pack of three I purchased were all good, but there have been reports of some receiving non-functioning parts.
Doing that now, soon as I finish trimming this tree. Gotta get ready for another catastrophic hurricane season here in Tampa.
Thanks for dropping in, Balti. I haven't even looked yet, but do you know where the boost solenoid is located? I'd like to check that as well. That would be really something if this was indeed just a vacuum issue! Then I could actually put some worry-free miles om the car! It sat for about a year because the front pano roof glass was shattered, but I recently replaced that myself and now I don't have to worry about the car getting rained on once in a while. But then I finally replace the glass and this surging/transmission/vacuum whatever problem started so I just leave it in the garage again! I really want to start getting the stereo installed. Once this surging issue is fixed I'll throw the air filter risers on, flash the tune onto the ECU and finish the exhaust. Then we will have a fun car! Just in time for hurricane season!
Doing that now, soon as I finish trimming this tree. Gotta get ready for another catastrophic hurricane season here in Tampa.
Thanks for dropping in, Balti. I haven't even looked yet, but do you know where the boost solenoid is located? I'd like to check that as well. That would be really something if this was indeed just a vacuum issue! Then I could actually put some worry-free miles om the car! It sat for about a year because the front pano roof glass was shattered, but I recently replaced that myself and now I don't have to worry about the car getting rained on once in a while. But then I finally replace the glass and this surging/transmission/vacuum whatever problem started so I just leave it in the garage again! I really want to start getting the stereo installed. Once this surging issue is fixed I'll throw the air filter risers on, flash the tune onto the ECU and finish the exhaust. Then we will have a fun car! Just in time for hurricane season!
in the 278, it should be directly under the engine cover towards the front. You will see that it has what I would call an F shape with your vacuum lines running to it.. there’s videos out there on how to test it.
I pulled the check valve. The inside cap and rubber diaphragm separated and the diaphragm and inner cover remained inside the vacuum pump. I fished those out with picks and tweezers. The center nipple was separate from the otherwise intact orange rubber diaphragm. I assembled the components of the check valve and blew and sucked through it with my mouth. It worked, sorta, but it's toast anyway.
Next, I disconnected the other end of that line from the boost controller. I put a rag under the check valve end and blew into the boost controller end and a crapton of oil came out onto the rag. Does this mean my boost controller is contaminated and needs replaced? I will remove it and play around with it on the bench in the meantime and report back.
Anyone think this might be the culprit of the surging issue? If so, Balti, you are my hero! If not, you're still my hero! This needed to be done.
New check valve from Amazon will be here tomorrow. I went to three parts houses and looked up the check valve using Ford and Merc part numbers and no one had one.
I pulled the check valve. The inside cap and rubber diaphragm separated and the diaphragm and inner cover remained inside the vacuum pump. I fished those out with picks and tweezers. The center nipple was separate from the otherwise intact orange rubber diaphragm. I assembled the components of the check valve and blew and sucked through it with my mouth. It worked, sorta, but it's toast anyway.
Next, I disconnected the other end of that line from the boost controller. I put a rag under the check valve end and blew into the boost controller end and a crapton of oil came out onto the rag. Does this mean my boost controller is contaminated and needs replaced? I will remove it and play around with it on the bench in the meantime and report back.
Anyone think this might be the culprit of the surging issue? If so, Balti, you are my hero! If not, you're still my hero! This needed to be done.
New check valve from Amazon will be here tomorrow. I went to three parts houses and looked up the check valve using Ford and Merc part numbers and no one had one.
no worries. That’s what we are here for. The boost controller having oil in it means that vacuum pump has been letting oil blow by for quite a long time. A bigger question someone might pose is did that oil get all the way down into the wastegates as well. Hard to say whether the boost controller is toast, but since it was full of oil, it’s likely not going to have as good as seal as before even though it’s electrically controlled. The electronically controlled valve could also be moving slower due to the dirtiness that oil can bring with it.
if you are able, you can pull the vacuum line off the front of the wastegate and see if there is oil down there too.
as you get into this, you might want to check the rest of the PCV system and PCV human being needs to maintain his sanity and his dignity I wrote lipstick hose valves as well. The PCV valve itself is a bear to do but is also standard maintenance.
Boost controller looks good, clean, no oil. I blew into the tube that actuates the waste gates and seems clear. Both actuators were crisp and active, not slow and wet/oily feeling. Did not pull the tube from the waste gates but I suppose I could. Check valve will be here this afternoon, so we have some time.
I have the centrifuge and PCV stuff for my W212 but I have been hesitating on that because it's such a pain in the posterior. I would really like to replace PCV stuff on the W221 because I am a PCV **** but I'm fine with an Italian tune-up with this car for a bit (:
Upon visual inspection, I'm again amazed at just how clean this motor is. It's just spotless. It leaks nowhere. Everything looks fantastic. It almost warrants making a quick video of, with covers off. 51k mi 13 year old car that is this clean under-hood? I'm probably in a crowd of only a handful of those!
IT IS FIXED!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Balti, I OWE YOU ONE!
New check valve installed, vacuum lines cleared of oil, wastegate rods as still as a statue at idle, STUDDER IS GONE ON LIGHT ACCELERATION!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
IT IS FIXED!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Balti, I OWE YOU ONE!
New check valve installed, vacuum lines cleared of oil, wastegate rods as still as a statue at idle, STUDDER IS GONE ON LIGHT ACCELERATION!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
I really can't tell you how much I appreciate your tip with the check valve. I remember reading up on it long ago before I was symptomatic and didn't think much of it, and it did not cross my mind when this issue started to present itself.
I was about to start down a long, expensive path (plugs and coils, drop the electrohydraulic unit, replace tranny solenoids, etc.) and all that can now wait because of you and a $12 part and a few breaths of air to clean out some oily vacuum lines.
Thank you so much! I have been really dreading this for months and months. I have a refreshed interest in it now and will be getting back to work on it finishing up several projects I have had in wait for so long because of being so discouraged about this issue.
I'm going to buy a few more check valves from different vendors just to have on hand in case they fail (cheap Chinese parts?) because it's so easy to replace. I'll look into vacuum pump ($700 new) and PCV stuff as well because PCV **** especially with DI motors.
In a couple weeks (remember broke and basically unemployed right now so takes longer) I'll have completed the exhaust, intake risers (making my own with aluminum flat stock and PCB risers to lift everything up) and have the tune on the car. Then we'll really start breaking things Lol
Took the car out and put 40 miles on it. Although markedly improved, it's still chugging a bit under the original conditions.
Which means at least we are on the right track with arrows pointing to the turbos and have ruled out (I'm hoping) transmission issues.
I got home, popped the center cover, pulled both ends of the vacuum line and blew into it again. Still dry, no oil in the line. Which means all vacuum lines from the check valve to the wastegates are still patent. Perhaps this means a vacuum pump replacement is in order? I need to research more.
I will pull the vacuum solenoid and bench test it with my PSU and get back soon.
regardless - when was tranny serviced - 37k miles is sensible fluid swap time - yes they improved the later ones (just enough to reach the end of warranty) its much cheaper than a rebuild
don’t forget an S class is driven by granddads that have only pressed the pedal down once, scared themselves and have driven the last 25k miles on tickover.... and you have turbos and a penchant to rip it
Oh and throw a Crank sensor on there - they give up about that mileage and age - it gives strange behaviour as they start to go strange - stumbling and stalling in to junctions is the most common misbehaviour
Can you describe the issue again? At times I can catch my E63 surging noticeably during lower speed acceleration. I've never really solved it completely but with everything I've done, it's as good as it's even been and is no longer anything frequent enough to chase. List of things that have helped:
- Unplugging oil pump solenoid
- 5W-50 oil
- Boost solenoid
- Vacuum pump check valve
- Replaced a vacuum pipe thing that runs along the back of the intake manifold that has two more check valves. I can provide my P/N if that helps. Also see this thread: https://mbworld.org/forums/w212-amg/...ak-points.html
Also
- I did do wastegate vacuum lines but I do not think my old ones were leaking so this made no difference.
- Plugs and coils made no difference and my coils were original at over 100k
The current state of tune has me satisfied and pleased with my M157, finally. 111k on it now.
I really can't tell you how much I appreciate your tip with the check valve. I remember reading up on it long ago before I was symptomatic and didn't think much of it, and it did not cross my mind when this issue started to present itself.
I was about to start down a long, expensive path (plugs and coils, drop the electrohydraulic unit, replace tranny solenoids, etc.) and all that can now wait because of you and a $12 part and a few breaths of air to clean out some oily vacuum lines.
Thank you so much! I have been really dreading this for months and months. I have a refreshed interest in it now and will be getting back to work on it finishing up several projects I have had in wait for so long because of being so discouraged about this issue.
I'm going to buy a few more check valves from different vendors just to have on hand in case they fail (cheap Chinese parts?) because it's so easy to replace. I'll look into vacuum pump ($700 new) and PCV stuff as well because PCV **** especially with DI motors.
In a couple weeks (remember broke and basically unemployed right now so takes longer) I'll have completed the exhaust, intake risers (making my own with aluminum flat stock and PCB risers to lift everything up) and have the tune on the car. Then we'll really start breaking things Lol
I had my vacuum pump replaced since my old one was full of oil. My check valve was toast. In my situation I only had a loud rattle on start up. Yep it was $700 and it comes with a new check valve. Also you will not be able to buy the check valve separately from Mercedes since they do not offer it. They want to sell you the whole pump!!
Oh and throw a Crank sensor on there - they give up about that mileage and age - it gives strange behaviour as they start to go strange - stumbling and stalling in to junctions is the most common misbehaviour
I replaced the crank sensor when I installed the downpipes. No change.
Can you describe the issue again? At times I can catch my E63 surging noticeably during lower speed acceleration. I've never really solved it completely but with everything I've done, it's as good as it's even been and is no longer anything frequent enough to chase. List of things that have helped:
- Unplugging oil pump solenoid
- 5W-50 oil
- Boost solenoid
- Vacuum pump check valve
- Replaced a vacuum pipe thing that runs along the back of the intake manifold that has two more check valves. I can provide my P/N if that helps. Also see this thread: https://mbworld.org/forums/w212-amg/...ak-points.html
Also
- I did do wastegate vacuum lines but I do not think my old ones were leaking so this made no difference.
- Plugs and coils made no difference and my coils were original at over 100k
The current state of tune has me satisfied and pleased with my M157, finally. 111k on it now.
Thank you for sharing! I replaced the check valve and all vacuum lines to wastegates are dry. I don't think oil ever made it to the wastegates. When I cleared the lines from the boost controller solenoid to the wastegates they were already dry. So they have never seen oil. The oil in the vacuum lines existed only between the faulty check valve and the solenoid. It wasn't completely obstructed, but enough to cause the low RPM shudder. After clearing the line, a marked improvement was noted. I ordered a new boost controller solenoid yesterday. Will report back when that is replaced!
Thanks to all for contributing. I made some more exciting progress today on a different topic that I'll start a new thread on now. I was bummed and discouraged about this engine issue before you guys helped me out and I think we're on the right track with the turbos being the issue. If the new boost controller solves the shudder issue then I am a "go" to start/finish all these other projects I have had lined up for the car but quit thinking about months ago because of my somewhat dire financial situation and this relatively new (4 months or so) engine issue. But we'll start chipping away at it as I can now (:
try moving to an sp oil. Less zinc (more is not good for cats, not sure if you have them) and sulphur (a supposed major component of scoring). And better stability so as to not burn onto the valves through recirc or blowby. Created for lspi and gdi engines/ cleanliness. Effectively supersedes the original oil rec…in standard use cases.
It’s not a full answer to your problems, but it is a solution for future problems..
try moving to an sp oil. Less zinc (more is not good for cats, not sure if you have them) and sulphur (a supposed major component of scoring). And better stability so as to not burn onto the valves through recirc or blowby. Created for lspi and gdi engines/ cleanliness. Effectively supersedes the original oil rec…in standard use cases.
It’s not a full answer to your problems, but it is a solution for future problems..
Thanks for the info! I'll find a good SP oil for the next oil change in 1500 miles.
Thanks for the info! I'll find a good SP oil for the next oil change in 1500 miles.
not sure where you are from but people have much success with 5/40 and 5/50. I’m not a huge fan of zero weight oils. People like Motul, Amsoil, Mobil and castrol, with each offering something a tiny bit different. I’ve been happy with long-term use of Motul 5/40 or some castrol 5/50. Lots of good threads in the M157 forum with much of the oil conversation happening in the oil solenoid thread. Be aware to try to buy new stock of oil because some of these specs have changed over the past year and a half to two years..so what is on the bottle is most important.
The NEW FS is properly rated. Zero weight may be within spec but absolutely un-needed especially in your warm climate. Im in a four season state and use 5, and have for 30 years. I like more oil sticking to things at all temps, and 5 flows fine down to -22 degrees, which I never see. The "W" is the winter weight or COLD weight.
Last edited by Baltistyle; Sep 2, 2025 at 09:07 PM.
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