Vacuum Check Valve Repair



I was playing around with my car and had the hood open and thought of the issue with waste gate actuators fluttering. I looked down and sure enough just like the videos in the other posts.
So, I took the vacuum port off of the vacuum pump (pretty easy once the hose was out of the way) and inspected the little orange diaphragm
and there was nothing left but the nipple.
Obviously broken. So I started the search for a replacement that did not involve buying the whole vacuum pump. I found some things on Ebay from China and the Ukraine but costs were stupid and shipping was worse. $90 for a little piece of orange rubber!
Anyway, I noticed that this pump system is used on a variety of vehicles including Volvo and Ford. Volvo had a similar looking part but they wanted $70-80 for it. I also saw some references to a small Ford turbo engine so I looked a bit and found something on Amazon that seemed very close. Price was $25, shipping was free and I could send it back if it did not fit or work. So I ordered.
Got it in a day, tried it out and it sort of fit. The nipple seemed a bit too small but the diaphragm itself was perfect. Once you put it in its cage there is nowhere for it to go so I thought I would try it out.
Put it on and started it up...actuators are still as church mouse. I actually think it helped the bottom end a bit.
Anyway, hope it helps with the issue. It had been discussed before but no one ever said where to purchase (that I could see). So try:







I purchased the inexpensive Amazon check valve and replaced it this morning. There was no diaphragm left in the original check valve. There was no visible flutter on the wastegates. It was very oily when removing. The new valve went in and I can tell an immediate difference. You will have to use a pic on the hose.
stock p30 13 wagon. 68k miles.
This is a great repair that’s easy and yields big. I have always hated the little bit of hesitation between 1500-2000 rpm. It’s been hard to determine whether it was mct, vacuum, or the oil pressure. Between this and the solenoid disconnect, my car feels great.
Last edited by Baltistyle; Dec 16, 2023 at 02:48 PM.
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For reference.
I’ve not seen anyone mention a part number for the valve on the other side of the pump but had that side been inspected yet by the forum?
Last edited by Baltistyle; Dec 16, 2023 at 02:49 PM.




Brake booster output check-valve??
It's known to be trouble free.
The small check-valve takes the blunt of crankcase pressure inside vacuum pump. It's lower and weaker to act as a pressure relief.
> Check for oil swamped into diaphragms down the small vacuum line.
> Brake booster output is located high up and immune to oil invasion to stay reliable.
Last edited by CaliBenzDriver; Dec 16, 2023 at 05:42 PM. Reason: ESL




Brake booster output check-valve??
It's known to be trouble free.
The small check-valve takes the blunt of crankcase pressure inside vacuum pump. It's lower and weaker to act as a pressure relief.
> Check for oil swamped into diaphragms down the small vacuum line.
> Brake booster output is located high up and immune to oil invasion to stay reliable.




Both PCV and vacuum pump are impacted by the piston blow-by. It's all inter related.
High blow-by messes up everything. It makes the engine behave like an old Pinto.
Once it's back under control with sealed rings, it's smooth operations for the ECU to remap power...




I did check my valve today and it was broken.
Is this the right part?
https://www.ebay.co.uk/itm/364560723...hoCcS8QAvD_BwE
And do Mercedes sell this part at all?? I would like buy original not China if I can choose.
I did check my valve today and it was broken.
Is this the right part?
https://www.ebay.co.uk/itm/364560723...hoCcS8QAvD_BwE
And do Mercedes sell this part at all?? I would like buy original not China if I can choose.





I installed it anyway as my original check valve looked the same as Baltistyle's in the photos above - completely broken.
Using long nose tweezers, and a mirror, I fished out the old broken part, cleaned up some residual oil around the line and installed the new part.
Went for a long drive today, but no WOT. Still, the engine pulls like an absolute freight train under 3k rpm. But as I've only applied the oil pump solenoid mod in the last week it's hard to know what benefit replacing the check valve has had yet.
I'm planning to re-inspect the new part in a week or so to observe any oil leakage around the vacuum line, the MagiDeal part could well be a dud.
as i mentioned in one thread our 278 s500 has a low boost pressure code and the shop showed this video where there was play in the wastegate actuator on passenger side.
After a couple of days with new valve - "it feels" like low/mild acceleration is better, no engine rpm flutter.




next to troubleshoot - remove ecu tune(easy to put back), replace oldest coils, check spark plugs indexing







