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Rather than suffering check valves issues, how about cancelling that problem at once ?
AMZ Prime $3Ea. selected check valve
A simple replumb of your vacuum rubber line at the vaccum pump output...
Add a "T" fitting plus two check valves connected to old outlet without original membrane.
-- One valve connected pressure release valve.
-- One valve connected as vacuum check valve.
This should effectively protect your vacuum circuit from the high crankcase blow-by pressure that explode undersized OEM part.
The real best fix is to minimize piston-rings blow-by with proper oiling circulation, you know piston squerter pressure.
Last edited by CaliBenzDriver; Feb 7, 2024 at 02:26 AM.
Make no mistake, you CAN get the part. It just so happens to be available ONLY with the entire vacuum pump.
Maybe I am naive...maybe I have my priorities off...but for the cost of the entire pump? Not a deal breaker, not for me at least. Certainly not for piece of mind knowing I had the exact right thing. I do know it costs less than a a short block.
At $300 and what could possibly wind up being an almost annual replacement due to a failed 12mm round bit of silicone, it's a tough pill to swallow. I'm sure if you're doing your own work, it's not exactly cost prohibitive. Pretty sure it's at minimum a $1000 bill at the dealer, though.
Can't argue against OEM in most cases, but the check valve is a weak point that fails often. As little as 25k miles, on the C43's I've seen.
There's a better way. To do it 100% correctly, it would be best to test a known good check valve for opening pressure/vacuum. Certainly not difficult to figure out.
Mitsu - good idea in theory, however, we are talking tiny variations in BAR here to actuate the waste gates. I have had turbo cars for ever....never have I had one nearly as hot as the 5.5, the 4.0 from what I have seen is even hotter. While there are many theories as to a better way to skin this or that cat - I can tell you from my "Mitsubishi" days....I had a (aging myself)....Blix SBC Id boost controller on DR650 turbos...I had to change the vacuum lines to route a gReddy(?) BOV - anything out of the ordinary on that vacuum line and things went bad, fast.
The nice thing about the wastegate actuators on these cars is that any sort of fault will generally result in the gate being opened wide, as the actuators are absolutely not opened by boost. Rather, they're held shut by vacuum. If the line comes off or loses vacuum, the gates open by default. The mitsubishi way, as i'm sure you know, is for the actuator to default to the closed position by way of spring pressure. Our AMG actuators default to the open position by way of spring pressure.
Last edited by Mitsuturbo; Feb 9, 2024 at 10:12 AM.
Thanks for this thread. I just replaced this valve with a $10 ebay valve.
2019 C43, M276, stock-stock no tune. 140k miles, I'm getting ready to do the spark plugs a second time. Car is kept up, mostly highway miles at speed, no drag racing.
Drove inconsistently at lower speeds....occasional lack of response around town. No code, no CE lights.
Read up, and replaced the valve.....at least on M276 you'll need a short torx screwdriver, the dipstick blocks straight access. Otherwise uncomplicated.
No photo, but the top came out, the bottom was picked out of the hole, and the diaphragm was not to be found.
All the "bobbles" are gone, it drives well again, especially off idle.
What a bizarre thing to have fail, and cause such significant issues.....
While Benz doesn't list it as a part number, I find it interesting this valve is a commodity part and they make it a one screw fix......this should probably be replaced every time you replace spark plugs and done as routine....the whole car's feel depends on a $1 valve at OE cost ?????
This car has a mostly useless boost gage, no numbers. I am happy to see that it definitely is showing more boost, even if a useless unlabled color gage.
Last edited by speedlaw; Jun 5, 2024 at 01:16 PM.
Reason: mileage is important !
Not long ago I helped a buddy put an eBay kit onto his E350 (3.5). About a month later we did it again....with parts from mboemparts.com. With the ebay ones he got what he paid for....
I didn't have any luck with the three el cheapo check valves purchased from AliExpress.. one was faulty on arrival and the other two leaked oil from the O-ring.
Now running the original factory check valve with the diaphragm from one of the Chinese parts. Seems to be working well.
All the "bobbles" are gone, it drives well again, especially off idle.
Mine does this but only when warm (the oil I mean, not the coolant, my oil takes 12 minutes to warm up in the summer and more like 17 in the winter, because E63S I guess). I replaced my check valve assembly with the more expensive one from Ukraine last year. So last night I pulled it out to examine and it is perfect. It holds a vacuum in the suck direction but passes in the blow direction. The one I pulled off the car last year was also fine but I think the whole vacuum pump is not original (prior owner).
Installed another cheapo valve today, my replacement failed (was disassembled on removal), there was some oil in the line. Will be checking for oil in the line (no need to remove the valve), have another one standing by just in case
It seems there is a slight difference between Ukaraine Klifex to the China Amazon.
.
Below :
# 1 = It seems the Klifex has plastic material at the middle of the star shaped opening, while the China one has none.
#2 = I seems the Klifex silicone membrane maybe a tiny tiny bit wider diameter than China one.
#3 = If I were to use the China one someday, I will power glue the black round membrane holder to the check valve body. The silicone membrane is thick enough to be robust, I believe so.
What I think can fail is the black round membrane holder which is only friction fit into check valve body, slipped out of its parking position and then hell broke loose.
If say the membrane dot lock get cut, that is another failure point. I mean the membrane sits and lock itself to the black round membrane holder is also a friction fit of a rather fat membrane
dot, as a lock....but this dot does not do much work actually.
I suggest try the power/crazy glue to secure the black round plastic membrane holder to valve body when you have the China one or even the Klifex one.
Checked mine; original part with 46k miles on the engine. I can blow through the hose side no problem but when I suck air from that side it's sealed and no air passes. Seems it's doing it's job correctly
fully intact, and I have no performance issues
Last edited by PeterUbers; Jul 26, 2024 at 12:02 PM.
Something I did a while back . And reduced the amount of oil in the check valve by almost 80%. That 1" distance was enough to keep the oil that comes out of the pump away from the check valve . I used a more rigid vacuum hose to attach the new check valve to the old. I gutted the old check valve so it was free flowing but still snapped back in place the rubber guard that holds the rubber in place. . The new check valve is from a Volvo s90 if I can remember clearly because it was so long ago. But it was slightly bigger because I remember I was able to blow through the one way direction easier then the factory one. So far it's been over a year and works perfectly
Something I did a while back . And reduced the amount of oil in the check valve by almost 80%. That 1" distance was enough to keep the oil that comes out of the pump away from the check valve . I used a more rigid vacuum hose to attach the new check valve to the old. I gutted the old check valve so it was free flowing but still snapped back in place the rubber guard that holds the rubber in place. . The new check valve is from a Volvo s90 if I can remember clearly because it was so long ago. But it was slightly bigger because I remember I was able to blow through the one way direction easier then the factory one. So far it's been over a year and works perfectly
The diaphragm killer is when crankcase pressure overcomes vacuum... then check valve gets pushed inward then blown back out by line pressure that should have never entered.
Wastegates should not get filled with pumped oil.
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
Originally Posted by Mitsuturbo
The nice thing about the wastegate actuators on these cars is that any sort of fault will generally result in the gate being opened wide, as the actuators are absolutely not opened by boost. Rather, they're held shut by vacuum. If the line comes off or loses vacuum, the gates open by default. The mitsubishi way, as i'm sure you know, is for the actuator to default to the closed position by way of spring pressure. Our AMG actuators default to the open position by way of spring pressure.
Same thing for Audi (or at least older ones). The default was closed. Had an actuator line fail and voila, melted piston on WOT.
The diaphragm killer is when crankcase pressure overcomes vacuum... then check valve gets pushed inward then blown back out by line pressure that should have never entered.
Wastegates should not get filled with pumped oil.
So on turbo application your best bet is having a T to sort out vacuum from pressure coming out if pump.
One check valve vents positive pressure OUT and second holds oil-free vacuum down the line.
Cali what do you mean by "T".. Also when you mention 2 checkvalves are you referring to the original one still being in place with membrane removed and second one is this metal one you have shown?..
Cali what do you mean by "T".. Also when you mention 2 checkvalves are you referring to the original one still being in place with membrane removed and second one is this metal one you have shown?..
Yes! The original stays installed (good or bad) to serve as a hose adapter.
-1- Then you have a metal check valve oriented to hold vacuum in circuit. That's a normal replacement.
-2- Now to exhaust any positive crankcase pressure punching the diaphragm add a "T" between pump and new check-valve to vent out pressure and hold available vacuum when present.
This should help preserve vacuum for your boost control.
A don't have the TT to test drive this fix.
The vacuum pump works from crankcase pressure. As we know TT do NOT have intake vacuum but mostly pressure.
So pump output can see pressure that chews up tiny silicone diaphragm. Blowing the pressure out of this circuit give it an easy escape path.
Is test drive improvement noticeable with that vacuum saver ??
Last edited by CaliBenzDriver; Jan 21, 2025 at 07:03 PM.
Something I did a while back . And reduced the amount of oil in the check valve by almost 80%. That 1" distance was enough to keep the oil that comes out of the pump away from the check valve . I used a more rigid vacuum hose to attach the new check valve to the old. I gutted the old check valve so it was free flowing but still snapped back in place the rubber guard that holds the rubber in place. . The new check valve is from a Volvo s90 if I can remember clearly because it was so long ago. But it was slightly bigger because I remember I was able to blow through the one way direction easier then the factory one. So far it's been over a year and works perfectly
👌
Last edited by berti_00; Jan 21, 2025 at 08:35 PM.
I got a CEL and found that it was a P029900 code (low boost turbo 1). I know it cannot differentiate between the two with the vacuum being split coming out of the controller.
I saw that the passenger get side waste gate rod was oscillating. Driver side was steady.
So I ordered a Volvo check valve as was mentioned above. I remember my check valve and sure enough it came out in two pieces (body was solid but the diaphragm was inside the cavity). I reassembled without the diaphragm so I could use the nipple, then added the Volvo check valve.
Initially, I noticed that passenger side waste gate rod was moving just a little but then a few minutes later it was solid.
Took the car for a drive. I could not hear the turbos whistling. Damn. The far also felt flat. Still powerful but not a lot of response.
Checking with Xentry, the duty cycle for the waste gate actuators was sitting at 63-64. Minimum is 65. Removing the Volvo check valve dropped the duty cycle to 5. I did try driving it without the Volvo valve but it wasn’t much different. Next item to check is the boost controller per Xentry.
Wild that I cannot hear the turbos. It was working fine, pulled into the driveway a couple weeks ago, the CEL turned on, and now they’re silent.
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