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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; 02-07-2024 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; 02-09-2024 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; 06-05-2024 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).
02-07-2024, 02:13 AM
