BenzWay

pm’d you

BenzWay

From what I’ve heard, the vacuum pump gives vacuum to the wastegate lines on the turbos which actuate the turbo and under low rpm a weak vacuum pump won’t actuate enough vacuum into the wastegate lines delaying turbo response until reached at higher rpm’s.

S-Prihadi

Vacuum pump in M276 3.0TT uses vacuum negative pressure to KEEP CLOSED the wastegate small flap.
If a tune is set to boost turbo higher than stock of 0.8BAR, a vacuum pump if not so healthy can' generate the near 100% vacuum, and weaker to hold against higher turbo boost pressure.
A good healthy vacuum pump can generate near 30inHg.

You can always install a stand alone vacuum gauge if you want
https://mbworld.org/forums/e-class-w...ing-issue.html

If you guys MOD your car, do you monitor and logged your basic ECM OBD2 parameters and more like my Banks iDash ?
When I used to do mods, those days analog, I always add extra important gauges but no logging.

DubVBenz

My JB4 also plugs into the ODB2 and I can log and export graphs. I'l have to see if vacuum is one of the statistics available.

S-Prihadi

Vacuum value is available using Xentry in the ESP/Brake system. It won't be available from OBD2.
There is a vacuum sensor there to trigger DTC if brake booster has very low vacuum value consistently. I do not know what is the DTC trigger parameter, never tried yet to trigger it.


When you do brake boost or anytime a long press of brake pedal is done, it will take away approx 15% of vacuum ( at engine idle ), but the vacuum pump will catch up.
When you do lots of brake pedal pressing and fast in a test scenario, you can loose 75% of the vacuum reserve.

Watch here...... remember I am using an absolute sensor and the parameter i use is the CCP. Zero PSIA is the "perfect vacuum". 14.5 or atmospheric means no vacuum.

Left Coast Geek

A drag racing engine builder sells t-shirts that read...

Left Coast Geek

oh, let me add. every time you do a high throttle 1st gear launch, you are taking many many miles off the life of your transmission, and drive train.... Mercedes are much more suitable for road racing than they are for drag racing.

Chevota

DubVBenz: What others said about the vacuum used to power the turbos, meaning closing the wastegates so you can make boost, is correct. From what I can tell, based on my experience and that of others, the most likely culprit to low Tbo vaccum is the check valve on the vac pump that specifically feeds the turbos. I think everyone should check this puppy if they notice any power power loss at all, especially at higher rpm. It's a somewhat delicate silicone? disc that sees a lot of abuse in normal operation and I'm surprised they last as long as they do. They're easy to swap out, and less easy to find a good replacement because places like ebay will try to sell you a cheapo chinese knockoff. Imo the chinese ones "may" work to make oem boost, or close to it, so I'd imagine most people will never notice? If you want peak power or have a tune, you need good vacuum.
There is also the solenoid, which is imo a crude device and you have to wonder if it works well enough to provide the needed vacuum to the turbos to net the boost you ask. I bought a new one to ensure I had a good working one, and the new one was far worse than my original. This drove me nuts until I discovered that was the cause.
Then there's the vacuum lines, so you have to check all those for leaks. Check from the vac pump to solenoid, and solenoid to turbo(s) to ensure it's all 100% leak free. The solenoid is a controlled leak fyi. The pump provides vacuum, which closes the wastegates, the solenoid lets in air to open them. The ECU uses that solenoid to control how much a leak there is to get the wastegate position it wants and thus boost it wants. In my car the system cannot make enough vacuum to truly make full boost so even the slightest loss of vac to the turbos will cost you power. I don't think I'm losing much power but the point is even the slightest leak or inefficiency of the pump, valve or solenoid would cost more power. At least in my car, but each eng is different so I can't say, but I'd imagine they're all somewhat similar?
There is no way to check vacuum to the turbos without manually checking, at least in my car and any I've seen. I plumbed a line to that vac circuit leading to a gauge I had in the cabin, which is how I know all this. I kinda doubt any model has an oem sensor for that line but who knows. My car just estimates based on an assumed vacuum, then adjusts up/down from there based on the MAP and power output. So it can adjust for low vacuum, to a point, but full power at full rpm my car needs 100% vacuum and some.
The normal vacuum the PID will read normal even when the turbo vac is completely dead. At least in my car because the vac sensor is in the intake, where I'd imagine everyones is. If there is one for the brakes, it would again be isolated from the turbo vacuum on my car.
The vac pump itself can fail too, but imo far less likely than the turbo check valve in it. If you get a new check valve, try to get the orange one. Same black plastic housing but the actual valve disc inside it is orange, which you can see from one end, or by taking the valve apart. My oem valve was orange, so I bought one from ebay that claimed specifically was the good orange one, but it was a classic bait n switch and had the cheap black one, and a fail. So I bought a whole new pump, which had a good valve that happened to be green. Same apparent quality as the orange. I've not seen a green one for sale by itself btw.
With a bad check valve you may see oil in the vac line at the turbo solenoid, because rather than sucking all the time it's allowing flow both ways and the vac pump has oil in it, so you get the picture.
For oem boost I'm sure my car would be ok with some vac loss, but as mentioned, full boost is another story. I'm sure it varies with eng, turbo, back pressure, diaphragm spring etc, but to net max boost I need all the vacuum it can make. The only way to tell what vacuum your car needs to net max possible boost, or the min boost you want, is experimenting.
Just an fyi so others can learn from my time wasted troubleshooting this crap.

As for the OP, I don't know what to say but I'll give it a shot. Apparently oil got into the exhaust but if the eng looks fine via the borescope then I'd assume a turbo bearing gave up the ghost? The bang I don't know, maybe the turbo spinning at xxK rpm and suddenly stopping, or maybe oil igniting in the exhaust? Maybe some part decided to dump oil into the intake, but wth does that? Even the PCV, if completely failed, can only dump so much oil in. Same with valve guide seals but neither should make a peep. Then there's the intercooler, which could dump in water when it fails/leaks but I assume you checked its water level? It wouldn't make blue smoke but I'm just thinking of things that could do weird stuff like that. So I guess I'd pop the turbo inlet pipe(s) off and see if the tbo spins freely and has no play, if you haven't done that already. Best of luck...

Idklol69

Thanks for this. I believe I'm gonna get the vacuum pump swapped out for a new one on Tuesday. I will post back with the results to see if it helped with creating boost off a first gear dig.

Left Coast Geek

vacuum is easy to test with a pressure gauge, like a mityvac with the push-pull gauge (+/- pressure)... if you have a vacuum pump, hook it up to the gauge, and hot-wire it, and verify it works. hook up a t connector under the hood, and run a skinny tube back to the drivers compartment so you can check it while you're driving, and seeing the problems, and if you have erratic vacuum when driving, but the pump tests positive, then look for leaks.

parts swapping based on hearsay and anecdotes leads to chaos, many folks call that the 'parts cannon'. problem is, "NEW" parts aren't always GOOD parts. Much better to run actual tests that show what the real problem is, and fix that specifically.

Idklol69

So my mechanic tested my vacuum pump and said there's no leaks and it's functioning fine. Idk if replacing it will improve the launch delay then? I could go ahead and swap it out it's not too expensive.. What are your guys' opinions?

Aussie_E350_Wag

But what did the mechanic say....?

Idklol69

I'm looking to fix the issue because the issue is still there.. A forum member swapped it out himself and I'm not sure if they tested for leaks or to see if it was functioning properly before they swapped it out.

Aussie_E350_Wag

What are the symptoms of the issue you're having?

Idklol69

If I launch the car (I rarely ever do this), or simply just fully accelerate from first gear, there is a delay in power until it hits 4000 rpm and then there is a surge in power. This wasn’t as big of an issue as it once was, but now it’s so noticeable. I barely ever get into races but man the delay in power makes me only want to do a roll race if ever lol.

Chevota

Idklol69; Did you swap that pump or valve out? Or check vacuum at the turbos while driving?

When I first had low power/boost issues I used the phone app Torque Pro and a cheapo OBD dongle. It allowed me to see misc things like the boost and turbo command. So if boost is low you can see if it's being commanded low, or commanded high and it's just not happening. The latter would likely be low vacuum. In my case it was being commanded low and I never did figure out why, I just commanded more (using HP Tuners) until I got what I wanted.
It could also be the throttle closing on you, which it will do some degree anyway, but if something isn't right it'll close more than it should. Or spark timing, same deal where it may retard more than it should for some BS reason. While tinkering/tuning I ran into both scenarios for various reasons but you won't know until you get some app/program to see it happening.
The OBD Dongle I bought was a cheap little blue one from Amazon: I tried other dongles, including the much more expensive OBDLink LX that claimed to be so much better and transfer data faster, but it was no better. So get the cheapo and the $5 app and it should work fine.
Now that I have HP Tuners, which connects the dongle with a wire to my laptop instead of stupid Bluetooth to my phone, it's much faster. It was also $400, so I'd go the cheap route first.

blackmagic; any updates? We're all curous. Well, I am...

Idklol69

Hey, everything is good with my vacuum pump and the engine. Had my mechanic check it out and all, and he tested it all.