swedepat

Well.. i though i´d luck and had a problemfree m156.
Anyway, this weekend i had some issues.

I was about to make a pull from a red-light just for fun.
1st gear - all good
2nd gear - started misfire badly at ~5500rpm, let off ofcourse.
Pulled to the side of the road and shut it off.
Never heard any bad mechanical sounds so i started it again, and it ran on 7cylinders(not locked at this point).
I was close to home so i limped home as there was no bad sounds from engine other than running on 7 cylinders.
When opening garagedoor(i let it run on idle meantime) it started misfire more on more cylinders.
Got into the garage and connected the computer, yup the 4 rear cylinders all had misfire so computer had shut them down.
(i´m guessing fuel was bouncing around in inlet manifold)

I didn´t know at that point why, so i deleted the codes and tried to start it.
It just fired on a couple of cylinders before it was hydrolocked on 4th cylinder on right side(the most rearest one)
So i pulled the plugs at that point, 4th soaking wet.
I turned the engine by hand with no plugs and it squirted quite a lot from that cylinder.
After that i turned the engine on the starter for about 30s
And as i don´t have any compressiontester for this plug threads i just put in a sparkplug in that cylinder, and tried on the starter again(no coils attached)
It was hydrolocked again.

That´s the story that leads to my question.

You other guys that had the same problem, did any engine parts got hurt?
(bent rod,cracked piston or anything else)

swedepat

I know i´ve got a non leaking cylinder, so no cracked block.
This due to when pulling out the plug after second lock about a minute later, i heard air seeping though the threads of the sparkplug when i loosened it.

But ringland can still be bad and rod can still be bent.
That´s why i´m asking.

5Hundred

Everyone's nightmare. My buddy's 6.4L Hemi hydro-locked and it broke a piston and rod. To my knowledge the best way to do it is have a complete rebuild and boring out of the cylinders to mate with the set of new internals. Sounds like you could probably get away with leaving some parts in tact but I don't want you to have to take the engine out and re-do everything again.

5Hundred

How do you think water entered your engine?

Jasonoff

It likely would have been fuel from a leaky injector.

VektorPerforman

How many miles were on this car/engine? Stock injectors?

swedepat

Yes, it was fuel.
Yes stock injectors (q4)
About 74000 miles

I´ve been diagnosing and testing, filmed inside cylinder etc etc.
Did a compressioncheck, it was actually down quite a bit at first, but i squirted in some wd40 and it came back as it should(this is the only thing that might be a problem, i figure the cylinder was totally washed out from any lubricants on cylinderwalls)
Measured piston height in tdc through sparkplug hole, compared it to another cylinder.
Ran it on starter with no plugs(listened for noices)
Everything seems fine at this point. *cross my fingers*

I received new injectors today, but i figured while i was at it, i took off the inlet manifold to check if it has corroded any on the inside, i´ll be checking that tomorrow.

Other than that i´m about to start it and listen for noices when running and do a compressioncheck again when warm to verify if the pistonrings are fine, i couldn´t see any problems with the camera.

swedepat

I made an adapter today at work so i can do compressioncheck myself.
My old gauge has M14x1.25 threads and cant reach down anyway, i had my rubber thingy and a friend to turn the key when i tested.
Now the old gauge fits into this, and this into cylinderhead that has m12x1.25 threads.

sventastic82

That is how I ruined my first C63. It had a stuck open injector and it washed too much of the cylinder wall off which then caused deep gauges and loss of compression.
Drain your oil and run it through a coffee filter to check for shavings.

swedepat

Yes, i´ll check that, it is planned.
But as i wrote earlier, i didn´t find any scoremarks or anything when i went down with a camera, i just found some loose soot that might have been washed loose.
And compression came back with a light squirt of wd40 into cylinder.

Still keeping fingers crossed, but is there a problem i will ofcourse pull engine apart.

BalanBro

Alex from Legit Street Cars just dealt with the same issue on his CL65 V12. Looks like you pretty much went through the same diagnostic steps as he did, but I'm linking the video in case you want to compare.

AMGonFire

Replace the oil, plugs, and injectors. Check compression. If good. Try starting the car.

swedepat

Did a cold compressiontest yesterday, all seems fine:

1 = 15bar
2 = 14.8
3 = 15
4 = 15 (The one that were affected)
5 = 15,2
6 = 15
7 = 15
8 = 14,8

I also did some horrible maintenence, i glassblasted it and painted etchprimer directly onto it, and to top it of some 2 component kawasaki green.
It had started to corrode, but still not any leak, but i did it anyway.
It is sure fortunate that it doesn´t show *lol*

swedepat

I ordered 82mm throttlebodies yesterday, will buy or make own plate.
I figured while i´m here fiddeling with stuff, why not kind of

Also a comparison betwwen old Y-pipe and new below, i´ll make an catchtank that looks like the vacumbox that sits on the newer one in aluminium as it is a perfect place for that.
A small vacumtank is easy to hide if there is a need of it.

The older one is quite a bit less restrictive(on the right and dirty), i see no reason for bigger throttlebodies if not opening up other areas too.

VektorPerforman

Interesting on the y-pipe. Would be nice to have the two flow tested or dyno tested. I would assume the newer one is improved either in design/reliability or performance. Don't let the open area fool you. Sometimes closing off an area can reduce turbulence and increase flow by quite a bit. Only way to know for sure. Throw it on the dyno for a before/after test.

Enjoying the updates!

skratch77

The old one doesn't have the vacuum canister sitting on it. They used a metal canister on the engine block instead.

VektorPerforman

Interesting. I've never followed the schematic to know what that even leads to. The dead end cannister is nothing more than a vacuum dampener. To what I don't know :P

Jasonoff

So your brake booster still works for a bit of time if your car loses power.

skratch77

It's for sound harmonics I think lol but some German engineers figured it helps.

swedepat

There´s no connection to the inlet runners of the Y-pipe from oem canister, so therefor it is not a soundharmonics damper box.
It is also such a small hose to the canister that it cant feed the brakebooster with vacum.

skratch77

From memory it ties right into the manifold

swedepat

I would bet the newer one is just smaller to make room in more bodies.
And is just good enough with a little margin.
I´ve been porting a lot of heads in my days and got a small idea about how airflow behaves

Let´s just say this: all area differences steal energy from incoming air., i can almost bet that it will give a small increase from torquepeak and upwards in engine rpm as you can fill the 'secondary' plenum underneeth the throttlebodies more efficient.
And combined with bigger throttlebodies i would say this mod is a must(or even bigger if possible)
My next mod would be to get rid of the restriction coming in into the filterboxes.

I made a homemade Y-pipe on my C55 AMG and it gained a lot(it was dynoed 467hp) together with bigger throttlebody.

swedepat

Yes,, but there are no holes between them, nothing to make a helmholtz resonator of it

Jasonoff

Humm. What happens if you yank the hose and put your thumb over it with the engine running?

VektorPerforman

The you must have a flow bench?

I have the FlowBench and Mustang Dyno here... and the C63. Send them here if you want to know for sure

Textbook vs software flow simulation vs Flow Bench does not always = power on the dyno. I've come across OEM parts that look OK and perform like garbage, and some that look restrictive, and perform exceptionally well. Some of the newer intake stuff especially. Shape/geometry can do some impressive things even vs a larger cross section. The OEMs have upped their game over the last 10 or so years, trying to eek every bit of power and efficiency out of ICE technology. I've been surprised more than once over the last few years, which is why we test and verify.