[Joe-V12]

Searching around I didn't find a thread or guide specifically for M120 vacuum leaks so I decided to start one here. Floating around on the net is a good vacuum leak guide to the M104 engine with some great generic but period correct MB info, but not for the M120.

Maybe over time this thread can turn into a reference go to guide for anyone chasing those elusive vacuum leaks on the M120. Anyone with any info and/or pics of leaks they have found please post it up. I think I have one so I'll be looking around tonight.

 

[Ayhan]

I had issues with the air flow meter (changed,resolved)and throttle body.I have a spare in my trunk but couldn't fix it yet.No vacuum issues so far...

 

[Merc-S600]

At 6 minutes you see the pipe I mentioned to you yesterday ,watch all of this video Joe and check his other videos out as well ,might not be a w140 but its an M120 Engine ,same thing for all .:thumbsup:

 

[Joe-V12]

I found nothing last night, but I did notice the pipework at the rear of the engine that connects to that crankcase ventilation tube. My symptom is smooth idle/low revs when cold, gets rough with low idle when hot. Removing a charcoal purge valve vacuum line makes it worse, that is, idle rougher and lower. If I remove and block the purge lines no difference at all.

Not sure if it's related but I noticed that removing the oil filler cap or dip stick makes no difference, when I thought it would. Mine is possibly a spark plug and/or O2 sensors problem as well.

I am going through the process of elimination. Car had a loose ground wire, and a leaky fuel reg. and currently has wrongs plugs. Cleaning plugs on the right bank (the bank that inhaled all the leaky fuel reg fuel) brought my cold idle back to perfect.

Anyway, that's off topic.

 

[MAVA]

You are on topic here on this forum..

When I repair the PSE and close assist pumps for the moment I use Chinese Insist Sticks to watch the suttle leaks on these pumps internally. Come independence day here on July4. I'm going to get the fire-works ignighters or as we called them when we were kids...I'm going to get some "punks".

You may have to take off the accessory belt, so there is no movement of air to find leaks...

For a permanent little smoke machine, I saw a YouTube on a DIY of one with a Nichrome wire in a new empty metal paint can with lamp oil with a wick, and a voltage applied to the nichrome wire, and fish tank pump. I will need to make one of these to find those stubborn leaks..

MArtin

 

[Joe-V12]

It may just come to that. Hook up a smoke machine and pump it full LOL!

 

[Merc-S600]

Watch all of this video ,this is in regards of your misfiring or possibility .:thumbsup:
Its in steps if you see it stuttering along .:thumbsup:

 

[Joe-V12]

I can't wait to do that job!!! Ok that was a lie...


I have not checked the MAPs or the vacuum lines for them. I was looking everywhere for them and I didn't think to look behind that cover! You saw my engine the other day. There is the possibility of vacuum leaks through the valve covers itself and/or the valve cover gaskets. That magnesium really falls apart.

I put a thread up HERE about the workflow on my problem, which turns out to be multiple problems. After new O2 sensors and new plugs I'll turn my attention to wiring issues.

 

[hoffmonster1]

joe trojan,how y going ,i have been reading your threads ,sounds like y got a lot of problems as well,keep posting ,i am just about to try my new knock sensor to day.i to have been chasing my issue ,best of luch hoffmonster1 cheers.

 

[Joe-V12]

Hoffmonster there will be plenty of updates.

M120.982 anatomy of the crankcase breather that connects to the throttles just before the butterflies, joins at the rear of the engine and goes under the intake manifold between the banks under the runners.

 

[Joe-V12]

I just confirmed my crank case breather is leaking bigtime somewhere.

 

[Merc-S600]

Its called (Crankcase ) Ventilation pipe , two versions ,early models plastic & later Alloy . :thumbsup:

 

[Joe-V12]

What a disaster of a design. Must have come out of the same factory as those rear view mirrors that fall to pieces.

I had an interesting talk to Chris today. He might chime in with his findings and ideas.

 

[Merc-S600]

Joe if I'm not wrong didn't you buy the updated Alloy Breeder pipe , if so can you post a pic with the part number since member MitchellNY is looking for one but cant find the part number.:thumbsup:

=================================================================================================

This is the Breeder pipe that was in the old V12 , the engine that was smoking .
The previous owner fixed it by just adding ordinary radiator hose or crankcase breeder hose that is found on top of engines , it appears that it is a good way of fixing this breeder pipe with it , there are no leaks or visible cracks on the rubber .
If no alternative part is available consider this .I think to modify this part and make it alloy with just some extra tubes is not a to hard of job to do , even using the alloy from a Mop/broom should do the trick ,cut it to perfect size with some L & T joins ,and you're done , all someone wants is this part not to crack ,use steel if you could lol, its not a part that activates anything like a waterpump or module etc ,it's just a hose where oil fumes pass thru towards the Throttle actuators .:thumbsup:

 

[Joe-V12]

No I havn't bought the new replacement sorry.

 

[Merc-S600]

Ok thanks , currently searching for the updated part number ,so far I only found this #PN 120 018 32 12 . but don't know if it is the Alloy or plastic version yet ,if you look at my part number in the above picture within my previous post ,it does look like an updated number if you compare them with the one posted above here .:thumbsup:

 

[Joe-V12]

I have EPC pdf's here with that same part number. I doubt MB would sell the old POS.

In that pic the old part number looks to be 120 018 27 12.

 

[Merc-S600]

I have EPC pdf's here with that same part number. I doubt MB would sell the old POS.

In that pic the old part number looks to be 120 018 27 12.

I would guess so as well .:thumbsup:

 

[anziani]

Guys, off subject but Victor has been a lot of help to me and others over the years. I think we should all chip in and buy him a couple of shop florescents and a drain pan so he doesn't have to blow up in the dark!
Anziani

 

[ppp111]

Maybe a stupid question: but what would be the sympthoms of such leaks in daily driving ? Loss of power, delayed response ? Any sounds (hissing...) ???