Mercedes-Benz Forum banner

Mystery vacuum tube need identified

658 views 6 replies 3 participants last post by  dolucasi 
#1 ·
I posted this yesterday on the W201 thread but did not receive a response just yet. Can someone identify the tube that is an off-shoot from the breather hose in the picture.
It disappears under the air filter and I'm too lazy to pull off the filter canister to have a look.
Mine is a 2.6L engine.

Anyway it has a profound effect on idle roughness and low RPM "sputter" and fixing a very slight leak there has made my car run like brand new.

Your help would be appreciated and would be enlightening.
 

Attachments

See less See more
1
#2 ·
The small line running from the crankcase breather pipe goes to the fuel pressure regulator. In the event the FPR ruptures, raw fuel will be drawn up into the intake air box and on into the engine. It is a safety measure and should have no impact on the runability of the motor

Jayare
 
#3 ·
Thanks for the quick response Jayare. Now I'm puzzled. The small white plastic connector on mine inside the rubber tubes is somewhat aged and distorted and the fitting was rather loose. All I did was wrap Teflon plumbing tape around the plastic (inside the rubber) and re-inserted it. Now it is a tight fit.

And now the car runs much much better idling and low RPM (<1500) roughness is completely gone. Also mine is a manual transmission and every bit of roughness is felt especially when the micro-switch cuts-off. All of that is gone too.

I did one more thing at the same time - change the 85W-90 transmission oil back to Dextron-III ATF as it is supposed to be but I can not see how that would effect idle.

I swear the car is running like the day I pulled it off the Benz lot back in 1989.
Sure would like to understand this, maybe it would help others too.
 
#5 ·
Jayare your right. And if any fuel is in there can dilute the oil when it get in to the oil system through the rocker box .But i would lift the air filter box and look for cracked hoses .On the vacuum side as well , your tick or rpm is to high 800 to 850 is the norm . You have a leak some place .Look on the speedo console do you have a economy gauge ? wher on it is trhe needle pointing .It should be on the far left on the stop .But no good looking at this at the rpm youir running at . Your looking at getting thiose revs down
 
#6 ·
I think you guys misread the original thread (I actually omitted a key word "vacuum"). I did not mean there is a "fuel" leak. There must be a slight vacuum leak at the breather hose end of that plastic tube. When I properly seal it, the engine runs like new again. I was also not saying the idle is 1500 rpm. It idles nicely at 650-700RPM. I meant when the engine is <1500RPM the engine was a little rough now the engine is smooth at any RPM.

So basically, I was just trying to find out if others experienced the same thing. I lot of other users complain about rough idle. The plastic part of that tubing gets worn out since it gets a little hotter at the engine side of things. And the rubber hose tends to not hold the vacuum as well. I was just shocked how big a difference it made. That's all
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top