M117.xxx Vac leak. - PeachParts Mercedes-Benz Forum

PanzerSD · #1 10-27-2009, 09:11 PM

How big does a vacuum leak have to be (in terms of where vac can leak) in order to effect idle?

tinypanzer · #2 10-27-2009, 10:20 PM

Not very big at all.

According to my tech, M117 commonly manifests leaks at the injector seals and cups, as well as the 8 o-rings in the intake plenum under the fuel distro. The air injector hoses are also common culprits.

Spray some carb cleaner around, you'll find it.

PanzerSD · #3 10-27-2009, 10:56 PM

Then I must have a very large leak. not enough vacuum to operate locks, Hvac, or modulator.

I too suspect sealing rings, but never thought to look at the injectors!

I was planning on re-sealing everything, but didn't expect to be doing it quite yet.

It shakes real bad when its cold, as I imagine rubber parts contracting, and kind of settles out when the engine warms up, as I imagine the parts expanding.
I also have my idle screw nearly bottomed out. I know my Aux-air valve works, because I made it work

(I will be re-engineering THAT system)

Oh well...

tinypanzer · #4 10-27-2009, 11:07 PM

Yikes, that does sound like a bad leak. However, aren't the locks actuated by a seperate vacuum pump? I know that they are on my 126s.

PanzerSD · #5 10-27-2009, 11:11 PM

No, sadly they started doing that in 81

However, I will be eliminating much of the vacuum needy systems or feeding with an electric pump.

dhjenkins · #6 10-28-2009, 08:54 AM

Is there a vacuum reservoir on that car? I'd imagine there'd have to be in order to lock/unlock your doors with the engine not running. If so, I'd check that for leaks.

tinypanzer · #7 10-29-2009, 07:39 PM

Quote:

Originally Posted by dhjenkins

Is there a vacuum reservoir on that car? I'd imagine there'd have to be in order to lock/unlock your doors with the engine not running. If so, I'd check that for leaks.

Yeah, if engine vacuum is used for that, there must be a good sized reservoir and some check valves to keep it charged. I'd check the reservoir, the hoses, and the check valves to make sure they aren't leaking the vacuum back out.

PanzerSD · #8 10-29-2009, 09:27 PM

It's most definitely a leak from the intake manifold.
the CLS doesn't even operate with the car running, all connections are good. I have gaskets on order, and I have a 126 vac pump. the locks are getting converted to electric, and the brake booster and the CCU will be fed by the same pump.
the only thing that will rely on real engine vacuum, will be the warm up and fuel related things and the modulation..Even that I'm thinking of adapting a VCV from a diesel to control the vac..I'll have a much broader adjustment with my modulation as well that way.