Mercedes-Benz Forum banner

1 - 3 of 3 Posts

327 Posts
Discussion Starter #1
yeh that's what it says in method #23

so if I want to shut off my EGR, I have to run direct vacuum to them.
not unplug them.
I suspected this in previous posts.
it may be why Marcin has a shaky idle as well,
one of his EGR's may be hanging up.
as a matter of fact, it may be why so many of these cars,
run lousy for no apparent reason.
I first noticed it when I ran direct vacuum to the EGR, and the idle smoothed out.
it should stall the car when opened at idle.
and that's probably why, the EGR's leak smoke, when tested by Victor, on youtube,
the proprietor of
today, I will run direct vacuum to both EGR valves,
from the intake manifold on each side,
and see what happens.
this assumes the EGR isn't stuck open, or partially stuck open
really the only way to bypass them, in this case,
is bolt a blocker plate under the EGR inlet tube, on bottom of intake manifolds.
think about it, raw exhaust gas going into the manifold, along with the intake air,
it's a stupid half-arsed way of controlling emissions,
by ingesting more emissions.

327 Posts
Discussion Starter #2 (Edited)
just got back from tinkering on my W140 coupe V12,
yes the EGR valves are actually CLOSED when vacuum is applied.
I ran a vacuum line from each small port on each side of the intake manifold,
directly to the EGR valves.
one on each side.
the car idled down lower rpm, sounded richer, more powerful
backing out of the driveway, it spun the rear tires in the driveway,
and I didn't hardly give it any gas.
took it down the road, and floored the gas.
it took off like a jet. pushed me back in the seat.
flatboarded it a few more times,
at one point the traction control kicked in,
and pushed the gas pedal back up towards me.
it was on the threshold of breaking the tires loose.
the car is a rocket at the slightest touch of the throttle.
I still have to pull the o2 sensor out of the left side exhaust.
it is dead and no longer transmitting.
but case closed, EGR valves on these cars, close with vacuum applied.
first one I've seen like that in my lifetime.
read about them, never actually saw one until now.

327 Posts
Discussion Starter #3
here's the test on StarTek Manual Info page
it is test #23, link below:

Left or right EGR valve
Mechanical test​
Test connection note:
Connect vacuum tester directly to left or right EGR valve.

Using vacuum tester, apply 500 mbar vacuum.
Disconnect vacuum line on EGR valve

Left or right EGR valve closes audibly.
EGR valve.​
1 - 3 of 3 Posts