auto gearbox slipping - PeachParts Mercedes-Benz Forum

scortmad · #1 07-08-2009, 07:32 PM

my dads car 1996 c class i fitted the engine and auto gearbox from a 1987 250 td estate "non turbo"
the auto box has started slipping very light throttle in top gear slips a bit then no drive until you stop the car and set off again. this car has always shifted funny some times hard and sometimes very slow flaring i believe the is the name for it . now the funny thing is that some 5-6 years ago the engine would take 2 mins or so to shut off i put this down to a vacuum fault at the pump as there was no leaks i put a t into the brake vacuum hose and piped the engine shut off to this
tonight i drove the car and disconnected the vacuum pipes that were still connected to the pump this made the gear changes very hard but no slipping , so i am thinking that the vacuum pump is causing the problem ,can i connect these pipes to the brake servo vacuum or will there be too much vacuum, or can i rebuild the vacuum pump maybe its gummed up with something
please help
thanks tris

kerry · #2 07-08-2009, 08:24 PM

Flaring is caused by high vacuum, not low vacuum, that's why your shifts tightened up with the vacuum pump disconnected. Beyond that I can't help since I don't know anything about the 87 250TD.

Shawn T. W. · #3 07-08-2009, 08:29 PM

Where are you located?

pawoSD · #4 07-08-2009, 09:27 PM

Going to guess he is in the UK.....they have 250's there.....and call their cars estate.

kerry · #5 07-08-2009, 09:32 PM

Quote:

Originally Posted by pawoSD

Going to guess he is in the UK.....they have 250's there.....and call their cars estate.

Plus auto gearboxes don't exist in the US.

compress ignite · #6 07-08-2009, 10:54 PM

scortmad,

In the Engine Compartment the Mechanical Vacuum Pump (Mounted on the
front of the Engine) is the ONLY Vacuum source for both Transmission and
Brakes.

With that age on the Vacuum Pump you're probably looking at a replacement.
(If it's the Piston Type Pump , Failure of the Pump Scatters Metallic Schrapnel
all over the Timing Chain Cavity
['Pisses off the Timing Chain so Much,it Breaks!]
And then you get to replace the engine!)
There are no rebuild kits from Pierburg (the Manufacturer).

This is a typical explosion in which the older style pump's bearings lept out into
the Timing Chain Cavity (New Pump's have enclosed Bearing Races):
http://picasaweb.google.com/oliviersp1/Mercedes_300D_turbo#
FROM MB CLUB FORUM UK post:http://www.mbclub.co.uk/forums/engine/57924-w124-vacuum-pump.html

member GSXR here suffered an unusual failure:
OM603: Vacuum pump explosion, bearing intact! Injection Pump Timing device wrecked

The "Trick" to adjusting any Mercedes Transmission is to First make sure the
engine is in proper tune (Making Power) otherwise engine power problems
will Masquerade as Transmission Maladies.

Stevebfl posted a great DIY on Vacuum Adjustments to the Transmission:
http://www.peachparts.com/Wikka/TransVacTune

scortmad · #7 07-09-2009, 08:12 AM

Quote:

Originally Posted by Shawn T. W.

Where are you located?

hi i am in the uk cornwall

compress ignite i dont like the look of that and dont like the thought of just inspecting it ,i think i will look for a replacement
after reading the reply's and other posts it would seem that i may have too much vacuum would this be a sign of the pump failing ?
if not could this be a problem with vacuum adjustment that this car "engine and gearbox" had for a long time as it has always had a little bit of flaring problems

kerry · #8 07-09-2009, 10:39 AM

You could simply remove the vacuum to the transmission and live with hard shifts. Turns out on my W116, removing the vacuum line resulted in nice firm shifts and no flaring.

scortmad · #9 07-12-2009, 08:10 AM

ive had a good look at dads car today and i have found this pipe split

would this cause the slipping i have made a repair to it but it still slips when changing from 3rd to 4th

i cannot find any adjustment for the vacuum can someone please help me i have looked at the guides but i cannot find anything that looks similar

thanks tris

compress ignite · #10 07-12-2009, 11:11 PM

The device the hard Black Plastic line "Plumbs Into" is the Vacuum Control Valve.

Where does the Hard Black Plastic Vacuum line go to?

(On my OM602 the Hard Black Plastic line is a "Vent" line just allows atmospheric
compensation of the system.)

compress ignite · #11 07-12-2009, 11:15 PM

"The "Trick" to adjusting any Mercedes Transmission is to First make sure the
engine is in proper tune (Making Power) otherwise engine power problems
will Masquerade as Transmission Maladies."

"Stevebfl posted a great DIY on Vacuum Adjustments to the Transmission:
http://www.peachparts.com/Wikka/TransVacTune