C250D back on the road

[spock500]

C250D back on the road :bannana:

Yup, quite pleased as today she passed her MOT with only minor advisories after an extensive rebuild.

OM605/6 piston advice - PeachParts Mercedes ShopForum

The ATF was changed along with the filter just before being taken off the road and garaged. At the time I was quite meticulous about the fluid level being exact so went for several journeys and topped up as necessary.

The procedure I used, get engine/tranny up to normal working temp then pull over onto a flat surface, put transmission in park and check fluid - is this correct?

The transmission was smooth after this but today unless softly accelerating there is a small thump on all of the gears as she changes 9up only) - I pulled over and checked the fluid, it's miles over perhaps a litre or more

What's happened here?

I suspect a valve may have jammed not letting fluid all the way around the box - any thoughts before I drain off the excess?

Thanks,

 

[spock500]

You can see it better on the Fahrenheit side of the dipstick better.

The level is to the far right of the picture, engine is cold (left overnight)

 

[spock500]

Heres the only vacuum pipe going to the gearbox I could find, it's a bit confusing using WIS or EPC as they list several different layouts.

 

[spock500]

Solving small probs one by one

Using as my daily hack now so have a good chance at ironing out the problems during the day.

Transmission level, this was driving me crazy until I discovered the reason - don't shift from 'P' to '1st' when hot as this throws the level out by around 500 - 750ml

Get the car up to working temp pull over on flat service and leave in 'P', pull dipstick, wipe and check then repeat - drained about 600ml and she's back to being smooth

 

[Number_Cruncher]

Well done in getting your engine rebuilt!

What gearbox is fitted in your car?

Is it an older 722.4/5, or is it a more modern 722.6?

If it's an older type of gearbox, then, it's worth checking the vacuum system carefully. A blockage, or partial blockage of the vacuum control valve on the injector pump can give some odd symptoms like you describe. The valve can be stripped down and cleaned - but you may end up drilling rivets out to open the valve.

 

[spock500]

Thanks,

I can only see one vacuum pipe in the picture above which goes into a harness up over the near side wing then into the control area where the accelerator linkage is.

No vacuum control valve on the injector pump that I could see?, the transmission is 722.4

I think it was just overfilled by about a litre, will check again tomorrow.

 

[Number_Cruncher]

If it's a 722.4, then, you will have a modulator valve on the passenger side of the gearbox towards the front edge - this valve depends on the correct vacuum level to work properly.

If there isn't enough vacuum, you'll get a hard shift.

The vacuum supplied by the pump is usually passed through a restrictor - these are little plastic pipe couplers - there's a piccie on the Russian site which indicates where they should go.

Then, there's the vacuum valve I mentioned above, which opens a leak to atmosphere as you open the throttle - on W124s it's on the side of the injector pump, I don't know about your C250D.

The combination of the restrictors and the variable leak means that the vacuum level at the gearbox should mimic that from a petrol engine.

Leaks elsewhere in the vac system may also mean there's insufficient vacuum at the modulator valve - checking with a mityvac or similar is a good way to rule out leaks.

I'm not sure if this is the exact page for your car, but, here's an example of the type of vacuum diagram I was thinking of;

http://www.detali.ru/cat/oem_mb2.as...436&VIN=*&CT=GA&cat=09S&SID=27&SGR=195&SGN=09

 

[spock500]

Just been out for a fairly long trip, 1st, 2nd & 3rd are all ok now - bit more noticeable than the box in the 300TD but acceptable.

4th you can still feel a hard shift though under full acceleration, if you let off the power it's ok.

Maybe still a small vacuum issue, those diagrams NC, is that the layout for four different systems fitted to these boxes?

I will print them off and compare to mine tomorrow,

Thanks,

 

[Number_Cruncher]

>>those diagrams NC, is that the layout for four different systems fitted to these boxes?

If you go back up a level or two, to this page,

??????? ????????? MB. ????? ??????.

you can click against the chassis numbers for your car, and follow the path back down. You'll get back to a screen with the same piccies, BUT, the parts list below changes, and by comparing which part numbers are in the list, and which parts are in which piccie, you casn identify which diagram is appropriate.

The only thing to be wary of is that some variants never make it onto the Russian site - there are some types of injector pump which exist on cars, but which aren't on any of the Russian sites pages.

 

[spock500]

Many thanks NC, owe you a beer

 

[Number_Cruncher]

Thanks David,

I've just remembered, there's a post by "pikeydave" on the other side, where he describes stripping and cleaning the vacuum control valve on the injector pump - it may be helpful.

 

[spock500]

Success

Removed the inlet manifold and traced back the vacuum 'harness' to the various components which terminate at two destinations.

First under the panel next to the accelerator linkage into a small control box, then on the other side of the engine bay into what looks like two valves with one pipe going into the regulator on top of the air inlet/manifold well at least it should be

Popped that on and all sorted, smooth as the 722.6 now