240D potential transmission failure - Page 2 - PeachParts Mercedes-Benz Forum

steeleygreg · #1 01-30-2014, 08:27 AM

Thanks Stretch. The above pics where taken with the car in park. I will get some long hose and route the line pressure gauge thougth the firewall and in to the car as the other two gauges are. I'll also pic up a device to measure temps.
The forecast for the weekend calls for much more tolerable temps.
Stretch, documentation which the modulating pressure was set to was at 2.8 bar with the modulator disconnected from the vacuum line. What's shown in the pic is with the Vacuum modulator connected to the VCV.

whunter · #2 01-30-2014, 11:14 AM

Quote:

Originally Posted by steeleygreg

Thanks Stretch. The above pics where taken with the car in park. I will get some long hose and route the line pressure gauge thougth the firewall and in to the car as the other two gauges are. I'll also pic up a device to measure temps.
The forecast for the weekend calls for much more tolerable temps.
Stretch, documentation which the modulating pressure was set to was at 2.8 bar with the modulator disconnected from the vacuum line. What's shown in the pic is with the Vacuum modulator connected to the VCV.

Ambient temperature has little impact once the engine is at operating temperature, unless it is seriously sub zero.
In the OE climate chambers, it is called a slush box, where they test transmissions to -80° F..

If the engine is at 80° C, the transmission should be at operating temperature.

They share the radiator.

On a cold start, Running for 5 minutes will not reach anything near transmission operating temperature.

.

Stretch · #3 01-30-2014, 02:02 PM

...I've suffered...

...I had to boot up Windows to find this data - dreadful experience!

Looking through the German FSM the data for USA models is given in a separate section.

Use the headings from this table =>

But the data from here =>

As Roy mentioned above the transmission operating temperature is 80 degrees C - this is in the owners handbook. I reckon the best way is to use a IR thermometer reading off of the transmission oil pan. (Or thermocouple and multimeter)

steeleygreg · #4 01-31-2014, 12:47 AM

Stretch, a thought accord to me. When I set the modulating pressure, the document stated to disconnect the modulator valve from the VCV. 2.8 bar was the obtained setting.
For these modulating and working pressure settings documented above, do I also disconnect the modulator valve ? Currently the VCV is connected to the modulator.

Stretch · #5 01-31-2014, 03:24 AM

First things first - the transmission needs to be at the right temperature and you need to have it at stand still in drive - then the measurements will start to have some meaning. (The test for in reverse at stand still is also there)

Ignore the vacuum measurements at the moment; concentrate on the hydraulic pressures in the table posted above.

whunter · #6 01-31-2014, 07:57 AM

Be sure to convert the pressure between BAR and PSI.
Here is a great utility for doing conversions.
Convert.exe

.

Stretch · #7 01-31-2014, 10:15 AM

^^^

Hee hee

"old money" : "new money" = "aaaaarrrrrggggggggg"!

steeleygreg · #8 02-01-2014, 01:54 PM

Getting ready to change trans fluid and filter, but just for giggles I wanted to see what pressure readings I'd get before and after fluid and filter are changed.

Reason for this test was because the modulating press would go to 0 within a minute of running the car.
When I jacked the car up to connect a gauge to read working pressure, I couldn't get the modulating press to drop even after 5 minutes.

After warming the car to operating temps, that's 80C I still couldn't get it to fail, so I took it for a road test in my community.
If the car broke down, I wouldn't have far to walk.
The attached file has the finding.
Currently the car is cooling and I'll drop the pan shortly.

.

Stretch · #9 02-01-2014, 04:04 PM

If you do a screen shot of your spreadsheet it might help with the more lazy of us about here who don't want to upload PDFs!

I assume the values are bar

Your working pressure is way too low - 3.2 bar is way down on the 7.2 bar it should be - the reverse should be more than 16 bar and you only have 6.6

This looks like a weak front pump problem - but - we should see how a new filter and oil behaves before we read it the last rites

whunter · #10 02-02-2014, 05:55 AM

Quote:

Originally Posted by Stretch

If you do a screen shot of your spreadsheet it might help with the more lazy of us about here who don't want to upload PDFs!

I assume the values are bar

Your working pressure is way too low - 3.2 bar is way down on the 7.2 bar it should be - the reverse should be more than 16 bar and you only have 6.6

This looks like a weak front pump problem - but - we should see how a new filter and oil behaves before we read it the last rites

Greg and I spoke Saturday, Filter change is NEXT.

Best of luck Greg.

.

Stretch · #11 02-02-2014, 01:03 PM

Quote:

Originally Posted by whunter

Greg and I spoke Saturday, Filter change is NEXT.

Best of luck Greg.

.

Come on Greg - get a shift on! I can hardly contain my excitement (OK I don't get out much) => is this going to be proof that a new filter makes a difference in working pressure or not?

Stretch · #12 02-02-2014, 04:43 PM

Have you got a magnet Greg?

Is this stuff magnetic?

It looks a little like brake band / clutch lining to me - which is paper based...

...dry it out and see what you think.

This still doesn't explain the low working pressure but it could indicate more trouble to come.

97 SL320 · #13 02-02-2014, 06:42 PM

In person, it looks like separation of oil and not a pile of material correct?

Seen it before, not cause for alarm, likely graphite from friction plates maybe some graphite from cast iron.

Stretch · #14 02-03-2014, 01:47 AM

Quote:

Originally Posted by 97 SL320

In person, it looks like separation of oil and not a pile of material correct?

Seen it before, not cause for alarm, likely graphite from friction plates maybe some graphite from cast iron.

I can't think of a single part in a 722.1 that's made of cast iron - what do you mean by graphite? Do you mean very fine swarf?

97 SL320 · #15 02-03-2014, 06:52 PM

Quote:

Originally Posted by Stretch

I can't think of a single part in a 722.1 that's made of cast iron - what do you mean by graphite? Do you mean very fine swarf?

I can't say for sure on the .1 , but in many transmissions, cast iron is found in the front pump housing. Clutch drums are usually cast steel but modern transmissions use stamped steel. Cast steel is a sort of cast iron but more towards steel but not quite. One piece rotors / hubs are made from cast steel as well. As these materials wear they make a dust where steel makes flakes.

Graphite is a form of carbon.