It's CRITICAL... how you set your transmission's vacuum system on your diesel MBZ... - Page 36 - PeachParts Mercedes-Benz Forum

beerlover · #**526** 11-24-2008, 02:15 PM

I don't have a good vacuum diagram for the 95 E300D. I have two "manuals" (the E class owner's bible and another one) but they don't have a good diagram for the 606. It sure would be helpful if I could find one!

Samuel M. Ross · #**527** 11-24-2008, 07:48 PM

Quote:

Originally Posted by beerlover

I don't have a good vacuum diagram for the 95 E300D. I have two "manuals" (the E class owner's bible and another one) but they don't have a good diagram for the 606. It sure would be helpful if I could find one!

Help us out here... we are looking for what I call the "Tranny-Shifter/Engine Vacuum Control Diagram for 1995-1999 E300D diesel engines that are in 210 and 124 chassis!
Regards,

ckamila · #**528** 11-24-2008, 11:04 PM

Quote:

Originally Posted by Jeremy5848

I'll check the boost line for the appropriate pressure, thanks.

[edit] Boost is getting to the amplifier. With the engine at operating temperature, the vacuum level to the transmission drops to below 5" Hg at full throttle (the Mityvac is not calibrated below 5) so I think the system is working as it is supposed to.

Last night I re-read my collection of Mercedes manuals. In addition to reinforcing in my mind Mercedes' assumption (that readers of any one manual know about and have access to all of the other manuals), I finally figured out how and why the transmission vacuum system works. At least I think I did. Bear with me . . .

When we forum members use the generic term FSM (Factory Service Manual), we usually mean the "how to fix it" service manual for the engine (and I use it in that meaning here). As we become more experienced, we discover that there is also a maintenance manual, a body manual, a climate control manual, and others. One of the "others" that I have found most useful is the annual "Introduction into service" manual. It not only gives service information for models new in any particular year, but goes into more detail than the FSM.

Speaking specifically of the 1987 300D Turbo (W124) and the 86-87 300SDL Turbo (W126), which uses the same OM603 engine, the 1987 "Introduction into service" manual has almost nothing on the 603 engine. Why is this? Because the 603 was new in the 1986 model year, even though most cars sold in the US of A were imported in Fall 1986 or later and sold as 1987 models. Thus, to get the complete poop on the 603, you must read the 1986 "Introduction into service."

As regards the transmission's "temperature and boost-pressure-dependent vacuum control" (the subject of this whole thread), it gets worse: on page 179, the 1986 Introduction says that the vacuum control system "is the same as on engine 617.95 (model year 1985)."

So it is in the 1985 "Introduction into service" manual that one finally finds the how and why of this vacuum control system. This is covered in the section on the automatic transmission fitted to the 1985 300D (W123) and 300SD (W126) on pages 97 through 106.

The section on the "Temperature and boost pressure dependent vacuum control" includes the how and why and pictures of the components including the "Vacuum transducer" (we have been calling it an "amplifier"), the "Coolant temperature switch," the "Switchover valve," and the "Aneroid compensator (Alda). The heart of the whole thing is on page 102, the "Functional description" and the "Turbo boost pressure effect."

As simply as I can put it, the "transducer" uses vacuum from the vacuum pump, more vacuum from the VCV, and boost pressure from the intake manifold to create a vacuum signal that controls the "hydraulic modulating pressure" in the transmission. "More vacuum" gives softer shifts while "less vacuum" gives harder shifts. (This is why the transmission shifts hard when a vacuum line falls off.)

Below 50C coolant temperature, the "Coolant temperature switch" turns off the vacuum signal from the VCV at the "Switchover valve." Instead, the transducer gets (more) vacuum from the vacuum pump. This has the effect of increasing vacuum to the transmission, softening the shifts while the engine is cold. Once the coolant temperature rises above 50C, the switchover valve is turned on and the VCV controls the transducer. An increase in throttle produces less vacuum to the transmission, thus firming up the shifts.

Turbo boost pressure from the intake manifold also has the effect of reducing the vacuum produced by the modulator. Thus, as the engine develops more power, the shifts get firmer (to prevent slipping). All of these "signals" (throttle position, turbo boost, coolant temp, and vacuum from the pump) must be present and in the correct amounts for the transducer to do its job and control the transmission.

One final addition: sometime in 1987, the factory added a "no load" microswitch to the throttle linkage. This switch turns off the boost pressure signal at the transducer when you take your foot off of the accelerator. The resulting increase in vacuum to the modulator helps the transmission to not 'clunk' as it downshifts (such as when you are coming up to a stop).

Anyone struggling to fix this vacuum control system would be greatly helped by access to the information in the 1985 "Introduction into service" manual. I can scan pages 97-106 into a PDF if someone can help me get it into the forum.

Sorry to be so long winded but as Sam said at the beginning, "it's critical."

Jeremy

Hi Jeremy - did you ever post the 1985 "Introduction into service" pages 97 - 106 in PDF? I have an 85 300D Turbo with rebuilt transmission that performs less than i'd like - clunking with taking my foot off the pedal, harsh 1-2...those pages may shed a little light.

beerlover · #**529** 11-25-2008, 07:47 AM

I found the vacuum diagrams for the OM606. The following site has the whole manual on-line.

http://www.w124performance.com/service/w124CD1/Program/124avi1.htm

I re-ran my vacuum lines according to this diagram (which was quite a bit different from the way my car was plumbed) and now the thing shifts like a dream. Unbelievable difference!

Samuel M. Ross · #**530** 11-26-2008, 05:45 PM

Quote:

Originally Posted by beerlover

I found the vacuum diagrams for the OM606. The following site has the whole manual on-line.

http://www.w124performance.com/service/w124CD1/Program/124avi1.htm

I re-ran my vacuum lines according to this diagram (which was quite a bit different from the way my car was plumbed) and now the thing shifts like a dream. Unbelievable difference!

The WebSite/Page your gave the address for worked only partially for me... up to the point where you try to access one of the " *.PDF " files!
Consider yourself lucky... unless you signed up for OnLine access to these manuals. I currently own the 2-CD sets for the W123 & W126 manuals.
I'd love to get my hands on the Vacuum Diagrams for the W124 series... hint, hint!

Regards,

Samuel M. Ross · #**531** 11-26-2008, 05:47 PM

Quote:

Originally Posted by beerlover

I found the vacuum diagrams for the OM606. The following site has the whole manual on-line.

http://www.w124performance.com/service/w124CD1/Program/124avi1.htm

I re-ran my vacuum lines according to this diagram (which was quite a bit different from the way my car was plumbed) and now the thing shifts like a dream. Unbelievable difference!

Oh, I forgot to congradulate you on clearing up your problem... and the means by which you did this only serves to support why I almost always start out by getting the correct vacuum diagram whenever I have tried to help someone participating in this THREAD!
Regards,

Jeremy5848 · #**532** 11-26-2008, 08:11 PM

Quote:

Originally Posted by ckamila

Hi Jeremy - did you ever post the 1985 "Introduction into service" pages 97 - 106 in PDF? I have an 85 300D Turbo with rebuilt transmission that performs less than i'd like - clunking with taking my foot off the pedal, harsh 1-2...those pages may shed a little light.

I have it scanned as a pdf but have not been able to access the little web site that my email service provider gives me. I haven't used it in ages (http://www.cds1.net/~jeremy) and the password must have been reset. As soon as they answer my email, I'll get the document sent up and post the link here. I also tried my Photobucket account but they won't host pdf files, only images. Although I can take the pdf apart in Photoshop and save each page as a separate jpeg image, I am reluctant to do that.

In the meantime, anyone who wants a complete file of these pages (3.3 MB) can PM me their email address and I will send it direct.

Jeremy

bob_98sr5 · #**533** 11-29-2008, 12:37 PM

Hi Samuel and Brian,

(I edited this post instead of writing a 2nd one)
I for one appreciate all the time you and Brian have put into answering everyone's questions. After reading as much as I've could and writing down all the relationships as well as taking some key vac readings, I am stumped at what I can do next.

First, I have a 87 300D Turbo with the OM603 engine. My Vac Control Valve may be giving up the ghost and as I understand it, it cannot be repaired. So as you can see, I have 19 inHg going into the VCV from the main pump. I am certain that is within specs, though on the lower side. So with the engine off, I unplugged both the green dash pot and the other vac connection from the VCV. I stuck in my vac tested and I pumped it up. It is giving up some funky readings and behaving strangely. I can pump it up to 12 inHg...it'll stick at 12 for about a split second then shoot down to 9. The vacuum will go to zero in about 6 minutes. The fact that the VCV vac pressure will hit 12 but shoot immediately down to 9 is a very key point because I believe this is causing my erratic, stacked shifting from 2 to 3 and 3 to 4.

Second, at idle, I measured for pressure to see if the trans modulator would hold pressure. It does. However, it is not bleeding at all: I pumped it up to 15, but it is hardly bleeding if at all. After 2 mins, it did not even move. Brian, for reference sake, you mentioned that it should bleed 1inHg per second in one post. Am I doing this test incorrectly?

Also I tested the pressure at idle. I put the tester between the 2nd green dashpot (after the vac amplifier, the blue UFO) and the transmission modulator itself. At idle, it reads as high as 17 inHg. So I read that it should be about 15 at the highest. In the early part of this thread, I saw that you and Brian vs. Sun Valley and Peterschmid.com differed on this amount, as Brian said that he advised on older transmissions that it should be around 8 to 10. Since my transmission has around 225K miles, I adjusted downwards. I turned the small 4mm vac amplifier nut down to 12 inHg. Of note for anyone reading, mine went down 5 inHg and that's all because I could not turn the adjustment nut anymore.

So what happens is this when I'm driving: when I am in 1st gear going into 2nd, the vac pressure to the transmission modulator will go from 12 to 0, but it will *hold* at 0 and won't shift until it hits 3,000 rpm or if I left off the pedal. Once it hits 2nd gear, it will shift rather quickly into 3rd. Classic stacked shifting, which Brian says is too much pressure going to the trans modulator. So how can I further decrease the vac pressure to the modulator down to 8? Have I exhausted all my options?

I'm going to try to correlate something here, guys. Let me know if this is right or wrong. Related to the cold VCV test and the VCV's erratic behavior of hitting 12 inHg, but dropping a split second later to 9 inHg, that perhaps the inability of the transmission to shift from 1 to 2 (holding on too long) and the stacked shift is because VCV is *not* filling up quick enough AND dropping too quickly AND that the trans modulator has too much pressure going to it?

Also, when I am doing 0 - 60 runs, the shifting will be (what I consider) pretty good. However, it is holding way too long from 1 to 2. I am assuming b/c of the rapid loss of vacuum and WOT, it shifts better. Or am I mistaken in my understanding of how the vac system works?

Please note too that I've installed a Superior spring kit to soften up 1 to 2 and firm up 2 to 3.

I'm off to the junkyard right now to find some nozzles to try to get down the vac pressure to the trans modulator down to 10 or 8 (per Brian's recommendation). But what concerns me still is the vac pressure drops down to 0 inHg, but does not shift from 1 to 2 and 2 to 3 very well.

Thanks,
Bob

bob_98sr5 · #**534** 11-29-2008, 10:40 PM

Ok, I fixed my problem...sorta. A few days ago, I got some really good advice on cleaning out the overboost solenoid (aka switchover valve Y30) and the other switchover valve by the vac amplifier (aka blue ufo). I sprayed it clean with WD40 and did the electrical test to see if it was in order. it passed the electrical test and all the gunk came out of it. I was also advised to route the hose from the ALDA directly to the intake manifold nipple and wow, there was a huge power increase!

so as I reported, my shifting was really great, but needed a little more oompf from stop. however because of my cleaning and tests above, I decided that I'd hook up the vac hoses to Y30 again and adjust accordingly.

Well whatever the case maybe, all my headaches the last 2 days were solved by taking the overboost solenoid (Y30) out of the loop. i just unhooked it and the shifts are where they are supposed to be. 2 to 3 shifts a little quicker than i'd like, but as of right now, I'm tired of messing with the transmission, the shift points, bowden cable, accelerator adjustments, etc. i still have not unhooked the kickdown switch, so i'll see if that makes a differene.

I still want to fully comprehend the "why?" in my previous post. however, i dont want to plunk down the $200 or whatever to buy a new VCV. i may plunk down some bucks to buy some smaller orifices, but for now, I'm happy where things are at.

oh, i do plan to hook up the autometer boost gauge that I purchased last week as i dont want to pass the 14.5 psi boost limit (it seems to be set at 10 psi-ish)

also i plan to install the unused unused vac pressure gauge i had hidden in the garage between the dashpot off of the vac amplifier (blue ufo) and the trans modulator.

bob

tangofox007 · #**535** 11-29-2008, 11:13 PM

Quote:

Originally Posted by bob_98sr5

So with the engine off, I unplugged both the green dash pot and the other vac connection from the VCV. I stuck in my vac tested and I pumped it up. It is giving up some funky readings and behaving strangely. I can pump it up to 12 inHg...it'll stick at 12 for about a split second then shoot down to 9. The vacuum will go to zero in about 6 minutes. The fact that the VCV vac pressure will hit 12 but shoot immediately down to 9 is a very key point because I believe this is causing my erratic, stacked shifting from 2 to 3 and 3 to 4.

Did you test the VCV with the engine running and control rod disconnected as per the instructions furnished with the Superior kit? It does not seem to me that a static test of the VCV is meaningful.

bob_98sr5 · #**536** 11-29-2008, 11:23 PM

tango,

I tested the VCV w/ the engine running too, but i did not disconnect the control rod. how hard was it to remove and then reattach the control rod? and what will this method of testing do that the static testing won't?

Brian Carlton · #**537** 11-29-2008, 11:39 PM

Quote:

Originally Posted by bob_98sr5

First, I have a 87 300D Turbo with the OM603 engine. My Vac Control Valve may be giving up the ghost and as I understand it, it cannot be repaired. So as you can see, I have 19 inHg going into the VCV from the main pump. I am certain that is within specs, though on the lower side. So with the engine off, I unplugged both the green dash pot and the other vac connection from the VCV. I stuck in my vac tested and I pumped it up. It is giving up some funky readings and behaving strangely. I can pump it up to 12 inHg...it'll stick at 12 for about a split second then shoot down to 9. The vacuum will go to zero in about 6 minutes. The fact that the VCV vac pressure will hit 12 but shoot immediately down to 9 is a very key point because I believe this is causing my erratic, stacked shifting from 2 to 3 and 3 to 4.

On the 603, you cannot simulate the engine vacuum with the mityvac. The bleed is much too large and your results are meaningless. You can only use the Mityvac to measure the vacuum at various places while the engine is running. The only exception is vacuum directly to the modulator to check its integrity.

Quote:

Originally Posted by bob_98sr5

Second, at idle, I measured for pressure to see if the trans modulator would hold pressure. It does. However, it is not bleeding at all: I pumped it up to 15, but it is hardly bleeding if at all. After 2 mins, it did not even move. Brian, for reference sake, you mentioned that it should bleed 1inHg per second in one post. Am I doing this test incorrectly?

If the modulator holds vacuum, it's working perfectly. What I mentioned previously is that a leak of 1" per second would probably be tolerable for the engine driven vacuum pump..........although, it's certainly not desirable.

Quote:

Originally Posted by bob_98sr5

Also I tested the pressure at idle. I put the tester between the 2nd green dashpot (after the vac amplifier, the blue UFO) and the transmission modulator itself. At idle, it reads as high as 17 inHg. So I read that it should be about 15 at the highest. In the early part of this thread, I saw that you and Brian vs. Sun Valley and Peterschmid.com differed on this amount, as Brian said that he advised on older transmissions that it should be around 8 to 10. Since my transmission has around 225K miles, I adjusted downwards. I turned the small 4mm vac amplifier nut down to 12 inHg. Of note for anyone reading, mine went down 5 inHg and that's all because I could not turn the adjustment nut anymore.

You tested vacuum at idle.........not pressure.

One of the obligations of the reader is to make note of the specific vehicle for which recommendations are offered. My previous comments on the 617.95 are not applicable to the 603.96.

Your reading of 17" at idle is acceptable, provided that your shifts are not unduly soft and mushy which wil result in greater than desirable clutch wear. Reducing the vacuum will firm the shifts and is always advisable if the driver doesn't object to the shift quality. I did not recommend any specific value for the 603.96. In my specific case, I have reduced the vacuum to the lowest possible level and I cannot reduce the vacuum below 11" on either engine.

Quote:

Originally Posted by bob_98sr5

So what happens is this when I'm driving: when I am in 1st gear going into 2nd, the vac pressure to the transmission modulator will go from 12 to 0, but it will *hold* at 0 and won't shift until it hits 3,000 rpm or if I left off the pedal. Once it hits 2nd gear, it will shift rather quickly into 3rd. Classic stacked shifting, which Brian says is too much pressure going to the trans modulator. So how can I further decrease the vac pressure to the modulator down to 8? Have I exhausted all my options?

You don't describe the pedal position or the boost levels during your tests, and, therefore, no conclusions can be drawn.

Quote:

Originally Posted by bob_98sr5

I'm going to try to correlate something here, guys. Let me know if this is right or wrong. Related to the cold VCV test and the VCV's erratic behavior of hitting 12 inHg, but dropping a split second later to 9 inHg, that perhaps the inability of the transmission to shift from 1 to 2 (holding on too long) and the stacked shift is because VCV is *not* filling up quick enough AND dropping too quickly AND that the trans modulator has too much pressure going to it?

No, the modulator does not have too much vacuum.

Quote:

Originally Posted by bob_98sr5

Also, when I am doing 0 - 60 runs, the shifting will be (what I consider) pretty good. However, it is holding way too long from 1 to 2. I am assuming b/c of the rapid loss of vacuum and WOT, it shifts better. Or am I mistaken in my understanding of how the vac system works?

The delay in shift is caused by too much tension in the Bowden cable. Find the white nut just forward of the oil filter housing and turn it counterclockwise (viewed from the back of the vehicle) by two turns.

Quote:

Originally Posted by bob_98sr5

Please note too that I've installed a Superior spring kit to soften up 1 to 2 and firm up 2 to 3.

Why would you do that? The 603 never sufferred from a firm 1-2 or a soft 2-3? Is the Superior kit even applicable to the 603?

Quote:

Originally Posted by bob_98sr5

I'm off to the junkyard right now to find some nozzles to try to get down the vac pressure to the trans modulator down to 10 or 8 (per Brian's recommendation).

That was never my recommendation for the 603, nor do I deem it necessary. The shifts are very firm at 11".

Quote:

Originally Posted by bob_98sr5

But what concerns me still is the vac pressure drops down to 0 inHg, but does not shift from 1 to 2 and 2 to 3 very well.

The vacuum levels are modulated by pedal position and boost levels. Without those definitions, the results cannot be interpreted.

tangofox007 · #**538** 11-30-2008, 12:11 AM

Quote:

Originally Posted by Brian Carlton

Is the Superior kit even applicable to the 603?

It's a transmission kit, applicable to the 722.3 and 722.4.

tangofox007 · #**539** 11-30-2008, 12:20 AM

Quote:

Originally Posted by bob_98sr5

tango,

I tested the VCV w/ the engine running too, but i did not disconnect the control rod. how hard was it to remove and then reattach the control rod? and what will this method of testing do that the static testing won't?

Disconnecting the control rod in not essential; it just prevents having to actually increase the engine rpm during the test. I suspect that the instructions recommend disconnecting the lower end of the rod to avoid breaking the plastic lock on the upper end.

The VCV is a regulator; you can't test its function by without a constant vacuum being applied.

bob_98sr5 · #**540** 11-30-2008, 01:10 AM

I seemed to have struck a nerve with you by misquoting you in one or two places---sorry about that. I thought that some of the 617 info was applicable to 603 engines. Or any engine for that matter, regarding vacuum. Thanks for clearing that up as well as the terminology too.

As for the pedal and boost levels, i'll probably do this during the week if I have time or definitely next weekend. I'll post back.

Thanks for all your help and advice,
Bob