Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   PeachParts Mercedes-Benz Forum > Mercedes-Benz Tech Information and Support > Diesel Discussion

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 08-14-2002, 06:14 AM
adamb's Avatar
Registered User
 
Join Date: Jul 2001
Location: Chapel Hill, NC
Posts: 321
Shifting clunk solved!!!

Shifting clunk solved!!!
Hello, thanks to all on this forum for making it what it is. I have saved immeasurable amounts in both money and time in the assistance you have all provided in your posts. One thing that has eluded me for the past year with no resolve until a few days ago was the darn clunking that seemingly came from the rear end whenever shifting up or down under light load. My car has 157k, is a 1985 300d turbo Californina model and i figured that all the stuff I replaced to chase down this clunking would benefit the car even if it didn't fix the clunks. The problem, just as many had already pointed out, was vacuum. My initial ignorance about Mercedes vacuum systems and poor troubleshooting strategy has tought me several things. First, the reason I bought this car was to save money and enjoy a first class car from a build standpoint. But, I feel obsessed with making everything work properly and even after I change the oil I almost feel an itch to change it again after a week, but resist until 2-3k (I bought DELO 400 from Walmart for 1.08 a qt). I learned most importantly that I need to troubleshoot by learning the system more thouroughly, i.e. - I need to buy the dang manuals and read them as opposed to doing everything from my supposed all-encompassing mechanical ability (I thought). I wound up learning backwards the entire vacuum system only to find the culprit being at the end of my learning journey. The Californina model I have has a diaphram in the turbo in addition to the wastegate that controls boost. The diaphram had developed a small leak and caused an intermittant vacuum problem affecting everything, but most significantly the shifting. While I have been unable to find a replaceable diaphram (anyone have any ideas?) I simply disconnected and plugged the vacuum hose leading to the offending part. The first clue for me shoule have been when I hooked the mighty vac up to the tube going to the tranny modulator and assessed the vacuum dropoff that occurred (most of the time) and gone backwards from there. The reason why i strayed is that the clunk seemed far too significat to be caused by vacuum, like it was eminating from the rear end, but happily it was not from there. I will stop writing there, as I, like all of you, can write novels about our adventures with hese cars when our wives are telling us diner is ready and we say, "just a minute" and come in only after we are threatened. Once again, thanks to all of you for your guidance. Adam Bush


Reply With Quote
  #2  
Old 08-14-2002, 10:23 AM
Steve 300D
Guest
 
Posts: n/a
lol adamb, my mom calls for me when it's dinner time(only 16, don't want or need a wife, to much money ) I always say, In a minute. She got tried of it so she lets me work on the car, but I have to eat cold food, things we do for our MB's :p
Reply With Quote
  #3  
Old 08-14-2002, 12:57 PM
BWatson's Avatar
Registered User
 
Join Date: Jan 2002
Location: Los Angeles
Posts: 222
I'm glad you found the problem. I would hate to see a MB owner get raked over the coals by a transmission shop thus furthering the rumour that these cars are expensive to maintain, when all it takes is some vacuum troubleshooting.
__________________
1982 300D Turbo "Helga"
380,000 miles
Reply With Quote
  #4  
Old 08-14-2002, 01:16 PM
surfblau's Avatar
neue Dieseler
 
Join Date: Feb 2002
Location: san francisco - immer kalt, immer windig, I want to move
Posts: 382
adamb- were there any other symptoms?

Like did it always shut down with no runon?

Were there any other vac related problems?

I am trying to track down a hard shifting clunk in my 87 SDL and keep reducing the problem (by about 50%, mostly through vac leak fixes), but can't seem to reduce it enough....
__________________
84 300TD - 235k - Farbe "Surfblau" bought at 213k
87 300SDL - 131k - Farbe "PimpGold" bought at 115k
00 Klepper Faltboot Expedition Double
Reply With Quote
  #5  
Old 08-14-2002, 02:29 PM
gsxr's Avatar
Unbanned...?
 
Join Date: Aug 2001
Location: USA
Posts: 8,101
Adam,

That's the air recirculation valve on the turbo. Leave it disconnected and plugged, and also disconnect and plug the EGR valve. Both are evil, reduce HP, and reduce MPG. If you want the car to appear stock you can insert a "BB" into the hose at each item, which makes the fix invisible. I plugged mine & removed all of the vacuum hoses, so my engine compartment is much neater.



Regards,
__________________
Dave
Boise, ID

Check out my website photos, documents, and movies!
Reply With Quote
  #6  
Old 08-14-2002, 07:13 PM
Registered User
 
Join Date: Aug 2001
Location: Evansville, Indiana
Posts: 8,150
Surfblau:

Have you replaced ALL the rubber hoses on the vac amplifier on the dirvers side fender? Mine were all leaking, and also the vacuum transducers for the air recirc and the EGR (under the air filter) were bad, caused me to have little or no vac at idle on the tranny vac lines.

Also, check that the modulator is not leaking -- try your MitiVac on the line labeled "trans" on the blue vacuum amplifier. If it won't hold vac, you need to check the rubber bit there, and also the modulator may be shot. They can also be adjusted. You can also get a long piece of hose and adjust the vac to the tranny while you drive the car -- route the hose out from under the hood and into the window. If you can make it shift properly with pump supplied vac, you still have a leak.

And pull the vac supply line off the vac pump up at the front of the engine -- there is a restriction in it that can get plugged, very likely if you have leaks, and you won't get enough vacuum to run the tranny correctly. Clean it out and replace it, and if that doesn't work, try removing it. You should be getting at least 12" vac at the modulator ("trans") connection on the blue thing at idle.

Replacing all the rubber bits helped, but pluggin the lines to the transducers cured the problem -- I now have to watch that I dont' drive too fast, it's so smooth!

Peter
__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
Reply With Quote
  #7  
Old 08-14-2002, 07:29 PM
adamb's Avatar
Registered User
 
Join Date: Jul 2001
Location: Chapel Hill, NC
Posts: 321
hello again. very infrequently the door locks wouldn't work and the shifts would get so bad that it felt like someone used a sledgehammer to put it into gear. the first indication i should have had that it was vacuum was with vacuum reading i got from the mighty mighty vac at the line going to the modulator. it should read about 14 at idle and drop off gradually as rpm is increased. mine went from idle at 13 to zero the majority of the time. i now simply disconnected the bypass just like the other gentlman suggested and viola!! perfect shifting. i can not tell you how great it was to drive to work today and have it shift the way it should. i was lead astray from the vacuum system because the severity of the clunk, but fear not, i would bet my paycheck that 99.9999% of the time it is the vacuum system. i wonder what else i can plug in the vacuum that would lessen the likelyhood of developing leaks? thanks to gsxr, psfred and surfblau for the extra info. cya later, adam
Reply With Quote
  #8  
Old 08-14-2002, 08:01 PM
gsxr's Avatar
Unbanned...?
 
Join Date: Aug 2001
Location: USA
Posts: 8,101
Actually, the clear thingy in the vacuum line above the pump is a little filter. I wouldn't remove it, if it's plugged or broken, just replace it. Cost is about $1 or so. This is on OM60x engines, I'm not sure it applies to OM617's... the 5-cyl's only have one main vac line off the pump to the brake booster. These models feed trans and ancilliaries (sp?) from one or two different tees (with built-in restrictions) off that main black line. I don't think they have any filters from the factory, but I've read that it's a good idea to install them.

Either way I recommend replacing ALL the Tecalan (plastic) vacuum tubing, and rubber vacuum hoses, in the engine compartment. I did this when replacing my cylinder head. Cost about $25 for ALL new stuff, and boy did it need it... most lines were so brittle they snapped like balsa wood twigs when I tried to remove them. At 15+ years they're probably due. Part numbers are here:

http://www.mbz.org/info/articles/engine/vacuum/



Quote:
And pull the vac supply line off the vac pump up at the front of the engine -- there is a restriction in it that can get plugged, very likely if you have leaks, and you won't get enough vacuum to run the tranny correctly. Clean it out and replace it, and if that doesn't work, try removing it.
__________________
Dave
Boise, ID

Check out my website photos, documents, and movies!
Reply With Quote
  #9  
Old 08-20-2002, 04:03 PM
surfblau's Avatar
neue Dieseler
 
Join Date: Feb 2002
Location: san francisco - immer kalt, immer windig, I want to move
Posts: 382
thanks fred and dave, here is what I have done

So here is what I have done to attempt to get to the bottom of my hard shifting trans. Symptoms are hard shifts, especially 1-2 and 2-3 at all temps, especially on smooth roads, at all acceleration speeds.

1.) replaced all the vac connectors and half the hoses in the engine compartment
2.) checked all the orifices (all were carbon/blockage free)
3.) replaced a leaking vac pump check valve at the vac pump
4.) replaced a leaking AC vac element
5.) replaced a leaking AT modulator cap
6.) replaced the differential mount (a stretch, I know, but it needed to be replaced)
7.) replaced both vac switchover valves in engine compartment
8.) reconnected overboost protection circuit
9.) disconnected the EGR/Recirc circuits from the system
10.) changed AT fluid and filter to mobil 1
11.) changed diff fluid to mobil 1
12.) changed the 50 degree switch (old one was dinged)

13.) performed the following tests
- got +/- 20" of vac off the distributer
- loose less than 1" of vac per minute in entire system
- no real vac leaks in any of the circuits as far as I can tell
- modulator holds vac with no leaks at all
- watched vacuum applied to vac control valve go to zero as linkage is pushed forward.


14.) next step - connect tester to TRANS output from vac amp and watch pressure at modulator while driving

It seems to me, the failing component must be one or more of the modulator, the vac amp or the vacuum control valve.

Let me know if you have any other ideas about specific tests for those components.

thanks
__________________
84 300TD - 235k - Farbe "Surfblau" bought at 213k
87 300SDL - 131k - Farbe "PimpGold" bought at 115k
00 Klepper Faltboot Expedition Double
Reply With Quote
  #10  
Old 08-20-2002, 05:35 PM
gsxr's Avatar
Unbanned...?
 
Join Date: Aug 2001
Location: USA
Posts: 8,101
#14 sounds like a good test.

#15, silly as it sounds, is to make sure the line from the vac amp TO the trans isn't plugged. Once while patching that line I accidentally used a piece or hose that had a BB inside. Drove me nuts trying to diagnose it!

If you confirm a normal vacuum signal present at the transmission modulator, then the problem must be internal... either a bad modulator or something else inside. I'd try the modulator first, it looks fairly easy to R&R...



Good luck
__________________
Dave
Boise, ID

Check out my website photos, documents, and movies!
Reply With Quote
  #11  
Old 08-20-2002, 07:06 PM
Registered User
 
Join Date: Aug 2001
Location: Evansville, Indiana
Posts: 8,150
Have you checked Bowden cable adjustment? Should be just all the way out with no compression of the spring at idle, it goes back in as the throttle is opened. Mine was WAY out, in an attempt to mask the vac problem.

Peter
__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
Reply With Quote
  #12  
Old 08-20-2002, 07:43 PM
gsxr's Avatar
Unbanned...?
 
Join Date: Aug 2001
Location: USA
Posts: 8,101
Good point, the cable should be checked too. The transmission uses the cable to tell at what RPM to shift, and it uses the vacuum signal to tell how firm to shift. Also wouldn't hurt to check throttle linkages, that will affect both the cable and the vac signal.
__________________
Dave
Boise, ID

Check out my website photos, documents, and movies!
Reply With Quote
  #13  
Old 08-20-2002, 09:01 PM
engatwork's Avatar
Registered User
 
Join Date: May 2000
Location: Soperton, Ga. USA
Posts: 13,647
Wait a minute Peter are you saying the Bowden cable goes "back in" toward the cable housing when applying throttle? This does not sound right. The cable end pulls "out" of the cable housing as the throttle is applied isn't it?
__________________
Jim
Reply With Quote
  #14  
Old 08-20-2002, 09:17 PM
Registered User
 
Join Date: Aug 2001
Location: Evansville, Indiana
Posts: 8,150
Jim:

On the 603, it's pulled all the way out at idle, should be all the way in at full throttle. On the 617, it's all the way in at idle, all the way out at full throttle

Don't ask me, I didn't design it!

Peter
__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
Reply With Quote
  #15  
Old 08-21-2002, 12:11 PM
surfblau's Avatar
neue Dieseler
 
Join Date: Feb 2002
Location: san francisco - immer kalt, immer windig, I want to move
Posts: 382
so here are my latest results.

I did my test 14.) connect tester to TRANS output with a T, from vac amp and watch pressure at modulator while driving.

At idle, in park, I got 14" of vac most of the time. While driving, the vac would drop to as low as 4" under moderate throttle (my mom was driving- she has a mellow idea of what "floored" means).

When I would stop the car and rev it, some of the time, the pressure would increase from 14 to 4 and sort of get stuck there. This is when shifts were always bad. Generally, when it was between 12 and 14 (either naturally or with me assisting on the mity vac), the shifts were smoother.

I attempted to measure the same sticking effect on the VAC input to the vac amplifier, but could not.

I also attempted to measure the sticking effect on the black and red line from the top of the vacuum control valve that runs to the switchover valve near the amp, again no dice.

Bowden cable - I haven't adjusted mine since I removed all five or so of the vac leaks in the system (I will check it today). It seemed a little slack when I looked at it last time. Under full throttle, the SDL shifts at about 4300rpm for all gears. That seems maybe a little high.

Tentatively, it seems to me that the vac control valve or vac amp may have a leak. Anyone know how to evaluate?

Also, should I tighten the bowden cable up (to lower the shift point)? I guess it can't hurt to try it and see if the slamming goes away.

many thanks

__________________
84 300TD - 235k - Farbe "Surfblau" bought at 213k
87 300SDL - 131k - Farbe "PimpGold" bought at 115k
00 Klepper Faltboot Expedition Double
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -4. The time now is 11:05 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2024 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page