Mercedes-Benz Forum banner

92 300SD headache....

3K views 12 replies 6 participants last post by  whiranrat 
#1 ·
Hello W140 owners. I've posted here once, but need more help. My mom purchased a 92 300SD and has some problems that I've been searching high and low for and can't seem to get a clear answer. The car comes with some problems...

1. Its sluggish. (both parents complain. I haven't drove it yet..) I check the turbo with a vacuum gauge and it works, but I don't really hear that familiar turbo whine; even with the windows down.

2. The automatic climate control air direction buttons don't work. Only auto lights up and pushing the other 3 buttons does nothing.

3. Center air vent doesn't blow air. It did like twice, but then when I push some other button it stop. Air does come out the sides, top (dash) and rear vents.

4. Transmission flares while shifting from 2 to 3rd. But when foot is at the right position (speed is about 25 and rpm is about 2000) it doesn't. Again, judging from parents driving. I saw a youtube vid on adjusting this, which I'm gonna try, but I'll wait for your guys opinions.

5. If I pull fuse 9 to reset the door closing assist, the two front doors will assist close, but after a while, it won't. Leak somewhere or bad pump? but both pumps work as it should. Times out correctly and stuff.

6. ASD and ABS lights on. ABS light comes on when you step on the brakes and stays on after that (after starting the car of course) ASD light stays on when engine is running.

This car is a bit of a challenge for me, but I'm willing to learn and fix it. I'm more use to the simpler ones like w123 and w124, so I'm handy. But since we've bought the car I'm basically the one searching up and trying to find cures for these problems, but haven't really found a straight answer. Well I hope you guys can help me out with this one as I'm stepping out of my comfort zone and taking on a challenge :) Thank you :) Sorry if this is too many problems to assist at once.
 
See less See more
#2 · (Edited)
This may help you with your car's turbo's performance...http://www.benzworld.org/forums/w140-s-class/1607486-300sd-turbo-issue.html
Transmission flare...http://www.benzworld.org/forums/w140-s-class/1639073-94-s350d-bad-flare-between-2nd.html
I used the 'search' tool here and on Google which led to other this site, as well as other sites with opinions, trial and error scenarios to assess and address issues with W140's...give it a shot and you'll be surprised of the outcome! Let us know how it works out!
 
#3 ·
Sounds to me like you have a few problems, I'll address the ones that I can provide assistance on.

It would help to know more information about the car, like how many miles etc. Anything about the history of the car would help with your problems.

1. The sluggishness could probably be related to the turbo. These cars have a very rudimentary diesel control system that determines whether the there is a problem or not. You can investigate stored codes in the computer with a blink tester. There are probably examples of ones you can make / buy in other threads. At any rate, the EDC (electronic diesel control) has only one function and that's to sense whether air coming in through the flapper box (crude AFM) is reduced when the EGR valve is opened. If the EGR is functioning properly then the EDC will see reduced airflow through the flapper and it will let everything perform as it should. If it does not see a reduction in airflow it will tell the turbo boost controller vacuum pod to shut down the turbo.

The loss of turbo will not be instantaneous, it may take driving a couple blocks before the EDC senses the problem the turns off boost but it will. Boost will remain offline until the next time the car is started at which time the process will repeat.

There is no sure fire remedy for the problem but cleaning the EGR valve might fix it or checking your vacuum lines behind the driver headlight may also reveal something. Or it also might be the boost control switchover valve or the vacuum actuator as well. Others complain of this problem and I have it as well. For the time being I've routed vacuum around the problem so that the turbo remains active. I don't recommend this for cars in regular service. The W124 chassis is very similar to the W140 in this respect.

A vacuum diagram for the W140 can be found on p12 of the transmission diagnostic manual here. That might help you if you figure out that you have a vacuum routing issue. There are also some tests you can do to make sure the vacuum actuators are working properly but I don't have those handy. You can find the test procedures online or maybe here as well.

4. Transmission shift flare can be the result of improperly adjusted vacuum modulator. You can test modulating pressure on the port near the vacuum modulator and see whether the modulator needs to be adjusted. You should also check to be sure that your bowden cable is adjusted to spec to begin with before checking the modulator. You might also have a bad line to the modulator. Check vacuum to the modulator first and then if present check modulating pressure. If out of spec adjust and see whether that will help the shifting.

5. The close assist pump is failing if you have to repeatedly remove the fuse to reset the pump. Diminished service (i.e fails to close doors after x number of times) indicates that your pump is not working properly.

6. ABS and ASD lights might be related because I think that the ABS functions as part of the ASD system. You will have to do some research about this to determine what the problem is here I have nothing to help you out, my car does not have ASD.

Overall just be sure that all typical maintenance is up to date, like air filters, fuel filters, cabin filters etc.

Steve
 
#5 ·
Sounds to me like you have a few problems, I'll address the ones that I can provide assistance on.

It would help to know more information about the car, like how many miles etc. Anything about the history of the car would help with your problems.

The car's odometer was replaced with a digital one. I heard Mercedes had a bulletin on this, but it was done somewhat recently. The car has 53,009 on it, but judging the miles it had before the change added to current one it equals to about 260 ish thousand miles (from service records)

OH. The engine was replaced with a factory rebuilt (long block), so it doesn't have that dreaded problem the OM603.971 has.

And thanks for your assist :) I'll tackle it little by little when I have the free time since I'm a full time college student and taking a 6 weeks English class is overwhelming itself... :surrender:
 
#4 ·
for #'s 2 and 3, I can tell you that pse pump under the pass. side rear seat controls the flaps in the vent system to change from dash to center vents to floor vents... this may also be related to your question 5... you may also have broken or leaking vac lines.

I also think that same pump provides intake manifold pressure for the engine... my be related to your turbo. But I am not sure of this.
 
#8 ·
4) The Bowden cable has a 1" thread adjustment. if you screw it in the shifts soften. Make sure the vacuum line to the modulator has a complete path. If you disconnect the line from the transmission, it should be dry, and not dribbling oil.

5) If you tried resetting the fuse, the pump vanes need to be cleaned with denatured alcohol to remove the fine dust, so the pump has more suction. All of this providing you hear the motor, and it does not have broken loose nipple on the pump.

Best of luck,

Martin
 
#11 ·
Best solution to your problem is like I did with mine when I was heaving exactly the same problem as you with turbo boost.
Your waste gate is operated by a vacuum controlled actuator that gets signal when to open from a ECU,and you need to buy a pressure controlled actuator(from a W124,W126...) and put it on your turbo.Then you can block EGR,and every other gismo,because you now have completely mechanical operated turbo pressure :).

Here are a few pictures that will make it more clear.

On the first picture circled in red is the actuator.

On the second picture number 1 shows original place where hollender is stock.
Number 2 shows where i have put it(drilled a hole).
 

Attachments

This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top