turbo vacuum/wastegate problems, need advice - PeachParts Mercedes-Benz Forum

Grdenko · #1 03-26-2004, 05:59 PM

in some of my past posts ive talked about my vacuum wastegate problems. my turbo has never been operational since ive owned the car because of faulty vacuum solenoids that control the wastegate. i tried finding out about replacing the wastegate with a pressure controlled one like oldsouth did, but the people he referred me to were not helpful, so i had all of the solenoids (transducers) replaced.

the car worked great after i had this done, it wasnt losing any vacuum, the transmission shifted smoothly, and i had gained ALOT of power. but 2 days later, the power went away and i was loosing vacuum again. my indie ahop that i had do the work couldnt figure it out and told me to take it to the dealership, which told me i needed a new computer, for $2,100!

so $500 later im back where i started, but worse. now ive felt how fast my car can be and i want it back again. i just spent $2400 fixing my a/c so im not going to buy the new computer.

i need to know if there is any other way to make it work again. I called the people at M$D distributors again and they kind of blew me off again (i got the feeling that if its not a ford or dodge, they wont work on it)

what kind of parts do i need to switch out the wastegate? ive decided that this would be the easiest way to fix the problem.

anybody that has suggestions or comments that could help would be greatly appreciated

thanks

wolf_walker · #2 03-26-2004, 06:28 PM

I don't know your model car at all, but..

Is the turbo one which was used on something with a more traditional wastegate setup you could swap in? I have only a vague idea of how yours is suposed to work. Will it muss up the computer controls to not have that vac solonoid working?

TMAllison · #3 03-26-2004, 06:45 PM

I had the same issues on a 1990 300E 2.5 Turbo. Would operate when cold,. As soon as warmed up no turbo. Never did resolve it.

Looking on eBay for entire turbo could be an option? The older 300d turbos I've seen are cheap.

dieseldiehard · #4 03-26-2004, 07:05 PM

A search found this:
http://www.xmission.com/~dempsey/perform/nospike.htm
I haven't digested it yet and leave that to you.

I don't have direct experience with the E300D but I recently had an interesting problem in my W124 OM603 engine which was related to the wastegate.
After a lot of $$ and effort was put into restoring the engine(rebuilding the top end) my car still ran poorly. It had new lifters, a reconditioned head, new IP seals, timing chain etc (the car had received basically zero maintenance other than oil changes for 250 K miles - IMHO a testament to great reliability!)
I was afraid the turbo was bad because boost was low. It was about to be sent to be rebuilt when I discovered the flapper was sticking in carbon buildup in the wastegate. The actuator was only partially operable and never completely closed. Perhaps you have a similar problem?

DDH

TimFreeh · #5 03-26-2004, 07:52 PM

I doubt your computer is blown, in your first post you said your were losing vacuum. Did your independent shop tell you that?

The boost control system on the 2.5 turbo will default to a no-boost condition if there is no vacuum available to run the actuators for the wastegate, EGR and intake manifold flap. Your problem could be as simple as a vacuum leak somewhere - if you have no vacuum find the leak and fix it.

The boost control system on these engines is impressive - it builds boost much faster than the manual system on the OM602/OM603 set-ups, at least the ones I've driven. It makes the engine seem much more powerful than the rated 121 horsepower.

If you wanted to replace the computer operated system I would try to find the intake/turbo/wastegate control for an 87 190D 2.5 turbo. I'm pretty sure these setups were not computer controlled, trying to jury rig something to operate the three transducers on your car would be complicated.

If you want to try the approach outlined in the previous post don't try to use the intake manifold as a source of vacuum - this will work on a gasser but your car will not produce any vacuum in the manifold because it does not have an intake manifold flap.

Tim

coachgeo · #6 03-26-2004, 10:36 PM

Im an amatuer but I concur. You finally have vuccume. This put use/stress on a vaccume line that was not recently under stress like it should be.. The hose stressed out... now you back to square one.

Look for leaks.... Start replacing hoses. Maybe you can bypass some vaccum things and make them non opperational. If all the sudden you get your turbo back then you know that the leak is somewhere in the area you just bypassed.

Another thing... maybe you have a bad ??? that is causing excessive heat or vibration orrr?? to damage a vaccum line. If so this problem probably existed before and is what caused the orginal problems.

Grdenko · #7 03-27-2004, 06:26 PM

i really appreciate all of the responses

all of the vacuum lines have been checked and replaced within the last month, the vacuum transduceres were replaced because they were found to be faulty, they worked fine for two days, then the computer quit sending a signal to the wastegate transducer, when the transducers dont get any signal, they dump all of the vacuum that is being supplied to them, (so ive been told) so vacuum is lost throughout the entire system.

right now i have the vacuum line going to the 3 transducers disconnected and plugged so that my transmission, a/c and rear headrests will work properly. both my local shop and the dealership have told me this and i have tested it myself with my own mityvac at home, so im afraid the problem isnt as cheap and easy as replacing a vac line.

oldsouth had the vacuum operated wastegate switched out on his car with a regular pressure actuated one so that he could remove his EGR, his car is newer than mine so this made me think that doing this in my car would solve the problem, and i have a strong feeling that it will.

all of the shops i have approached about doing this either dont know how, or wont do it for whatever reason, but now it looks like oldsouth is going to help me find the right part to do this to my car, which is great.

id like to know if anyone else has had a problem like this that they solved in an unusual way, or if anybody thinks that this might not work for some reason.

thanks

TimFreeh · #8 03-27-2004, 06:53 PM

Who checked the vacuum lines and what did they use to do the checking?

You are correct that when the transducers are not supplied a signal (in this case 12+ with a varying amount of current) they will dump vacuum however the amount of vacuum they can dump even with no control signal input is very, very small compared to the amount of vacuum your vacuum pump can generate. There is NO way that a properly connected set of lines and a transducers could dump enough vacuum to effect the operation of your transmission shifting even with no computer control. When I shut down my 2.5 turbo I can hear the vacuum leaking out of the control transducers, it takes 30-40 seconds for the transducers to stop "ticking"

There are several small vacuum restrictors in the control circuts that are responsible for restricting vacuum supply. I would check these restrictors and I would get a proper OM602 vacuum diagram and check it again. Its just too coincidental that two days after its fixed its broken again, I don't buy it.

The ECU in the diesel control system does have an exellent diagnotic mode, all you need to read the codes is an impulse counter. Did the shop read the codes? There is a code for ECU malfunction as I recall.

I'd keep fighting to get the factory boost control system working but let us know how you make out with your alternative system.

Tim

#9 03-27-2004, 09:51 PM

A friend of mine is having the exact same problem as you on his 1991 300D 2.5 Turbo. His computer will randomly communicate with the vacuum transducers. Sometimes it has boost, sometimes it doesn't. Ok, slightly different symptoms than you're having... your computer never communicates.

It's either time for a new computer, or a pressure actuated wastegate. The latter is less expensive.

Grdenko · #10 04-05-2004, 12:09 PM

tim,
there are actually 3 transducers, and all were replaced, and when they aree hooked up, i can hear vacuum running out of them when i shut off the engine, and it does take about 20 seconds. my egr also operates fine when it is hooked up.

the dealership charged me $200 just to tell me that the computer was broken, so if they were wrong, i would be surprised, and i believe they did check the codes, i was going to check them myself, but its kind of a pain.

veedub,
i dont even know why they started putting computers in these cars anyway, the old ones run fine without them.