1987 300tdt - Loss of power - wastegate rod disconnected - PeachParts Mercedes-Benz Forum

skylerw · #1 07-25-2015, 02:52 PM

Good afternoon,

This is my first post on this site, and I'm looking forward to finding others on here who know more about the w124 diesels. I've been on a 3000 mile road trip with mine and am getting close to the finish now. I'm slowly returning to Phoenix and am currently in the Salt Lake City area with friends.

North of Salt Lake, my car suddenly began experiencing power loss issues. It began suddenly and I've been trying to determine the cause. It seems as though the turbo is not engaging at all. The previous owner disconnected some of the vacuum lines near the egr valve and plugged them but that has never caused issues in the past. The only thing I found that I never observed before is that the rod from the wastegate actuator to the wastegate is disconnected. I don't know if it is possible that it popped off while I was driving. The rod is not broken but I'm not able to reconnect it. I can't pull the rod at all so I'm assuming that the actuator needs vacuum pressure for it to come out. Could that be the obvious issue. I never looked to see if it was connected in the past so don't know if it was always like that. I been driving the car for 8 months and on this trip have driven about 2500 miles already with no issues. I attached some pictures of the disconnected rod.

Looking forward to any assistance.

Skyler

vstech · #2 07-25-2015, 03:04 PM

Welcome!
Here are a lot of 87 wagon owners on this site... I've got 3 myself!
We'll figure out he issue with ya!

The 603 wagon uses boost pressure to shut off the waste gate, you should be able to move the waste gate pivot arm to line up with the actuator rod.

skylerw · #3 07-25-2015, 03:11 PM

I am able to move the waste gate pivot arm but the hole in the rod doesn't quite line up. If the rod was extended a little bit I could get the hole in the rod reconnected to the pivot arm but doesn't quite reach. When I try to pull the rod towards the pivot arm on the wastegate seems like won't move at all.

Thanks for the quick reply

vstech · #4 07-25-2015, 03:19 PM

You might need a little pressure on the boost hose... No more than 5 psi should do it... You could get some new fuel line, hook it to the actuator and blow on it to get it to line up.

Mxfrank · #5 07-25-2015, 03:36 PM

I misunderstood...if you can move the pivot arm, you can just wire it shut (all the way towards the front of the engine) in the worst case. Just don't drive hard. A picture of a 124 vacuum waste gate actuator attached. There should be a clip on the end to hold it in place. I bet he screwed it in very tightly to keep the waste gate closed all the time.

Your power loss may be due to the alda line becoming plugged. If you look at the left side of the intake manifold, you will see a big brass sensor. Directly below that is a hose that plugs into a brass hose fitting. Undo the hose, remove the fitting, and ream it out. I bet it's plugged with goop.

skylerw · #6 07-25-2015, 04:39 PM

mxfrank, if I end up needing to wire it shut, what do you mean by don't drive hard. It wouldn't be a problem to drive a long distance on the freeway right? Thanks for the picture of the actuator. That helps.

I would like to try to get the rod reattached so maybe I should try to blow some air into it like vstech recommended. I was surprised how big the vacuum line is on the actuator and that that line seems to be connected to something that looks similar to the actuator.

I'm assuming that not having that rod connected is at least related to the problem since there is nothing to control the wastegate. I hope I'm on the right track with that and will check the alda line if I can find it also.

Mxfrank · #7 07-25-2015, 05:25 PM

The wastegate is supposed to limit turbo boost to around 1.1 bar. If you keep the revs to under 3500, you won't be near that. If you go over, the ALDA should limit fuel, but since the previous owner was "improving" things, you can't be sure. So yes, highway driving will be ok, just don't use a heavy foot.

Pressure won't help on a 124, it's a vacuum actuator.

skylerw · #8 07-25-2015, 06:35 PM

Mxfrank, thanks for all the advice. I'm assuming you mean that if I attempt what vstech suggested it won't enable me to reconnect the rod. I thought if I put some vacuum on the actuator then the rod would move a little and I could connect it but from your image you sent it looks like the rod would only move in closer to the actuator, not out away from it and closer to wastegate pivot arm.

Just to confirm, I would want to wire the pivot arm shut so it is in the position closest to the front of the car, which would mean that it is fully closed. Just want to be sure.

Thanks so much

jay_bob · #9 07-26-2015, 11:25 AM

Quote:

Originally Posted by Mxfrank

The wastegate is supposed to limit turbo boost to around 1.1 bar. If you keep the revs to under 3500, you won't be near that. If you go over, the ALDA should limit fuel, but since the previous owner was "improving" things, you can't be sure. So yes, highway driving will be ok, just don't use a heavy foot.

Pressure won't help on a 124, it's a vacuum actuator.

On the 86-87 603s in the 300D/TD/SD they used the first gen EDS that was only pollution control and idle speed regulation. The waste gate is pressure actuated using a direct connection to the charge pipe with no additional control. The overboost protection is a simple switch tapped into the manifold that actuates a switchover valve that kills the boost signal to the ALDA (thus limiting fueling).

Starting in 90 with the second gen EDS they went with a MAP sensor instead of the pressure switch in the manifold. This allowed the boost pressure to regulate both the wastegate and ALDA line valve. The waste gate was changed to a vacuum actuated type and controlled via a vacuum transducer from the ECU.

The vacuum wastegate control in the 90 and up can be problematic so there is a thread on here to retrofit a pressure type wastegate actuator on the later turbos and abandon the ECU controlled system.

skylerw · #10 07-26-2015, 02:56 PM

I just want to confirm that if I wire it shut I want it to be in the position closest to the front of the car. I was looking at it last night trying to determine the best way to wire it in place and want to be sure to do it correctly.

I have lots more tools at home in Phoenix that could help me get the rod reattached but it is tough trying to do it while out of town.

Can someone also please confirm that if the wastegate is not completely closed I will lose most if not all of my turbo boost. That is what I am understanding from what I've read. This rod being disconnected is the only thing that I'm thinking can explain the sudden loss of power. Whatever tweaks I've done like checking vacuum connections and such have improved low end power but when I'm trying to get from say 50 to 70 miles per hour on the freeway the speed increases at a snails pace. I'm thinking its definitely because the wastegate has nothing holding it closed and so is a lot or a little open all the time.

Thanks for all the feedback. Really missing the power that this thing could put out before.

Skyler

Mxfrank · #11 07-26-2015, 03:59 PM

Yes, wire it towards the front of the car. You'll eventually need to find a clip to hold the actuator rod in place...a c-clip will do.

The wastegate "dumps" pressure into the exhaust pipe. Without the actuator, no boost. Worse comes to worst, you can drive home as-is without boost, but it will take all day to accelerate to highway speed.

Thanks for pointing out that the '87 has a pressure actuated gate, I stand corrected.

skylerw · #12 07-26-2015, 04:37 PM

Let me ask one final question on the basis of it being a pressure activated gate. If I can attached some fuel hose as suggested by vstech and blow into it to achieve some small pressure will the rod move slightly towards the back of the engine or will it move towards the front of the engine and away from the wastegate pivot arm. Obviously reconnecting the rod would be the best solution if there were an easy way to extend the rod just long enough to attach it.

Thanks, Skyler

Mxfrank · #13 07-26-2015, 07:08 PM

Quote:

Originally Posted by skylerw

If I can attached some fuel hose as suggested by vstech and blow into it to achieve some small pressure will the rod move slightly towards the back of the engine or will it move towards the front of the engine and away from the wastegate pivot arm.

Thanks, Skyler

A pressure activated actuator would move towards the rear of the engine, the opposite of my picture. Sorry for the confusion.

Maxbumpo · #14 07-27-2015, 10:36 AM

Sudden power loss: There are other possible causes, including a clogged fuel filter (actually there are two, a pre-filter and a main filter, and if you've never changed them, now would be a good time).

Clogged air filter limiting the air? Plugged exhaust: does your car still have the original oxidative catalyst? History of WVO use in the car? That can introduce many possible sources of trouble.

skylerw · #15 07-27-2015, 12:51 PM

I just changed my filters (fuel and air) before this trip so I think it is related to the turbo, especially since the wastegate is not held in place by anything so can flap open.

I was excited to get out this morning and try to reattach the rod but I think that the diaphragm in the actuator must be gone. If I try to blow air into the actuator the rod does not move at all so I'm thinking the actuator is no good.

I'm thinking my only option is to wire the wastegate shut for now until I can get home and try something else. I've looked in the wastegate pivot arm area and just wondering if any of you have ever wired it where you wired it. There aren't many spots to wire it to to hold in place. Hope that isn't a dumb question but just trying to wire it so it stays in place for the remainder of my journey. I will remember to go easy on it so as not to cause an overboost.

Skyler