87 300D Wastegate Stuck? - PeachParts Mercedes-Benz Forum

mbehensky · #1 06-28-2014, 04:31 PM

I have a 1987 300TDT wagon. I just swapped a used engine into it that I think was from a 1986 300SD. The car now runs, but I'm only getting around 1 PSI of boost out of the turbo. The turbo shaft turns freely, and there is no noticeable play. It sure sounds like it is spinning pretty fast when I gas it. I have checked the EGR valve, and it is closed with no vacuum applied.

I have tested the boost at 4k-5k rpm with no load, and also driving full throttle up my steep driveway (car isn't registered yet, so I can't take it out on the road). I only got 1 to maybe 2psi on the gauge I hooked up to a hose I ran through the window.

I haven't tried to debug the ALDA yet, since it seemed to me that if the engine wasn't making any boost to speak of it wouldn't get activated anyway.

The new engine has the KKK-K24 turbo with air recirculation valve on it (my old one has what I think is the Garret with the external large wastegate control diaphragm). Unfortunately, that turbo is completely siezed, so I can't just swap it in.

I'm thinking that the wastegate could be stuck open. It also might be that the air recirculation valve is leaking. I haven't got all the vacuum lines sorted out yet, so I didn't hook anything up to the air recirculation valve.

My questions are:

1. Can you take off the wastegate control valve on the KKK-K24 without taking the turbo out? This looks like it just might be possible to do, although it won't be easy.

2. It looks like the air recirculation valve is opened by vacuum, so it shouldn't reduce boost to have it not hooked up. Is this correct?

3. If I have to take the turbo out, is there some sort of walk through on how to do it? It looks pretty hard to do, and I sure wish I had checked the wastegate before I put the engine in..

Thanks for any info..

Max Behensky

mbehensky · #2 06-28-2014, 05:41 PM

Well, I took off the trap oxidizer replacement pipe, and crammed a hose into the upper passage inside the turbo exhaust entry, the passage that looks like it goes to where the wastegate valve is.

I plugged the area around the hose as best I could with a wad of paper towels, and connected the hose to my air blowgun from my air compressor. When I sent in the compressed air, pressure built up, indicating that the wastegate valve was closed.

I'm going to dis-assemble the air recirculation valve and see if it looks OK inside. I can get at that pretty easily.

Max Behensky

vstech · #3 06-28-2014, 06:08 PM

Pics?

mbehensky · #4 06-28-2014, 08:59 PM

Well, I took the air recirculation valve partially apart, and it seemed to move freely. I don't think it is stuck open, and it definitely seems to need vacuum to open it. I hooked up a hose to the control, sucked on it, and it seemed to reduce the boost when I did that.

I then took off the intake cross pipe and started the car up. At high rpm, a huge blast of air came out of the turbo, and when I plugged it up with my hand I got 7-10 PSI.

Thinking maybe things had fixed themselves, I put the cross pipe back on but only got 1psi again.

It seems like the compressor on the turbo is pumping, but not very much. It is putting out air, but it can't keep up with the amount the engine is sucking in so the boost doesn't build up.

It is possible that the wastegate is open after all, but it sure seemed closed to me. I'm going to take off the exhaust pipe tomorrow and run the car that way to see if I get any more boost.

I've had enough for one day, but maybe I'll post some pictures tomorrow.

Max

Mxfrank · #5 06-28-2014, 10:23 PM

How are you measuring? if you're measuring through the Alda takeoff fitting, try cleaning the fitting.

jay_bob · #6 06-29-2014, 11:52 AM

+1
That pressure port on the OM603 is notorious for filling up with sludge thanks to the EGR

It can be unscrewed and cleaned out

Also (temporarily!) bypass the solenoid valve on the firewall, go straight from the manifold pressure port to the ALDA and see what you get. That valve can get stopped up, or the electrical over pressure switch can get stuck "on" and that dumps all your boost.

mbehensky · #7 06-29-2014, 01:25 PM

I tried running the ALDA directly to the port yesterday, and it didn't help. I wasn't surprised, since I wasn't getting any boost at the port.

I poked a wire through the port on the manifold yesterday, thinking maybe it was blocked. If it is filled up with goo that might not help, so I'll try unscrewing it and see if it is free flowing.

I haven't tried disconnecting the exhaust yet.

Thanks for the help, everyone..

Max Behensky

mbehensky · #8 06-29-2014, 02:57 PM

Well, I took off the exhaust pipe where it connected to the turbocharger and fired the car up. Immediately, I could tell by the sound of the turbo that things were working better. I'm getting up to 10 psi of boost at high rpm with no load now. I hooked the ALDA back up and the engine revs quickly and sounds much more powerful. Yay!

Now, I'm going to try and figure out where the restriction lies. I'm betting it is in the catalytic converter thing that is before the muffler.

jay_bob · #9 06-29-2014, 07:28 PM

Yup cat plugged is a common problem. If you don't have to get inspected, rebar roto rooter is an option. If you do that wear a respirator and protective gear, the innards of the cat will hurt you if you inhale the dust or get it on your skin or in your eyes.

If you are subject to inspection then you'll have to bite the bullet on a new cat, they are not cheap.

Plugged cat will make the car run like Beverly Hills Cop where he puts a banana in the tailpipe of the detective's car (and then makes his getaway in a nice 450SL).

Mxfrank · #10 06-29-2014, 07:42 PM

Is there an FSM procedure for measuring exhaust restriction?

mbehensky · #11 07-20-2014, 12:29 PM

Catalytic converter was, in fact, plugged up. The old engine had a cracked head, and I've heard that coolant in the exhaust stream can plug up your converter.

A new converter costs $2100 from the mercedes dealer, so that is out. Anyone know of aftermarket options for a 603 with the trap oxidizer replaced?

There is a shop in town that will supposedly put in a new converter for $800 including labor, so somebody may make something. I suspect that the quote was for a gas car, though. It is hard to believe that anybody bothered to get an aftermarket diesel catalytic converter approved in CA for the few 1987 603 diesels that are around.

I don't want to destroy the innards of the existing CAT because I'm not keen on getting palladium poisoning or causing my driveway to turn into a superfund site. I don't want to cut out the cat and replace it with a pipe either.

If I didn't live in CA, I could get an aftermarket diesel cat that looks like it would fit for $150..

Mxfrank · #12 07-20-2014, 07:54 PM

The wagon exhaust is truly difficult to find. There were two completely different front and center pipes, depending on whether you have the recall cat or not. You can't just change the front section and be done with it. Here's a photo writeup I did on the two options:

MBexh

I think the Bosal center and front sections are still available, but not the Mercedes piece. Another option would be to get a front pipe from a 190DT, which will include a cat. Then cut it out and weld it into your exhaust. You also might try Dave Hendy, who sometimes has exhaust pieces off salvaged cars. If you need his contact info, drop me a PM.

CARB has never issued an exemption order for a Diesel emissions component, so don't expect to find a legal aftermarket cat.