Turbo guru - 1987 300D wagon turbo has no boost. - Page 2 - PeachParts Mercedes-Benz Forum

ah-kay · #16 05-28-2023, 06:15 PM

The first part of the exhaust is the catalytic converter, part number is 124 490 64 14.

I attached the exhaust but disconnected the downstream muffler and the problem came back. No boost and car is like a snail. It is proven beyond doubt. Thanks for 87 for his excellent help.

JHZR2 · #17 05-28-2023, 09:01 PM

Huh? Since when does any diesel have a cat converter in that area?!?!?

I get the trap oxidizer underhood in some engines for a while. A catalytic converter, with no controls or feedback? Really? That’s new to me.

What years had this?

ah-kay · #18 06-01-2023, 04:24 PM

Car is fixed and now has power and boost, not a snail anymore. The car had been neglected because I never bother. Now I need to put everything right to make it a daily driver, e.g. suspension, ball joints, paint, seats. Just to name a few. I would never suspect in a million years that a clogged exhaust could cause no boost.

FYI: I cut the catalytic converter open, emptied the inside and patched it back it. The inside is a honey comb, square not hex, structure and is mostly plugged. If I knew there is no metal partition inside then I could just put a big screw driver through the exit port and trash everything inside, saving me cutting it open and patching it. You can also straight pipe it if necessary. Thank 87 for the excellent information.

87tdwagen · #19 06-01-2023, 05:33 PM

ah-kay,
Glad it worked out for you and is motivating you to turn the wagon into a DD. One more survivor on the road! I'm sure you'll enjoy both the journey and destination.

JHZR2,
I don't know of all the MB diesel models with catalytic converters installed. A partial list is all of the US spec W124, W201 diesels should have come with a cat equipped starting 1986. The W126, ironically with the same 603 did Not have one in 86-87, but did starting in 1991 in the 350sd/l.

The location, so far downstream of the turbo was less than ideal to burn off the soot and oil buildup. Later my2000+ designs place the Cat directly off of the turbo. I believe all US diesels 2007 onwards were required to have a cat in addition to DPF.

The clogged cat issue was something I first learned with a gasser Chevy 350 van that would start, but immediately die. Clogged cat. Second time was on my 87 wagon, like yours, that had diminished boost/power and higher EGTs. Same issue. So really just life's lessons learned.

In the end, I try to keep in mind that engines are big air pumps. Turbos, are no different. In order for it all to work well, the intake and exhaust need to flow free, and the pump mechanicals need to function. Diagnostics is merely the process of eliminating known parts of the equation, to discover the unknowns.

JHZR2 · #20 06-01-2023, 05:48 PM

Quote:

Originally Posted by 87tdwagen

ah-kay,
Glad it worked out for you and is motivating you to turn the wagon into a DD. One more survivor on the road! I'm sure you'll enjoy both the journey and destination.

JHZR2,
I don't know of all the MB diesel models with catalytic converters installed. A partial list is all of the US spec W124, W201 diesels should have come with a cat equipped starting 1986. The W126, ironically with the same 603 did Not have one in 86-87, but did starting in 1991 in the 350sd/l.

The location, so far downstream of the turbo was less than ideal to burn off the soot and oil buildup. Later my2000+ designs place the Cat directly off of the turbo. I believe all US diesels 2007 onwards were required to have a cat in addition to DPF.

The clogged cat issue was something I first learned with a gasser Chevy 350 van that would start, but immediately die. Clogged cat. Second time was on my 87 wagon, like yours, that had diminished boost/power and higher EGTs. Same issue. So really just life's lessons learned.

In the end, I try to keep in mind that engines are big air pumps. Turbos, are no different. In order for it all to work well, the intake and exhaust need to flow free, and the pump mechanicals need to function. Diagnostics is merely the process of eliminating known parts of the equation, to discover the unknowns.

I’ve never once heard of some random catalytic converter being in the exhaust system of all cars.

The trap oxidizer? Yes. And they were removed/recalled. And I think they may have only been in CA cars.

Where on here in the epc is the converter? For a 91 350sd for example it’s just a center exhaust.

https://webautocats.com/epc/mercedes/1/fg/126134/570/49/285/

Ditto for a 91 300D. Just called an exhaust pipe.

https://webautocats.com/en-us/epc/mercedes/1/fg/124133/576/49/285/

There may be a monolith in there for muffling sound and resonance, but I have my doubts that there’s a catalytic converter in there…

And to be clear, I’m NOT trying to be argumentative. I just have two of the cars you mention, and I have no indication of such a device in a 49 state car. So I’m trying to get to ground truth

87tdwagen · #21 06-01-2023, 07:25 PM

Do a part number search and you will likely find various naming conventions, but Catalytic Converter is the most frequently referenced term by Mercedes.

Here are the 2 examples you cited from mbusa

https://mbparts.mbusa.com/v-1991-mercedes-benz-350sd--base--3-4l-l6-diesel/exhaust-system--exhaust-components

https://mbparts.mbusa.com/v-1991-mercedes-benz-300d--2-5--2-5l-l5-diesel/exhaust-system--exhaust-manifold

These have a ceramic honeycomb interior which is only used for a catalyst or DPF, unlike the mufflers which are chambered or baffled.

You can always inspect yours to verify, it's state. As mentioned, the location will lead it to clogging eventually.