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Thread: Middle exhaust rust

  1. #1
    Join Date
    Sep 2020
    Location
    Europe
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    25
    My Cars
    E24 1987

    Question Middle exhaust rust

    Hello. It's my 1st post here and I am in the process of acquiring E24.. Seen a few cars now, a lot reading here and there, but there are some that I could not get help with... While I'll dig and dig in the meantime, looking for answers, I made some shots of the middle exhaust from U.S. specs MY87. Car is super nice, but a lot of rust & holes in the middle exhaust area (orange material coming thorugh the holes).

    And the question is: is this a middle silencer/catalysator or it's just a metal cover with sort of daming material inside? I ask because want to know if its a super important stuff that needs replacing NOW (silencer/cat.) or just a heat cover that could be welded, repaired or removed. Car drivers without any bad exhaust noises.

    Photos:
    https://www.dropbox.com/s/m5rl7v3ta6nrvv3/1.jpg?dl=0
    https://www.dropbox.com/s/pfapn3j5w4pplxg/2.jpg?dl=0

  2. #2
    Join Date
    Oct 2015
    Location
    Illinois
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    My Cars
    740 735 635 535 318is
    That is difficult to confirm without some more info and pictures. Is that a Euro model car?

    I would go to the website RealOem.com and put in the serial number to get a parts diagram for the specific car. I searched just for a MY87 Euro, and got diagrams for exhaust with Catalyst and ones without Catalyst. Evidently they made cars both ways for sale to different regions.

    To me, I'm guessing that item is a muffler with the heat shield rotting away thus creating orange (rust) colored fiberglass insulation coming through. As long as no exhaust gas leaks it's not an immediate issue. But, that exhaust is very expensive to replace if you desire the original sound quality.

    Sent from my moto g(7) power using Tapatalk

  3. #3
    Join Date
    Jan 2016
    Location
    Ca
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    2001 525it
    Or go to a muffler shop and just by pass it

  4. #4
    Join Date
    Sep 2020
    Location
    Europe
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    My Cars
    E24 1987
    Thanks guys

    As I mentioned before, it's U.S. car.

    (similar diagrams) http://bmwfans.info/parts-catalog/E2...thout_catalyst
    Fro those it looks like non-cat systems have 3 different silencer/mufflers, and CAT systems pipes are integrated and only hav 1 rear muffler

    Is this correct?

    So, those pictures what I saw are mufflers/silencers, not the heat protection stuff, right?

  5. #5
    Join Date
    Oct 2015
    Location
    Illinois
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    My Cars
    740 735 635 535 318is
    The heat protection stuff is integrated into the pipe assemblies in multiple layers and it's all welded together. The Cat systems will have the Cat brick in a chamber and also have another chamber that acts as a muffler. It is all welded together so it's only serviceable in the groups shown in the parts diagrams.

    If there are no exhaust leaks, you can leave it although cosmetically deficient. If you want OEM sound quality, you can replace the pieces shown in the diagram's. I doubt anyone can repair what is there and add any life to it. Any repair welds will not last, and it will look worse than it does now.

    The other option if you are on a budget is to use aftermarket pieces to replace the corroded items. The sound quality will be changed.

    Sent from my moto g(7) power using Tapatalk

  6. #6
    Join Date
    Feb 2009
    Location
    Pittsburgh, PA
    Posts
    1,718
    My Cars
    '86 635CSi, '08 128i
    Yours looks a lot like mine. That's definitely a stock "green" catalyzed system, as sent to America & other low-emission regions. I believe all the Motronic 1.0 cars (both E24 & E28) used the same system, like from '84-'87. Our system has a large two-chamber catalyst, a resonator and a muffler. The original system on mine was made by Boysen, it's in two huge sections that bolt together between the cat & resonator.

    Dschart is 100% right on all points.

    The first picture is definitely the resonator. There's an outer heat shield crimped onto the resonator with an inner layer or insulation. The heat shield has rusted through, exposing the inner layer of fiberglass/asbestos(?!?) packing around the actual resonator itself. It looks like it'll last for a good while yet. You could possibly replace the heat shield if you're good with fabrication, or maybe replace that resonator section with a standard off-the-shelf part to resolve the rust problem. There are a few aftermarket cat-back systems too, like Billy Boat or Ireland Engineering in the USA. Straight pipes are another choice, but it'd likely increase noise. Exhaust droning is a common problem with straight pipes.

    The 2nd pic is the catalyst. It's the original BMW two-chamber design, very well made, very effective, very expensive to replace. I'm stuck with the same problem as you - the BMW part is incredibly expensive, but I want it to run cleanly. You can't replace the heat shield easily. There are plenty of aftermarket OBD1 catalysts, including some high-performance ones, but I've heard they don't last. We also have some legal vehicular obligations in stricter states that may prevent installing aftermarket catalysts; not sure if that might apply to your locality as well.
    Save the manuals!
    '08 128i 6MT, '86 635CSi 5MT (B32, Motronic 1.3, WBO2, G265, 18# FW, 3.46 torsen)
    Past projects:
    '96 318iS, sold 4/23 '90 535iM, RIP 1/23 '90 535iA RIP 6/22 '91 318i, sold 7/19 '97 M3 sedan, sold 11/18 '85 735i, RIP 2/18 '92 325iC, sold 7/16 '91 318iS, sold 6/16 '84 745i, sold 10/14 '82 633CSi, traded 9/12 '90 325i, RIP '87 325 sold '89 525i, traded '87 325iS, RIP

  7. #7
    Join Date
    Jun 2008
    Location
    Boston, MA
    Posts
    77
    My Cars
    '85 M635; '08 535XiT

    Middle exhaust rust

    My car’s exhaust has been dissolving for a few decades. Patches and repairs worked for 5-10 years but now it’s beyond saving the original. It sounds real mean but I need to replace it. Note, that can get pricey if you go for a quality exhaust. My car is a Euro M but I was quoted $1600 plus labor for a Supersprint exhaust.
    Last edited by Sixracer; 10-20-2020 at 06:08 PM.
    ................'85 M635...............'08 535XiT (6-spd!)..................

  8. #8
    Join Date
    Sep 2020
    Location
    Europe
    Posts
    25
    My Cars
    E24 1987
    Thank you guys so much for your help. I really appreciate that!

    Quote Originally Posted by DesktopDave View Post
    The 2nd pic is the catalyst. It's the original BMW two-chamber design, very well made, very effective, very expensive to replace. I'm stuck with the same problem as you - the BMW part is incredibly expensive, but I want it to run cleanly. You can't replace the heat shield easily. There are plenty of aftermarket OBD1 catalysts, including some high-performance ones, but I've heard they don't last. We also have some legal vehicular obligations in stricter states that may prevent installing aftermarket catalysts; not sure if that might apply to your locality as well.
    The cat would not the a problem here (can be cut) but the common work in old cars is to replace it not for regular pipe, but for some kind of "ejector" (don't know if it's a good word to describe it?), so it does not have emission control like catalysators have, but otherwise it functions the same. Flow is a bit better. Do you know what I mean?

  9. #9
    Join Date
    Oct 2015
    Location
    Illinois
    Posts
    120
    My Cars
    740 735 635 535 318is
    Yes, Sat159, I'm following you. Buying overpriced OEM factory parts is taboo to me.

    I fabricatefd and welded the exh system for my 635csi all out of 316 stainless. Proud of the custom work.

    Another name for exh extractor is a turbocharger. Yes, the M30 engine responds very well to turbocharging.

    Sent from my moto g(7) power using Tapatalk

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