Dealership STUMPED. Can Not Find Problem.
Super Member
Joined: Sep 2016
Posts: 571
Likes: 92
From: New England! :-)
2005 C230K Sport Coupe
Fwiw, it's easy to check for clogged cats.
ASE, and others, specify using a back-pressure tester. It screws in place of the oxygen sensor(s).
There are cheap ones ~$50 US, and better ones for ~$150 US.
If you have a MAPP torch and a good quality O2 socket, it's not hard to check. For a garage, it takes ~30mins or so.
Btw, most local garages don't have ASE certified mechanics, nor do they "spend time" doing many of the ASE recommended tests/verifications. Local garages often care more about selling stuff and pulling in as much money as fast as possible. To be semi-fair, many have to just to survive. :-|
How to test for a restricted exhaust (catalytic converter)
ScannerDanner
ASE, and others, specify using a back-pressure tester. It screws in place of the oxygen sensor(s).
There are cheap ones ~$50 US, and better ones for ~$150 US.
If you have a MAPP torch and a good quality O2 socket, it's not hard to check. For a garage, it takes ~30mins or so.
Btw, most local garages don't have ASE certified mechanics, nor do they "spend time" doing many of the ASE recommended tests/verifications. Local garages often care more about selling stuff and pulling in as much money as fast as possible. To be semi-fair, many have to just to survive. :-|
ScannerDanner
Thread Starter
Super Member
Joined: Aug 2004
Posts: 791
Likes: 37
From: Detroit Area
W203 C230, W210 E350, W166 ML63
UPDATE:
It seems that most of the exhaust shops in my area get amnesia after they tell me a price and then I come in to get the work done. I got quoted $190 to replace the headers to the resonator from a shop. When I get to the shop the next day they have no idea what I'm talking about even though I see the man I spoke to was there. They then quoted me $700+ for the work lol. I decided to go back to a shop that quoted me $300 after that and when I got there they tell me its $550.
I find another guy that is somewhat out of the way and in a not so good area and he quotes me $180 but he's about 40 minutes away, I'd have to go back next Saturday, and I don't know how much I can trust the shop.
I'm going to go to one more shop tomorrow to get a final quote and then I'm going to make a decision.
I sometimes feel that when I say its a "Mercedes" they uncharge me. My car is 13 years old and worth $5k. They need to relax.
It seems that most of the exhaust shops in my area get amnesia after they tell me a price and then I come in to get the work done. I got quoted $190 to replace the headers to the resonator from a shop. When I get to the shop the next day they have no idea what I'm talking about even though I see the man I spoke to was there. They then quoted me $700+ for the work lol. I decided to go back to a shop that quoted me $300 after that and when I got there they tell me its $550.
I find another guy that is somewhat out of the way and in a not so good area and he quotes me $180 but he's about 40 minutes away, I'd have to go back next Saturday, and I don't know how much I can trust the shop.I'm going to go to one more shop tomorrow to get a final quote and then I'm going to make a decision.
I sometimes feel that when I say its a "Mercedes" they uncharge me. My car is 13 years old and worth $5k. They need to relax.
Thread Starter
Super Member
Joined: Aug 2004
Posts: 791
Likes: 37
From: Detroit Area
W203 C230, W210 E350, W166 ML63
Finally got my exhaust manifold and second cat swapped out. WOW. What a difference. I feel that my car has not ran this way in a long time. The magnaflow does give a kind of different exhaust note which idk if I like but as long as I'm getting the power that I need and the MPG are correct than I am okay with it.
Check out how clogged my primary cat was. The guys at the shop couldn't believe it because they kept saying my exhaust flow was good but the problem was under load which is why they couldn't diagnose it right.
Check out how clogged my primary cat was. The guys at the shop couldn't believe it because they kept saying my exhaust flow was good but the problem was under load which is why they couldn't diagnose it right.
Super Member
Joined: Sep 2016
Posts: 571
Likes: 92
From: New England! :-)
2005 C230K Sport Coupe
Fwiw,
1) From what you described, the dealer and ?your friend?did ~1-3 hours of ?free/cheap? diagnosis on your car. Imho, they helped to narrow down the possible causes.
2) They offered to further look/diagnosis the problem, at their normal shop rate (?~$200+/hr?).
You declined.
3) You guessed what the problem might be, also using information that the shop found/didn't find/gave to you.
4) Given the opportunity (for a paying customer), ANY even marginally competent ASE certified Dealer mechanic could've found the problem. As I mentioned, the ASE and Dealer diagnostic procedures call for doing a back pressure test at idle, at ~1K, at ~2K, and ~3K rpms. Actual data points will vary. The back pressure should be very low at idle, and often under 1psi at ~3K rpms. Iirc, anything over ~2psi is often considered bad.
With multiple convertor and muffler systems, it can be hard to pinpoint the bad component. Mechanics often do a "tap" test, use their knowledge of the common causes, and use their best judgement to make the best guess on which component to replace first.
Very often, it's the primary convertor. But, it can vary by model, year, engine, etc.
*If* I was worrying about the cost of replacing a convertor, I would've bought a cheap back pressure tester, and did the tests myself.
Or, have a local garage do the test. It would take less than a hour's total time.
However, I know that after ~8-10 years, and ~70K-120K miles, convertors and oxygen sensors often could/"should" be replaced. By replacing them, that results in better gas mileage (less gas - save money), and more power.
Also, as C230 Sport Coup mentioned, the non-dealer replacement convertors may last only ~50K miles (or less).
Many reasons for that. The convertors are often not of the same quality, and you're putting a convertor on an older engine that very likely has more oil blow-by, more particulates, and more emissions than when the engine was new ~10+ years ago and ~80K+ miles ago.
Last edited by RedGray; Nov 9, 2016 at 11:16 PM.
Thread Starter
Super Member
Joined: Aug 2004
Posts: 791
Likes: 37
From: Detroit Area
W203 C230, W210 E350, W166 ML63
Fwiw,
1) From what you described, the dealer and ?your friend?did ~1-3 hours of ?free/cheap? diagnosis on your car. Imho, they helped to narrow down the possible causes.
2) They offered to further look/diagnosis the problem, at their normal shop rate (?~$200+/hr?).
You declined.
3) You guessed what the problem might be, also using information that the shop found/didn't find/gave to you.
4) Given the opportunity (for a paying customer), ANY even marginally competent ASE certified Dealer mechanic could've found the problem. As I mentioned, the ASE and Dealer diagnostic procedures call for doing a back pressure test at idle, at ~1K, at ~2K, and ~3K rpms. Actual data points will vary. The back pressure should be very low at idle, and often under 1psi at ~3K rpms. Iirc, anything over ~2psi is often considered bad.
With multiple convertor and muffler systems, it can be hard to pinpoint the bad component. Mechanics often do a "tap" test, use their knowledge of the common causes, and use their best judgement to make the best guess on which component to replace first.
Very often, it's the primary convertor. But, it can vary by model, year, engine, etc.
*If* I was worrying about the cost of replacing a convertor, I would've bought a cheap back pressure tester, and did the tests myself.
Or, have a local garage do the test. It would take less than a hour's total time.
However, I know that after ~8-10 years, and ~70K-120K miles, convertors and oxygen sensors often could/"should" be replaced. By replacing them, that results in better gas mileage (less gas - save money), and more power.
Also, as C230 Sport Coup mentioned, the non-dealer replacement convertors may last only ~50K miles (or less).
Many reasons for that. The convertors are often not of the same quality, and you're putting a convertor on an older engine that very likely has more oil blow-by, more particulates, and more emissions than when the engine was new ~10+ years ago and ~80K+ miles ago.
1) From what you described, the dealer and ?your friend?did ~1-3 hours of ?free/cheap? diagnosis on your car. Imho, they helped to narrow down the possible causes.
2) They offered to further look/diagnosis the problem, at their normal shop rate (?~$200+/hr?).
You declined.
3) You guessed what the problem might be, also using information that the shop found/didn't find/gave to you.
4) Given the opportunity (for a paying customer), ANY even marginally competent ASE certified Dealer mechanic could've found the problem. As I mentioned, the ASE and Dealer diagnostic procedures call for doing a back pressure test at idle, at ~1K, at ~2K, and ~3K rpms. Actual data points will vary. The back pressure should be very low at idle, and often under 1psi at ~3K rpms. Iirc, anything over ~2psi is often considered bad.
With multiple convertor and muffler systems, it can be hard to pinpoint the bad component. Mechanics often do a "tap" test, use their knowledge of the common causes, and use their best judgement to make the best guess on which component to replace first.
Very often, it's the primary convertor. But, it can vary by model, year, engine, etc.
*If* I was worrying about the cost of replacing a convertor, I would've bought a cheap back pressure tester, and did the tests myself.
Or, have a local garage do the test. It would take less than a hour's total time.
However, I know that after ~8-10 years, and ~70K-120K miles, convertors and oxygen sensors often could/"should" be replaced. By replacing them, that results in better gas mileage (less gas - save money), and more power.
Also, as C230 Sport Coup mentioned, the non-dealer replacement convertors may last only ~50K miles (or less).
Many reasons for that. The convertors are often not of the same quality, and you're putting a convertor on an older engine that very likely has more oil blow-by, more particulates, and more emissions than when the engine was new ~10+ years ago and ~80K+ miles ago.
Last edited by PeteyV; Nov 10, 2016 at 12:59 PM.
Super Member
Joined: Nov 2010
Posts: 681
Likes: 134
Benz
Fwiw,
1) From what you described, the dealer and ?your friend?did ~1-3 hours of ?free/cheap? diagnosis on your car. Imho, they helped to narrow down the possible causes.
2) They offered to further look/diagnosis the problem, at their normal shop rate (?~$200+/hr?).
You declined.
3) You guessed what the problem might be, also using information that the shop found/didn't find/gave to you.
4) Given the opportunity (for a paying customer), ANY even marginally competent ASE certified Dealer mechanic could've found the problem. As I mentioned, the ASE and Dealer diagnostic procedures call for doing a back pressure test at idle, at ~1K, at ~2K, and ~3K rpms. Actual data points will vary. The back pressure should be very low at idle, and often under 1psi at ~3K rpms. Iirc, anything over ~2psi is often considered bad.
With multiple convertor and muffler systems, it can be hard to pinpoint the bad component. Mechanics often do a "tap" test, use their knowledge of the common causes, and use their best judgement to make the best guess on which component to replace first.
Very often, it's the primary convertor. But, it can vary by model, year, engine, etc.
*If* I was worrying about the cost of replacing a convertor, I would've bought a cheap back pressure tester, and did the tests myself.
Or, have a local garage do the test. It would take less than a hour's total time.
However, I know that after ~8-10 years, and ~70K-120K miles, convertors and oxygen sensors often could/"should" be replaced. By replacing them, that results in better gas mileage (less gas - save money), and more power.
Also, as C230 Sport Coup mentioned, the non-dealer replacement convertors may last only ~50K miles (or less).
Many reasons for that. The convertors are often not of the same quality, and you're putting a convertor on an older engine that very likely has more oil blow-by, more particulates, and more emissions than when the engine was new ~10+ years ago and ~80K+ miles ago.
1) From what you described, the dealer and ?your friend?did ~1-3 hours of ?free/cheap? diagnosis on your car. Imho, they helped to narrow down the possible causes.
2) They offered to further look/diagnosis the problem, at their normal shop rate (?~$200+/hr?).
You declined.
3) You guessed what the problem might be, also using information that the shop found/didn't find/gave to you.
4) Given the opportunity (for a paying customer), ANY even marginally competent ASE certified Dealer mechanic could've found the problem. As I mentioned, the ASE and Dealer diagnostic procedures call for doing a back pressure test at idle, at ~1K, at ~2K, and ~3K rpms. Actual data points will vary. The back pressure should be very low at idle, and often under 1psi at ~3K rpms. Iirc, anything over ~2psi is often considered bad.
With multiple convertor and muffler systems, it can be hard to pinpoint the bad component. Mechanics often do a "tap" test, use their knowledge of the common causes, and use their best judgement to make the best guess on which component to replace first.
Very often, it's the primary convertor. But, it can vary by model, year, engine, etc.
*If* I was worrying about the cost of replacing a convertor, I would've bought a cheap back pressure tester, and did the tests myself.
Or, have a local garage do the test. It would take less than a hour's total time.
However, I know that after ~8-10 years, and ~70K-120K miles, convertors and oxygen sensors often could/"should" be replaced. By replacing them, that results in better gas mileage (less gas - save money), and more power.
Also, as C230 Sport Coup mentioned, the non-dealer replacement convertors may last only ~50K miles (or less).
Many reasons for that. The convertors are often not of the same quality, and you're putting a convertor on an older engine that very likely has more oil blow-by, more particulates, and more emissions than when the engine was new ~10+ years ago and ~80K+ miles ago.
Thread Starter
Super Member
Joined: Aug 2004
Posts: 791
Likes: 37
From: Detroit Area
W203 C230, W210 E350, W166 ML63
You mention ASE like it actually means something. To be fair, those tests are very basic and can be passed by anyone with even the slightest amount of knowledge about cars. I know several ASE certified techs that simply got the paper for a pay raise and can't diagnose anything. I also know several non ASE certified techs that could fix anything that comes their way. It really means nothing aside from a marketing standpoint IMHO. I have several ASE certs and keep them up to date primarily for myself, I don't display them anywhere and nobody asks if I'm certified. I really think it just puts uneducated consumers at ease when they see the ASE sign in the shop window.
Thread Starter
Super Member
Joined: Aug 2004
Posts: 791
Likes: 37
From: Detroit Area
W203 C230, W210 E350, W166 ML63
Fwiw,
1) From what you described, the dealer and ?your friend?did ~1-3 hours of ?free/cheap? diagnosis on your car. Imho, they helped to narrow down the possible causes.
2) They offered to further look/diagnosis the problem, at their normal shop rate (?~$200+/hr?).
You declined.
3) You guessed what the problem might be, also using information that the shop found/didn't find/gave to you.
4) Given the opportunity (for a paying customer), ANY even marginally competent ASE certified Dealer mechanic could've found the problem. As I mentioned, the ASE and Dealer diagnostic procedures call for doing a back pressure test at idle, at ~1K, at ~2K, and ~3K rpms. Actual data points will vary. The back pressure should be very low at idle, and often under 1psi at ~3K rpms. Iirc, anything over ~2psi is often considered bad.
With multiple convertor and muffler systems, it can be hard to pinpoint the bad component. Mechanics often do a "tap" test, use their knowledge of the common causes, and use their best judgement to make the best guess on which component to replace first.
Very often, it's the primary convertor. But, it can vary by model, year, engine, etc.
*If* I was worrying about the cost of replacing a convertor, I would've bought a cheap back pressure tester, and did the tests myself.
Or, have a local garage do the test. It would take less than a hour's total time.
However, I know that after ~8-10 years, and ~70K-120K miles, convertors and oxygen sensors often could/"should" be replaced. By replacing them, that results in better gas mileage (less gas - save money), and more power.
Also, as C230 Sport Coup mentioned, the non-dealer replacement convertors may last only ~50K miles (or less).
Many reasons for that. The convertors are often not of the same quality, and you're putting a convertor on an older engine that very likely has more oil blow-by, more particulates, and more emissions than when the engine was new ~10+ years ago and ~80K+ miles ago.
1) From what you described, the dealer and ?your friend?did ~1-3 hours of ?free/cheap? diagnosis on your car. Imho, they helped to narrow down the possible causes.
2) They offered to further look/diagnosis the problem, at their normal shop rate (?~$200+/hr?).
You declined.
3) You guessed what the problem might be, also using information that the shop found/didn't find/gave to you.
4) Given the opportunity (for a paying customer), ANY even marginally competent ASE certified Dealer mechanic could've found the problem. As I mentioned, the ASE and Dealer diagnostic procedures call for doing a back pressure test at idle, at ~1K, at ~2K, and ~3K rpms. Actual data points will vary. The back pressure should be very low at idle, and often under 1psi at ~3K rpms. Iirc, anything over ~2psi is often considered bad.
With multiple convertor and muffler systems, it can be hard to pinpoint the bad component. Mechanics often do a "tap" test, use their knowledge of the common causes, and use their best judgement to make the best guess on which component to replace first.
Very often, it's the primary convertor. But, it can vary by model, year, engine, etc.
*If* I was worrying about the cost of replacing a convertor, I would've bought a cheap back pressure tester, and did the tests myself.
Or, have a local garage do the test. It would take less than a hour's total time.
However, I know that after ~8-10 years, and ~70K-120K miles, convertors and oxygen sensors often could/"should" be replaced. By replacing them, that results in better gas mileage (less gas - save money), and more power.
Also, as C230 Sport Coup mentioned, the non-dealer replacement convertors may last only ~50K miles (or less).
Many reasons for that. The convertors are often not of the same quality, and you're putting a convertor on an older engine that very likely has more oil blow-by, more particulates, and more emissions than when the engine was new ~10+ years ago and ~80K+ miles ago.
FYI FWIW IMHO I even called my guy at the dealership to let him know what the problem was and that it is fixed. You know the "certified technician". He was pretty shocked himself since they took apart the engine to check the timing before they checked the exhaust. He admitted that he messed up. And I paid them their diagnostic fee ($120). The only reason I took it to them is because I trust his instincts more and he would not tell me to throw parts at the car, like most dealerships do. And that is exactly what he did, he told me him and his shop foreman had no idea what was wrong and that having them diagnose the issue would just be throwing money away because they would charge $300+ to just call MBUSA and have their engineers advise them on what parts to change until the problem was solved.
I then took it upon my self to check the cats because EVERYWHERE I went (PAYING DIAGNOSTIC FEES) said that my exhaust was fine. I did not think this was the case because of the fact I scanned a P0420 code since last year and I could actually hear the back pressure in my heads as I tried to accelerate. So I guess you could say all of these ASE mechanics f*cked up the diagnosis even after driving my car because it was clear that the cats were clogged on sheer fact that you could hear the air pressure trying to escape backwards and back to the engine from the cats. (E.I. the numerous hoses that kept popping off when the car was under load).
Maybe I just needed someone like you to diagnose the problem, but IDK. I paid everyone for their work, never got a discount. Just wanted their opinion to match mine which was that my cats were clogged and no one thought that until I took it to MR MUFFLER to have them cut the cats and not diagnose anything.
Last edited by PeteyV; Nov 15, 2016 at 04:24 PM.
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