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Old 01-11-2011, 04:16 PM   #51 (permalink)
BenzWorld Junior Member
 
Date registered: Dec 2010
Vehicle: 1999 ML320
Location: South Lake Tahoe CA
Posts: 31
Warning - Additional Damage!

Hello Waltzonice,

I'm just now getting into this same repair. I started with a check engine light (P0410) for the secondary air pump, and found that I had a bad air pump. After studying lots of threads, along with help and instructions from Witek, I can answer your question about permanent damage from open reed valves. In a nutshell, the reed valves protect the entire upstream air injection system.

The valves exist to prevent exhaust gas from entering the valve and pump. When the air pump is not on, exhaust gas will destroy the diaphragm in the top of the valve, and proceed through to destroy the plastic air pump. The pump only runs for 150 seconds during a cold start, and is off most of the time.

It's doubtful that these reeds get bent by air pump pressure. I am only speculating that exhaust crud gets stuck under the reeds. With the help of cyclic heat treatments from the exhaust, they end up permanently bent open. I haven't had a chance to inspect a new valve. I guess it's possible that the reeds are not tight against their mating surface when new, with the design intention that exhaust back pressure keeps them sealed tight. Seems unlikely, but I'm regularly surprised by this vehicle's engineering details. If anyone knows how a new valve looks that would be helpful information.

Replacement valves are definitely expensive. At around $200 each they are more expensive than the electric air pump! If anyone knows where to find them less expensively I would appreciate knowing that too.

Turning the reeds over might be a possible repair. If the heads of the screws break as they did on Witek, a solution for that may be to drill out the screws, and tap for slightly larger replacement screws. First center-punch the broken screws so your drill bit doesn't wobble off center. Use a drill press to drill straight. At a minimum, screws are work hardened during their manufacture. Use a cobalt drill bit and some lubrication to make the project easier on yourself. Don't forget to use a drill press vise to save your hands and body. If you don't know about all this, better to take it to somebody that does - a machinist.

Hope that helps. Let me know how it goes if you get to it before I have the experience myself. Hopefully the valves on our ML are fine. I'm doing the research beforehand to be armed with the right tools. Plus it's damn cold outside!

John
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Old 04-08-2011, 01:03 AM   #52 (permalink)
BenzWorld Junior Member
 
Date registered: Oct 2006
Vehicle: 1993 Pontiac Firefly
Location: Seattle
Posts: 32
Quote:
Originally Posted by jolson View Post
Hello Waltzonice,

I'm just now getting into this same repair. I started with a check engine light (P0410) for the secondary air pump, and found that I had a bad air pump. After studying lots of threads, along with help and instructions from Witek, I can answer your question about permanent damage from open reed valves. In a nutshell, the reed valves protect the entire upstream air injection system.

The valves exist to prevent exhaust gas from entering the valve and pump. When the air pump is not on, exhaust gas will destroy the diaphragm in the top of the valve, and proceed through to destroy the plastic air pump. The pump only runs for 150 seconds during a cold start, and is off most of the time.

It's doubtful that these reeds get bent by air pump pressure. I am only speculating that exhaust crud gets stuck under the reeds. With the help of cyclic heat treatments from the exhaust, they end up permanently bent open. I haven't had a chance to inspect a new valve. I guess it's possible that the reeds are not tight against their mating surface when new, with the design intention that exhaust back pressure keeps them sealed tight. Seems unlikely, but I'm regularly surprised by this vehicle's engineering details. If anyone knows how a new valve looks that would be helpful information.

Replacement valves are definitely expensive. At around $200 each they are more expensive than the electric air pump! If anyone knows where to find them less expensively I would appreciate knowing that too.

Turning the reeds over might be a possible repair. If the heads of the screws break as they did on Witek, a solution for that may be to drill out the screws, and tap for slightly larger replacement screws. First center-punch the broken screws so your drill bit doesn't wobble off center. Use a drill press to drill straight. At a minimum, screws are work hardened during their manufacture. Use a cobalt drill bit and some lubrication to make the project easier on yourself. Don't forget to use a drill press vise to save your hands and body. If you don't know about all this, better to take it to somebody that does - a machinist.

Hope that helps. Let me know how it goes if you get to it before I have the experience myself. Hopefully the valves on our ML are fine. I'm doing the research beforehand to be armed with the right tools. Plus it's damn cold outside!

John
Were you able to fix your problem? or is the check engine light still on?
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Old 04-08-2011, 07:01 AM   #53 (permalink)
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Date registered: Aug 2006
Vehicle: 02 ML320
Location: Bronx, New York
Posts: 10,154
Quote:
Originally Posted by realog View Post
Were you able to fix your problem? or is the check engine light still on?
realog, why don't you just explain your problem and state whether the CEL is on and what you have checked/and or replaced to date.

Please update your profile so we may help you better.

Click on USER CP.
Click on EDIT PROFILE.
Scroll down to ADDITIONAL INFO. And fill in the year and model of your truck and where you live.
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Old 04-08-2011, 05:04 PM   #54 (permalink)
BenzWorld Junior Member
 
Date registered: Oct 2006
Vehicle: 1993 Pontiac Firefly
Location: Seattle
Posts: 32
Quote:
Originally Posted by 43sqd View Post
realog, why don't you just explain your problem and state whether the CEL is on and what you have checked/and or replaced to date.

Please update your profile so we may help you better.

Click on USER CP.
Click on EDIT PROFILE.
Scroll down to ADDITIONAL INFO. And fill in the year and model of your truck and where you live.

Hi thanks for the response. My truck is a 2003 Mercedes ML320. I did a OBD scan since my CEL was on and it gave me this code. I deleted it and it came on the very next day after some driving. I took a look under the hood and everything seemed fine. The one thing I didn't do was check the relay because I don't know which relay is associated with this problem. The truck runs find and appears to be fine as ever but the CEL is on.

I don't know which relay it is, I was thinking about swapping the relay out because I don't know how to test if a relay is faulty or not.

Any feedback to my on-going problem would be helpful,


thanks
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Old 06-07-2011, 11:30 PM   #55 (permalink)
BenzWorld Junior Member
 
Date registered: Oct 2006
Vehicle: 1993 Pontiac Firefly
Location: Seattle
Posts: 32
Bump...same problem. P0410

My truck is a 2003 Mercedes ML320. I did a OBD scan since my CEL was on and it gave me this code. I deleted it and it came on the very next day after some driving. I took a look under the hood and everything seemed fine. The one thing I didn't do was check the relay because I don't know which relay is associated with this problem. The truck runs find and appears to be fine as ever but the CEL is on.

I don't know which relay it is, I was thinking about swapping the relay out because I don't know how to test if a relay is faulty or not.

Any feedback to my on-going problem would be helpful,
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Old 06-08-2011, 03:36 AM   #56 (permalink)
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Date registered: Aug 2006
Vehicle: 02 ML320
Location: Bronx, New York
Posts: 10,154
Quote:
Originally Posted by realog View Post
Bump...same problem. P0410

Bump.......same problem.
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Old 06-08-2011, 08:47 AM   #57 (permalink)
BenzWorld Junior Member
 
Date registered: Dec 2010
Vehicle: 1999 ML320
Location: South Lake Tahoe CA
Posts: 31
Fixed

Quote:
Originally Posted by realog View Post
Were you able to fix your problem? or is the check engine light still on?
Realog:

"Looking under the hood" is not likely to tell you anything about this air injection system - unless it's on fire!

Sorry I missed your message back in April. Seems like you still have the problem now.

I have managed to fix the entire air injection system on our ML 320. I did not clear the computer check engine light (CEL) as it clears itself a few cycles after this system is repaired - a good verification for me.

The entire repair is very quick and inexpensive depending on how resourceful you are with finding a replacement pump and cleaning/repairing/purchasing replacement valves. I found a replacement pump very inexpensively on Ebay, and repaired the valves.

Ultimately it takes far more time to read about the system on the threads here than doing the actual replacement/repair. Reading the information on this site will save you lots of time and money! The beauty of the threads is that it arms you with the knowledge to tackle the job correctly, and it's clean too! There are three related threads you really need to study;

1. This thread.

2. http://www.benzworld.org/forums/w163...operation.html

3. http://www.benzworld.org/forums/w163...ystem-diy.html

In the end, I'm a bit skeptical of the entire air injection system. I had a mechanic explain that he felt the system is only to pass an emissions requirement on start. His explanation was simple. There is plenty of air in the intake combustion flow in all cases - even when cold. Adding additional air to the exhaust head during cold start in no way helps unburned fuel burn further. His simple conclusion is that all it does is dilute the concentration (parts per million) of unburned hydrocarbons (gasoline). The dilution gets the concentration within government regulations and specifications! Crazy eh!

That explanation makes a lot of sense to me. The position of the automobile manufacturers is maybe that the catalytic converter needs the extra air to burn the unburned fuel. Problem with that explanation is that the cat is cold (and not doing a good job) anyhow at start. I know from watching a smog check in progress, that catalytic converters take some time to warm up. So I have pretty much concluded myself that the entire system is just to trick the emissions test - and a result of very mis-guided government regulation - what a surprise! If anyone else has a better theory, I'm all ears.

However, in any case you want to clear a CEL on your vehicle so this diagnostic system warns you of future problems. I fixed my air injection system. Maybe somebody here knows how to modify it so the diagnostic CEL system thinks it is working fine (even though it's dismantled). If my memory of Witek M's posts is correct, I believe it is measuring current to the pump during a fixed time. Tricking this may be more difficult than fixing it. Maybe the pump can be replaced and the outlet left unattached (along with sealing off the valves). If you live in a state where the emission system is checked regularly, you might get in trouble for this or any modification anyhow! So I'm happy I repaired it to work as it should - even though it's probably an entirely useless complicated system.

Read all three threads in their entirety and you will be on your way.

John
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Old 06-08-2011, 02:55 PM   #58 (permalink)
BenzWorld Junior Member
 
Date registered: Oct 2006
Vehicle: 1993 Pontiac Firefly
Location: Seattle
Posts: 32
Quote:
Originally Posted by jolson View Post
Realog:

"Looking under the hood" is not likely to tell you anything about this air injection system - unless it's on fire!

Sorry I missed your message back in April. Seems like you still have the problem now.

I have managed to fix the entire air injection system on our ML 320. I did not clear the computer check engine light (CEL) as it clears itself a few cycles after this system is repaired - a good verification for me.

The entire repair is very quick and inexpensive depending on how resourceful you are with finding a replacement pump and cleaning/repairing/purchasing replacement valves. I found a replacement pump very inexpensively on Ebay, and repaired the valves.

Ultimately it takes far more time to read about the system on the threads here than doing the actual replacement/repair. Reading the information on this site will save you lots of time and money! The beauty of the threads is that it arms you with the knowledge to tackle the job correctly, and it's clean too! There are three related threads you really need to study;

1. This thread.

2. http://www.benzworld.org/forums/w163...operation.html

3. http://www.benzworld.org/forums/w163...ystem-diy.html

In the end, I'm a bit skeptical of the entire air injection system. I had a mechanic explain that he felt the system is only to pass an emissions requirement on start. His explanation was simple. There is plenty of air in the intake combustion flow in all cases - even when cold. Adding additional air to the exhaust head during cold start in no way helps unburned fuel burn further. His simple conclusion is that all it does is dilute the concentration (parts per million) of unburned hydrocarbons (gasoline). The dilution gets the concentration within government regulations and specifications! Crazy eh!

That explanation makes a lot of sense to me. The position of the automobile manufacturers is maybe that the catalytic converter needs the extra air to burn the unburned fuel. Problem with that explanation is that the cat is cold (and not doing a good job) anyhow at start. I know from watching a smog check in progress, that catalytic converters take some time to warm up. So I have pretty much concluded myself that the entire system is just to trick the emissions test - and a result of very mis-guided government regulation - what a surprise! If anyone else has a better theory, I'm all ears.

However, in any case you want to clear a CEL on your vehicle so this diagnostic system warns you of future problems. I fixed my air injection system. Maybe somebody here knows how to modify it so the diagnostic CEL system thinks it is working fine (even though it's dismantled). If my memory of Witek M's posts is correct, I believe it is measuring current to the pump during a fixed time. Tricking this may be more difficult than fixing it. Maybe the pump can be replaced and the outlet left unattached (along with sealing off the valves). If you live in a state where the emission system is checked regularly, you might get in trouble for this or any modification anyhow! So I'm happy I repaired it to work as it should - even though it's probably an entirely useless complicated system.

Read all three threads in their entirety and you will be on your way.

John
Thank you for the very informative write up. I will defiantly read the threads you have recommended and buy the parts online. I think you are right about the air pump, I will defiantly be swapping it out. Thank you so much for the very informative write up!
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Old 09-07-2013, 07:35 PM   #59 (permalink)
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Date registered: Sep 2013
Vehicle: Mercedes ML270
Location: Brisbane
Posts: 1
can't see the pictures
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