Auxiliary Air Valve Repair & Refurbish, Including Idle Controls

1979-1991 280SE, 300SE, 300SEL, 380SE, 380SEL, 380SEC, 420SE, 420SEL, 420SEC, 500SE, 500SEL, 500SEC, 560SEL, 560SEC
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mrsecman
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Model you own: w126
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Auxiliary Air Valve Repair & Refurbish, Including Idle Controls

Post by mrsecman » Sat 13 Apr, 2019 7:51 am

All, Following on from prior posts and research below which I've consolidated here for our future record and reference; the repair of the notorious Auxiliary Air Valve/Slider.

Paul Noren did a good work up here in 2014: https://paulnoren.com/all-posts/2014/4/ ... lve-repair
I followed that thread for general guidance but ordered in specific gaskets and parts for the job, plus some new hoses for reconnection to the idle control and vacuum lines (thought I'd go all in on the job).
Another reference thread here: http://www.topklasse.net.au/forums/show ... f830&t=179

My work took several hours and including some readjustment of the fuel and idle at the local Indie shop. The results are pretty good; a very smooth idle and pretty good control of the warm up process. It did uncover some worn motor mounts but that's not critical just yet.

Brief process:

- Removed the air intake housing and vacuum lines, and the brackets that hold the AAV hoses in place.
- Loosened off coolant to reduce pressure (did lose some coolant to pressure leakage once AAV was removed).
- Cleaned off old gasket and compared all removed hoses to ensure the right parts were supplied (previous hoses carefully removed just in case).
- Used degreaser, brake cleaner and brush/soaking to clean up parts and did a general clean and brush of the idle control area.
- Boiled up AAV to test closure. See images.
- Using vice (very carefully) and some metal brackets, crimped two slots just slightly into opposing sides of the temperature nipple on the AAV. Some guesswork here - full closure never quite happened in the end (see other closure image), but we suspected this was because of built up grit inside the unit. Our crimping was a best guess in the end, plus another deep clean and soak and a silicon lube of the interior and final soak and small blow out with compressed air.
- Reinstalled with new gasket and hoses, final clean down and test. *There sounded like an air leak from a vacuum line but this was put to bed during the fuel and idle tune at the shop. Also noted a random spark from a lead - so it's time to replace them!
- Car in great condition and warming up, idling very well - needs a summer test next year though when new air conditioning system is installed.

I've attempted to adjust the images in order with some detail, but do your best to follow along. Note also the rubber part numbers I've included (also replaced the air intake rebreather hose at the driver's side rear tappet cover). There's probably a host of other rubbers that could do with eventual replacement but they'll remain in place as long as they don't crack. Also seeking information on some replacement covers for the wiring and vacuum lines, and will seek some replacement ignition leads as well.

Please enjoy! And I hope you can use this as a reference in future.
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Last edited by mrsecman on Sun 12 May, 2019 9:02 pm, edited 2 times in total.
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mrsecman

1984 380SEC ('83 Update) - Thistle Green, Top Condition, 2-1/4" Magnaflow Exhaust w/HiFlow Centre Mufflers, Interior Modifications
1994 Honda Accord VTi-S - Daily Runabout - SOLD 2015 (Good New Home) - Thanks for the Service

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Astro-Benz777
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Re: Auxiliary Air Valve Repair & Refurbish, Including Idle Controls

Post by Astro-Benz777 » Fri 10 May, 2019 11:16 am

I've got a 280SE (W126) so the location of the Slide Valve is different (see below) but a great summery of past threads with some added very useful/practical info and pics .
This should be read by virtually all W126 owners/DIY'er's as I'm sure 90% of W126 owners on this forum could relate stories of their own idle speed issues (whether fast, slow, erratic or other) a resource such as this really ought go in the "Tech Library" or be made "Sticky" because this really is a "Must See" for those troubleshooting or looking for the missing link in their idle speed issues.
As a 280SE/L owner (the last S-Class to use the famous M110 engine) I thought I'd add for those interested or working on a W126 M110; the Slide Valve can be found bolted to the side block on the passenger side of the engine towards the front, behind the Power Steering Pump and underneath the front of the intake manifold.
:wav:
W126's: truly the last real Benz (IMHO) :notworthy:
FORMER FAMILY:
1989 300SE (W126) Midnight Blue, Blue/Grey Interior (Gearhardt)
1982 380SE (W126) Thistle Green, Tan Interior (Sherman)
CURRENT DAILY DRIVE & BELOVED FAMILY MEMBER
1984 280SE (W126) Thistle Green, Tan Interior (Hilda...after my late Gran)

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mrsecman
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Posts: 134
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Model you own: w126
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Re: Auxiliary Air Valve Repair & Refurbish, Including Idle Controls

Post by mrsecman » Sun 12 May, 2019 9:07 pm

Astro-Benz777 wrote:
Fri 10 May, 2019 11:16 am
I've got a 280SE (W126) so the location of the Slide Valve is different (see below) but a great summery of past threads with some added very useful/practical info and pics .
This should be read by virtually all W126 owners/DIY'er's as I'm sure 90% of W126 owners on this forum could relate stories of their own idle speed issues (whether fast, slow, erratic or other) a resource such as this really ought go in the "Tech Library" or be made "Sticky" because this really is a "Must See" for those troubleshooting or looking for the missing link in their idle speed issues.
As a 280SE/L owner (the last S-Class to use the famous M110 engine) I thought I'd add for those interested or working on a W126 M110; the Slide Valve can be found bolted to the side block on the passenger side of the engine towards the front, behind the Power Steering Pump and underneath the front of the intake manifold.
:wav:
Agree, definitely something to note and log to the major reference library for all W126 and similar owners. The change to how smooth the engine responds now at low rev after further tune is quite impressive. I can only imagine how great these were straight out of the factory, and mine is as good as you can get for a sub-300,000km engine given the TLC I've afforded it. Magnificent machine to preserve.
--
mrsecman

1984 380SEC ('83 Update) - Thistle Green, Top Condition, 2-1/4" Magnaflow Exhaust w/HiFlow Centre Mufflers, Interior Modifications
1994 Honda Accord VTi-S - Daily Runabout - SOLD 2015 (Good New Home) - Thanks for the Service

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John Green
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Re: Auxiliary Air Valve Repair & Refurbish, Including Idle Controls

Post by John Green » Mon 13 May, 2019 7:40 am

mrsecman wrote:
Sat 13 Apr, 2019 7:51 am
All, Following on from prior posts and research below which I've consolidated here for our future record and reference; the repair of the notorious Auxiliary Air Valve/Slider.

Paul Noren did a good work up here in 2014: https://paulnoren.com/all-posts/2014/4/ ... lve-repair
I followed that thread for general guidance but ordered in specific gaskets and parts for the job, plus some new hoses for reconnection to the idle control and vacuum lines (thought I'd go all in on the job).
This method can end badly, either crush it too much or worse, you break the brass bulb. The air slide in the video can be adjusted by pushing down on the top section. I do it in a vice with a socket covering the bulb. Our theory is that over the years the spring pushes it up.

Also of most importance is that before you push or crush anything that you make sure they is as little carbon residue in it as possible. I use carby cleaner, sometimes an entire can of it and leave it to soak as long as possible. Have even seen them return to normal with just cleaning.
M.B Spares & Service 14-16 Lyell St, Fyshwick ACT. Ph 02 6239 1099

http://mbspares.com.au - Supporting Australia's Mercedes-Benz Enthusiasts.

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Astro-Benz777
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Re: Auxiliary Air Valve Repair & Refurbish, Including Idle Controls

Post by Astro-Benz777 » Mon 13 May, 2019 7:46 pm

Mr Green, you have saved me countless hours stuffing around both on the net and working on the car with exactly this kinds of sage advice.
Manuals can show/explain to one exactly what to do but nothing can beat practical experience working on these cars and dealing with the exact same issues.
Sooo.... I will need to remove the Slide Valve to clean it out with Carby cleaner or am I better off leaving it in place, removing the moulded vacuum lines and spraying the heck out of it a few times?
I need to pick your brain about the EGR on my 280 W126 one day soon too John.
Many thanks
W126's: truly the last real Benz (IMHO) :notworthy:
FORMER FAMILY:
1989 300SE (W126) Midnight Blue, Blue/Grey Interior (Gearhardt)
1982 380SE (W126) Thistle Green, Tan Interior (Sherman)
CURRENT DAILY DRIVE & BELOVED FAMILY MEMBER
1984 280SE (W126) Thistle Green, Tan Interior (Hilda...after my late Gran)

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John Green
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Re: Auxiliary Air Valve Repair & Refurbish, Including Idle Controls

Post by John Green » Tue 14 May, 2019 7:51 am

Astro-Benz777 wrote:
Mon 13 May, 2019 7:46 pm
Mr Green, you have saved me countless hours stuffing around both on the net and working on the car with exactly this kinds of sage advice.
Manuals can show/explain to one exactly what to do but nothing can beat practical experience working on these cars and dealing with the exact same issues.
Sooo.... I will need to remove the Slide Valve to clean it out with Carby cleaner or am I better off leaving it in place, removing the moulded vacuum lines and spraying the heck out of it a few
remove it and block one end, spray enough in to flood it and then wait for an hour or so. It will evaporate by then. Repeat only this time block both ends and agitate it. You will be amazed what comes out if you drain the cleaner out after the second time.
M.B Spares & Service 14-16 Lyell St, Fyshwick ACT. Ph 02 6239 1099

http://mbspares.com.au - Supporting Australia's Mercedes-Benz Enthusiasts.

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Astro-Benz777
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Posts: 79
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Re: Auxiliary Air Valve Repair & Refurbish, Including Idle Controls

Post by Astro-Benz777 » Tue 14 May, 2019 10:06 am

You're a scholar & a gentleman, thank you kindly.
One last thing... I'm going to need to have a new gasket for it ready to go aren't I?
W126's: truly the last real Benz (IMHO) :notworthy:
FORMER FAMILY:
1989 300SE (W126) Midnight Blue, Blue/Grey Interior (Gearhardt)
1982 380SE (W126) Thistle Green, Tan Interior (Sherman)
CURRENT DAILY DRIVE & BELOVED FAMILY MEMBER
1984 280SE (W126) Thistle Green, Tan Interior (Hilda...after my late Gran)

User avatar
John Green
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Posts: 6753
Joined: Mon 20 Jun, 2005 3:49 am
Model you own: w112
Region: Australian Capital Territory
Location: Canberra-center of the known universe
Contact:

Re: Auxiliary Air Valve Repair & Refurbish, Including Idle Controls

Post by John Green » Tue 14 May, 2019 1:03 pm

Astro-Benz777 wrote:
Tue 14 May, 2019 10:06 am
You're a scholar & a gentleman, thank you kindly.
One last thing... I'm going to need to have a new gasket for it ready to go aren't I?
Yes, but you can just cut one out of gasket paper.
M.B Spares & Service 14-16 Lyell St, Fyshwick ACT. Ph 02 6239 1099

http://mbspares.com.au - Supporting Australia's Mercedes-Benz Enthusiasts.

User avatar
Astro-Benz777
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Joined: Tue 03 May, 2016 7:40 am
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Region: Tasmania
Location: Melbourne

Re: Auxiliary Air Valve Repair & Refurbish, Including Idle Controls

Post by Astro-Benz777 » Sat 25 May, 2019 5:56 am

Of course I could always do that which of course I already knew *coughs* :bs:
In all honesty, I had imagined it to be a far more complicated procedure, especially on an M110 with the slide valve being located so inconveniently but knowing that the refit is only slightly more complicated than removal (so long as I remember to buy gasket paper) makes "Reconditioning Aux Air Valve" this weekend's Mini-Project.
The more I think about it, even in the unlikely event the valve is functioning perfectly, no harm can come from giving such an integral part a good clean & check for correct operation.
Once again, many thanks for your advice.
W126's: truly the last real Benz (IMHO) :notworthy:
FORMER FAMILY:
1989 300SE (W126) Midnight Blue, Blue/Grey Interior (Gearhardt)
1982 380SE (W126) Thistle Green, Tan Interior (Sherman)
CURRENT DAILY DRIVE & BELOVED FAMILY MEMBER
1984 280SE (W126) Thistle Green, Tan Interior (Hilda...after my late Gran)

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