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Garage => Mechanicals => Topic started by: ptashek on 03 October 2021, 03:28 PM

Title: Is my AAV in order?
Post by: ptashek on 03 October 2021, 03:28 PM
I might have a problem with my AAV (Auxiliary Air Valve) on the 450SE, in that it's not closing fully on a hot engine affecting idle. When started, the car goes into high idle and then nicely and gradually drops RPMs, but even with the idle screw all in I can't get below ~850 rpm. There's no vacuum leaks elsewhere, that I can find.

Below are pics of the AAV open (~20*C), and closed (~90*C). Does this look right to you folks?
It takes 2-3 minutes for it to close when the feeler is put into hot water.

I have a spare from my 350SE, but realised they're a different part number (A0001410825 - 350SE/M116 A0001410525 - 450SE/M117).
The difference being in the size of the air channel as the valve closes, which is considerably smaller on the M116 one, including when it's fully open.
I'm guessing they're definitely not interchangeable?

Title: Re: Is my AAV in order?
Post by: Jan S on 03 October 2021, 04:32 PM
ptashek, can I join "your club" - I believe I'm having the same problem .... idle warm never below 850-900 rpms, and the idle screw at end point. It's a 6.9 K-jet.

I suspect my aux air valve to be gummed up preventing the valve to fully close. And I suspect my cooling water thermostat to be shot and always open resulting in water not heating up to spec. I will start there and then move to the aux air valve.
Title: Re: Is my AAV in order?
Post by: rumb on 03 October 2021, 05:18 PM
Yes, the valve should be fully closed when hot. You can put in boiling water to test.

This guy does a great job showing taking apart and cleaning. I recall from somewhere else that the bulb can be crimped slightly with pliers to make the valve close even more when it reaches the correct temp.

https://www.youtube.com/watch?v=pBDMq0isxQw
Title: Re: Is my AAV in order?
Post by: ptashek on 04 October 2021, 06:26 AM
I've rebuilt the spare as a test run. Lightly tapped out the internals from the bottom, then cleaned and polished all sliding surfaces in the piston and the housing using glass polish. I've reassembled everything back using my vice as a makeshift press, and haven't used any lubricant between the piston and the body.

The end result is that "fully closed" it now has a gap of 0.65mm, instead of 3mm as before. Still not ideal, but I don't see how the remaining opening could be reduced further without messing with the thermal element itself.

Now to the main patient...

Edit: after posting this, I've realised that there may be some tolerance with the top cap, and maybe it can be pressed in further. Turns out there is, and it can. No gap. Success!

Title: Re: Is my AAV in order?
Post by: ptashek on 04 October 2021, 07:56 AM
Success!
Title: Re: Is my AAV in order?
Post by: ptashek on 04 October 2021, 09:10 AM
Right, I've put it all back together, warmed her up and finally got perfect hot idle of 700rpm. Had to back off 3.5 turns of the idle screw, which should give you an idea of how big of a leak the stuck AAV created.
Title: Re: Is my AAV in order?
Post by: Jan S on 04 October 2021, 11:39 AM
Fantastic news, ptashek, congrats! Well done

I'm considering taking the AAV off and checking it, cleaning, etc. this evening ..... how much cooling water comes out? close to zero?
Title: Re: Is my AAV in order?
Post by: ptashek on 04 October 2021, 12:34 PM
Quote from: Jan S on 04 October 2021, 11:39 AM
Fantastic news, ptashek, congrats! Well done

I'm considering taking the AAV off and checking it, cleaning, etc. this evening ..... how much cooling water comes out? close to zero?

None at all. Just make sure the overflow tank cap is off, so there's no pressure in the system. There's a paper gasket too, which technically should be replaced every time. I've used a thin layer of Loctite SI5660 (glycol resistant) with the old gasket and all is good.
Title: Re: Is my AAV in order?
Post by: TNNBENZ on 04 October 2021, 01:27 PM
 Great job ... This will help me also. 
It does seem to me that there should be some sort lubrication needed.  I guess maybe the the parts are not rubbing together.  Any thoughts anyone ???
Title: Re: Is my AAV in order?
Post by: UTn_boy on 04 October 2021, 01:35 PM
No lubrication is necessary.  The oil vapors from the inside of the engine take care of that.  That's also why and how the AAV gets dirty over time.  Especially when oil changes aren't done regularly. 
Title: Re: Is my AAV in order?
Post by: ptashek on 04 October 2021, 01:53 PM
Quote from: UTn_boy on 04 October 2021, 01:35 PM
No lubrication is necessary.  The oil vapors from the inside of the engine take care of that.  That's also why and how the AAV gets dirty over time.  Especially when oil changes aren't done regularly.

On the two I've done today, both had carbonised oil residue on the piston walls preventing it from sliding the full range. And on the 450 oil gets change either once a year, or every 5000 miles, whichever comes first.

Hopefully this will fix it for years to come, but if not next time I'll try ultrasonic cleaning in carb cleaner.

I'm betting there's a limit to how many times the press fit parts will keep their tolerances. It's all aluminium in there.

Title: Re: Is my AAV in order?
Post by: Jan S on 05 October 2021, 01:28 PM
My AAV seems to be working (see pic). Tested it tonight, closed at boiling water temp.

I will do a new test at 60 deg C, because I believe the cooling air thermostat to be fully open all the time, leading to 60 deg C water in that area (I assume).

After the test I will take the AVV apart and clean it.
Title: Re: Is my AAV in order?
Post by: Jan S on 05 October 2021, 02:05 PM
I did a few tests:

Fully closed at 80-85 deg C
2-3 mm opening at 70 deg C
4-5 mm opening at 60 deg C

I suspect my AVV do not fully close due to a shot thermostat. That is next on my to-do list, after I have cleaned the AAV.
Title: Re: Is my AAV in order?
Post by: ptashek on 05 October 2021, 02:12 PM
You have a tiny leak at the very top, going by the pics. Fully closed, there should be no air getting through at all.
Title: Re: Is my AAV in order?
Post by: Jan S on 05 October 2021, 05:19 PM
Really? That is enough to cause trouble? The pics are before cleaning.

I have now cleaned the valve and used glass polish. Testing tomorrow.

In case that 1 mm gap remains, I will try to press the top a tiny bit in direction towards the "piston".
Title: Re: Is my AAV in order?
Post by: rumb on 05 October 2021, 05:51 PM
Quote from: Jan S on 05 October 2021, 05:19 PM
Really? That is enough to cause trouble? The pics are before cleaning.

I have now cleaned the valve and used glass polish. Testing tomorrow.

In case that 1 mm gap remains, I will try to press the top a tiny bit in direction towards the "piston".

When the engine is warm then no air at all should flow thru the AAV.  Extra air would create a lean condition and raise the idle.  Remember that all the players in the CIS system have to be in top shape to all work correctly.
Title: Re: Is my AAV in order?
Post by: daantjie on 06 October 2021, 09:49 AM
Seems like a new batch of these came onto the market, they used to be eye wateringly expensive NOS, now much better on ebay for brand new:

https://www.ebay.com/itm/363334744807?hash=item5498703ae7:g:rGoAAOSwyZVgXZ5i

Title: Re: Is my AAV in order?
Post by: ptashek on 06 October 2021, 10:11 AM
Quote from: daantjie on 06 October 2021, 09:49 AM
Seems like a new batch of these came onto the market, they used to be eye wateringly expensive NOS, now much better on ebay for brand new:

https://www.ebay.com/itm/363334744807?hash=item5498703ae7:g:rGoAAOSwyZVgXZ5i

These are remanufactured, but same difference.
Title: Re: Is my AAV in order?
Post by: Jan S on 06 October 2021, 10:17 AM
Thanks, ptashek, for keeping a close eye on my AVV!

I have now cleaned it, polished it with glass polish and tested it at 85 deg C. See pic.

I consider it fully closed. Agree?
Title: Re: Is my AAV in order?
Post by: ptashek on 06 October 2021, 12:06 PM
Looks pristine :)
Title: Re: Is my AAV in order?
Post by: Jan S on 06 October 2021, 02:58 PM
Thanks, good to know  :)

Installed the AVV tonight. For the first 30 sec the rmps stayed at 1200, then went slowly up to 1500 for 2-3 min and then slowly down to 900 within 10 min.

Probably several issues ... in parallel. First I need to fix the thermostat - it's probably open all the time resulting in approx 60 deg C and an open AVV (approx. 3-4 mm according to test yesterday).

The journey continues  ;)
Title: Re: Is my AAV in order?
Post by: revilla on 06 October 2021, 03:21 PM
Hi, if your thermostat was fully open it would manifest in your temp gage, showing less than 90 degrees.  Is that the case?
Changing it however it's not a bad idea, they are still chreap and quite accessible.
Good luck
Title: Re: Is my AAV in order?
Post by: Jan S on 06 October 2021, 04:42 PM
My normal temp when warm is approx. at the yellow mark.

100 deg F = 38 deg C
137,5 deg F (white mark between 100 and 175) = 59 deg C
175 deg F = 80 deg C

My temp is probably close to 52-55 deg C, maybe up to max 60 deg C, which is WAY TOO COLD.

What is normal temp? 85-90 deg C?
Title: Re: Is my AAV in order?
Post by: daantjie on 06 October 2021, 04:55 PM
"normal" will depend on ambient of course.  87C is what you should get with a 87C thermostat and 20C-ish ambient.
Title: Re: Is my AAV in order?
Post by: Jan S on 06 October 2021, 05:02 PM
Yes, that's the one, with part number A 110 200 05 15.
Title: Re: Is my AAV in order?
Post by: celberg on 08 February 2022, 03:56 PM
What do you think about this? https://aavpart.com/
Title: Re: Is my AAV in order?
Post by: Jan S on 08 February 2022, 05:36 PM
The link leads me to a dead end. Wrong link?
Title: Re: Is my AAV in order?
Post by: rumb on 08 February 2022, 07:40 PM
Quote from: Jan S on 08 February 2022, 05:36 PM
The link leads me to a dead end. Wrong link?

Worked for me.

https://aavpart.com/
Title: Re: Is my AAV in order?
Post by: daantjie on 08 February 2022, 09:04 PM
Quote from: rumb on 08 February 2022, 07:40 PM
Quote from: Jan S on 08 February 2022, 05:36 PM
The link leads me to a dead end. Wrong link?

Worked for me.


https://aavpart.com/
I think the guy also sells on ebay:
https://www.ebay.com/itm/262906084689?fits=Make%3AMercedes-Benz&hash=item3d366c7d51:g:-hYAAOSwstxVba0A
Title: Re: Is my AAV in order?
Post by: ptashek on 09 February 2022, 04:10 AM
Quote from: Jan S on 05 October 2021, 05:19 PM
Really? That is enough to cause trouble? The pics are before cleaning.

In my case that small gap was not allowing hot idle RPM to go below 850(ish) even with the idle screw all-in (at which point the engine should stall).
Title: Re: Is my AAV in order?
Post by: Berggreen on 09 February 2022, 04:42 AM
Quote from: ptashek on 03 October 2021, 03:28 PM
I have a spare from my 350SE, but realised they're a different part number (A0001410825 - 350SE/M116 A0001410525 - 450SE/M117).
The difference being in the size of the air channel as the valve closes, which is considerably smaller on the M116 one, including when it's fully open.
I'm guessing they're definitely not interchangeable?

Hello,

In another thread I created yesterday, I describe a problem with a too high idle (around 1800 rpm) during warm-up, but only when in P for some reason - if I move to D rpms drops down to 700-750 rpm - very puzzling.

In any case, I saw your old thread from last year, where you point out that there are two  different versions of the AAV, and I did change the AAV last year to another used one from Ebay, which has the BOSCH part number: 0280140038 (casted on the AAV housing)

Is that the one for a 350SE/M116 or a 450SE/M117?

I see on Ebay that sellers sell these AAV's as interchangeble between the 350 and 450, and I guess it will still work. But maybe you will then run into problems like I have now, with too high warm-up idle, if you use the wrong one?

Cheers,

Christian
Title: Re: Is my AAV in order?
Post by: Jan S on 09 February 2022, 04:48 AM
Quote from: Jan S on 08 February 2022, 05:36 PM
The link leads me to a dead end. Wrong link?

Works now, my mistake. Sorry.

The AAV is easy to take apart, clean and polish. You can test it in warm water. Should be fully closed at around 75-80 deg C.