Topic: D jet Aux Air Valve refurb ( AAV )

[djenka018]

As a further confirmation of previous statement:

Mercedes D-Jet EFI training manual dated back to early 70's commands that AAV has to be fully open @ -20*C and fully shut at 65*C (149*F).




https://www.dropbox.com/s/vix6tag56l0btyr/2013-09-15%2013.12.46.jpg

[Tony66_au]

Ta for the clarification djenka,

I have come to realise that the AAV seems to cause an awful lot of issues when not maintained and even more issues when people try to work around it re idle RPM.

Such a simple fix too!

As a further confirmation of previous statement:

Mercedes D-Jet EFI training manual dated back to early 70's commands that AAV has to be fully open @ -20*C and fully shut at 65*C (149*F).




https://www.dropbox.com/s/vix6tag56l0btyr/2013-09-15%2013.12.46.jpg

[djenka018]

Ta for the clarification djenka,

I have come to realise that the AAV seems to cause an awful lot of issues when not maintained and even more issues when people try to work around it re idle RPM.

Such a simple fix too!

As a further confirmation of previous statement:

Mercedes D-Jet EFI training manual dated back to early 70's commands that AAV has to be fully open @ -20*C and fully shut at 65*C (149*F).




https://www.dropbox.com/s/vix6tag56l0btyr/2013-09-15%2013.12.46.jpg

I mean to scan this training manual and post it here.
It is solid gold in terms of understanding the D-Jet engine management. Most of it is documented in country specific (or properly named: national version) printed manuals but some of them are not readily available.

[Tony66_au]

worth scanning for sure.

Once understood the system is quite simple

[1974450SEL]

Tony,
    This is a great write up.  After 8 years of a surging idle (till it warms up) I've decided to take on this challenge.  I've successfully removed the AAV, minus one broken Y house (I just ordered new AAV hoses from Pelican parts).  I'll have to find replacement screws since I (feeling so good about uninstalling it) misplaced them.  Thanks for posting this and I'll keep my progress posted.

Brian

Portland Maine

[Tony66_au]

My pleasure Brian,

One of the most commonly neglected service items sadly and little info out there for a simple refurbishment plus brand new D jet AAV's are hard to come by and K jet AAV's are expensive.

Good luck and keep us posted on the results.

Cheers,
Tony

[1974450SEL]

Tony,
   Well a week into the adventure, I've followed just about all steps and have the valve to the "nearly" closed position  while is boiling water as shown in your last photo but air still passes through.  I have it soaking in Trans fluid tonight.  Previously have used degreaser and brake parts cleaner and have had some black gunk come out.  I've tried squeezing the bulb and it is a S.O.B.  I reread your write up and see you've used vice grips, I've been using just needle nose pliers.  I'll keep you posted about tomorrow's results.  I've not had access to a thermo but can borrow one from my mother n law. 

[Tony66_au]

A few points
meat thermo is under 10 bucks and will make your Thanksgivings day safer too!

The AAV's dont close off completely especially the K jet units

Dunno about the trans fluid soak, Parts cleaner is cheaper.

And yep you will get trace amounts of carbon from the AAV for a few cleans which was why I usually flushed em out with brake or carby cleaner into a white container so I could see how much carbon was left.

AAV should be shut at the temp mentioned above (Air will still pass through though) and no need to nip the bulb unless its not closed at 60 ish (150f )

[1974450SEL]

Well,  after the soak and a shot of degreaser and brake cleaner it does fully close now at the proper temperature. It is good to now air will still pass through, that had me worried.  Now on to installation, I have found one screw underneath the car with a long magnetic tool (best purchase next to meat thermo) I can go to the hardware store and try to find a 2nd screw to match.  Keep you posted on how she runs.  Thanks again!!
 

[Tony66_au]

Once again my pleasure,
I am currently working on a better tutorial to add the info people have clarified and corrected for me and I have a few other D jet tricks I have yet to document and verify.
I am not a mechanic by any means and my approach to repair can be a bit slap dash and half arsed however working with my German toys I have found that it is always best to do it right and with solid information on the project at hand.
I also believe that if you give Bosch GMBH a wheelbarrow load of cash they will refurbish and return your AAV in an as new state as well as MPS's etc and if you are happy to spend some money and wait a month or so id recommend you take this path if your own attempts at a refurb are not to your expectations as not all AAV's come up 100%.

Finally id like to add some observations on common issues and their effects with the main issue being air bleed idle screw fiddling NOT being a cure or work around for a Dud AAV and as im currently finding with a D jet 350SE removal of the cold start system causes more problems than it allegedly "Fixes".

As mentioned elsewhere the whack it with a hammer "Fix" is for the larger K jet AAV's and finally ignoring the idle RPM must do horrible things on a cold start as the RPM I have seen was in excess of 2000 rpm AND on 2 of the cars I have seen decidedly groaning torque convertors which I found to be broken vanes in one instance being a bit under 50% and id hate to see what the damage to the clutch packs are.

All in all folks?

Fix it.

[atatexan]

I am following this thread with great interest. My Austrian 350SE, a US resident since 1984, has a rebuilt/returned AAV (by Peach Parts CA subcontractor). It still surges at idle when cold. I can't see that it moves at all!

Am staying tuned to this thread.

[Tony66_au]

Sounds like it may be a TPS or Vac leak somewhere.

Read this thread for a better understanding of D jet, its piss easy to understand.


http://forum.w116.org/mechanicals/how-it-worksbasics-of-the-d-jet-injection-system/

[atatexan]

Hopefully not the TPS. Bought new foil piece from a guy on the Porsche 914 forum.

If I used the throttle after a cold start to override the surging, idle levels out after 3-5 minutes.

Thank you for the quick reply from Oz.

[Tony66_au]

Not a problem and i hope it helps!

[WGB]

This is an old photo that I posted many years ago when I purchased a new K-Jet AAV valve for my 1979 450SEL.

It suffered from a slowly decreasing idle on a very hot day when run up in the hills and would not idle at all after being parked with a hot motor but was fine when cool but with a slightly erratic idle.



This must be one of the last AAV's sold new and shows new and old in the same cup of water.

The K-jet type is a straight through from side to side configuration while the d-jet comes out the top via an elbow in the casting.

Bill