D jet Aux Air Valve refurb ( AAV )

[Tony66_au]

This is a copy n paste from the thread I created on another forum.

Hope it is helpful.

I've recently had a shot at refurbishing my AAV for my D jet 450, The AAV is common to the 280/350/450 M116/M117 in both D and K jet and I believe the AAV's themselves are the same.

So I've collected up my ramblings and pics and im placing them here as an easily searchable resource.

Feel free to add your 2 cents worth and correct me if im wrong.

Cheers,
Tony

[Tony66_au]

THE TESTING!

One x Pyrex high temp glass jug

One x Meat thermometer

Boiling water, add AAV to taste.

[Tony66_au]

The method is simple, fill glass jug to 75% with boiling water, place thermostat in jug and check temp.



Place AAV in hot water making sure to NOT get the insides wet.

Using the torch check the progress of the slide.

[Tony66_au]

A few traps to observe, I am told the valve should not allow air to pass @ 66 Celsius.

This usually means putting your lips to the AAV and sucking or blowing,

Problem #1 is that the AAV is currently at or around 80 Celsius so I liberated the short air hose and left it on the unit .

Problem #2 is more of a cautionary note as your AAV is likely still contaminated with brake cleaner or degreaser which is toxic at normal temps and very much so at near the boiling point of water so resist the urge to suck test the valve.

Sadly my valve didnt seal shut as the picture has shown so my next task is to pinch the bulb in the bottom of the AAV and retest in hot water which im told works "Sometimes".

The bulb is a bugger to squish even a little bit BTW

[Tony66_au]

 Testing phase over we go to cleaning the AAV

  Ok, this after noon I removed my AAV for testing Pn# 0280140017.

2 x 4mm hex screws held it in place and when she popped out of the jacket I lost half a cup of coolant and no more.

I gave her a quick squirt of brake cleaner to get rid of any grunge on the outside and wiped the bulb on the bottom clean so it was ready for testing.

I noted that the bulb has -30 celcius stamped on the bottom, any idea what that's about?

Anyway, with a kettle full of boiled water, a pyrex jug and my thermocouple and multimeter telling me the temp was @ 90 degree's I immersed the bulb and base of the AAV in the water and watched the slide to see if it closed by blowing down the outlet.

Yes the slide moved to almost closed but air still freely passed through the valve even though it was now too hot to hold in my hands.   
  So the unit is faulty and slow to move.

Next step meant back to the bench where I had a few cans of brake cleaner and some parts wash along with an empty 5 lt oil bottle with the side completely cut out.
I usually try for a nice bright colour but today all I had was a grey bottle as the colour helps to show how much crap is being washed out of the part you are cleaning and I wasn't disappointed with a fair amount of fine black dust washing out into the oil container.

BTW I alternated between the cheapy degreaser @ $2 a can and the brake cleaner to get good results with a bit of a soak.

Why? Because brake cleaner evaporates quickly and degreaser does not.

Ive also used a trans fluid 1 lt bottle to soak the AAV fully immersed in parts wash fluid and tomorrow after a blast out with brake cleaner and then compressed air I will test the closing and speed again before going to step 2.
  Day 3 and more soaking overnight, I removed the AAV from the wash and gave it another blast of brake cleaner washing out a substantial amount of  fine black grit before dropping the valve back into the wash, tomorrow I give it a final clean with brake cleaner and leave it to dry before another 80 celcius dunk test, if that fails to close the valve all the way I will try pinching the bulb in the vice or with vice grips to see if that method works and retest again!

Tony

[Tony66_au]

 The semi finished product, back to testing the unit!

 

 
  Finished soaking the AAV a few hours ago and well and truly blasted out the unit with brake cleaner so there is nothing but cleaner coming out of the unit now.

Uploading a few piccies I took as I type this and I will post them shortly. [/t][/t]   
The Aux air valve after cleaning.

[Tony66_au]

And a quick M117 D jet mug shot!


Excuse the grubbiness

[Tony66_au]

A reliable source (MBGraham) tells me a new AAV should be fully closed @ 66 Celsius and Ive edited my posts to reflect the correct temp.

I've pinched the bulb twice now with vice grips adjusting them up half a turn and closing them, opening them and repeating @ half a turn.

The result is that at 80 degree's the AAV is almost shut with a fair restriction when I blow through the valve.

So its back to pinching the bulb but this time im shooting for a lower closing temp of 66 - 70 Celsius......

Tony

This evening late I reinstalled the AAV using sensor safe copper maxx hi temp silicone and a new graphite gasket I cut from a sheet of gasket paper.

Topped the coolant off with 500 ml or so and turned the key.

I noticed the temp graduation on the guage is in 20 Celsius increments and just in the 60 degree mark the high idle started to come down until at a needles width past the 60 mark she settled for a nice resting RPM rate.

Test run minus air cleaner assy fitted and without the sensor in the air cleaner assy attached, Idle tested with AC on in neutral, park, drive and reverse and its all solid although probably a smidge low loaded up.

Checked the idle screw and it has been screwed fully clockwise already so I cant lower the idle there anymore and turning it anti clockwise raises the idle speed so I suspect the system is out of whack somewhere probably during an attempt to drop the idle before I got the car.

All in all a good result!

I should pull a dud AAV apart some time I guess but my understanding of how it works is that the brass bulb that sits in the coolant has oil in it that expands with increase in temp and this pushes the piston up in the bore of the valve reducing the air flow.

I suspect the spring just keeps the piston square in the bore so it is less likely to jam and to aides in the return of the piston to fully open as the coolant drops in temp and that this expanding oil or fluid weeps past over time making the reaction to heat slower and less effective.

So the simple action of crushing the bulbs a bit restores the static pressure to what it should be to operate effectively.

This is further backed up by the pictures I've seen of factory refurbished AAV's having 4 neat uniform indents on the bulbs.

The refurb is fairly simple and cost me 5 cans of Repco degreaser and a full can of brake cleaner so under $30 and maybe 3 hours over 4 or 5 days once the AAV is removed with an hour of static testing with a jug and hot water.

[scraf]

Hope it is helpful.

Tony

VERY helpful ! ( although had already read this at the other source, just wasn't registered to comment )

Scored an AAV a couple of days ago, travelled 40km not to buy a rusted out headlight for my W114, while I was there I extracted the AAV for the grand sum of € 10,-.

It's exactly the same one as you've documented ( D-Jet ? ), but as far as I can tell it will only need a change of pipes and it will fit on my 450 SEL K-Jet.

The AAV closes completely when tested in boiled water, am going to invest in a meat thermometer tomorrow to see if I need to do any bulb squeezing to get it to the 66 degree optimal.

MANY thanks.

[Tony66_au]

My pleasure Scraf, D jets are perceived as a black art to maintain and repair and im buggered if I know why because they are far closer to modern EFI than bloody K jet is lol.

Id also like to add that these AAV's are fairly substantial as a heatsink and as most kettles dont actually bring water to 100 Celsius id consider microwaving the water, dunking the AAV base in the water until it heats up and then checking and possibly reheating the water again as it does drop in temp significantly.

Also I have conflicting reports on the closed temperature of the AAV when functional and my theory is that some may open for different temps due to climate variations in the marketplace in the same manner as Mercedes have tropical spec cars etc.

That said 66 degrees Celsius seems a good middle ground for D jet cars operating outside the Arctic circle.

[Tony66_au]

Im flicking through my photos from the refurb looking for a pic of the AAV fully closed showing the slot that remains open to allow air to flow through at a greatly reduced rate.

But here's one clearly showing the temp 66 Celsius = 150 Fahrenheit

[Tony66_au]

Here tis!

After refurb, yes the temp is higher than 66/150 as it was before I squished the bulb to bring the wax pressure back to near normal.

Note the slot at the top of the slide piston allowing air to pass although fully closed.

K jet AAV's I have played with seal off completely.

[thysonsacclaim]

Excellent post!

[Tony66_au]

Bumpitty bump!

Might be worth making this thread sticky?

[TJ 450]

I concur with that.

Tim