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1973 280SE not holding idle at cold start

Started by yxi, 24 November 2014, 09:41 AM

yxi

So I got the AAV out, have soaked it in diesel for many hours, shaked it, rattled it and so on. Tried boiling it, freezing it, it still looks stuck in same position. I even tried to put a screwdriver into the top hole and hit it with a hammer a couple of times, but nothing happened. I is now resting again, soaked and drowned in WD40 until tomorrow. Here is how it looks now.





So help me understand please. Am I correct assuming this:



The green arrow is the spring, pushing downwards in the arrow direction. The red is kind of a piston, and the blue is something that is pushing the red upwards against the spring, depending of temprerature of the thermostat. When cold, red and blue is at the bottom, opening up the hole so air passes by. When warm, blue is expanded and red closes the hole.

Did I get it right? If so, my theory is that the red piston is corroded and stuck. Would it be right, after a night of WD40 soaking, to do this setup with maybe a little more effort to try to get it loose?




I might be totally out swimming in deep waters here, so it would be great to get how it works from someone how knows it, not just guessing like I do :)

daantjie

Yup, most definitely seized closed.

Honestly, if I were you, bite the bullet and buy a new one if you can find it.  They are very pricey, but if you intend to keep the car, why not?

To me, fooling around with lubes and such to try and get it to former glory is a waste of time, it will never work as well as a new one.

Just my 2c.
Daniel
1977 450 SEL 6.9 - Astralsilber

revilla

after a quick search google returned this piece. 

https://www.youtube.com/watch?v=aZBGpX9hETc

it will show you how it works.  not sure about the method used to repair, but if avv is stuck closed and it is NLA, it could be an option.... (?)

good luck

yxi

That is not the same unit, but i guess the basics are the same.

I found this one, i think i will go this route, it looks pretty straight forward.

http://forum.w116.org/mechanicals/succesful-aux-air-valve-repair-on-m110-983-engine/

As i understand a new one is NLA(?), and a used one is like $300-500 (and who knows the condition of a used one), so i think it is worth the effort to try to save the one i have if it can be done.

beagle2022

I got a good used one from MB Spares in Canberra (Australia) for about $100 a year ago.  They were really helpful, tested it before sending and were all round good guys.  If you are in North America check it out as the Aussie $ has just tanked against the US.
Sydney, Australia

yxi

#20
Thanks for the tip, will remember that in case my solution won't work out.

After soaking it in WD40 over the night, i tested freeze and boil, no movement at all. I now managed to move the "piston" a bit by hitting it with the hammer setup i pictured earlier, but it was obvious that it would never going to function properly at all without opening it and clean/sand all the parts.
So that is what i have now done by using wacotechs method. It was a little tricky to get it separated but it came apart in the end. Now everything is clean, without any corrosion, and moving freely. Tested functionality hot/cold, looking good. Only thing left is to assemble it and close it with some strong epoxy.

yxi

AAV reassembled and tested. Looks like it is functioning very good.

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