ZLS / AAV repair part on ebay

Hello Volker and all. This seller has what he describes as direct fit replacement part for the ZLS. I saw from your repair write-up that available replacement parts were not the right size to fit the holder ring. But perhaps this one is different?
I'd appreciate your thoughts.
m.ebay.com/itm?itemId=261933548138
I've not worked with my BMW for a while, but with spring here, it's time...
Regards,
Paul

Also, here is a US Benz forum post on disassembling a ZLS. Simply taps apart using a piece of pipe. I remember you talked about using a special puller to disassemble. Do you think the approach here would cause damage? It seemed to go well. (If you don't see the pictures in that post try clicking on icons.) www.benzworld.org/forums/r-c107-sl-slc-c...age=3&postid=4764787

Hi Paul,

I cannot comment on the AAV element offered on eBay. It looks like it could fit the old holder. Before I comment on the holder: I do not know what thermal characteristics their element has. Bosch sells one here that is the new element with the correct characteristics.

I can also not read the instructions how to replace on ebay. But I can tell you that it is difficult to pull the AAV open. This is due to a non sealed fitting between holder and housing. Several people have destroyed their housing and that is the end of the story. The housing is cast aluminum and breaks easily. If you manage to pull out the holder you still would have to open that holder, insert the new element plus a fitting rubber (the old one is mostly hard as a stone) and finally close it, if still possible. The technology to do so is a seal curling (German: Bördeln, not too sure I have the right English word here). Normally the holder is broken when you open it. I replace it with a new part that also fits the new Bosch thermostat element. I consider it a sloppy sale if you just sell a thermo element for the repair of an AAV. That is why I only do complete overhauls. And if I were in their position I would offer at least the complete new holder including the expansion element and new rubber sealing, newly seal curled.

Now to the US MB technology. They open by hammering on the top part to drive out the bottom expansion holder. I have written earlier that I see this critical. The upper part is a sleeve with an orifice plate and an air inlet pipe. The sleeve is maybe 1 mm thick in aluminum. Inside of it a piston glides up and down against a spring. Guess what happens if you put too much force on this sleeve? It will be forged and bend a little. That is enough for the piston to not freely glide any more. And then you have a non-functioning AAV even with a new thermostat element.

That is why I always pull out from the bottom and replace more than just the thermostat element. And knowing how difficult it is to pull out the old holder without doing harm to the rest plus how to readjust after reassembly, I do not even think of offering a repair kit. Recently someone contacted me who had cracked his AAV when he tightened his AAV in the car. Unfortunately I do not have that picture any more. BTW Bosch offers new MB AAVs that look somewhat different. Maybe they will also do BMW AAVs one day.

My experience with BMW AAVs: I had two that were broken beyond repair. And that was because the piston was stuck in the upper sleeve. Could be that someone tried to repair by the hammer opening method. Even when I finally managed to get the piston out, it wouldn't glide inside the sleeve even after cleaning and polishing.

Here is a picture of the sleeve, then you will understand how bad the idea is to hammer it downwards from above.

Thank you Volker. Very informative.
I wrote the eBay seller in Norway and got this reply:

"Initially there may be slight differences in the temperature range of different cars. This part is designed to close a little earlier than originally. Because it is good for a classic car to have shorter time with high idle.
When the engine is cold AAVpart is full open. AAVpart is starting to close at 30 degrees celsius. It is fully closed at 50 degrees celsius.
Along with the AAV-part element is attached a complete disassembly-, and assembly instruction guide. "

So closes more rapidly than original. I suppose the result could be a short period of rough idle?

I got restless and decided to try tapping apart a spare unit I had. I applied PBblaster, waited, then tapped, not hard, on bottom using aluminum pipe. It worked OK. And after cleanup, piston slides smoothly. But now I see how it is built, I'll use a puller if do again...

Hi Paul,

a statement of "It starts to open at 30°C and is closed at 50°C" is definitely wrong or hints that this is an element with a much faster moving curve. The real element moves from -20°C to +100°C and AAV is adjusted to close at 70°C. It seems that he sells elements with wrong characteristics or he does not know better. Arguments that this is even better for old cars are simply bullshit to justify sales.