Air compressor piston design, S212

[Conor]

Hello all,

So my S212 stopped building air pressure for the suspension a while back. Last evening I got around to looking at the compressor. Looks like the ring/seal or whatever slipped off due to wear etc.

It doesn't look like most pistons out there that have a kind of PTFE ring that slides on around it... this one seems to be a very wide and flat o-ring.. It then look like the piston might be two part and use some kind of press fit... i'm wonder about this design and why it's different than the traditional?

In any case, I've just dropped a few quid on Ali Express for a new piston and head.. will see how it goes. It looks like most of the usual sources don't have a rebuild kit for this particular design.

Just curious about other peoples experiences?

 

[Conor]

Right.. another quick update on this.

Apparently this is a new design (obviously!). The wear component is the soft looking seal (again, obvious).

I have pieced together how it is replaced. As shown in the image below, the red marks represents a "press fit" ring that holds the seak (marked blue) in place.

I think you basically cut/scrape out the seal and then use the gap to pry off the press fit ring... then replace seal, and re-install press fit ring.

Not knowing this and also making some mistakes on the (deceptive) AliExpress user interface, I ordered a new head, seal and two o-rings (€43) .. I then went back and ordered a new piston complete with seal (€32) as I wasn't sure that the first order was correct.

If both these arrive (slow boat from China) then i'll have a spare which is handy..

Now, knowing all of this.. I can tell you that you can buy the seal on its own for a simple €14.

-----------

I'm now playing the long game waiting for the items to arrive from China, so in the mean time I think i'll do a bit of a clean up and try and pressure test the remainder of the system.. thinking out loud.. it would be nice if I could introduce some pressure from my workshop air.. and then do the soapy water test.

I have a feeling that there is a leak somewhere, because I have noticed over the last (long!) while that when I sit in car with ignition on, engine off.. I can hear the compressor kick in very frequently.

 

[Conor]

Ok everybody. Quick update. My parts will probably not be here for another while.

But in the mean time I plan on setting up a test rig to check the clean down the system and check for leaks.

My plan is to use my workshop air compressor, regulated to very low pressure. Then connect up directly to the air line that goes into the cars air compressor outlet. I will also connect up the car compressor back up to the electrics so it doesn't throw a fault. I will have the piston/conrod removed from compressor so the motor just spins.

The theory will be that the car will power the compressor, and when I hear it engage I will open the workshop air.. when the compressor stops running I will close workshop air.

In theory the system is now pressurised and the bigs filled to what the car wants. I then just go around with my soapy water.

Hopefully (and i'm 50/50 on this) the compressor doesn't have a pressure sensor in it that triggers a code. Because if it does then this probably wont't work... I suppose a backup is to just discard the compressor idea and just fill the system with air, enough so I see the bag fills.. but not too much as to blow the bags.

Interested to hear if others have done this.

A push fitting like this would be great. I'll keep ye posted.

 

[ajlsl600]

Ok everybody. Quick update. My parts will probably not be here for another while. But in the mean time I plan on setting up a test rig to check the clean down the system and check for leaks. My plan is to use my workshop air compressor, regulated to very low pressure. Then connect up directly to the air line that goes into the cars air compressor outlet. I will also connect up the car compressor back up to the electrics so it doesn't throw a fault. I will have the piston/conrod removed from compressor so the motor just spins. The theory will be that the car will power the compressor, and when I hear it engage I will open the workshop air.. when the compressor stops running I will close workshop air. In theory the system is now pressurised and the bigs filled to what the car wants. I then just go around with my soapy water. Hopefully (and i'm 50/50 on this) the compressor doesn't have a pressure sensor in it that triggers a code. Because if it does then this probably wont't work... I suppose a backup is to just discard the compressor idea and just fill the system with air, enough so I see the bag fills.. but not too much as to blow the bags. Interested to hear if others have done this. A push fitting like this would be great. I'll keep ye posted. View attachment 80720

 

[ajlsl600]

Ok everybody. Quick update. My parts will probably not be here for another while. But in the mean time I plan on setting up a test rig to check the clean down the system and check for leaks. My plan is to use my workshop air compressor, regulated to very low pressure. Then connect up directly to the air line that goes into the cars air compressor outlet. I will also connect up the car compressor back up to the electrics so it doesn't throw a fault. I will have the piston/conrod removed from compressor so the motor just spins. The theory will be that the car will power the compressor, and when I hear it engage I will open the workshop air.. when the compressor stops running I will close workshop air. In theory the system is now pressurised and the bigs filled to what the car wants. I then just go around with my soapy water. Hopefully (and i'm 50/50 on this) the compressor doesn't have a pressure sensor in it that triggers a code. Because if it does then this probably wont't work... I suppose a backup is to just discard the compressor idea and just fill the system with air, enough so I see the bag fills.. but not too much as to blow the bags. Interested to hear if others have done this. A push fitting like this would be great. I'll keep ye posted. View attachment 80720

Ok everybody. Quick update. My parts will probably not be here for another while. But in the mean time I plan on setting up a test rig to check the clean down the system and check for leaks. My plan is to use my workshop air compressor, regulated to very low pressure. Then connect up directly to the air line that goes into the cars air compressor outlet. I will also connect up the car compressor back up to the electrics so it doesn't throw a fault. I will have the piston/conrod removed from compressor so the motor just spins. The theory will be that the car will power the compressor, and when I hear it engage I will open the workshop air.. when the compressor stops running I will close workshop air. In theory the system is now pressurised and the bigs filled to what the car wants. I then just go around with my soapy water. Hopefully (and i'm 50/50 on this) the compressor doesn't have a pressure sensor in it that triggers a code. Because if it does then this probably wont't work... I suppose a backup is to just discard the compressor idea and just fill the system with air, enough so I see the bag fills.. but not too much as to blow the bags. Interested to hear if others have done this. A push fitting like this would be great. I'll keep ye posted. View attachment 80720

 

[ajlsl600]

Used to be outfit called oil seals and bearings a number of such places can do those kind of seals if dealer not able

 

[Conor]

Used to be outfit called oil seals and bearings a number of such places can do those kind of seals if dealer not able

Interesting thanks.

I suppose it shouldn't be difficult really just take the various measurements and off you.

Also.. Question for people on here:

I've heard from a couple of people in the past and most recently a person in parts department was saying that rebuilding the compressors was a waste of time and would give you nothing but trouble..

But my question is this.... if it's such a crap idea then how come people successfully replace piston rings in engines all the time to solve compression issues? I mean, it is literally the same principle really.. And also, why is there a core charge on these things? I would assume that they go back to get rebuilt (albeit professionally).

I am guessing the parts guy just wants to sell new compressors and the other guys, perhaps there was a fault elsewhere in the system too?

I trust and respect the friends who told me that but I genuinely don't understand where a rebuild can go wrong (assuming done properly).

 

[malcolm E53 AMG]

Or, you could buy this:

Pardon our interruption...

www.ebay.co.uk

 

[ajlsl600]

Rather depends on correct dia seal and bore condition, also there likely some one way valves that in. My experience often fail. Find a schematic of ur particular compressor.

 

[MJJ]

I've heard from a couple of people in the past and most recently a person in parts department was saying that rebuilding the compressors was a waste of time and would give you nothing but trouble..

I have no S212 experience, but I replaced the compressor piston ring on my S211 about 6 months ago courtesy of the excellent kit and instructions that Bagpiping Andy does.

As long as the work is done without introducing dirt into the piston bore, there is no reason why it won't last many more years. What I would say though, from experience on my S211, is that the compressor will cope with small leaks for a long time without throwing any sort of fault code nor warning. This means that the compressor wearing out may well be a symptom of a leaking system elsewhere. In my case, one of the suspension airbags leaked and was replaced 18 months ago, and the compressor took another 12 months before ultimately operating poorly enough for me to be aware.

Martin.

 

[Snake Charmer]

i'm wonder about this design and why it's different than the traditional?

The compressor is known as a "Wobl" type and runs without any lubrication to produce clean oil free air. The piston moves in a figure 8 within the bore and the seal flexes under pressure as the bore shape changes from round to elliptical through the stroke.

 

[malcolm E53 AMG]

One thing I did notice about this type of pump is that it’s very noisy from new until it beds in which could be up to a years motoring for some and when run in it’s hardly noticeable when it kicks in

 

[mersum1es]

I have repaired to compressors, both still working. Other I replaced only piston ring, second I also changed cylinder head part because I could sense the edge where upper dead center of piston ring were. Of course I dried silica beads and changed rubber seals.

 

[rf065]

Could this guy have helped rather than getting bits from China?

https://www.bagpipingandy.com/

 

[Conor]

Oh yea I opened up the pod with Silica and will give them a blast in the oven before refitting.

I actually spoke to Bag Piping Andy and he doesn't do anything for the S212 as it's a different design.

 

[Conor]

So I replaced this seal 4k miles ago and it seems to have worn out prematurely.

I guess te material was low quality. I'm trying to figure out what went wrong here. Was it simply a low quality material.

As an aside. When I ordered the piston seal, I ordered a new piston also by mistake. We fitted that piston last evening and it hardly runs.. its like it's jammed in the system.

For the moment, I have ordered a new compressor fron Aerosus as I need this car.

It's annoying as I just got back to London and don't have any tools etc as my workshop and lift are now based in Ireland...

 

[ajlsl600]

Looks another crxp dtf design wud be interesting to know output required there are lots of compressors about maybe blanking it off and fitting electric compressor is option

 

[Snake Charmer]

Looks another crxp dtf design wud be interesting to know output required there are lots of compressors about maybe blanking it off and fitting electric compressor is option

It is electric and the design has proven itself reliable over many years.

 

[ajlsl600]

It is electric and the design has proven itself reliable over many years.

Sorry bud that piston is too small in depth and will be loading the seal as piston tips in the bore under load , that's not a design for longivity. I wud say design is more about install space, or lack of it. Think modern racing pistons, reduces reciprocating weight/ facilitates higher rpm But don't last long.

 

[Snake Charmer]

Sorry bud that piston is too small in depth and will be loading the seal as piston tips in the bore under load , that's not a design for longivity. I wud say design is more about install space, or lack of it. Think modern racing pistons, reduces reciprocating weight/ facilitates higher rpm But don't last long.

The piston has to tip being part of the connecting rod, only the seal has contact with the bore. I regularly saw 60,000+ hours on twin cylinder Thomas Wob-l type compressors in oxygen concentrators. They are used widely in systems that require oil free compressed air such as medical equipment and suspension systems.