Potential Vacuum Modulator Diaphram needs replacement. Part number ?

[Paul99]

My 230 1966 Auto is smoking on tickover and gearleaver shifting.  i have had all the valve stem seals replaced, but still the same issue. 
 Plug 6 is also fouled and I have lost some auto box oil.  I found a previous forum entry that suggested replacement/checking of the Vacuum Modulator Diaphram which my be leaking and causing the issue.

Anyone know the part number or availability please?

[ja17]

Hello Paul,

Yes it sounds like you may have a bad modulator diaphragm. You will notice some trans fluid missing. You may also see traces of red automatic transmission fluid in the fitting connecting the transmission vacuum line to the intake manifold. The diaphragm part # is 112 270 00 79.  They were out of stock for a while. Hopefully they are available again.

[rgafitanu@gmail.com]

I got it from eBay and they still have it. Search for "Auto Trans Modulator Valve Mercedes 280SE", I don't know how to insert that here.
Radu

[Paul99]

Thanks Joe.  Managed to find one from a Mercedes classic dealer in Poole. Cost around £25 which is great.

Did look at taking off the copper pipe at the inlet manifold end but didn't see any oil. Would it be very visible and obviousl?  Could be just a coincidence with the symptoms. But for that cost to replace might do it anyway.   

I will do a compression test as well on all 6 clys just in case. 

Shame as the car runs so well just very embarrassing when you start or move off and a cloud of smoke is seen.

Paul .

[rgafitanu@gmail.com]

You may not see oil at the intake manifold connection. Under acceleration the vacuum from the intake will suck oil from the transmission through the pierced diaphragm which will flow to the lowest cylinder (6). I had exactly the same symptoms. It took me 15 minutes to change the diaphragm but you will have to get under the car or lift it.
Radu

[ja17]

Yes it could be a coincidence on the #6 cylinder. However the alternatives are far worse. Next possibility would be a loose intake valve or seal on #6 or a damaged piston ring. You will either be consuming ATF or engine oil depending on the problem. Low compression may not happen right a way, even if it is an engine problem.

[Paul99]

Checked the compression all around 9 to 11 bar.   

When I replace the diaphragm will the gear box oil pour out?  Or is it just a quick replacement?


Many thanks for the help and info etc.

[ja17]

No, the fluid will not drain out.