We have retrofitted hundreds of MBs and many 240Ds. We have been running our shop 280TE with 134a refrigerant for 7-8 years with no problems. We changed to a rotary Seltec compressor at the time and its been a workhorse ever since.
The R4 compressor seems to take the addition load OK, but unless you are doing major repairs there is no reason to change refrigerants. We have had many conversions that had compressor leaks within two years when the compressor wasn't replaced.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician
[This message has been edited by Webmaster (edited 03-14-2000).]