Water pump question
 

I am helping my neighbor replace the water pump and short hose on the water pump housing on his 1984 300SD. I got it all back together and I noticed this little washer pn#621 990 03 40 that is supposed to go between the housing and the engine block to make up for the thickness in the gasket. Is this absolutely necessary?

I don't know specifically what you speak of but I would think if its included it must be necessary.

Do you realize that the aluminum housing usually does not need to be removed to change the pump?

Tom W

The 617 engine manual failed to provide any enlightenment on the topic.

I assume the washer came from a parts order and was not on the engine...
Browsing the EPC,I found that the gasket A6162030180 is a direct replacement of the older number A1802030980 on later type om 615,616,617.However,on om 621and early om 615 the replacement of original gasket(A1802030680) needs A6162030180+the washer(or A1802030980 +the washer)
Links to confirm:
http://www.detali.ru/cat/oem_mb2.asp?TP=1&F=115100&M=615%2E912&GA=722%2E107206&GM=716%2E002&CT=M&cat=005&SID=20&SGR=001&SGN=0 1
http://www.detali.ru/cat/oem_mb2.asp?TP=1&F=110116&M=621%2E918&CT=M&cat=020&SID=20&SGR=001&SGN=01
..there is no mention of the A621XXX compensating washer on engines newer than 1968....:
*001 UP TO ENGINE:
910 000002
912 10/50,20/60 000148
912 12/52,22/62 000014
913 10/50,20/60 000020
913 12/52,22/62 000002 (the very beginning of manufacture,some old stock parts used on new w115 models)
you can check this on the epc.
http://www.detali.ru/cat/oem_mb0.asp?TP=1

However,some online parts stores may list this as valid to all om61X models...
http://www.***************/search/product.aspx?sid=axsfht45m2bzy4bmrl3023r0&partnumber=6162030180

IMHO,you really do not need this washer.

Thanks Guys for the input
 

:DI really don't want to do it all over again. My neighbor took it apart and had to go away on a business trip and he wanted to replace the short hose between the pump housing and the thermostat housing which means that the pump housing must be removed for those who have never done it before. I am going to take a chance and run it and see if it leaks.