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Discussion Starter #1 (Edited)
Since aftermarket S38 water pumps are almost NLA and the OEM is 400 EUR, I searched for a solution to rebuild my old S38 pump.

I read somewhere that the M30 pump can be a direct replacement. THAT IS NOT TRUE! THE M30 WATER PUMP HAS A DIFFERENT HOUSING AND DOES NOT FIT THE S38B36 & S38B38 ! The hose connection is at the wrong angle and the wrong diameter.

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But..... they are similar in someway....

since I bought the M30 pump for only 40eur (aftermarket Airtex pump), I disassembled both S38 and M30 pumps to compare the internals. The shaft with integrated bearing is the same, the impeller is the same. The hubs are slightly different and the housings are different.

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So I made a fully functional rebuilt S38 pump from the two of them.

End product:
  • S38 housing
  • S38 hub
  • M30 shaft/bearing
  • seal from the new M30 pump
  • S38 or M30 impeller
Procedure:
- press off the hub (on the old s38 pump it was seized - I drilled a hole into the shaft to ease the pressure)
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- remove the spline underneath that holds the bearing in the housing (aftermarket pump did not have this)
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- press out the shaft and bearing in the direction towards where the hub was, let the impeller seat on the housing
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- press out the seal towards where the impeller was
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Installation in reverse order.

There are no pins holding the hub or impeller onto the shaft! Everything is press-fit!

Here are the shaft with integrated bearing dimensions

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Final result + 350eur saved in my pocket. Cheers!
 

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Nice bit of work. I'm interested in how you dealt with the seal - isn't is pressed onto shaft and housing? How did you manage to install it and still maintain the cartridge seal faces?
 

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Discussion Starter #4 (Edited)
The seal has a metal jacket on the outer diameter as well as on the inner diameter. It is also press fit, but very lightly. The outer diameter is even being held in with blue loctite. No problems when pressing it out. Just clean the old loctite and add new.
 

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Great, thanks.
What I was getting at with those unitised cartridges is that they have two faces, the static one connected to the housing edge, and the dynamic one attached to the shaft. When they are installed at the pump supplier this is a finely controlled process to ensure that the bearing assembly and the seal all go into the housing at the same time, and with tuned machine press parameters.
The risk being that fitting one side or other first might put the seal faces either in two hard a contact (very small traces of coolant lubricate the faces,) or too far apart (leak).
I hope it works out for you - might be worth doing a static pressure check before you deck the engine to be sure.
Cheers, and all the best.
 

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Discussion Starter #6
The seal has a metal spring between the cartridges. When you press on the impeller, it contacts with the inner cartridge of the seal and with that pressing together the spring. This makes additional pressure between the inner cartridge and the shaft.
 

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I did this mod once a few years ago too. Using an aftermarket M30 pump was the only option I had. As you say, It was very easy to do - however as uk_bm implies above, I did have sealing issues. It worked fine for a period but the seal started to weep after a while.
 
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