I will be switching to an external oil cooler and remote oil filter.
When bypassing the factory water/oil cooler, should I plug the hole in the block and in the water pump, or should I reroute the line from block to the pump?
If I reroute block straight to pump, does anyone have part number for the nipple and o ring in the block?
If I block off the hole in engine block, is there a water pump without the output for the cooler?

My guess is more water circulation through the block is better, but not sure if that is taking cooling away from cylinder head?

Looking for input and your experience. Thank you

Have a look at post my post 3 and 6 here. 6 has a diagram, take a screen shot, add your current oil cooler piping using paint then repost it. Or post a pic of your system.

Generally, the lines need to be blocked not connected together as this effectively bypasses the radiator to some extent.

1993 W124 M104 NEED HEATER CORE BYPASS ADVICE.

Seal it off at the block and pump. There isn't a loop in the versions without the oil to water cooler. There is a plug available for the pump like a small freeze plug to block it off. Will likely have to get creative on the block side.

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Thank you guys for your replies. Good to hear I can block them off, will also be bypassing heater for now, and will unplug monovalve and aux pump after reading sl320's link.

I believe I found the plug for block, listed on this diagram as 35, 53 is what is currently installed.

Is there a part number for the water pump freeze type plug? I'm also replacing the water pump so if there is a specific pump with no output for the cooler I'd love to find one

Link to diagram
https://www.ilcats.ru/mercedes/?function=getParts&class=1&catalog=505&aggtype=M&model=103942&group=01&subgroup=015&language=en

https://www.pelicanparts.com/More_Info/103-200-37-01-M52&SuperCat=Y&SVSVSI=3382.htm

It looks like these m103 water pump don't have the resr exit drilled/finished. Will these replace a m104 pump, not just bolt up but flow wise?

Are metal impellers bad on the pumps?

I'm on the run at the moment, can't post much.

There are a bunch of M104 pumps with various ports / temp sender threads. You probably could find something that is what you need.