I also agree that it does not sound internal. Something is loose and perhaps an exhaust leak, which can sound like a knock. You need to find someone in your area to look at it. I love the idea of going to a rental place to find someone .... Never thought of that before.
Dawn soap and hot water work fine for degreasing. The 642 I bought had about 6 inches of oily crap in the bottom including the engine area. Took me about 6 hours to get it presentable enough to find the bottom. From there used hose and many brushes to finish it up. It also had 2 leaking...
I have the non-B 642... It has the ford 4 cylinder engine. Glad too, as the ford is dead simple and I have no experience with diesel engines.
I would check your wiring. IMHO there is no way a water pump should cause an oil pressure issue. Simple things first.
Same as you, none of the usual places have any stock. Might have to find another sender/gauge combo and replace both.... Do you have a pressure gauge, or idiot light? I just replaced my 2 wire sender for my 642 which feeds a light. That sender is still available.... 6631695
I may have misunderstood this. Is this the oil pressure sensor for the motor, or the hydraulics pressure sender? If for the motor, what motor is in the 731?
I just checked my 642 and the distributor vacuum advance hooks to a fitting at the top part of the intake manifold. Right by the larger hose. I hope this helps
I have a 642 with the ford motor. The only vacuum line goes to the vacuum advance on the distributor. Can't recall where it connects to the motor, but can check when I get back home...