ZF 220A Continued Low Oil Pressure

[Scott A]

Replaced pump, replace oil cooler, replaced vent/pressure valve, cleaned oil screen, used wire to ensure oil pickups in screen housing were not clogged, ensured trolling valve and gear levers all in correct position, pulled spool valve (pics below), changed oil to use Rotella T4 Triple Protection (ZF says acceptable), replaced oil pressure sending unit (same reading). No leak present at shaft coupler. There does appear to be a leak beneath the valve housing from a bolt/plug on the underneath side. (Last picture) There is no other apparent leak above that from the spool valve or the pump or oil cooling lines. The leak does not appear after a short run, it only seems to get wet after it sits.

What’s next, pull the gear and take it apart? Is this a leak at the clutch seal or what? Anything else I am missing at this point short of pulling the gear? Could it be in the guage itself, should I try a manual pressure gauge first?

Pressure is reading about 280 psi at 1500 rpm and at cruise. The pressure sending unit is on the starboard side of the gear next to the trolling valve.

Topic

[Scott A]

Two shots, one from above and one from behind. It is in the position 11, high pressure gauge connection port.

[Tony Athens]

Post a good picture(s) of exactly what “place” / port you are referring to.. NOT too close up..

[Scott A]

Tony, reading through the SBMAR website, I am starting to think that when they installed the pressure sensor on the trolling valve housing, it looks like the shop that installed it may have used an NPT fitting instead of a G or BSPP fitting. The fitting does not screw down tight – or at least I am apprehensive to do so based on the way it looks and feels as I am screwing it in place. I put some thread tape on it before I stuck it back in after changing the pressure sender. It had thread tape on it originally – which I don’t think it should need if it is a G or BSPP fitting, right? I do not see any fluid leaking from it after running. Shouldn’t a G or BSPP fitting have a o-ring washer on it?

[Scott A]

Will check it again this weekend with liquid gauge. Ran it after changing piston rings. One of the piston rings on the forward shaft came apart during removal of the trolling valve block. The others were pretty warn. Once everything was replaced, I thought I might have it fixed. But no such luck. Initially, it ran up to 330 psi, then started dropping. Once warm, it would raise up to about 300 psi, then suddenly drop to 250 psi… then in three or four seconds it would rise back up to 300 psi and as soon as it got there it would drop back down. I have already replace the pressure valve. The pressure gauge is presently located on the trolling valve. Also, looks like I’ll need an adapter if the liquid gauge is 1/4″ NPT male, I will need to reduce it down to a 1/8″ G male fitting, correct? Could the trolling valve be malfunctioning as the pressure rises in the gear?

[Tony Athens]

Measured the ID of the spool valve bore & OD of the spool itself? The tolernce is under .002″ clearance.

Have ypu checked all with an accurate liquid filled 0-600 PSI mechanical gauge? Chect it on on the line coming from the pump before the cooler.Post a good picture of when you do it.

[Author]

Replies