MF50b bubbles

Hi all, I'm new to this forum. I have an old MF50b which is an absolute workhorse of a machine. It's the same age as me! (41). But recently it has started getting air in the hydraulic fluid. Now I've had a couple of leaks on the rams so I've repaired these but the air bubbles in the sight-tube on the side of the tank just keep on coming thick and fast. Sometimes it even froths out of the filler cap! Now I've also had a problem where the 2" suction hose underneath from the filter housing got squashed so I replaced it. But I'm now thinking that it may have disturbed the "seal" between the filter housing and the tank. I say "seal" in commas as it looks like the previous owner just filled the gap with silicone gasket. I' haven't checked this area yet as I'm working offshore at the moment but does this sound like a reasonable thing to check when I'm home? If so does anyone know where I can get (in the uk) a proper replacement seal for this? One other quick question, I've got new fan belts but I don't know how to get them on as there is a shaft from the drive pulley to the hydraulic pump preventing me from slipping the belts on. Any ideas how it's done?

Welcome mibazza!

Sounds like you are on the right track, air being drawn in from a leak on the suction side. The siliconed area would be a good place to start, also if there is a suction strainer be sure it it clean or replace it.

As for the belt, the pumps are generally not that hard to separate from the crank. But if you don't want to separate it, go with one of these. They work surprisingly well.
Linked Belt

Bubbles in oil typically indicate suction leak, look for wet places in suction.

OK thanks for the good advice guys. I now have somewhere to start looking when I get home. Is a strainer the same as a filter? I have a spare new hydraulic filter so I'll fit that too. If I seperate the pump shaft at the crank pulley its bolted onto I presume I'll need to unbolt the pump too so I can move it forward and create space between the pump shaft and crank pulley to fit the belt? Nice idea with the link belt, never seen that before and I fit a lot of belts for a living (HVAC engineer). But I've already got an MF belt for it so I'll go with that. Haven't seen any wet areas arount the suction side but I'll be sure to check it closely now. I've been concentrating on the leaking rams before now but they're all good now (I hope!)