I have a Melrose Bobcat 7753 Loader and I have an O-ring on the fitting coming out of the hydraulic drive pump that I can not keep sealed. I replaced it twice; have felt I had it tight and it blew out and leaked all by fluid out within 30 minutes of use time. May there be another problem that is causing this O-ring to blew out? Or am I just not getting it tight enough?
Welcome to HEF Carteracres. :drinkup What o-ring are you using? If that's a typical SAE o-ring fitting (o-ring boss), then you have to use a 900 series o-ring, i.e., 568-901, 568-902, 568-903, whichever size is appropriate for your fitting. If you're not using a 900 series o-ring you'll blow them quicker than you can install them.
The cross width on a 900 series is different than a 100. The 900 are also 90 durometer rated for higher pressure, where as a standard 100 or 200 series o ring is a 70
If the fitting is an elbow or tee that has a nut and washer you tighten to seat the o-ring, replace the fitting and make sure the o-ring is in the sweet spot where there are no threads to cut it. Sometimes in order to get the rotation right you have to either back off a turn or go in a turn and the o-ring ends up on threads instead of where the fitting is smooth.
If it doesn't have Power Bobtach, which I don't thing that machine does, I think most of those Bobcat machines used a #12 o-ring boss 90 degree adjustable fitting like you mentioned lantraxco. On those fittings post-install, I back the nut off, slide the seal seat washer outward until it hits the threads, then run the nut down until it hits the washer. Install the fitting. If it contacts the o-ring before it reaches desired position, back the fitting out to proper position then seat the o-ring with the nut.
Thanks Willie, that's just the way I does it, but didn't know how to say it! LOL
are you refering to the drive hose/fitting on the hydrostat, or the fitting in the hyd pump? :drinkup
Did you get it sealed up? I had a similar problem on my 763's gear pump, upon closed inspection it turned out to be a cracked pump housing right at the threads. A new pump fixed her right up.
hi.my 753 appears to be leaking from under the end pump .I have removed the feed pipe & replaced the clamps.when the feed pipe was off the oil level sat on the top of the tube for days, then dissappeared ( drained ) so it lost oil without pressure .you can see it dripping at times under the pump.is there a simple o-ring between the x2 pumps ? or may it be a cracked housing ? just trying to do some reasearch before dismantle
It could have an outing or a gasket betwwwn thr hyd pump and hydrostats. Orting is most common.