Bobcat 743 Oil Cooler Massive Leak

[theNEWT]

Hi Folks I have a well used 743 that I only use occasionally on my property, generally its been pretty good. Its done a lot of work, about 8000 hrs. Yesterday it suddenly pissed hydraulic fluid....everywhere, massive leak. After inspection I have traced it back to the cooler, under the radiator. I wiped things down, briefly ran the engine (~ 5secs) with exhaust and inlet filters removed, and the doors under the cooler. From the back, the LHS coupling appeared to be the leak spot, new fluid all over it and surrounds. There was a lot of crud built up around the end so I assume it may have been leaking slowly for a while. The two pipes were tightly fitted, not loose, and dont appear damaged etc. I have removed the cooler and will give it a good clean up for inspection. Any ideas as to what might have happened ?? Cracked cooler? Hose join leak? Excessive pressure??

 

[mmsllc]

remove the oil cooler, submerge it in a tub of water & pressurize the ports to test for a leak. If there was too much CRUD packed around it, it might have rusted thin in a spot.

 

[mmsllc]

remove the oil cooler, submerge it in a tub of water & pressurize the ports to test for a leak. If there was too much CRUD packed around it, it might have rusted thin in a spot.

Another thought, you could also make a jumper hose that connects the hoses together that would normally hook up to the cooler it self. It's only an idea to isolate the leak. Wash it down after you bypass the cooler. Check for leakage. Just don't think that the cooler doesn't serve a purpose if the leak is gone.

 

[theNEWT]

Another thought, you could also make a jumper hose that connects the hoses together that would normally hook up to the cooler it self. It's only an idea to isolate the leak. Wash it down after you bypass the cooler. Check for leakage. Just don't think that the cooler doesn't serve a purpose if the leak is gone.

Thanks. I've removed and given the cooler a really thorough cleaning. I cant see any signs of damage, cracks etc. The end where it appeared to have sprung the big leak was chokkas with crud as if its been leaking there slowly for some time. I dont have any way of pressure testing it...I'll see if I can find someone who does. I also dont have any hydraulic hoses laying about. Its in a very dry semi-arid location, kept in a shed and the connections were petty much sealed in oil, so I doubt rust, cant see any signs of any.

 

[theNEWT]

Thanks. I've removed and given the cooler a really thorough cleaning. I cant see any signs of damage, cracks etc. The end where it appeared to have sprung the big leak was chokkas with crud as if its been leaking there slowly for some time. I dont have any way of pressure testing it...I'll see if I can find someone who does. I also dont have any hydraulic hoses laying about. Its in a very dry semi-arid location, kept in a shed and the connections were petty much sealed in oil, so I doubt rust, cant see any signs of any.

And I assume these fittings being flare-type dont require O-rings, as neither had one.

 

[mmsllc]

And I assume these fittings being flare-type dont require O-rings, as neither had one.

I don't think they require O-rings to seal those lines. I'd have to see them in order to know for sure. As far as the CRUD goes, I see a ton of leaves, dirt & pine needles collect in the area that you are describing. If there is anything that holds moisture there, rust is soon to follow. A radiator repair shop should be able to leak test that cooler for you. They should also be able to clean really good for you as well.

 

[oracle_of_ferndale]

And I assume these fittings being flare-type dont require O-rings, as neither had one.

My 743 had a leak in the same spot. The threads on the fitting were stripped and fluid poured out at the connection - even though I could not see a leak when it was not running. Replaced the fitting with this one http://www.discounthydraulichose.com/product_p/2403lh-10-10.htm. Ground off one end and brazed it on to the cooler. To put a little bit of pressure in the cooler, I capped one end (it takes a -10 jic cap http://www.discounthydraulichose.com/product_p/304c-10.htm) then shot a bit of compressed air in the other side. Hope this helps.

 

[theNEWT]

My 743 had a leak in the same spot. The threads on the fitting were stripped and fluid poured out at the connection - even though I could not see a leak when it was not running. Replaced the fitting with this one http://www.discounthydraulichose.com/product_p/2403lh-10-10.htm. Ground off one end and brazed it on to the cooler. To put a little bit of pressure in the cooler, I capped one end (it takes a -10 jic cap http://www.discounthydraulichose.com/product_p/304c-10.htm) then shot a bit of compressed air in the other side. Hope this helps.

Well DERR me! I inspected the cooler, couldnt see anything at all wrong with it, so decided to put it back and watch carefully at first start...after a thorough cleaning so I could actually see what was going on. OIL is being thrown UP towards the cooler mostly from the LHS (from rear) by the engine fan I guess., blowing it up under the cooler from inside the plastic shroud.. So which pipe has gone? Is this typical of one of the low pipes at the rear base of the engine.....I guess the engine has to come out.

 

[Tazza]

Well DERR me! I inspected the cooler, couldnt see anything at all wrong with it, so decided to put it back and watch carefully at first start...after a thorough cleaning so I could actually see what was going on. OIL is being thrown UP towards the cooler mostly from the LHS (from rear) by the engine fan I guess., blowing it up under the cooler from inside the plastic shroud.. So which pipe has gone? Is this typical of one of the low pipes at the rear base of the engine.....I guess the engine has to come out.

Sounds like engine out job. It could be the main hydraulic pump seal at the back, it could be the lift/tilt lines that run behind the plastic cover. Sadly you need to get the engine out then try and find it.
Without an engine to give pressure, it may not be easy to find....

 

[theNEWT]

Sounds like engine out job. It could be the main hydraulic pump seal at the back, it could be the lift/tilt lines that run behind the plastic cover. Sadly you need to get the engine out then try and find it.
Without an engine to give pressure, it may not be easy to find....

Ive pulled the engine with minimal blood loss, but on soft dirt outside away from the shed it was no mean feat. I have cleaned up the floor so I can work in there without looking like I've taken an oil bath. The plastic shroud has a deep pool of oil in it. I'm wondering how it managed to get in there. The drive input area is dry. Im now at the stage where I need to remove the shroud, it seems to be held down at the base with a castle type nut and I think the whole thing is turning so I may need to grind the bolt off from underneath. One pain in the butt after another, that means taking the genny down there to run the grinder. FUN! NOT! Any ideas as to which hose may have blown considering the shroud has a deep pool of hydraulic fluid in it??? Cheers

 

[theNEWT]

Ive pulled the engine with minimal blood loss, but on soft dirt outside away from the shed it was no mean feat. I have cleaned up the floor so I can work in there without looking like I've taken an oil bath. The plastic shroud has a deep pool of oil in it. I'm wondering how it managed to get in there. The drive input area is dry. Im now at the stage where I need to remove the shroud, it seems to be held down at the base with a castle type nut and I think the whole thing is turning so I may need to grind the bolt off from underneath. One pain in the butt after another, that means taking the genny down there to run the grinder. FUN! NOT! Any ideas as to which hose may have blown considering the shroud has a deep pool of hydraulic fluid in it??? Cheers

Removed the bottom bolt that holds the base of the shroud down. Had to grind it off from below. I now think the hydraulic input shaft may be leaking. At first I thought the build up of mud around it all was dryish, but it isnt, it looks quite wet as are the uni couplings in the engine, which would explain the pool of hydraulic oil in the shroud. Uni joints appear very good as are the splines, no sign of wear. I pulled the shroud out enough at the bottom to have a look at the pipes and it doesnt appear to be freshly wet there, grime build up, but no signs of a massive leak, quite dry and the pipes look to be fine. Is there any way to be sure the input seal has gone?.....I guess not, I'll replace it anyway.

 

[Tazza]

Removed the bottom bolt that holds the base of the shroud down. Had to grind it off from below. I now think the hydraulic input shaft may be leaking. At first I thought the build up of mud around it all was dryish, but it isnt, it looks quite wet as are the uni couplings in the engine, which would explain the pool of hydraulic oil in the shroud. Uni joints appear very good as are the splines, no sign of wear. I pulled the shroud out enough at the bottom to have a look at the pipes and it doesnt appear to be freshly wet there, grime build up, but no signs of a massive leak, quite dry and the pipes look to be fine. Is there any way to be sure the input seal has gone?.....I guess not, I'll replace it anyway.

If there is no oil dripping from the oil cooler, it will have to be the shaft seal. They are cheap from loader parts source. The hardest part is removing the spline. I removed the bolt and installed a 1/4" socket and used a puller to put pressure on the spline. I then hit the pushing bolt on the puller to shock it off. It's a taper fit. Don't hit the soline, it's hard and they can crack.

 

[theNEWT]

If there is no oil dripping from the oil cooler, it will have to be the shaft seal. They are cheap from loader parts source. The hardest part is removing the spline. I removed the bolt and installed a 1/4" socket and used a puller to put pressure on the spline. I then hit the pushing bolt on the puller to shock it off. It's a taper fit. Don't hit the soline, it's hard and they can crack.

Thanks Tazza. I should be able to change the seal without bother - I hope. I have removed the shroud and done the best clean up I can for the moment, there was a lot of crud everywhere. Next Ill bring in a high pressure cleaner before anything else. After the initial clean up the steel pipes do look a little dubious, the very bottom one has surface rust and some pitting. I'm in two minds, should I assume its the pump seal and not touch the pipes or should I remove the pipes one by one to be sure? Can the pump seal blow out that badly to lose oil that quickly? It does appear as if its been leaking for a while as the oil cooler and the radiator have a build up of gunk directly above the engine fan,,,,LHS from the back. I previously removed the cooler as I thought it might have been leaking, gave it a through cleaning and inspection, put it back before running it and it didnt leak at the cooler.....just spraying up from the oil dam in the shroud. When it went, the fluid loss was violent and immediate. I couldnt get the lift to drive down, the arms kept going up so I killed the engine. Restarted and managed to bring them down.

 

[Tazza]

Thanks Tazza. I should be able to change the seal without bother - I hope. I have removed the shroud and done the best clean up I can for the moment, there was a lot of crud everywhere. Next Ill bring in a high pressure cleaner before anything else. After the initial clean up the steel pipes do look a little dubious, the very bottom one has surface rust and some pitting. I'm in two minds, should I assume its the pump seal and not touch the pipes or should I remove the pipes one by one to be sure? Can the pump seal blow out that badly to lose oil that quickly? It does appear as if its been leaking for a while as the oil cooler and the radiator have a build up of gunk directly above the engine fan,,,,LHS from the back. I previously removed the cooler as I thought it might have been leaking, gave it a through cleaning and inspection, put it back before running it and it didnt leak at the cooler.....just spraying up from the oil dam in the shroud. When it went, the fluid loss was violent and immediate. I couldnt get the lift to drive down, the arms kept going up so I killed the engine. Restarted and managed to bring them down.

If the seal was really bad it could spray out like that, the thing is, the metal tube lines should only have pressure when the hydraulics are activated, so the spray would be worse if you enabled the lift, or lift

 

[theNEWT]

If the seal was really bad it could spray out like that, the thing is, the metal tube lines should only have pressure when the hydraulics are activated, so the spray would be worse if you enabled the lift, or lift

I think I tapped the seal in too far...I wasnt expecting the seal to keep going, I'm used to them backing up against a rear face and I didn't look too hard when I took the old one out as oil was gushing out. So, the thing seems to be leaking as I turn the shaft, so I suspect being back too far is not good. Will pressure push it forward and up against the circlip to seal or do I need to remove this seal and replace with another and have it go only just past the circlip groove? I had to use heat to the get the spline off, it was a beeearch! Ive had the two lower metal hoses pressure tested and they are okay, the rest look fine, the lower ones looked dubious but handle 2500 psi no leaks.

 

[Tazza]

I think I tapped the seal in too far...I wasnt expecting the seal to keep going, I'm used to them backing up against a rear face and I didn't look too hard when I took the old one out as oil was gushing out. So, the thing seems to be leaking as I turn the shaft, so I suspect being back too far is not good. Will pressure push it forward and up against the circlip to seal or do I need to remove this seal and replace with another and have it go only just past the circlip groove? I had to use heat to the get the spline off, it was a beeearch! Ive had the two lower metal hoses pressure tested and they are okay, the rest look fine, the lower ones looked dubious but handle 2500 psi no leaks.

I would like to think the charge pressure would push it into place, but i can't say for sure it will....
When i do seals, i tap the seal in most of the way then install the circlip and tap it in, this way when it gets into place, it will snap out and stop pushing the seal inwards.