Bobcat 751 Hydraulic problem, after Lift and Tilt Seal Replacedments

[BobcatRookie]

I have a 1998 Bobcat 751. The Bucket Tilt spool seals were leaking so I replace them both. Front and Back. Complete and refilled with oil. 30 minutes of operation and the Lift spool seals blew (Backside ). I know now, that when you replace one set, you should go ahead and replace both. Completed the lift seal replacement. Things worked on for about 30 minutes and then the #1 cylinder fuel line from the pump to the injector broke at the line fitting. Lucky I had a one from a set I bought a while back. Fixed that and started the machines. Worked the machine a few minutes and the Hydraulic filter light started come on and going off. coming on and going off. As I continued to finish the small job I was doing the lift and tilt hydraulics and the drive motion all began to slow down and then shortly afterwards came to a stop. Nothing would work with hydraulics, no noises, whining, everything sounded OK just nothing would work. I rested the machine for about two hours and tried it again, both the drive ( forward and Reverse ) and the lift and tilt work. This lasted about two minutes and then slowed to a stop again. Talked around and felt the main hydraulic filter was plugged and both case drain filters. Purchase and installed both filter. The machine crank ups and the hydraulics worked about two minutes and then did the same thing, quickly slowed down to nothing and stopped working. I would think this is a simple problem for some, but it has me going crazy. Any help or direction would be greatly appreciated.

 

[BobcatRookie]

After I change the main and 2 case drain filters, The filter light went off. After just a few minutes of running the filter light came back on. I'm talking about the lower red light to right of the Key, three lights, one for Glow Plug, one for engine oil, temp etc.. and I believe the bottom light is the filter plugged indicator. Could the oil or particles in the control valve that I rebuilt spool seals in be contaminated and plugged my filter again, or could there be some bypass after the pump stuck open? This is driving me crazy.

 

[OldMachinist]

After I change the main and 2 case drain filters, The filter light went off. After just a few minutes of running the filter light came back on. I'm talking about the lower red light to right of the Key, three lights, one for Glow Plug, one for engine oil, temp etc.. and I believe the bottom light is the filter plugged indicator. Could the oil or particles in the control valve that I rebuilt spool seals in be contaminated and plugged my filter again, or could there be some bypass after the pump stuck open? This is driving me crazy.

Check the tension on the drive belt.

 

[BobcatRookie]

Check the tension on the drive belt.

I certainly will, is the thinking that as the belt gets a little warm it may be slipping. I would assume you are talking about the drive belt from the engine to the pump. It may have gotten hydraulic oil on it. It this belt a toothed belt?

 

[OldMachinist]

I certainly will, is the thinking that as the belt gets a little warm it may be slipping. I would assume you are talking about the drive belt from the engine to the pump. It may have gotten hydraulic oil on it. It this belt a toothed belt?

Yes the belt may be slipping, the light that comes on is also for low pressure. It may be toothed but but I think the pulleys are just grooved like a serpentine belt on a car.

 

[Tazza]

I certainly will, is the thinking that as the belt gets a little warm it may be slipping. I would assume you are talking about the drive belt from the engine to the pump. It may have gotten hydraulic oil on it. It this belt a toothed belt?

That indeed is the belt. Its a multi-V belt. It should have 2 or 3 V belts bonded together.
It would explain all the symptoms you have described. It should be pretty tight.

 

[BobcatRookie]

That indeed is the belt. Its a multi-V belt. It should have 2 or 3 V belts bonded together.
It would explain all the symptoms you have described. It should be pretty tight.

Removed the cover off of the drive belt and YES it is very loose, I can get my finger between the belt and the idler pulley. A little hot to tighten up tonight, still 101 outside. I believe I see a bolt on the bottom side of the assembly that will need to be loosened before I can tighten the pulley, should not be a big deal. and your right all the symptoms with low hydraulic power when going into a load of dirt and not being able to move forward and tilt the bucket back at the same time all makes since now. I could do one or the other but not both. I will tighten up on Monday and communicate the results. I believe Monday will be a good day. Thanks Guys