Willie and crewchief, bobtach question

[Mikefromcny]

I'm looking at an 01 883 bobcat tomorrow morning. 2900 hours, runs and drives good. Hydraulics seem to work fine and are strong. it has a bobtach that is not working. Guy thinks its the switch but I've also read a failing hydraulic pump will get the spool contaminated to the point where it binds. Anything I should check on this to make sure I'm not buying something with a failing pump? Thank you.

 

[willie59]

I've also read a failing hydraulic pump will get the spool contaminated to the point where it binds.

Well, a failing pump can be just one of the things that causes this, could be anything that gets metal fragments in the oil, such as a drive motor. And it doesn't take a large fragment to do this. A sticking Bobtach spool is only an indicator of a problem in the system, doesn't mean it's going to fail tomorrow.

As far as checking things before you purchase, that depends on how deep the owner will allow you to dig into it. Probably the easiest thing to do would be remove the hydraulic filter and drain it into a clean pan to check the debris in the oil. Once you've dumped the oil from the filter, it would be nice to pour some solvent into the filter, give it a good agitate, and pour into another clean pan to check debris. Of course this would require putting a new filter back on.

 

[willie59]

Oh, and check the loader arms for cracks or previous mending repairs. That model was bad about the loader arms breaking at mid-point.

 

[Mikefromcny]

Thanks Willie, I'll give that a shot. Do you see many 883's? My understanding is they are basically a 873 with counterweight and high flow. What are your thoughts? This one has a cab with heat! I didn't enjoy not being able to feel my knees with an open cab in the 873 at -10F as I was plowing snow.

This one appears to of had a decent life. He said its never left the yard except for repairs. Its at a nursery and is used for loading trucks.

 

[Mikefromcny]

Oh, and check the loader arms for cracks or previous mending repairs. That model was bad about the loader arms breaking at mid-point.

No cracks on this one but it is a G series.

 

[willie59]

The G series has much improved loader arms compared to the earlier models. It's no different than any machine, the kind of life it's lived has everything to do with how good a machine is. Aside from nothing man makes is immune from break downs, if it's been well cared for it's probably a worthy purchase.

 

[willie59]

And if the machine has 2000 hrs or more, ask the owner if the timing belt has been changed.

 

[Mikefromcny]

It has 2900 hours. He had no idea it had a timing belt. If I buy it I will order one and rent the tools to change it.

 

[willie59]

Well, there's not a "set" hour that the timing belt lets go, I'm just leery of one with more than 2K because it's easy and cheap to change one before it fails. If one waits until it breaks, yeah, fit hits the shan then.

 

[Mikefromcny]

How do you go about changing them? do you have the timing pins and special hydraulic tensioner or just loosen the tensioner and slip a new one on?

 

[willie59]

If you're attentive, careful, and make marks on the pulleys, it's easy to change before it breaks, no timing pins needed. If you wait until it breaks, timing pins required as well as valve push rods as needed. And if you plan on keeping the machine for a number of years, and can afford it, you might consider replacing the oil pump as well, I've heard of oil pumps locking up (go figure) which takes the timing belt out as well.

 

[crewchief888]

early pwr bobtach valves werent the greatest. they would get plugged with debris very easily.

later valves have a screened orifice in them that stopped a lot of the crap before it got to the valve stem.

without checking the filters INCLUDING the case drain, theres no way to really know if the valve is the problem.

elec test at the switch, and at the pwr bobtach harness connections, & ohm test the coils will isolate if it's in the harness or valve.

i agree with willie, change the timing belt before it breaks. bobcat's service interval is 3000 hrs.
timing belt kit comes with a new tensioner.
do not reuse the old tensioner, or reajdust the belt after 50 hrs of run time.


:drinkup

 

[Mikefromcny]

Great thanks guys.