JCB 3CX Brake issues....

[mht1156]

2005 model Backhoe that is losing brake oil somewhere not obvious.
It was by mistake topped up with brake fluid when level was low, mistake discovered and fluid replaced with right weight oil.
Now brakes are not working as in pedals have no feel and there seems to be no brakes working. When oil was placed in system after brake fluid mistake the braking system was bled and seemed to be ok.
Few days later brakes became unresponsive and lost pedal feel.
Could the brakes be losing oil inside (no obvious leaks) rear housing?
Owners manual of no help and no dealers close.
Only 3,000 hrs on machine.

Mike

 

[jcb jeff]

If you have put brake fluid in the res it has destroyed the seals they go all soft so the oil bypasses the seals in the axle on the pistons and goes into the axle housing.
Only way is to fit new master cylinders and brake piston seals and use mineral based oil .
I would change the brake plates as well whilst in there.
To do the rear axle seals you will need to either drop the axle out complete or do one side at a time depending on you equipment i used to do these one side at a time with a trolley jack and a plate i made with two prongs to fir into the axle mount holes .
To do it this way drain axle oil first and remove brake pipes top axle , you will need to take out the axle bolts on the right and put trolley jack in to the holes where the bolts were then undo the axle bolts on the left the 38mm bolts nuts to chassis right to the end flush .
Lower the right down so as the axle is hanging at a angle remove all 24 mm headed bolts from around housing and pull trumpet housing off.The brake pack will be left in the axle trumpet ,the brake seals are in the drive head of the axle there are two types some have pins for returning pistons and some are just push in pistons this you will see as the piston will have counter sunk holes with pins in.
I would guess yours has no pins on that age but serial number will help id it,
Use an air line to blow out piston flush holes through to remove all traces off brake fluid fit new seal one on piston and one on axle housing,lube seals with light hyd oil and put piston back in nice and square so as not to damage seals ,the seals do have a leading edge on one side .
Pull out brake pack note which way this goes with the gear and counter and friction discs and the three pins ,rebuild with new plates in correct order soak friction discs the brass looking ones prior to fitting so as you dont have a dry discs.
Gasket sealer is used on the mating surface between axle drive head and trumpet housing.
Reassemble and do the other side.
Change both master cylinders as well flushing all lines out to bleed brakes use a bottle half full of the correct light oil and with the dual brake un latched on the pedals hold the right half way down and bleed the left side out into the bottle with the tube in the oil so as not to suck air back in.
Then repeat by doing the same to the left this helps in bleeding the cross pipe on the master cylinder.
Its easier to do than explain but if you get stuck just shout.
Jeff

 

[jcb jeff]

If yours has this type of piston you will need to pull the bearing housing no 16 off so as to remove the circlip 31 to get the piston out depends on age and axle.

 

[mht1156]

Thank you Jeff
We suspected that the fluid had caused some damage, looks like a bit of a job, will let you know how it goes.
Mike

 

[Dominic Leonard]

Have 93 3cx with soft brakes and additions of new hydraulic oil doesn't last long before going soft again. Brake fluid was used by mistake once in the past so think seals are gone. Do instructions given by jcb jeff apply to a 93 3cx or are there differences? Would be planning on doing one side at a time as will be a home job.

 

[jcb jeff]

Have 93 3cx with soft brakes and additions of new hydraulic oil doesn't last long before going soft again. Brake fluid was used by mistake once in the past so think seals are gone. Do instructions given by jcb jeff apply to a 93 3cx or are there differences? Would be planning on doing one side at a time as will be a home job.

Hi
Yes it would be the same.