Have a D6D here where the brakes when used via the hand levers are erratic in operation.

When using the foot brakes everything works as it should.

The issue is with cold oil clutches work as designed but pull the lever further and the right side brake is slow to start working. Often you can pull it right out to the stops and eventually it will lock the track. When the oil is warm the problem lessens and the machine is usable. Today the left side started doing the same thing sometimes, then other times it returned to normal operation.

Pulling the lever half way just to disengage the clutch and use the foot brakes and there are no issues.

Seems to make no difference whether at high or low revs and cannot find a way to make the issue happen consistently. There are signs the machine in recent times has been worked on in that area,blue silicone and red cat gasket material showing up there. It is a new machine to me)

I am suspecting an issue with the control valve, and hoping as it can be got at without tilting the cab.

Anyone have any ideas? Given the clutch operation is unaffected would I rule out cross shaft bearings?

Put a gauge on the pressure port of the brake actuation part might tell me more. The machine is still quite usable, but not how it should be. And yes the brakes are adjusted up correctly.

Hi R.C.
The following test procedure may help--yes, it does cover the machines listed but, the D6D should be the same/similar--we used this at The Dealer for all later alike systems, but used the Service Manual pressure specs. for the particular later machine.
Sorry, the pages I have are photocopies handed out at a Cat Of Aust. Powershift Trans. Course I did in Oct. 1965.

Hope this helps.
Cheers,
Eddie B.

I will have to get some pressure testing gear then.

RC,
Maybe I missed it, but I didn't see the following info at a quick glance through the service manual: ch-part.com/i.caterpillar/smhs83540001/

Reckon if your linkage adjustments from lever to valve are all correct, then the control valve is the next step.

Most instructions for any work under the seat on the D4E, D5B, D6D start with '1. Remove Cab, 2. Remove Operater Station'

Thanks Glum, that is a good start to find the problem and I would suspect will fix it. It has been awhile, I hope you have upgraded from satellite internet by now.

Yes, RC, its been a few years.
We have progressed a bit, but nothing happens fast in these parts:)
That D6 with aircon looks like a nice upgrade from the old D4D.

Yes I do not miss this one bit.

I ended up getting the brakes repaired. The problem was in the steering control unit. The info Glum linked to was not applicable to my dozer, it is for the newer series of steering control unit. Mine has an older one and the cams that push the spool valves were plain worn out. Some new ones installed and the steering is how it all should be.

Glad you got it sorted, RC.
Got to have those integrated clutches and brakes when your feet can't yet reach the pedals.😀