Hi all. We have a 2008 312C with 4500hrs, we only have it a couple of months and we don't have any real history. The problem we are having is, when lowering the main boom, with the stick being held out ( full reach ) the is a horrible and loud screech. At first we thought it may be panel vibrating or a dry pin, but now we are fairly certain that its coming from the valve chest. When the stick isn't being held out, it dosn't seem to occur. This may require a change in driving habits to fix but it ain't easy to change habit and this dosn't happen with any of our other Cats. Thanks in Advance Brendan
Is this only happening when you are in the lowering down cycle or is it when you are at the point of stopping the travel … ??? …. is this happening with the bucket at struck capacity or when it is empty or both … ??? ….. Shooting from the hip from what symptoms you had mentioned, I would think you'd have a relief valve pressure issue in the valve bank ….. ??????
Not sure if this relates to your problem but Cat offers this: http://parts.cat.com/parts/machine-fluids/oils/additives/hydraulic-oil-additive We had a 980g that developed a noise in the tilt cylinders after having them resealed. A quart of this in the hyd. oil and noise went away. This is also used per the owners manual in the final drives of our 980 G and 988H loaders to prevent noise in brakes. I know the bottle says not for transmissions and brakes but the owners manual says to use it!
Are you sure it is the valve bank and not the cylinders screeching?
Yes I woudl try this first
Thanks for the replies, it happens at the lower half of travel & not just when coming to a stop, with the bucket empty or full and about 6 times out of 10. The additive sounds like a good place to start so i'll give it a try. Brendan
Collins, test and adjust the Boom Up line relief valve. With everything in that position you have a lot of leverage forcing oil out of the boom cyls. Later Bob