Hi Team,
often a squealing sound in a hydraulic cylinder is a sure sign of internal oil bypass leakage.
Would be either the travel limit valves as OM said, or the piston packing rings which may be a fibrous material similar to auto engine timing gears that was often used in these older units.
Cheers,
Eddie B.

I took the squealing cylinder apart this morning and only thing I noticed out of the ordinary was a piece of what looks to be maybe packing between piston and end cap, Maybe the other side is letting oil past and as a result the good cylinder is squeeling as oil has to get past its rings?????maybe?

Hi,
were you able to see if the pistons had travel relief valves in them--if so check if some packing is lodged in one of them and allowing oil to by pass.
A well used valve could also be damaged or have pitted seats. From memory I believe I saw a bent travel relief valve guiding stem in one I did that stopped the valve seating squarely.
From memory the piston simply slides off the rod after undoing the nut--be sure to refit the washers one each side of the piston when assembling.
The valves press out by pressing on one of the guide ends to push the seat out so you can inspect the condition of said components.
Scans below may help--not sure if the double piston ring update applies to your Cyls. as I do not have parts books for these units. I included the PB's to show the two ring update may happen and so you will be forewarned.
Cheers,
Eddie B.

It turns out to be the right hand lift cylinder piston is broke, missing some aluminum, looks like we need to find a hydraulic cylinder piston and a seal kit. Then try and find all the aluminum pieces. Lucky the barrel seems fine. It might be better to replace entire cylinder if I can find one.

If you can't find a second hand piston a good machine shop should be able to make one for you. Are you sure it's aluminum? I have never seen an alloy piston on a dozer before.

check the suction strainer in the oil tank the bits may have fount there way there and hopefully that's were they have ended up.

if you unbolt all the lines you can clean them using foam plugs and compressed air you would need to make a plate with a air fitting in it any hydraulics shop will have the foam plugs as they use them all the time this is sometimes reffered to as pigging a new plug is used for each line. you only need to use about 20 psi of pressure the idea is the foam wipes the inside clean.

the piston seals and rod seals are available from the dealer thats where we got ours. if they have a piston you would have to ask.

dont forget to hone the cyl bore it wont need much its just to clean it up a little.

Ok thanks , It sure looks like aluminium or me. I will take it to hydraulic shop next week and hopefully they can make one.

Is the strainer in the tank , or where exactly would I find it? Thanks for the info on foam plugs, I would not have thought of that.

Keep in mind the "foam plugs" are not normal foam that you find in seats etc. Also they are meant to clean sediment out of hoses and tubing when first manufactured. Not sure how effective they would be if there are metal shards embedded in the hoses. I doubt any steel shards would be in the steel piping. When I worked for a company building garbage trucks we used about three to four plugs. The first three were used over and over again and only the final plug would not be used again. They also come in different grades. I think the applicator was very expensive to buy ($500+) and the plugs were a few dollars each which added up when you are cleaning hundreds of hoses and tubes a day. We used to run them through at full air pressure.100psi anything less and the plug will get stuck in the middle somewhere.

Most suction strainers are fairly high micron and allow a lot of particulates through. This can be very detrimental to the pump but is usually taken out by the pressure filter between the pump and the valves. I am not sure if any Cat's have a return filter but if it does then it would have saved the pump. Most suction strainers are placed as far as possible from the return so that sediment can settle out before it gets to the pump suction. Quite often there will also be a baffle plate between the two to help settle the sediment and also to allow any aeration to settle out before the pump.

Do you have any pictures of the piston?

Regards

Phil

Here is a picture of the piston