Today I did the 1,000 hour service on our new Cat 980K loader. This included changing the hydraulic oil filters. I was a little surprised at the instructions on the filter canister and the ones that came in the box with the filter. I even had to check with the maintenance manual to be sure I was reading them right! Here are the last two steps right off the Cat Parts Store web site: 9. Insert the new filter element into the canister. 10. Install the canister onto the base using the hex nut on the bottom of the housing. Tighten the filter housing until the housing bottoms out in the base, then loosen 1/4 of a turn. I'm sure someone has a reason for running this filter loose but it escapes me right now. It is sealed by an oring in a groove about 1/8 inch down from the top so it doesn't need to be tight like a spin on filter such as the engine oil filter, but still 1/4 turn loose? There is a transmission filter right next to it that is larger but same basic design and that one is to be torqued to 37 lb. ft. That one was obviously installed by someone at the factory who did not read the book. I needed my 36 inch 3/4 drive ratchet to break it loose. Will see in another 1,000 hours if it self tightens. The one in question came off with just the drag of the oring holding it on.
I went to the manual and read it for myself as well..! Never seen anything like it in my life before but there's obviously a reason behind it. I'll try to find out what it is.
Well it ran for 8 hours today and didn't fall off or leak!
From what I have been told, you tighten it all the way to ensure the cartridge is fully seated then backing it off a quarter allows it to seal better.
Nige, it will unroll the seal for a tighter fit. The old Murphy injectors had to be instelled that way or they would leak. Later Bob
You learn something new every day, and what you say makes perfect sense. I'm in agreement with the OP, a filter installed in a bowl certainly doesn't need to be heaved up as tight as a spin-on filter. It's just that this method of installing the bowl was something I hadn't come across before. I suppose I need to get out more ................
Talking about spin on filters. We have a 769D that has two spin on hyd. filters that seem to tighten themselves over time. More than once I have had to use an air chisel to break them loose. Seems the outer housing will slip on the threaded part of the end. We use Donaldson filter and I know in the past the printed instructions called for hand tighten them plus I believe 16th of a turn. The filter I put on last week are marked to hand tighten only so I'll see what they are like to remove in a couple months time.
Cat spin-on filters are hand tight on an O-Ring lubricated with the same oil that's in the system until the O-Ring touches the face + 1 complete turn.