If the temp is cold you need a lighter oil then 68, and if hyd oil has never been changed then oil could break down. to check pressure for lifting just hook a pressure gauge into a side shift hose

Since I've had two leaks on this machine, cylinder seal, and O-ring on a connection under floor, noted earlier, its time to get the pressure checked. Thanks for all your suggestions.

I agree that other leaks should appear but the Clark was an electric unit & the tilt, s/s & p/s were all powered by the main hyd pump on this unit yet none of the other systems leaked. My theory was the hoist was the only circuit that accumulated oil rather than just use the pressure.

I think I would err on the side of caution & drain the hyd tank & check for debris at a minimum along with checking the pressures. I would think that high pressures would also cause other cyl's to leak or have other symptoms.

Do Linde's have a high pressure filter after the hyd pump? Do they use the hyd pump to power the hydros or do the hydros have their own pumps? Not trying to break your b*lls- just don't know how they're set up.

yeah bb that was one of my thoughts too but these linde's drive everything through the hydraulic system, drive, hydraulics, steering and in some cases even the cooling fan.
If contaminated fluid from a failing pump was the case he should be seeing fluid leaks from several sources, not just the one.

I'm thinking some sort of pressure issue.
He should have the pressures checked and make sure they are withing machine specs. If it's high this could cause this. That would be the first thing to check anyway on these machines.

I've had a faulty hydraulic pump throw sand like particles into the hyd system- learned this one the hard way- same cyl was repacked 4 times within a year (telescoping hoist cyl in a C500 clark)- after the 3rd time (hyd vendor would no longer warranty) apart we carefully inspected each seal, gland nut- etc & found metalic "sand"at each point- checked & found "sand" at bottom of hyd tank & covering filter media.

Truck had no hyd symptoms other than hoist cyl leak- removed hyd pump & found bearing surfaces rough (chrome was gone) & gears pitted. It's a long shot but worth a look if no other cause can be found.

well i guess that rules that possibility out.
weather might play a part in it but generally it wouldn't show till it got cold. Seals harden up when cold and get soft when warm. When warm they seal better.

well i would of thought dirt around the ram seals but he did say a clean environment so maybe thats not it as i originally thought. edited

Warehouse is not refrigerated. However, it is not heated in the winter. We're located in the northern U.S. So, warehouse definitely gets down into the lower 40's F. Maybe into 30's during the dead of winter.
I have checked the rod for scoring. No scoring, pitting, or flaking on the cylinder.

ok.... does it run into a refrigerated cooler at any time? or is this just a standard warehouse?

karait's suggestion has some merit...
look at the cylinder pistons real carefully and check them for any pitting or flaking. Extend them fully and check the whole piston and see if you find anything like this.

Using standard oil that came in truck when new.

You mention the truck is being used in a food warehouse.

Is it running on standard hydraulic oil OR has the customer insisted it have food safe hydraulic oil put in the trucks hydraulic system instead?

excessive high temperature does all seals to leak som oil can better resist high temperature

Environment is as good as it gets. Its a food warehouse. Lift is used to load and unload trucks, and stack pallets. Operator is extremely conscientious. Have not lost enough fluid to top off fluid.

Just make sure to inspect the old seals when the rebuild is done to confirm what the issue was- sometimes this is the most important part of the job to stop repetitive repairs

Stan_k
In 2011-12 there was a series of 386 Linde trucks with some problems with the lift cylinder pistons. The surface of the piston went rough and it caused the defects on seals. Perhaps this is the case with your truck.

The replacement of the seal kit on lift cylinder is a standard, altough hard job, no special tools required. Takes about 3 hours for skilled technician.

other then the previously mentioned incorrect hydraulic fluid

what type of environment does this truck run in?
what does it transport?

in alot of cases a dirty envrionment that allows production materials to get on the truck can cause something like this if those materials are caustic or gritty and can get into the cylinder packing seals.

just another out of the box thought :o)