his1911
Active Member
Where do y'all source your charging kits from, can't really justify the $1200+ that CAT wants for one, but then again we've been waiting on their field service to get out for almost a week!
I don't know of anywhere else that does them, unless you want to buy in bits & bobs from all sorts of different suppliers. Buy a kit and look after it, it will probably last 10 or more years.
I've seen charge kits at Grainger, I know Bosch makes one, I'm just not sure if they're the same set up as the hvy eqpt ones? Some of those are in the $500 range which is much more palatable.
Tony, Do you put 1/2" or 1" of oil in dumper struts..? We've found they work better with 1" of oil.
Also we've found a consistent method of charging that takes the tape measure (and things like seal friction) totally out of the game. First oil up the strut as normal, then give it a whiff of gas, maybe about 100psi, from the nitrogen bottle, then with gas in the strut jack the truck up until the strut tops out. Set the gas pressure to 260 +/- 5psi front or 160 +/-5psi rear with the strut extended. Drop it back onto its feet again.
I'll make a note of this and give it a try next time I do one of these. I do like the idea of over filling and letting it set then draw off the air and foam.The pressures should work for any size of Cat Truck from 769 upwards. The procedure (SEHS9411) for charging struts the way we do is in SIS but only allegedly covers 785 upwards. I see no reason to doubt that it would work on a smaller truck. If the truck has a payload measurement system installed then the easiest way to measure suspension pressures is hook the laptop up to the TPMS and look at the strut pressure. The electronic sensor in the strut will be far more accurate than any pressure gauge installed on a nitrogen charging kit, even a brand new one.
Make sure you put a good quantity of oil in the strut. I usually oil them up to 1-1/2" (manual says 1"), then go and have lunch. Come back and drain them down to 1" - most of what comes out will be air that was trapped in the oil when it was pumped into the strut. That gets your oil level/quantity correct.
Remember that the front struts will always ride at different heights (LH lower than RH) because of the weight of the cab, despite the fact that both of them might have an identical oil & gas charge..
Because the struts use 10W oil we hook a hydraulic test line up to the steering system test port and plumb it into the manifold for the nitrogen charging kit. That way we can use the machine itself to oil up the struts. If we are doing a simple "discharge & recharge" procedure then to oil up the 2 struts on each end of a 793 with the engine at idle speed takes about 2 minutes. Note to self: - Remember to top up the steering tank afterwards .......
You conveniently forget to mention that the "simple and brilliant idea" also saves you from the need to buy a 9U-5617 Oil Pump Group @ $7000+ to charge oil into suspensions and which takes about 1 hour for each strut rather than having the capability to do 2 struts in 2 minutes.
Also remember that I have a fleet of 36 trucks here, all of which needs suspensions doing as a PM Checklist item every 4000 operating hours or about 7-8 months. We actually have 3 nitrogen kits in our Tool Store; one set up for truck suspensions, one set up for truck steering accumulators, and a 3rd kit for "everything else". Saves time ...........
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Just a few more than one ....... we use 777F's as water trucks.I can't get my head around the work needed to keep 36 large haul trucks and all the other equipment in an operation of that size up and running. Guessing you have more than one mechanic handling the service and repair work!