Clark C300-40 Mast Cylinder Help, etc

[steamandsteel]

Hello,

Came across an old Clark C300-40, but it's got a few issues.

Most important one is that the main mast has small geysers coming out from around the larger seal atop the cylinder. This comes out to several quarts over a fifteen minute period of shuffling things around. At first, the lift didn't leak this bad, but it has gotten significantly worse with light use.

This is the main problem, as it currently makes an awful mess anywhere it is used.


Other issues include:

- No Brakes (no fluid in master cyl, inside is also rusted a bit)
- Side-shift cylinder spews fluid when engaged

I spent an afternoon pressure washing decades of grease and oil off of everything.
From there, I did the following work:

- Hydraulic oil tank drain and flush
- Engine oil drain and flush
- Topped off trans oil (clean and near full already)
- Replaced main hose feeding mast control valve
- Filed and gapped points, cleaned plugs
- New battery, other misc electrical

Everything else functions well, no strange noises, motor runs quiet and smooth, trans shifts without issue.


Now, I have read that these multi-stage mast cylinders are a PITA to rebuild and are expensive to find parts for.
Is there any adjustment of the seals/packing that could tighten up this leak, or is it too far gone at this point?

I'm willing to try anything, just looking for a little guidance first.

 

[dalmatiangirl61]

Pretty sure you are looking at rebuilds, never done a 2 stage cylinder myself so cannot say if its easier/harder. How many hoses feeding main lift cylinder, 1 or 2? If you have a hyd shop nearby they should be able to match up seals, if not then you will have to order and it might be best to order a full kit from Clark, just will need to make sure you get right kit as I'd bet that lift came with a variety of cylinders.

 

[ncjeeper]

I had to rebuild my 2 stage mast cylinder on my old Hyster 5K lift. The older seal kits can be hard to locate. I had a shop do mine and it ran about 500 bucks. I removed it, brought it to them, and then installed it.

 

[bsg]

Hello,

Came across an old Clark C300-40, but it's got a few issues.

Most important one is that the main mast has small geysers coming out from around the larger seal atop the cylinder. This comes out to several quarts over a fifteen minute period of shuffling things around. At first, the lift didn't leak this bad, but it has gotten significantly worse with light use.

This is the main problem, as it currently makes an awful mess anywhere it is used.


Other issues include:

- No Brakes (no fluid in master cyl, inside is also rusted a bit)
- Side-shift cylinder spews fluid when engaged

I spent an afternoon pressure washing decades of grease and oil off of everything.
From there, I did the following work:

- Hydraulic oil tank drain and flush
- Engine oil drain and flush
- Topped off trans oil (clean and near full already)
- Replaced main hose feeding mast control valve
- Filed and gapped points, cleaned plugs
- New battery, other misc electrical

Everything else functions well, no strange noises, motor runs quiet and smooth, trans shifts without issue.


Now, I have read that these multi-stage mast cylinders are a PITA to rebuild and are expensive to find parts for.
Is there any adjustment of the seals/packing that could tighten up this leak, or is it too far gone at this point?

I'm willing to try anything, just looking for a little guidance first.

Never dealt with a multiple stage cylinder…….if your uncomfortable with trying to reseal it, I would take it to a hydraulic shop and have it repaired?

I did the main cylinder on mine, here’s the thread.

Hyster S80 XL Main Cylinder Leaking, Questions?

My steering cylinder is leaking now, it looks like I will be repairing that one shortly!

Good luck on your repair!

Kevin

 

[matt_isserstedt]

I just saw your post, I have some experience with this.

Bottom line is my mast cylinder was weepy when I got it, after a heavy lift one time it got downright flood-y which made a huge mess.

I used the Hyster to lift the mast cyl out of the Clark. Its very heavy, I placed it on stout sawhorses, newspaper and heavy plastic as its going to make a giant mess. There's a significant amount of fluid within the cylinder itself, its mostly hollow in there.



The original seals, all basically U-cup seals were all cracked. I would advise making some special tools using your shop to loosen the end caps of the cylinder, I don't have a pic, but don't resort to hammers and cold chisels as you'll have a giant mess on your hands later. Spend the time to develop a shop-made tool then life gets a lot easier



I ordered new seals as a kit from Hercules Bulldog, which is now just Bulldog Hydraulics. I had to buy them thru Motion Industries otherwise I would have had to setup a credit account, they had no way to process a credit card...this was 2006-2007 ish. Hercules had an "upgraded seal kit" with some special polyurethane (?) formulation to allow the seals to last even longer, it was minimum extra cost and so I got that. Hercules needed a serial number stamped into one of the mast channels to source the correct kit. I had to go over it with a flashlight to find it, I was expecting little 1/4" characters, as I recall they were around 3/4" characters metal-stamped.

What I learned after an early disaster is this: its very simple to stretch the U-cup over the rod, but nearly impossible to push it into compression in its gland and not have the internal end-cap threads tear it apart as it passes. My solution to that is pictured. Make a 'thin band" by machining PVC pipes or I made some by silver-brazing standard steel strapping/banding together. Both work, the PVC is a lot easier to buy & machine vs trying to get a precision length of steel strap coiled and brazed.

The idea is to compress the U-cup into the band, carefully and incrementally using generous clean oil.



Into this state



Here's where the internal threads would be chewing away but now they just pass easily by, already under compression.



Last is to use a round or square rod to carefully tap the seal home, incrementally around the circumference.

IMG_1203 by Matt Isserstedt, on Flickr

This is the sum of the parts, the old rings are at left, the green ones were a Clark OEM part, but I ended up using the Hercules blue "upgraded seal kit". I had to develop 4 rings for the 4pc U-cup seals.



Forklift has run great, lts leaking from other areas now but not the mast cylinder. My other projects were to replace the master cylinder (corroded into oblivion). Replaced the wheel cylinders and brake pads. I found the final drives had greased the previous brake shoes very thoroughly and impressively. My forklift had an "inching pedal" as its described in the manual, its the 'left brake pedal" that's supposed to place the transmission in neutral so the engine can be revved to raise the mast more quickly.

I removed that pedal and also removed the "shuttle valve", and so I eliminated the fluid pathway that puts the transmission in neutral via fluid-power. I just idle around, rigging, and if I want to rev the engine I can place the transmission selector arm in neutral with the best of them.

This forklift also has an odd battery (E10 maybe?) and so I keep it on a battery minder a lot of the time to keep it in good condition.

All of the work over the years has paid off, its reliable and handy as anything in tight spaces, just some drips here and there.

 

[Ziggy2]

Never dealt with a multiple stage cylinder…….if your uncomfortable with trying to reseal it, I would take it to a hydraulic shop and have it repaired?

I did the main cylinder on mine, here’s the thread.

Hyster S80 XL Main Cylinder Leaking, Questions?

My steering cylinder is leaking now, it looks like I will be repairing that one shortly!

Good luck on your repair!

Kevin

The big thing about multistage cylinders is that the ones used in dump trunks tend to get bell mouthed due to side loading.

The two stage cylinder in your fork truck has almost zero side loading so it will not be anywhere as bad as what some people will make it to be.

 

[sscstablemachining]

Would happen to have parts numbers for these seals? Needing to rebuild the exact same one.

 

[86turbodsl]

It'll be easier to just pull the mast number off yours. That's what i did for my Clark rebuild kit. Side of the mast, about 3/4" high numbers.

 

[just Dave]

If you have done any hydraulic cylinder rebuilds before and you are comfortable with it , then you will be fine on this. No adjustments, your seals are old, hard and crumbling. You must rebuild. As said if you’re not feeling it, take it to a shop. If you take it on yourself it is best done on clean flat concrete. Cap your supply lines, remove cyl. Now you can use the fork truck to pull it apart and tap back together. It takes a big tap to start the new piston seals in each stage. KEEP IT STRAIGHT, don,t cut the seals. That’s it. Take your time draining and locate a seal kit before you start. Good luck

 

[john.k]

Never use NOS polyurethane seals off fleabay or whatever...always buy fresh stock...the poly U has a definite life,even in a blister pack ,and must be fresh