CAT 308 E2 intermittent won’t boom down

[HeavyMetalRepair]

TMX00470, just about 8,000 hours. Intermittently will not boom down. Just as a quick check I had the operator change the control pattern and tried it again, still wouldn’t boom down. Machine was brought back to the shop and I removed the filter and cut it open. Found a fair amount of black debris. Something is definitely coming apart. I’m going to dig into the control valve and check it out. All other functions work completely normal.

 

[HeavyMetalRepair]

I believe I’ve found the source of the black material in the filter. Part of what I think is the drift reduction valve is broken. It’s a black plastic disc that the spring for the valve pushes against. About half of it is gone.

It goes in the port that’s not blue plugged.

I think if the disc is moving around in there it will prevent the valve from shuttling over and blocking the oil from entering the return oil circuit. When it doesn’t boom down, it actually does just very very slow. New parts will be here Monday.

 

[HarleyHappy]

Good find!

 

[HeavyMetalRepair]

Good find!

Thanks @HarleyHappy. I like this forum a lot and the community. People trying to help others, lend a hand, inspire another etc… but I have to admit when I was getting all those pop up ads I said screw this! Such an interruption, so distracting. Anyway, thanks to the advice of @TXRweather i switched to brave and so far so good! So I’ll be back posting more! Glad you’re still around too Harley!

 

[HeavyMetalRepair]

New parts arrived. Installed the new valve. Went out and operated the machine. To my surprise, it still did it! And once it started not booming down it did it more and more frequently but not every time. I really thought that black piece was the problem, guess not. I’m going to get some gauges on this thing and see what’s going on.

 

[Nige]

Might the boom down issue be something related to the attached.?

 

[Mobiltech]

Is there possibly a piece of the drift reduction valve blocking an orifice or floating around in the valve.
I would think the problem will be something related to the drift reduction valve.
Or what Nige said.

 

[HeavyMetalRepair]

Might the boom down issue be something related to the attached.?

Interesting, my machine does not have the boom lowering control valve. Hoses from the cylinder go directly to the valve.

 

[HeavyMetalRepair]

Is there possibly a piece of the drift reduction valve blocking an orifice or floating around in the valve.
I would think the problem will be something related to the drift reduction valve.
Or what Nige said.

Yes very possible for debris to be in there creating problems. I’m going to remove it again and inspect.

 

[HeavyMetalRepair]

Couldn’t really see anything else in the valve that might be the problem. Installed a gauge for pump pressure, and tee’d into the pilot hose for boom down at the control valve. When it doesn’t boom down and I move the joystick to full boom down position it has about 600 psi of pilot oil, and just under 4,000 PSI of pump pressure. So it seems like that part of the system is functioning correctly. I know the spool is actually moving because the pump upstrokes. It really seems like there’s some kind of blockage some where not letting the oil go through, like that check valve i just replaced. But I don’t see anything wrong with it, it moves nice and smooth in its bore. I’m gonna do some more testing/checking.

 

[HeavyMetalRepair]

I tee’d in gauges right at the cylinder. When it doesn’t boom down there’s pressure on both sides of the cylinder. After I turned the machine off there was still a couple thousand psi on the head end of the cylinder. I cracked the bleeder on the adapter fitting at the valve and oil came out and the pressure dropped. So I know that pressure is making it all the way back to the valve.

So I removed everything in that valve section and thoroughly inspected it. It all looks ok, whatever the problem is I can’t see it.

 

[HarleyHappy]

So, being that you don’t have the boom lowering valve and your getting even pressure at both ends of the cylinder, I would have to take that cylinder off and take a look at it inside.
Looking at that plumbing, why not try and reverse the hoses and see if it changes to boom up issues?
I wonder if there is a valve in the cylinder base hanging up.

 

[HeavyMetalRepair]

I also had that thought of a valve in the cylinder, like a snubber of sorts. I was thinking having pressure on both sides rules the cylinder out. It seems like it’s trying to move but it can’t. The pressure is making it back to the control valve. The hose from the cylinder goes to a fitting on the valve that has a bleeder on it, when I opened the bleeder the pressure bled off and I heard the boom settle on the ground. I ordered a valve section yesterday, it should be here today. I’m thinking the problem is temperature related also. It took 2 hours for the problem to start happening, and once it started it happened frequently.

 

[HeavyMetalRepair]

After putting the valve back together, running it again, and getting the same problem, it’s getting a new valve. It seems like the valve may have a crack or something that I just cannot see. I would think it would have the problem all the time but… got the bank removed.
View attachment IMG_6508.jpeg
View attachment IMG_6515.jpeg
The valve part number updated, not sure why or if there is a change but I did notice it was made in China, it came with a new load check. Also replacing the line reliefs. One was made in Italy, the other was made in the US. Hopefully they’re all within specs! Seems like these components should be made under the same roof but what do I know…

 

[HeavyMetalRepair]

Boom valve replaced, installed valve bank in machine, and tested. Boom functions properly now.
View attachment IMG_6539.jpeg

 

[HeavyMetalRepair]

On a boom down function oil from the head end of the cylinder goes to the work port on the boom control valve. In the valve, oil is routed directly to that check valve where I found the damaged disc. Once oil can get past that check it can then enter the return oil circuit through the spool. The problem was it just wasn’t getting past that check. Why? I have no idea. I’m thinking if oil was getting to both the spring side of the check and the other side, the spring side would keep the valve closed. Pics show the work port going right to the check valve.


just a little more cleaning and install some tins and she’s back in action!

 

[HeavyMetalRepair]

Hey @Nige, where’s Granville?or is that a joke that went over my head?

 

[Nige]

Hey @Nige, where’s Granville?or is that a joke that went over my head?

You have obviously never been exposed to the comedy genius of the late Ronnie Barker.

 

[HeavyMetalRepair]

Haha! Never heard of him