As I type this, my Caterpillar dealer is out here modifying the plumbing and power link jaw on my 336E's center-lock pin grabber coupler BECAUSE "use of certain hydro mechanical attachments can cause the coupler to open inadvertently". HOW? All my Caterpillar bucket couplers are plumbed the same, but only a few machine/ linkage models are under review/ revision. And, Cat isn't kidding, as less than a month after receiving a " PI " notice, our 336E developed just such an anomaly. Coupler cylinder checks out good...no bypassing internally. Coupler cylinder check valve/ relief checks good...even swapped with known good valve. Coupler electromechanical valve checks good...also swapped with known good unit. Apparently, Cat has determined that an additional control valve needs to be installed to prevent unwarranted coupler activation. Pictures to follow. Even after their revisions, I am still left with a 3100 hour coupler with extensive mechanical parts damaged and or worn out. First inspection upon uncoupling complaint revealed the loss of one "link" from the cylinder mount can arm to the safety jaw. Further inspection, upon disassembly revealed can arm pivot bearing bores oversized, fractured cylinder mount bearings, cylinder side mounted bosses fractured loose from their welds and longer perpendicular to the bore, distorted bores under the cam arm saddle caps, damage to one safety jaw link anchor from cam plate to cylinder contact, sheared jaw to rod pin's roll pin (allowing said pin to walk side to side) and a few non-critical cracks in the coupler frame welds above the safety jaw. Has anyone experienced issues with the center lock coupler? Is there a more durable pin grabber coupler out there? I've had saddle bolt issues (breakage) on both of my other center lock couplers, one requiring cylinder repair when the cylinder struck the stick tip, resulting in the crushing of the steel lines integral to the cylinder (on two separate occasions). Also, "footballed" every bucket coupler cylinder on every Miller designed Cat pin grabber coupler here. In summary... Is there a better pin grabber coupler? Or Has anyone made changes to enhance the durability of the Caterpillar bucket couplers?
Our 385 the grabber was malfunctioning and the bucket came off and into the cab when the operator tried to lock or unlock it. I haven't heard or had a problem with our 336e. It always worked wonderful. Very curious about this issue.
Can you explain that a little more, like what was malfunctioning, and more importantly why did he have the bucket close enough to the cab to hit it when he was locking/unlocking it? Just curious.
I have yet to find a coupler that doesn't need as much welding or repair as all the buckets it uses combined....cylinder problems, hoses, breakage, cracks, pin wear, electrical.....I have lots of experience with 5 or 6 different manufacturers of machines from 120's to 700's all have problems....they are just a maintenance point if you don't need them for extended periods of time remove them!!! the machine has better digging performance and lifting capacity and less wear......TIO
I can't remember the full story but the gravity bar on the couple didn't always work and the bucket would have to be curled all the way in close to the cab to unlock. It was a fairly new operator on the machine and he was dropping one bucket and traveling to the other bucket and locked the grabber so the alarm wasn't going off. Grabbed the bucket and forgot flipped the switch and the grabber pushed it off IIRC. It was a while back so can remember for sure. That machine didn't have a safety bar to grab the pin unlike the 390-336 either.
I had a bucket come off a Cat with a Miller designed pin grabber. This was the original design without the extra flap at the back to hold the pin in. Not sure whether this would have helped though. It was a hire machine and they took it back, stripped it down and covered up the problem. As far as I could work out it was caused by an electrical fault that permanently opened the hitch, even when the safety arm was down and all the hydraulics were supposedly isolated. We were very luck no-one was hurt as we had just finished grading out a bank from the bottom. If it had happened the it could easily have come through the windscreen. Graham
We had the same issue with our early 336e's and a few 328d's. cat updated the coupler somewhere along the line to fix the problem and now our older buckets don't fit the new coupler. They changed the pin spacing on the new one so you have to buy new buckets or modify old ones. Just plain stupid in my opinion.