My D7E has not had much use in years but I need it now and revisiting a few things. 1. I am curious if anyone would know what kind of oil pressure these should run? I think the OE gauge was only a "good/bad" gauge but the one in it shows actual pressure. 2. The clock shows 14,000hrs. That concerns me i this thing has never been rebuilt? Is there anyway to tell if it has been touched? I don't know enough about the engine to make a good assumption on engine condition. I do know the machine seems to fire up reasonably. In warm weather, it will take about 30sec of pony time and seems to puff white smoke off 1-2 cylinders for maybe 30sec, then clean exhaust. The fuel is old though. I start it by engaging the main engine off the pony with fuel off until warmed, and they try it by kicking the throttle up a hair. I think oil pressure was running about 35psi. Certainly has blowby that sneaks out the dipstick when running. 3. One track is slacked after sitting for an extended period. I realized a glob of grease from the cylinder packing. I am not in a position to get into that right now. Curious if a guy can usually just keep adding grease to make use of a machine with this issue? Or is it that once they puke, they will not hold pressure? That would be a bummer to sideline the machine only because of the adjuster.
You will never keep the track adjusted enough to run the machine if the seal is blown. The track adjuster is pretty easy to fix if you have an alligator master link on the track. Just release all the grease and break the track with the master link situated over the front idler. Pull the track up out of the way with a come-a-long. Take the bolts out of the front of the track adjustment cylinder and roll the front idler forward. The piston will come out and you can replace the cylinder packing. This is somewhat of an over-simplification of the procedure but the point is that it is not an extremely hard job for anyone to do themselves.
So usually once the cylinder is puking grease, I could not even get say an hour between adjustments? I realize this might be somewhat of a guess but I am sure someone has fought this and it probably arises at a bad time in a job. It was my understanding that the D7E would not need the track broke or spring/idler removed? I seem to remember reading the cylinder can be removed separately?
If it is like our D4D, the adjuster can be removed without splitting the track. Ours had wishbone type linkage style going to the front idler which came apart. Our 941 loader was a different story.......we needed to split the track for that one, as it had a single rod type going to the front. Perhaps you could send a picture of the arrangement?
Well, I started into it. Got the cover off and it is a wishbone type yoke with a center pushrod pushing on the grease cylinder. From what I gather, the actual piston seal that is likely the issue is inside of the chrome rod? When I push the chrome rod back, the piston will poke its head out?
This is what the assembly on my D4D Dozer looks like when taken apart & cleaned up. Likely your arrangement will be similar. The piston does run inside of the chrome cylinder. Also, the 4 bolts fasten where the assembly comes apart. That yellow seal goes on the end of the piston (top) on mine when assembled & that is likely the cause of your grease leak. Yellow seal end faces forward.
Metalman, thank so much for the pics, that helps a LOT! So from the looks of this, the chrome cylinder is hollow, correct? I am curious how grease gets to the other side? Maybe I should clarify, when grease is injected, it would push on the piston so I will need the slotted side of the U cup seal to face forward or towards the grease zerk, correct? Does grease need to be on the other side of the piston to force the cylinder to move? Or does the piston actually seat against something at the end of the barrel so when grease is applied, The piston stays put and only the barrel moves? What I am trying to do is determine how the grease got to the outside. As well, it looks there are two wear rings there? Would I be able to get the piston all the way out to replace those or at least inspect them? IIRC, you can only get the piston out enough to change the seal? Not like this piston does a bunch of moving so I would not think the wear rings would be that bad? I showed up with chains and such to try to pull the idler forward but I realized that will be complicated as there is not much I can chain to. I can probably get around the track, but I probably should pull on the entire yoke?
Here is a parts breakdown of the hyd adjuster on my 941 that I had apart recently. Note that the back of the piston assembly (where the 2 sliders are) dead heads against the long bolt that runs back through the recoil spring & into the pilot. When grease is applied to the adjuster, the piston remains stationary & the chrome cylinder moves ahead, pushing the front idler in the direction of the blade forward. It is likely the front yellow seal (the one in my picture) that is the culprit causing the leaking. Not sure what your wishbone frame is like, but if you can get it out off, there should be enough room to get the hyd adjuster out. Perhaps someone with experience on the 7E can weigh in on that. In the other picture, the yellow round item with the wings on it is the pilot that the cylinder fits inside of & the long bolt fits in it.
Ah, gotcha! So that piston does actually set directly on that rod and is supposed to stay stationary so grease should never sneak by it anyway!? So when I see grease coming out around that chrome cylinder, that is nearly a guarantee that piston U cup seal is toast unless the barrel is hosed? It has been sitting a long time where it was but does have all the factory covers over it. I got my $12 seal kit coming so I guess we will try the seal and hope it works! I found some pics on the D7 and appears that if you get that cylinder pushed back home, there is enough room to either swap the seal in place, or pull the whole piston. I have the wear rings coming but I don't expect them to be worn but maybe old and brittle. I will swap what I can.
Here is where i am at. got the thing split, idler pulled forward, and so close to getting that piston out. Looks like I will have enough room to get it all the way out but I cannot get the chrome sleeve to go back any further, moved back easy and just stopped. I really don't think its bottomed out but maybe? If so, can I just grab the piston with pliers and pull it out or do I risk damage here?
If there can be enough room to get the cylinder out of the pilot, that may be better, just to clean everything up & get the cylinder moving freely in the pilot, if room permits. There is a large O-Ring at the front of the pilot that sort of seals crud from getting in where the cylinder slides & if that can come apart & everything cleaned up, it may be better. To answer your question about pulling the piston out, if it comes out with a pair of pliers, or even part way, the front lip seal could likely be changed if it is like my 941.
Just gunna let you know I got it knocked out today. Piston came all the way out. I just could not get cylinder to back any more. I think it was maxed out but I was able to just plier the piston and walk it out. Seal was in pieces. junk. New seal and wear rings and we are off like a prom dress. Thanks!
The D7E/F and the 977L have the same undercarriage components, I strongly suggest you carefully inspect the cylinder, if it is NOT bright clean chrome, replace it, cause I been there and done that, replaced just the seals and then had to take it all apart again and replace the seals and the cylinder.