Cat D6D track tensioner replacement and recoil tension spring lost preload

[jjdow68]

Hello
I have a D6D that has an issue. Can’t find exactly the same issue on the internet. Although there is some seal replacement videos I have not found any that explains my specific issue.
originallyi thought this was gonna be a tension piston seal rebuild. So I have the tracks split and the idler and yolk rolled forward. To separate idler yolk arm from the plate that connects the grease zerk and track bleed off valve the 4 nuts and bolts have been removed. The insert that houses the track adjustment piston is suppose to come out with the insert. Or at least that was my understanding however the piston remained inside the outer adjustment housing either being firmly stuck in the far back wall of that housing or it suppose to be attached to the spring tension rod?
Somewhere In this dozers life, the spring that is suppose to be preloaded and under extreme pressure seems to be decompressed. ?!? The large nut and bolt that goes through the center of the spring is completely loose. You can actually wobble around the shaft freely inside spring.
I have concerns about the releaseing of the spring in its current condition. The spring itself appears to be completely intact and nothing that appears cracked. So I prefer to keep the spring in tact. How risky is the spring at this point. Best I can tell, there is no tension due to preload. ‘Again the bolt shaft is completely loose. If there is any pressure still there it would only be what’s there from the spring hold down brackets located in front of the springs. Those brackets which are two piece, each bracket with a total of 4 bolts holding those down. What precautions should be taken to prevent any dangerous conditions. I was thinking of several straps looped around the spring and a chain binder to connect to the frame while removing the brackets that will grant me access to the spring for removal. My hope is to remove the spring and so long as if it is still safe to use , I would like for it to be preloaded again and finishing up the seal repair.
oh and speaking of the piston seal replacement is that piston suppose to be stuck tighter then dicks hat band Inside the dust cover. I’m including pictures for better reference.
‘everything I’ve read has painted a different picture rather than what I actually have on this dozer. Most video show that the piston comes right on out the inner open ended slide shaft. > clean it up and slide it back in and put it all back together

 

[.RC.]

 

[jjdow68]

as it is shown on this repair manual that piston was suppose to come out with the sleeve. But that piston is still in the cylinder and won’t budge. That’s what I’m showing in this picture.

 

[Nige]

I have a D6D that has an issue.

Can you post a Serial Number so that the appropriate Parts Manual can be pulled up.?
There can be differences in the tensioning/recoil mechanisms between different models of D6D. It is important to get the correct one for your machine. The illustration below may or may not be correct.

Somewhere In this dozers life, the spring that is suppose to be preloaded and under extreme pressure seems to be decompressed. ?!? The large nut and bolt that goes through the center of the spring is completely loose. You can actually wobble around the shaft freely inside spring.
I have concerns about the releaseing of the spring in its current condition. The spring itself appears to be completely intact and nothing that appears cracked. So I prefer to keep the spring in tact. How risky is the spring at this point.

Those brackets which are two piece, each bracket with a total of 4 bolts holding those down. What precautions should be taken to prevent any dangerous conditions. I was thinking of several straps looped around the spring and a chain binder to connect to the frame while removing the brackets that will grant me access to the spring for removal.

A WARNING....

The recoil spring is often referred to as the "Death Spring" for a very good reason. They have killed people in the past.

That spring will still have a tremendous amount of pressure in it, even with the bolt broken.
That broken bolt is key. It is what holds the recoil mechanism together for installation or removal
purposes. With the bolt having broken there is NO WAY that the spring can be safely compressed in order to remove the recoil assembly mechanism. IMHO the only safe way to attack that spring is to cut it with an oxy-acetlylene torch until all the forces have been released. At that point the rest of the mechanism can be disassembled.

I would recommend that you DO NOT attempt to remove the bolted brackets ahead of the spring, whatever safety measures you put in place. The force released as the bolts break loose will almost certainly kill you.

 

[jjdow68]

That piston in this picture “number5” is still in the cylinder.

 

[Nige]

Some reading for you.

https://www.heavyequipmentforums.com/threads/death-spring-removal.75004/

 

[1466IH]

That large bolt on the center of the spring os only for removal and installation purposes. After the spring is installed onto to machine and both dogs are bolted down to the track frame in front of it that bolt gets loosened to allow the spring to rest between the backing plate and the dogs. Unless there are broken bolts on the dogs or see any cracks or broken welds anywhere that spring should be perfectly contained. With that said they are still widow makers and should be treated accordingly. You could if you want wrap chains around it and the track frame. Those springs are very affordable aftermarket and readily available (at least the last I checked) so if you do decide to remove it just cut it one coil at a time until all tension is released. If you decide to go that route post back here before trying to compress and install new spring because you must compress it properly.

 

[jjdow68]

Can you post a Serial Number so that the appropriate Parts Manual can be pulled up.?
There can be differences in the tensioning/recoil mechanisms between different models of D6D. It is important to get the correct one for your machine. The illustration below may or may not be correct.

View attachment 335867



A WARNING....

The recoil spring is often referred to as the "Death Spring" for a very good reason. They have killed people in the past.

That spring will still have a tremendous amount of pressure in it, even with the bolt broken.
That broken bolt is key. It is what holds the recoil mechanism together for installation or removal
purposes. With the bolt having broken there is NO WAY that the spring can be safely compressed in order to remove the recoil assembly mechanism. IMHO the only safe way to attack that spring is to cut it with an oxy-acetlylene torch until all the forces have been released. At that point the rest of the mechanism can be disassembled.

I would recommend that you DO NOT attempt to remove the bolted brackets ahead of the spring, whatever safety measures you put in place. The force released as the bolts break loose will almost certainly kill you.

Thank you for the reply and the insight. The spring under load is 20 inches and at free release the spring is 25 inches. According to caterpillar.
I haven’t measured the spring but I will to verify the load.
If the spring measures to be under full load then perhaps I should leave it alone and just concentrate on removing this piston that seems to have lodged itself into the back of the housing cylinder.
My understanding is the piston should have come out with the sleeve but it did not.
Any recommendations on how to get that piston out.
after seeing the info that you guys have sent it appears to me that piston is suppose to float.
I haven’t seen a scenario in any repair manual or repair video so far that would lead me to believe that piston is supposed to be fastened to anything. But the fact that it so tight it made me hesitate to go at that piston not knowing for sure. I didn’t want make this worse by trying to remove something that is somehow bolted down.
4x 06525

 

[jjdow68]

That large bolt on the center of the spring os only for removal and installation purposes. After the spring is installed onto to machine and both dogs are bolted down to the track frame in front of it that bolt gets loosened to allow the spring to rest between the backing plate and the dogs. Unless there are broken bolts on the dogs or see any cracks or broken welds anywhere that spring should be perfectly contained. With that said they are still widow makers and should be treated accordingly. You could if you want wrap chains around it and the track frame. Those springs are very affordable aftermarket and readily available (at least the last I checked) so if you do decide to remove it just cut it one coil at a time until all tension is released. If you decide to go that route post back here before trying to compress and install new spring because you must compress it properly.

Oh wow this is interesting and makes me hopeful. so the fact that the rod is loose doesn’t necessarily mean it’s broken. There are no broken bolts on the dogs. Haven’t seen any cracks anywhere. To me nothing looks compromised concerning the spring. That loose rod is all I’m going by as the concern for the spring.
Hell it might be perfectly normal as it is.
However the piston be ing stuck in the cylinder is what lead me down this rabbit hole. Any thoughts on removing a stuck piston.

 

[Nige]

4x 06525

Then the illustration I posted above is correct.

However the piston be ing stuck in the cylinder is what lead me down this rabbit hole. Any thoughts on removing a stuck piston.

Can you post a photo of the area circled in the illustration below. Are the end of the bolt, the washer, and the nut all still there.?
EDIT: Thinking a bit more about it the possibility exists that the piston is seized right at the back (left side as per the illustration below) of the the track adjuster cylinder and this is what has pushed the bolt to the left and has it hanging loose.?

 

[pittsburgh cat man]

I’ve had ones that worked around drilling rigs be a real pain getting out because of the salt brine

 

[Nige]

If the spring measures to be under full load then perhaps I should leave it alone and just concentrate on removing this piston that seems to have lodged itself into the back of the housing cylinder.

In order to disassemble the tensioner cylinder and remove the piston it is likely that you will have to remove the entire cylinder from the machine. To do that will require the recoil spring to be correctly de-tensioned. I think you're stuck between a rock and a hard place.

 

[pittsburgh cat man]

I think you need to look at pilot between coils to see if there are any cracks. Was idler slammed the whole way back? Second thing to note is compressed length is so it will fit it during assembly

 

[jjdow68]

yes I will go get some better pictures to send. i thought I had better pictures than I actually have. If I haven’t said this yet I sincerely appreciate the help.

 

[Vetech63]

Did you remove the grease valve from the barrel? Trying to pull that out with suction on it will be near impossible.

 

[jjdow68]

In order to disassemble the tensioner cylinder and remove the piston it is likely that you will have to remove the entire cylinder from the machine. To do that will require the recoil spring to be correctly de-tensioned. I think you're stuck between a rock and a hard place.

I was thinking maybe welding a washer end wise on the top of the piston pin so I could attack a slide hammer and possibly dislodge the piston that way. Thoughts?
Everything went by the book,so to speak, right up until the piston stayed in the cylinder. Very straight forward then this.

 

[Nige]

I was thinking maybe welding a washer end wise on the top of the piston pin so I could attack a slide hammer and possibly dislodge the piston that way. Thoughts?

As per what @pittsburgh cat man posted above you should check very carefully that the 7M1859 Pilot Assembly (will be visible through the coils at the front end of the spring) is not cracked. If it is cracked then it will have to be replaced. Removing the existing piston and fitting a new one will not fix the problem. The issue is that to replace the pilot the spring has to come out.........

 

[jjdow68]

Did you remove the grease valve from the barrel? Trying to pull that out with suction on it will be near impossible.

Yes sir all that came out the sleeve etc. there was zero grease pressure on the tensioner piston. Here is a picture of the sleeve.

Did you remove the grease valve from the barrel? Trying to pull that out with suction on it will be near impossible.

 

[jjdow68]

Yes sir all that came out the sleeve etc. there was zero grease pressure on the tensioner piston. Here is a picture of the sleeve.

I cleaned up all the old grease inside the cavity to get a better visual. This is a picture of piston in cavity after cleaning it up.

 

[jjdow68]

As per what @pittsburgh cat man posted above you should check very carefully that the 7M1859 Pilot Assembly (will be visible through the coils at the front end of the spring) is not cracked. If it is cracked then it will have to be replaced. Removing the existing piston and fitting a new one will not fix the problem. The issue is that to replace the pilot the spring has to come out.........

View attachment 335883

Oh I see. Well there is grease in there around the spring. I just assumed the grease was due to the busted seals. But I see what you are saying here. I’ll need to clean up inside the spring to get that grease out to possible get a visual of the pilot assembly.