Cat 988B heating issue

[kshansen]

Well if the spec's call for 3000 ft/lbs and you have a 10 foot long handle on that spanner that's an easy one. Just get one 300 lb guy or two little 150 lb kids to hang on the end of the handle. 300X10= 3,000 and Bob's you mother's kid brother!

Or just divide the 3,000 by the length of the handle and that tells you how big a guy you need.

Wish I had the old service manual for the 74TD Euclids we had at the quarry in the 1970's. That book gave the torque for the rear axle wheel bearing nut as "a bar so long and a man so heavy on the end of it"

 

[Nige]

When the lift cylinder repairs are completed and everything is back together I suggest the next step should be to adjust the kickout on the Lift function to make sure that the lift cylinder pistons don't smack hard against the heads of the cylinders every time you raise the bucket up to full height. My only worry is that electrically-speaking it may not be functional or bits may be missing from it. Oh the joys of older machinery.........

 

[kshansen]

I tried to get the rod end into the towbar but unfortunately it just wont go in properly.
I have done the nut back up by reversing the spanner on the setup in the picture and pushing down with the 922b loader.

Now the fun of getting the new piston seal to go back into the cylinder.

One suggestion on getting that piston back in the barrel. Take some nice clean and shinny thin sheet steel, maybe some piece of stove pipe. Just needs to be a bit longer than it needs to wrap around the piston. Make real sure there are no sharp edges on it. Wrap it around the piston and hook together some screw type hose clamps and tighten them down centered right over the seal.

Let it set like that for the time you are getting ready to put it in the cylinder. Then remove the clamps and the stove pipe. Oil it up and if you go nice and easy keeping things lined up real close it should slid in pretty easy.

Of course you have the chamfer at the top of cylinder nice and shinny and the hose or line to the bottom of the cylinder off, not just loose right? No sense in fighting the air pressure in the cylinder on the way in! Don't try to rush it and it should go in with out too much work.

 

[ajginger]

When the lift cylinder repairs are completed and everything is back together I suggest the next step should be to adjust the kickout on the Lift function to make sure that the lift cylinder pistons don't smack hard against the heads of the cylinders every time you raise the bucket up to full height. My only worry is that electrically-speaking it may not be functional or bits may be missing from it. Oh the joys of older machinery.........

I cant see the lift kickout adjustment anywhere on the loader. The lever detent valves under the levers in the cab are stuck solid..... I will have to look into getting some new bits.

 

[ajginger]

One suggestion on getting that piston back in the barrel. Take some nice clean and shinny thin sheet steel, maybe some piece of stove pipe. Just needs to be a bit longer than it needs to wrap around the piston. Make real sure there are no sharp edges on it. Wrap it around the piston and hook together some screw type hose clamps and tighten them down centered right over the seal.

Let it set like that for the time you are getting ready to put it in the cylinder. Then remove the clamps and the stove pipe. Oil it up and if you go nice and easy keeping things lined up real close it should slid in pretty easy.

Of course you have the chamfer at the top of cylinder nice and shinny and the hose or line to the bottom of the cylinder off, not just loose right? No sense in fighting the air pressure in the cylinder on the way in! Don't try to rush it and it should go in with out too much work.

The instruction that came with the seal kit says :
" before installing piston ring onto piston, place piston ring into bore "......

I am not sure why this is done. But I have forced it into the bore a little and left it there an hour.

( it was as hard as heck to get it in there even though it isnt even on the piston yet.... my theory is it must help force the ring seal to contract a bit before fitting onto the piston for reassembly ??)

 

[Nige]

I cant see the lift kickout adjustment anywhere on the loader. The lever detent valves under the levers in the cab are stuck solid..... I will have to look into getting some new bits.

That's what I was afraid of.
Was there a Parts Manual amongst all the documentation the former owner handed over..?
You need to be looking for the "Bucket Positioner Group". It covers both Lift and Tilt function kickouts.

It may help you for the next one but dunking seals in really hot water always seemed to help them fall into place more easily.

 

[ajginger]

That's what I was afraid of.
Was there a Parts Manual amongst all the documentation the former owner handed over..?
You need to be looking for the "Bucket Positioner Group". It covers both Lift and Tilt function kickouts.

It may help you for the next one but dunking seals in really hot water always seemed to help them fall into place more easily.

I did look up the position kickouts in the manual, but cant see the loader arm kickout positioner anywhere.....I think maybe it was taken off by some previous owner.

 

[ajginger]

One suggestion on getting that piston back in the barrel. Take some nice clean and shinny thin sheet steel, maybe some piece of stove pipe. Just needs to be a bit longer than it needs to wrap around the piston. Make real sure there are no sharp edges on it. Wrap it around the piston and hook together some screw type hose clamps and tighten them down centered right over the seal.

Let it set like that for the time you are getting ready to put it in the cylinder. Then remove the clamps and the stove pipe. Oil it up and if you go nice and easy keeping things lined up real close it should slid in pretty easy.

Of course you have the chamfer at the top of cylinder nice and shinny and the hose or line to the bottom of the cylinder off, not just loose right? No sense in fighting the air pressure in the cylinder on the way in! Don't try to rush it and it should go in with out too much work.

I didnt have any shiny steel like you said but made up this ' hose clamp ' type of thing out of some springy pallet strapping steel to squeeze the piston ring while I things set to reassemble the cylinder.

P.s. The bottom cylinder hose is off.

 

[ajginger]

Got it back together this evening.

Question :
Do I need to crack a bleed off so the air in the cylinder can escape once I start her up & ttry to lift the bucket off the support pole ?.....or is it ok to just start it and play with the levers ?

 

[Cmark]

No need to bleed anything.
This applies to any empty hydraulic cylinder. Work the cylinder(s) s-l-o-w-l-y in and out several times, stopping before the end of the stroke. After maybe five or six strokes, start to dead head them, gently at first. Top up the hydraulic tank then you should be good to go.

In your case with one cylinder disconnected, leave the rod unpinned and carry out the above procedure. As the cylinders are connected in parallel the one with no load will happily move in and out without troubling the other one. The other advantage of this is that it will be much easier to line up the pin. Fine adjustment of an air-filled hydraulic cylinder is difficult if not dangerous.

 

[ajginger]

No need to bleed anything.
This applies to any empty hydraulic cylinder. Work the cylinder(s) s-l-o-w-l-y in and out several times, stopping before the end of the stroke. After maybe five or six strokes, start to dead head them, gently at first. Top up the hydraulic tank then you should be good to go.

In your case with one cylinder disconnected, leave the rod unpinned and carry out the above procedure. As the cylinders are connected in parallel the one with no load will happily move in and out without troubling the other one. The other advantage of this is that it will be much easier to line up the pin. Fine adjustment of an air-filled hydraulic cylinder is difficult if not dangerous.

Thanks for that info Cmark.

I know very little of these things, I have driven all sorts of machinery over the years but this is the first cylinder I have ever repaired so am a bit cautious to do it right.

 

[Nige]

Good on you for asking. Most people would have just blindly crashed on and only asked for help when they were up to their neck in the swamp.....

 

[kshansen]

While my suggestions should not be a problem, think it might still help some,
I guess it has been a long time since I did a 988B lift cylinder back in the dark ages the outer ring was not split and you had to stretch it over the piston and compressing it was very important. Main thing is to go slow and easy untill the piston is all the way in and if there is any doubt stop and check things out.

 

[kshansen]

I know very little of these things, I have driven all sorts of machinery over the years but this is the first cylinder I have ever repaired so am a bit cautious to do it right.

If you don't have the service manual with the kick out information let me know I have it saved to my computer.

 

[ajginger]

If you don't have the service manual with the kick out information let me know I have it saved to my computer.

Thanks kshansen.
Will do.
Cant say how great it is to have you guys sharing your years of knowledge on this projects like this one.
Its a real time/money/stress saver.

 

[ajginger]

At the risk of sounding over cautious.......here is another question :

I fired up the 988 and worked the hydraulics slowly till they were working good, then drove it over to the paddock near the shed ( about 150 yards away ) & gave it a bit of work at light digging/reversing/fowards ect...for about half hour. I idled it down, rested the bucket on the ground & shut it down. I then took the filler cap off the hydraulic tank and as I unscrewed the cap it was pressurized with air.
( air was escaping from the tank through the cap-threads as I took the cap off )

Question : Is that normal or does the tank have a breather that is blocked ?

P.S. ..... there was no sign of any heating problem with the little bit of work it did. The coolant temp needle sat about 5 mm into the bottom of the green. But I will hold my hopes that the temp issue has been solved till I put it to real work building a dam within the next few weeks.

 

[Nige]

Is this your tank..?


The tank does not have a breather.
Look at the section A-A in the illustration. That is a relief valve to prevent the tank pressurizing excessively. In your 988B the implement pump suction is above the oil level in the tank so the design is for it to pressurize once the oil gets hot. This assists with oil flow into the implement pump suction side. Provided nothing is stuck in that relief valve you should be fine. Strictly speaking you should only unscrew the tank cap when the oil is cold.

 

[John C.]

In general all hydraulic reservoirs that aren't plumbed to air compressors are made to draw in air as the fluid level in the tank goes down when the piston sides of the cylinders fill up. It forces fluid into the pumps helping to prevent cavitation.

 

[ajginger]

Is this your tank..?
View attachment 213279

The tank does not have a breather.
Look at the section A-A in the illustration. That is a relief valve to prevent the tank pressurizing excessively. In your 988B the implement pump suction is above the oil level in the tank so the design is for it to pressurize once the oil gets hot. This assists with oil flow into the implement pump suction side. Provided nothing is stuck in that relief valve you should be fine. Strictly speaking you should only unscrew the tank cap when the oil is cold.

It does look like this tank.

From this illustration and explanation I gather Since the pressure in the tank wasnt excessive when I took off the cap, I am going to assume everything was normal.

 

[ajginger]

In general all hydraulic reservoirs that aren't plumbed to air compressors are made to draw in air as the fluid level in the tank goes down when the piston sides of the cylinders fill up. It forces fluid into the pumps helping to prevent cavitation.

Thanks John C ....... thats a good explanation of how it works.