988B hyd problems

[gladiatore]

OK after you told me that I did some things, first check oil cooler was a bit clogged I put air to it, second changed the valve in chassis (next to cooler) next I drain all hydraulic oil from tank check all hoses and tubes ( all OK) after few time started do same (as bloody operator told me) I jump in machine and saw it works even in low rpm if you push an release clutch(left pedal) if you don't touch is impossible move lift and bucket, so I think is accumulator, I'm missing something?

 

[Bob/Ont]

Your neutralizer hose is hooked up wrong, maybe a lot more things.
Later Bob

 

[gladiatore]

Which is neutralizer hose?

 

[Bob/Ont]

Look at the valves on the plate on the frame side behind the cab. Have someone step on the brake pedals rh then lh and watch the brake valve will move both times but the neutralizer will only move with the lh pedal. Look for a hose or tube from it to the trans. That puts the trans out of gear for loading the bucket. Will it put the trans out of gear? The rh can stall the torque the lh will not. Verify this first.
Later Bob

 

[gladiatore]

I already checked all hoses and even change neutralizer this is almost in top of accumulator also I changed all Hosea and same trouble

 

[gladiatore]

ok let me show what i have been changed and checked so far

acumulators (3)



Pilot System



Spools



This valvle next to control unit over front axe



I think this is neutralizer



and valvles behind control sticks in cab, also several hoses from all these parts, the thing here is first (when cold) works great, later (now works and dont block) but you need push a bit clutch to realese lift and bucket


BTW this is the machine doesnt wants get fixed

https://www.youtube.com/watch?v=7RnPHv07cig

 

[kshansen]

I know you have checked the pilot pressure before but have you checked it before and during the failure since replacing these parts?

Also do you have the tooling to charge the accumulator? If you do can you check to see that you are getting the full brake pressure. If connected to the fitting the nitrogen goes in to charge the accumulator when engine is started pressure should raise from the 5735 kPa at 90ºC that is the nitrogen precharge point to 13440 kPa at the cut out of the accumulator charging valve.

If you are set up with the tooling to charge the accumulator and have the nitrogen to do it I might try draining the accumulator to see if there is oil on the nitrogen side of the accumulator piston. A small amount would not be a problem, like a coffee cup or less but several liters could indicate a internal leak. The way I do it is just connect the hose to the fitting on the top off accumulator and after the nitrogen is vented out start engine and let it run with hose in bucket. You will get air and a little foamy oil then when the piston is at the top it will stop. Then hook up the nitrogen regulator set at the proper pressure for the temperature and keep pumping the brakes till you hear the piston in the accumulator hit bottom then let it set with pressure on it for a while to be sure it is equalized.

 

[gladiatore]

well i checked all pressures and are normal, 0 when start problems and 348 when they push the pedal, btw i dont have a kit for nitrogen, what i can do? can i change complete the deposit from the other machine?

 

[kshansen]

Not sure what you can do about checking the accumulator without a way to charge it. At the least you would need the fitting to couple to charging fitting on the accumulator with hose to a gauge rated at around 3,000 psi or 15-20,000kPa then a regulator and the nitrogen tank full of nitrogen.

On the cold cooler and hot oil in tank there is a cooler bypass valve, I believe it's located fairly close to the cooler, just follow the hoses from the cooler and they should attach to a valve that works by opening when cooler inlet pressure goes over something like 45 psi. I'd be taking this off and open it up to see if everything inside looks good. No broken springs, plugged orifices or jammed up spools.

 

[gladiatore]

About the valvle next to cooler already checked and changed, really this is driving mad

 

[kshansen]

About the valvle next to cooler already checked and changed, really this is driving mad

Do the lines going to or coming back from this valve get hot? If not I would be tracing them back to where the start and see where you find things that are hot. I am having trouble seeing where the lines go by just looking at parts book in SIS. But if those lines to and from the cooler are not getting hot either the cooler is plugged inside or there is something blocking the flow or the oil. Can you remove lines from the cooler and check by blowing air through the cooler? I'd blow in both directions and try to watch if anything comes out like a rag or anything eles that could restrict the flow.

 

[gladiatore]

How looks the kit for recharge nitrogen? Because now they need push 2 times brake for work

 

[kshansen]

the kit we had at work was an older version of the 1755507 part number, this is the Cat Service tool that goes for around here for about $1,200US



It would might be possible to assemble a kit to do this job from locally available parts, might be best to contact local supplier of compressed gases.

If you do a Google search online there are several different kits with all kinds of prices. The two most important items I can see would be the regulator to connect to the tank and the chuck to fit the valve on the accumulator. Good gauges and valve capable of the pressures involved also important.

 

[gladiatore]

Well tomorrow ,I will try separate the other and see if nitrogen doesn't scape because cat dealer here told me it takes 1 month to arrive the manometers so I will risk myself wish me luck

 

[gladiatore]

well guys yesterday i changed nitrogen tank (from the one the other machine had, and a valvle that goes to brake and nitrogen tank, and innsted of getting better, become worst, now they need push brake from beggining even cold, so i think the problen could be the valve, or what you think? btw in pictures from the nitrogen tank, that is what i took out from it

 

[kshansen]

Well tomorrow ,I will try separate the other and see if nitrogen doesn't scape because cat dealer here told me it takes 1 month to arrive the manometers so I will risk myself wish me luck

The Cat Dealer does not have the tooling to charge the accumulator? That would be hard to believe as so many Cat machines have accumulators or use the nitrogen suspension systems. Or are you saying to buy a set for your own use will take that long to ship in? Have you tried contacting some place that sells welding and cutting suppies to see if they would have a regulator that was suitable for nitrogen? As that would be the most important part you would need to build your own tool kit. Not familiar with what is available in your area but if there are any industrial supply houses like Graingers or McMaster Carr they should be able to supply valves and gauges sutable for pressures you would be needing.

One other idea that maight work would be to take the removed accumulator to the Cat dealer and have them charge it to the correct pressure then return to site and install it. This may not be the recommended way to do it but sometimes you have to do what you can to get the job done. They should be able to see if it had an internal leak doing it this way.

Anyone else want to chime in on this thought??

Not having the means to charge an accumulator when owning and using these machines is like not having an air compressor to inflate a soft tire.

 

[gladiatore]

Yes ken, sorry I didn't make myself clear, I wanted buy one in cat dealer and is the time for the part arrive, but why the other nitrogen cilinder didn't also worked good, if the other machine was running great? So you don't think this valvle I posted can be the problem

 

[kshansen]

Yes ken, sorry I didn't make myself clear, I wanted buy one in cat dealer and is the time for the part arrive, but why the other nitrogen cilinder didn't also worked good, if the other machine was running great? So you don't think this valvle I posted can be the problem

Not really sure but seems like the problem has to be something in the system that is connected to the pump for the pilot system. I guess as a test you could put the one you took out back in to see if this changes the way things work.

 

[lantraxco]

Yep, sounds to me like you changed from a weak accumulator to one that has lost all it's charge?

 

[gladiatore]

One thing now drive me mad is I took nitrogen accumulator to cat draler , they already chargeed me for make the charge, an they just call me they don't have the tool for charge, in all country, this is insane