943 B It loses performance when warm.

[cat951b]

Helló srácok, üdvözlet Magyarországról. Van egy 951B és egy 943B rakodógépem.


Jelenleg nincs fotóm a 951 B-ről.-
Van egy problémám a 943-as géppel, hogy amikor a sebességváltóban lévő olaj felmelegszik, elveszíti teljesítményét és lassú lesz.
Tudna nekem segíteni, hogy mi lehet? Természetesen az olajat és az olajszűrőt kicserélték, de nem lett jobb.
Ez egy 1986-ban gyártott franciaországi gép, 19Z00530 9466 órával.

Előre is köszönöm a segítséget.

 

[OzDozer]

Hello cat951b. This forum requires users to converse in English, so you need to translate to English if you wish to receive replies to your query.

 

[cat951b]

Hello guys, greetings from Hungary. I have a 951B loader and a 943B loader.
I don't have a photo of the 951 B at the moment.-
I have a problem with the 943 machine that when the oil in the gearbox heats up, it loses its performance and becomes slow.
Can you help me with what it might be? Of course, the oil and oil filter were replaced, but it did not get better.
This is a machine from France produced in 1986 with 19Z00530 9466 hours.

Thanks in advance for your help.

 

[cat951b]

Hello cat951b. This forum requires users to converse in English, so you need to translate to English if you wish to receive replies to your query.

Hi Ozdozer. thanks for the information. I'll pay more attention next time.

 

[Nige]

This needs input from @Cmark who is the resident expert on Cat hydrostatic loaders.
I guess my question would be limited to confirming the type and viscosity of oil you are using in the hydrostatic transmission & pump dive.

 

[cat951b]

Greetings Mr. Nige.
Cat Transmission Oil TDTO 30W. Filter and oil were changed 03.2023.
When the oil is warm, it becomes slightly opalescent - do you infer from this that air can mix with it?!

 

[Dave Neubert]

should be 10wt

 

[Nige]

Yep. SAE30 is far too heavy.
Don’t you have the Maintenance Manual for it.? The hystat transmission and the pump drive box both require SAE 10W hydraulic oil.

 

[cat951b]

OK, then I drain the oil, but my question is that the performance is good when cold, but the oil is even thicker when cold.

 

[cat951b]

Yep. SAE30 is far too heavy.
Don’t you have the Maintenance Manual for it.? The hystat transmission and the pump drive box both require SAE 10W hydraulic oil.

Nige, but I have a manual for it.
I thought that an older, more worn machine and thicker oil might be better for it.

 

[Dave Neubert]

They don't like thick oil or clogged filters

 

[Nige]

I thought that an older, more worn machine and thicker oil might be better for it.

Not in the case of a hystat transmission it won't.

They don't like thick oil or clogged filters

And there is your answer.........

 

[sawmilleng]

You likely have worn main pumps or main hydraulic motors.

When they get worn they bypass more, and this bypass oil heats up very quickly. When the oil heats up it gets thinner and less oil will stay in the pump discharge lines and more will bypass. Any oil that bypasses doesn't do work so the energy in the oil comes out as heat.

Its an continuing race to the bottom. Years ago, my dad had an old backhoe that was thrashed and the hydraulic pump was in the same condition. To get any work out of it we had to turn a garden hose onto the pump to they to keep the oil cooled enough to at least allow a bit of digging. We tried thicker oil, too. No help. You are going down the same road.

I don't know if Cat puts the filter into the main pressure lines or in the charge pump flows but as others have noted, it is the first thing to check. Cut the filter open and see what you have for metal particles.

Check your pump bypass flows when the machine is warmed up. Cat will have a spec on the maximum flow allowed before the pump needs rework. Same with the hydraulic motors.

I'm willing to bet that if both tracks exhibit the same slowness when the oil is hot you have a serious problem.

Let us know!
Good luck,

Jon.

 

[Dave Neubert]

Under the valve cover there are metal lines that go to the servos the fittings sometime leak they are like a compression fittings and need replaced I have repaired a few by doing this. It would act up when warm

 

[cat951b]

Greetings, gentlemen. Thanks everyone for the helpful information, I will apply it. I would also wait for Cmark's comments. In a previous post, I read about the left and right valves on the transmission, on which the rubber rings tend to wear out. Unfortunately, I rarely have the opportunity to service this machine because it is on my brother's property 200 kilometers from me. Therefore, the repair time will be delayed.

 

[cat951b]

Not in the case of a hystat transmission it won't.

And there is your answer.........

Then I will definitely change the oil to TDTO 10 W.

If the drain screw is on the bottom of the transmission, does the entire amount of oil drain, or does it have to be drained somewhere else, for example from the oil cooler?

 

[cat951b]

You likely have worn main pumps or main hydraulic motors.

When they get worn they bypass more, and this bypass oil heats up very quickly. When the oil heats up it gets thinner and less oil will stay in the pump discharge lines and more will bypass. Any oil that bypasses doesn't do work so the energy in the oil comes out as heat.

Its an continuing race to the bottom. Years ago, my dad had an old backhoe that was thrashed and the hydraulic pump was in the same condition. To get any work out of it we had to turn a garden hose onto the pump to they to keep the oil cooled enough to at least allow a bit of digging. We tried thicker oil, too. No help. You are going down the same road.

I don't know if Cat puts the filter into the main pressure lines or in the charge pump flows but as others have noted, it is the first thing to check. Cut the filter open and see what you have for metal particles.

Check your pump bypass flows when the machine is warmed up. Cat will have a spec on the maximum flow allowed before the pump needs rework. Same with the hydraulic motors.

I'm willing to bet that if both tracks exhibit the same slowness when the oil is hot you have a serious problem.

Let us know!
Good luck,

Jon.

Hello John, thanks for the detailed information! - I hope you won't be right!
By the way, the machine is in good condition and was previously owned by a regular company where it received proper service. According to my observation, the oil will be warm opalescent, as if there are small bubbles in it (I have to examine this under a microscope), from this I conclude that air is mixed into the oil somewhere and this causes its elasticity. Could there be a leak somewhere?! That is why I would like the opinion of experienced mechanics on where seals and rubber ring wear can occur.
Of course, if I manage to find the error, I will report it here!

 

[cat951b]

Under the valve cover there are metal lines that go to the servos the fittings sometime leak they are like a compression fittings and need replaced I have repaired a few by doing this. It would act up when warm

Hi Dave. Thanks for the information!
I'm also guessing some sort of leak. Can you send me a photo and mark the critical places where it might be leaking?
Thanks in advance!

 

[Dave Neubert]

I'm not savy enough to do that just pull the big valve cover off the top of transmission and you will see the metal lines they are like 3/8 lines going down each side to the servos

 

[cat951b]

I'm not savy enough to do that just pull the big valve cover off the top of transmission and you will see the metal lines they are like 3/8 lines going down each side to the servos

Ok, Thanks Dave!