Cat 303.5e sticky hydraulics

[rmllarue91]

Imo when you get it back together tee in a line to load sense line and watch as you run it. I'm assuming no load pressure should stay low as you dig it should rise. When working correctly. My understanding super simplified is
Low load sense psi = upstroked
High load sense psi = destroked
I'm by no means a 305 expert but even if I'm backwards it should give you direction.

 

[TVA]

Imo when you get it back together tee in a line to load sense line and watch as you run it. I'm assuming no load pressure should stay low as you dig it should rise. When working correctly. My understanding super simplified is
Low load sense psi = upstroked
High load sense psi = destroked
I'm by no means a 305 expert but even if I'm backwards it should give you direction.

I am not 305.5 E expert either ( only worked on some C/CRs), but I know a thing or two in hydraulics.
LS will be lower then actuator pressure for the margin value!
The thing is this machine has variable margin set by flow of gear pump.

Yes, when you see drop in LS pressure under load - there’s something seriously wrong!!! The question is what exactly seriously wrong?!
The LS is reflection of the system/supply/discharge pressure lower for a margin value. So bucket cylinder bypassing and can only built 500 psi dead headed you will see 500 psi of LS pressure ( dead headed you will have next to no margin because there’s not much flow through the MDCV spool) - it will not mean that the flow compensator is bad!
That’s why when you try to diagnose LS controlled system the differential pressure gauge is a very valuable tool! But for some reason I think it would be not easy to find that in Trinidad.

So for now inspecting components for damage is the best thing IMO.

 

[TVA]

Low load sense psi = upstroked
High load sense psi = destroked

Kinda, but not exactly.
All depends on the difference between main/supply/system/discharge pressure and LS pressure signal

 

[TVA]

The springs I got the price from the Cat Parts website, so dealers sell them.

I couldn’t find a breakdown for the kit, so I have no idea if the bearings come in it or not. Are the bearings normally part of the swashplate or are they part of the case.?

By my logic the inserts should be sold separately because usually they wear more often, but how they are sold - you’ll never know!
For manufacturers it’s about making money, and not about help you fix your machine as fast and as inexpensive as possible!

 

[Nige]

Go back and look at the pdf I uploaded for the 374-2025 Pump Gp parts breakdown.
Is Item #12 (390-9455, qty 2) the swashplate bushing..? if so they are listed @ $143 ea.
In case anyone asks, apparently there is no Reman on the pump and a new one is $2460.

 

[TVA]

Go back and look at the pdf I uploaded for the 374-2025 Pump Gp parts breakdown.
Is Item #12 (390-9455, qty 2) the swashplate bushing..? if so they are listed @ $143 ea.
In case anyone asks, apparently there is no Reman on the pump and a new one is $2460.

I’ve must have missed it, because I was reading through list of parts by description and not item numbers.

 

[TVA]

IDK Nige! The parts list simply says “bushing” and arrow points to the housing/front cover mating surface.
At that price it should be swash plate bushings! But how do you verify?!
Dealers probably will have the same pictures and parts list as you and me.

 

[TVA]

At this point based on what we know, it seems that problem occurs at more advanced swash plate angles prompted by demand for higher flow and higher LS margin set by higher RPM and consequently higher gear pump flow

 

[TVA]

So my “fairy tale”:

The yellow is “we are leaking some pressure but we don’t really care about it because flow demand and pressure is low” zone!

The green is: “we are doing OK with medium flow demand” zone

And the red is: “Oh! Crap! We are in high flow demand and leaking pressure off”zone.

All this time I wondered: why there’s channel from pumps discharge to front cover?!
The problem is I haven’t paying attention to the pictures ( and I haven’t seen all the pictures of this thing)! The swash plate bearing lubrication doesn’t come from the swash plate face, it comes through the channel in the front cover, through slot in one of the swash plate journals, through channel inside the swash plate body and to the journal on the other side!

This is either design flaw or assemblers error, the swash plate bushing that on the side where journal do not have slot in it - should not have the lubrication hole in it ( or should e flipped 180*, to the side where the swash plate do not move to in open loop pumps)!
I think delamination started from the sharp edge in that hole where oil under high pressure started getting in between the coatings layers!

 

[TVA]

Still need to inspect both servo pistons!
Because there’s contamination scratches on the piston slippers, and both pistons are “dead ends”, and contamination just love to settle down in “dead ends”!!!

 

[Nige]

IDK Nige! The parts list simply says “bushing” and arrow points to the housing/front cover mating surface.
At that price it should be swash plate bushings! But how do you verify?!
Dealers probably will have the same pictures and parts list as you and me.

Looking at the parts drawing again I am 99.9% convinced those are the swashplate bushings. Reasons.? Location on the pump, price, & quantity.

Look at the view below which is "Section B-B". Now that section is cut straight through the centre of the pump and coincidentally right through the centre of the swashplate mounting pins, so all you are going to see is a thin sliver of the bushing (two actually) and one of those two slivers is exactly what the #12 arrows are pointing at.

 

[TVA]

You are right Nige!!! And screws (13) are there to prove it!
And this dark spot must be orifice, which also needs to to be checked, because of its gone or loose - it will bleed off more pressure then the swash plate lubrication supposed to take, might even washed out those bearings we see.

 

[Aaron.ampcon]

Hey guys so I've been away from the machine as soon as I get back to it I would check that orifice and servo pistons and give you all and update and some more pictures, I would use that part number for the bushings as the bearing inserts and try to source them.

 

[rmllarue91]

Any updates this one had my curiosity

 

[CapnDean]

Im with you rmll WHats the final analysis?

 

[AC Taylor]

Too many 303.5E options to take a guess which one you have. Need a S/N.

 

[AC Taylor]

I'm new to the Forum and don't know how to search threads. If someone has time I need help on replacing 303cr pilot lines after mechanic removed main valve and didn't mark lines? No power on front 3 valve functions, boom offset swing, blade and swing. Diagrams and parts book is confusing? Also, can't find accumulator, 2005 Cat 303CR, SN DMA04353. Thanks

 

[Nige]

The best suggestion is to create a new thread in the Compact Excavators section rather than revive one that's been dead for 2 years and was in regard to a different problem.
see here - https://www.heavyequipmentforums.co...estions-answered-hopefully.76199/#post-801587