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Hydro system clean outs? A waste? Filtration? Options?

fastline

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So dealing with an older dozer that was supposed to be good to go. Reality is the driveline hydro system has issue. On this unit, the trans oil is drawn in by an engine driven gear pump, from the trans/steer clutch area, to supply pressurized oil to the trans, TC, steer clutches, and control valving.

That oil is filtered via a magnetic filter screen system just before the gear pump, and is post filtered with two larger filter units. The post filters have bypass ability so if they are clogged, they will bypass oil to get the job done.

So, on personal inspection, i have confirmed the magnetic filter is plugged to the hilt. Mostly silver fines but I did not totally pull the filter yet to confirm every issue. It was simply obvious the magnets were doing their job and this is the reason the pump cannot supply proper pressure/flow to the trans and clutches.

The post filters did not initially show major concerns but I did not actually pull them and cut them open because I have concerns that removal will put even more metal in the outlet side. Not sure how the system is designed.

It is obvious there is moisture in the system. There is still some black oil indicating this might be a condensate matter as I don't see many other water intrusion possibilities. When I drained the trans gear pump, I had black oil, gray oil, and even droplets of straight water.

The symptoms previously were a loss of trans hydro pressure in the system. I think I can confirm that at least the magnetic filter to the pump caused most of that. However, those don't foul for no reason and something either died or is dying. I would like to get some experienced thoughts on how to proceed? Is it cheaper to just buy cheap oil and try to rinse the system? Will that even work? Can we rig up a crash cart to filter things and try to revive it that way?

I do not have a current oil analysis. Was told it was high in "metals" but knowing what those are would help! However, without knowing the composition of materials in all of the system, it might still be a guess as to what is going on.
 

Nige

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IMO if the amount of metal was enough to clog the magnetic strainer added to visible water in the drain stream you're in for a complete teardown and rebuild whatever is/was the root cause of the metal generation.
Pulling the filter and cutting it open will not permit any more particles to pass downstream so long as you disconnect the lines to the filter housing and drain it at before you remove the element to replace it. Oil flows from the outside of the element to the inside, so the "dirty" oil will be between the OD of the element and the filter housing.
An oil analysis would show huge numbers (of whatever) and be positive for water. Again another indicator to - "tear it down".
The symptoms previously were a loss of trans hydro pressure in the system. I think I can confirm that at least the magnetic filter to the pump caused most of that.
A false premise IMO. The screen plugged BECAUSE something has already died. It ain't dying - it's dead. The full screen is a road sign telling you to "look upstream and you'll find the mother lode".

If that screen is in the bottom of the converter housing than that's what you need to be pulling out first. Other components may follow. A replacement pump will most probably be required.

You need to be more worried about fixing what's broken than worrying about system cleanout at this point. The cleanout can be looked at once you've fixed everything that's broke.
 

JD955SC

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We have customers that like to play the gamble of replace the broken component change the oil and let her eat and see what happens

For some reason they never are willing to pay for the repair and proper clean out but have plenty of money to replace failing components repeatedly. Go figure

Pay me now or pay me later, truer words have never been spoken in regards to repairs and half measured repairs
 

fastline

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I have no idea where the debris are originating from on the mag filter. Very hard to determine where the pickup line is. The pictures in the books all suck so its just a guess.

Are the transmissions very sensitive to oil contamination? How about the torque converters? I might not mind digging into this one a bit but I think it might be stupid if it needs new clutches, transmission, TC, spools, pump, ring/pinion, etc, etc. They just aren't worth it.
 

Nige

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I have no idea where the debris are originating from on the mag filter
I said that above. The first component upstream of the screen. Where exactly is the screen where you found the material located, in the bottom of the transmission case or the bottom of the torque converter housing.? Also how about posting a pic or two of the particles.?

As stated before you have a major failure on your hands which caused the contamination. You have to find the failure and fix it before moving forward.
 
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Delmer

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All I see is this is an "older dozer" and it's not worth a rebuilt trans? change the filters and the oil and see what it does. Unless it's not worth a new set of filters? Then stick it on craigslist for parts?

Nige buys his trucks in sets, and assembles them himself, he has a little different standards than I do. I wonder if I could come up with an oil test for situations like this, my "white bucket flush oil analysis": drain all the oil into a clean white bucket, set aside and allow to settle, flush the component with diesel into another white bucket, allow to settle, repeat until no more debris is removed. Separate the debris with a magnet, the magnetic debris will cost $3,000/ounce to repair, the nonmagnetic will only cost $1,200/ounce to repair. Sorry for the bad joke, it would be about as useful as oil analysis on this one though.
 

fastline

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Unlike my other equipment, the manual just sucks so I am stumbling into info bit my bit. Apparently the TC has a pump and screen filter all it's own. The book of course does not say where the pickup is but does mention the "bevel". Which as I understand, the bevel gear and clutches all run together. However, there is a picture that indicates pickup might be from the trans....

The mag screen I pulled was for the "trans/clutch pump? which is located about 2" from the suction inlet of the pump, which is mounted on the engine bell housing.

The fact that the ring gear bearings were found to be bad previously would give me great concern that either something was missed by the techs (those bearings don't fail for no reason) or they did a poor job and those bearings ate themselves.

I guess the only right thing to do is gut it, pull the covers (floor, trans, and clutch) and see what I can see. I agree settling the oil out in buckets I am sure with the amount of sitting, most of the fun stuff will be the "first pour" off the drain plugs.

I DO know the TC and trans pump were replaced very recent. Indication was the TC vanes were heavily eroded. I am sort of wondering if that was the component that went bad, and sent its debris through the system. However, you would think an experienced CAT dealer wrench would know to look for this.
 

Nige

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The mag screen I pulled was for the "trans/clutch pump? which is located about 2" from the suction inlet of the pump, which is mounted on the engine bell housing.
Post a photo, but my bet is the "bellhousing" that you're talking about is actually the torque converter housing, which is where I figured the screen would most likely be.
 

kshansen

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Am I missing it has there even been a mention of the make of this "dozer"? The very last sentence from the poster does seem to indicate it was a Cat so at least that is a start!

A picture of the magnetic strainer as removed would be interesting if only for the shock value!

If it is as bad as it sounds might be worth dumping in some of the cheapest oil after cleaning strainer and replacing filters then run a bit and drain again the inspect them to see how much more comes out. At least that you make cleaning the housings easier if someone does attempt to salvage this thing.
 

fastline

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Yes, this is a continuation of my "D7E" thread. CAT

Nige, I can confirm that the pump mounted on the side of the engine is a different pump, though still not sure if it provides any oil to the TC. The TC actually has its own pump and filter that are very clear and obvious on the TC. It is a small gear pump and there is a filter unit buried down there.


Where I am at here, and just a hope, the condition that parked the machine was the clutches and trans would not operate correctly. It was confirmed that oil pressure to the clutches dropped drastically when activated. However, one look at the intake mag filter for that pump would prove "why" the pump cannot provide any volume. However, as we all know, that filter should not be plugged.

As I understand it, the pressurized oil simply actuates the big pistons in the clutches and locks the trans clutches together. I don't think there are any oiling port where that oil is pushed direct to critical bearings. With this hope in mind, I am hoping that the post filration did it's job, which "might" have saved a few things. For instance, those clutches are stupid simple devices, but there is a $5 Oring on the piston that if shredded, will take many hours to fix. I am hoping the oil inside the clutches is clean. hope......

I think I will first have to get all the filters out. I still am not even sure if the filter on the TC is a suction or pressure side filter...... The manual SUCKS!!! On my other CATs, the manuals are insane GOOD! They literally explain the entire theory of what everything does with very detailed hydro schematics. The schematic I have does not even show the TC pump, though it certainly shows the filter, and I know the pump is there....lol

Let me dig in the books some more and see what other clues I can find.
 

Nige

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Unlike my other equipment, the manual just sucks so I am stumbling into info bit my bit. Apparently the TC has a pump and screen filter all it's own. The book of course does not say where the pickup is but does mention the "bevel". Which as I understand, the bevel gear and clutches all run together. However, there is a picture that indicates pickup might be from the trans.....
Here’s the problem. There are no online manuals for that machine in the Cat system. Try taking some photos of the diagrams from the manuals you have and post them up so that everyone can see what you’re looking at. There will be plenty of people on here who will be able to help you interpret them.

Also post the Serial Number just in case someone has other manuals that might be applicable to the tractor.
 
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fastline

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Here are a couple pics from the PDF manuals I have. Serial is 75E70x
 

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  • 005370.pdf
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  • 005371.pdf
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kshansen

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Going by the 005371.pdf I'm seeing two separated magnetic strainers. One on the suction line to the pump #14 and one on the inlet to the oil cooler. That strainer is #4 and cooler is #3. Pump #13 is being called a scavenger and circulating pump.

As the pressure tap "C" is in the line from filter #2 and that filter is connected to pump #14. That would be the pump that works the transmission and steering clutches. I would be very interested in knowing what that filter caught before it went into by-pass mode. Because if there was/is anything of any size there you can be sure every place in the system has got it's share of the crap, control valves and bearings included.
 

92U 3406

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We have customers that like to play the gamble of replace the broken component change the oil and let her eat and see what happens

For some reason they never are willing to pay for the repair and proper clean out but have plenty of money to replace failing components repeatedly. Go figure

Pay me now or pay me later, truer words have never been spoken in regards to repairs and half measured repairs

Or they come back and want us to eat the bill for subsequent failures.
 

fastline

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Going by the 005371.pdf I'm seeing two separated magnetic strainers. One on the suction line to the pump #14 and one on the inlet to the oil cooler. That strainer is #4 and cooler is #3. Pump #13 is being called a scavenger and circulating pump.

As the pressure tap "C" is in the line from filter #2 and that filter is connected to pump #14. That would be the pump that works the transmission and steering clutches. I would be very interested in knowing what that filter caught before it went into by-pass mode. Because if there was/is anything of any size there you can be sure every place in the system has got it's share of the crap, control valves and bearings included.


I think all I can 'hope' is the filters did not bypass and the plugged up magnetic inlet screen restricted the pump thus causing the low pressure to the clutches/trans. The pump was observed to have proper pressure until certain hydraulics were activated. The #2 filter unit is pretty substantial. There are 2 filters, about 14" tall each. Not certain if one is for clutches and one for trans , or if they act in series as double filtration. A course and fine if you will. I will see if I can find parts diagrams that help paint that picture.

From the pics, I am not sure how the TC gets it oil. There are pics of the inlet coming from the trans, yet a spec for that inlet relief valve as position pressure, 110-120psi. That would mean the main pump supplies it? As well, it looks like the oil goes to the TC pump, through the TC, THEN through filtration? I hope that is not the case!
 

Nige

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Right, now the dog can see the rabbit. It's a simple system and pretty obvious how it works.
There are two pumps (13) & (14), but only one of them (14) actually supplies oil to the system.
The 2nd pump (13) is the converter scavenge and circulating pump. It has two fiunctions, first to circulate oil from the torque converter through the cooler and second to scavenge any oil from inside the converter housing and return it to the transmission housing. The oil inside the converter housing accumulates from internal leakage within the converter. Do you have a parts breakdown for that pump.? Is it a single-section pump or 2-section.? I think it is most likely a 2-section pump.

System Operation
The reservoir/tank/sump for the system is the transmission case (8).
The pump (14) sucks oil from the transmission case (8) and delivers it via the filter (2) to the inlet port of the transmission control valve (9). This is also the location of pressure tap (C). At that point the flow diivides. Some goes into the transmission control valve (9), the rest heads to the steering clutch hydraulic control (5) from where it is used to supply oil to the steering clutches (1 & 11) and also to lubricate the bevel gears and the cross-shaft.

The converter inlet relief valve (6) is part of the transmission control valve (9). This valve takes pump pressure and reduces to the required converter inlet pressure. It is also the location of pressure tap (D). Oil flows along the line from the inlet relief valve (6) to the torque converter (10). The pressure inside the converter is controlled by the converter outlet relief valve (7). From that valve oil flows through the magnetic screen (4) and the oil cooler (3), returning to the converter in what could be described as an endless loop. When it arrives back at the converter at the circulating pump (13) some of the oil is diverted to lubricate the transmission via the line with pressure tap (I), the rest of the flow is returned back into the converter.

Simples........

upload_2019-9-30_13-33-19.png
 
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kshansen

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Do you have a parts breakdown for that pump.? Is it a single-section pump or 2-section.? I think it is most likely a 2-section pump.

I agree that pump shown in the first attachment that shows the converter housing sure looks like a two section gear pump very similar to many Cat transmission pumps:
D7 Pump.png
 

Nige

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Oops, never looked much at that attachment when I saw it was a parts breakdown, i was concentrating more on the hydraulic circuit diagram. You're right, it does look like a 2-section pump. I know logic dictates that it ought to be 2-section, it would be nice to confirm that with an internal breakdown, or an illustration of the lines that connect to it.
 

fastline

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Yes, appears to be a 2 section pump. Question at the moment is what gets filtered and when? There is obviously a filter mounted inside the converter. I am trying to determine if that is the filter denoted in the hydro diagram or not.

The converter was very recently replaced. Because of the low hours on the machine, I would not expect it to fail even the first time. It is possible the converter is dead and it would seem the scavenge pump sends 'case drain' oil right back to the trans? Where the main pump would pick it up?
 

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