Diagnose? Shotgun? Or ignore? (hyd pump issues)

kylemorley · Apr 22, 2014

Got carried away while fixing a leaky lift cylinder, and pulled the
pump.

Pump has been making a tunk- tunk-tunk noise under load for
years, and the load bobs up down a few inches. Pump has never
been apart as far as I know, certainly not in the 30 years I have
owned the tractor.. So I assumed when I got the pump out I'd see
all kinds of worn out parts to explain the the lift's behavior.. But
everything appears fine! Bushing is within specs, cam blocks
(usually blamed for the a noisy lift) are a very snug fit in the
piston yokes, which are not badly worn either, and the valves
don't seem overly worn or damaged,

I was assuming I'd throw in a kit if the pump showed serious
wear, but I hate to shotgun a problem or put in new parts if they
are not going to make a difference.

Any thoughts on what I may be missing?

flembo · Apr 22, 2014

I have 3 n's and they all make that nock noise when under load, I have read many posts asking the same question and it seems most of the answers are don't worry unless it gets real bad. That said where do you draw the line, My 2n bounces on the way up a little but then smoothes out when all the way up,the 2 8n's are smooth coming up.I have a 300# weight on the 2n When I start it and raise the lift I can feel it in the seat of my pants when it stops I know its up.So now after I rambled on if it was me I would make sure it was clean, button it back up and fill with fresh oil and sleep well tonight.I am sure others will be along soon I will be interested to here others comments I might find out I am crazy.

souNdguy · Apr 22, 2014

remember. if the lift piston leaked. the unit will bob.. as in pump up and leak down then rinse and repeat.. etc.

not saying there aren't other areas to look at ( relief always good to check if you have the pump out.... etc.. )

but could be a ssimple as a leaky lift cyl

Royse · Apr 22, 2014

I'm no expert on hydraulics, but I have three of these tractors
that thunk under heavy load. They do not thunk any other time
and the lift does not bounce on any of them, so I think they are
two different problems. Thunk being the pump and the bounce
being the lift correcting for leak down.

JMOR · Apr 22, 2014

(quoted from post at 18:26:31 04/22/14) I'm no expert on hydraulics, but I have three of these tractors
that thunk under heavy load. They do not thunk any other time
and the lift does not bounce on any of them, so I think they are
two different problems. Thunk being the pump and the bounce
being the lift correcting for leak down.

also believe that a rhythmic bounce on the way up is different problem/source than leaking down from a fixed position & correcting, which also results in a 'bounce' on each correction.

Royse · Apr 22, 2014

(quoted from post at 19:03:39 04/22/14)

(quoted from post at 18:26:31 04/22/14) I'm no expert on hydraulics, but I have three of these tractors
that thunk under heavy load. They do not thunk any other time
and the lift does not bounce on any of them, so I think they are
two different problems. Thunk being the pump and the bounce
being the lift correcting for leak down.

Click to expand...

also believe that a rhythmic bounce on the way up is different problem/source than leaking down from a fixed position & correcting, which also results in a 'bounce' on each correction.

If that is what his does, would you think it was caused by the pump?
As I said, I'm not a hydraulics expert, so I'll learn along with the OP!

souNdguy · Apr 22, 2014

i think if your leak is significant enough.. you could get a bump on the way up by the pump fighting to keep up with the oil in / out issue. ie. 1 chamber pumps.. and befor ethe next one, you are already getting forced leak down from a high load and big leak.. think a 90% leak..e tc. upstream swim ..

or pumping a bike tire up that had a good elak. keeps yer arms moving on that t-pump handle.

However I do agree. bump on the way up is USUALLY a jug not squirting..

flembo · Apr 22, 2014

It sounds like he just repaired the leaky cylinder but hasn't got it back together yet so it will be interesting to see if the rise and fall problem goes away. I am betting it will.

kylemorley · Apr 22, 2014

That is indeed the case. Though how definitive the results will be will be questionable since I am reusing the old, scored cylinder.

It would be interesting to get a pump rebuild kit and try one item at a time - valves, cam blocks, pistons etc - and see what replacing them did to the functioning of the pump. Since everyone tends to buy a kit and shotgun them I'm not sure anyone really knows what really cures what. unfortunately it's a little more work than a feel like doing in the name of science.

Oh, if anyone reading this has installed a full pump kit like those $99 ebay ones with the valves, cam block, bushing and pistons, it would be interesting to hear how they worked out - and especially, did it quiet down the tunk-tunk-tunk.

(quoted from post at 00:27:09 04/23/14) It sounds like he just repaired the leaky cylinder but hasn't got it back together yet so it will be interesting to see if the rise and fall problem goes away. I am betting it will.

Dean · Apr 22, 2014

If the OEM parts look OK and are within spec, do not rebuild.

You will likely find that the aftermarket parts are not as good as the 60+ year old OEM parts.

You will want to clean the valve chambers.

Dean

souNdguy · Apr 23, 2014

depends on the condition of that pump...

carlntexas · Apr 23, 2014

(quoted from post at 19:56:45 04/22/14) That is indeed the case. Though how definitive the results will be will be questionable since I am reusing the old, scored cylinder.

It would be interesting to get a pump rebuild kit and try one item at a time - valves, cam blocks, pistons etc - and see what replacing them did to the functioning of the pump. Since everyone tends to buy a kit and shotgun them I'm not sure anyone really knows what really cures what. unfortunately it's a little more work than a feel like doing in the name of science.

Oh, if anyone reading this has installed a full pump kit like those $99 ebay ones with the valves, cam block, bushing and pistons, it would be interesting to hear how they worked out - and especially, did it quiet down the tunk-tunk-tunk.

I installed one of those kits and it did take the tunk-tunk away.My pump works much better, but the chamber valves were the real problem. here is the thread.

http://forums.yesterdaystractors.com/viewtopic.php?t=1093838&highlight=pump

(quoted from post at 00:27:09 04/23/14) It sounds like he just repaired the leaky cylinder but hasn't got it back together yet so it will be interesting to see if the rise and fall problem goes away. I am betting it will.

Click to expand...

/quote]

carlntexas · Apr 23, 2014

I'm not schooled very well on computers don't know how I got that post inside a quote.

Diagnose? Shotgun? Or ignore? (hyd pump issues)

kylemorley

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flembo

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souNdguy

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Royse

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JMOR

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Royse

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souNdguy

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flembo

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kylemorley

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Dean

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souNdguy

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carlntexas

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carlntexas

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