JD 8640 no steering or remotes

bison

Well-known Member
I was discing yesterday and all of a sudden i lost steering and remote hydraulics. i looked around the tractor if i saw oil leaks, when none found I unhooked the disc and tried to limp home. 500 feet down the field hydr transmission oil started shooting out under pressure between dr side tank and clutch housing that drained the oil reservoir rather fast.
Among a lot of other things i had installed a new clutch and transfer/charge pump drive gear and shaft and changed all filters and the trans fluid. tractor had not been used for a couple years before yesterday.
Tractor ran for 6 hrs with no issues till it lost the steering.
My repair manual does not seem to provide trouble shooting.

any pointers would be appreciated.
 
Where, exactly was the oil spraying out?

Did it fill the clutch housing with oil and is blowing it out the breather?

Or?

Obviously, the clutch/hydraulic charge pump was working to that point or you wouldn't have been moving.
 
(quoted from post at 17:55:44 05/21/23)
Where, exactly was the oil spraying out?

Did it fill the clutch housing with oil and is blowing it out the breather?

Or?

Obviously, the clutch/hydraulic charge pump was working to that point or you wouldn't have been moving.

i had a look last night. there's a small hose on the pressure regulator unit on the left side of the tractor that blew of the hose barb there( it might be the steering return hose, i have to have a look in the manual to verify that).
Clutch housing is ok, Suction screen is clean and transfer pump is working as it should.
 

Are you using the correct hose for that line?

Sometimes, fuel hose gets subbed for the ''oil cooler line''-rated hose that should be there.

If you replace it and it blows again, that would point to something causing higher than normal pressure in the main pump charge pressure or oil cooler plumbing area.
 
According to the manual the only hose on that pressure regulating housing is the metering pump return line so that's the one that blew off the hose barb.
 
I never replaced it, It is the original hose.
I lost steering way before that hose blew off. so whatever caused the loss of steering and hydr must be the cause of that hose blowing. But the question is what caused the loss of steering.?
 
The small ''drain'' flow from steering metering pump into that hose joins the flow going forward to the main pump and oil cooler.

As I said before IF the pressure is excessive in that area it would point to issues with the lines feeding the main pump and onward to the oil cooler and then ''lube'' circuits.

Could any rubber lines in that area have gotten ''pinched'', or POSSIBLY sometimes the lining of a hose comes apart and blocks flow.

IF something odd like that happened the front pump would be starved of oil and ''charge'' pressure would increase until the oil cooler relief valve opened. Or, the little hose popped off, LOL!

This post was edited by wore out on 05/22/2023 at 10:43 am.
 
(quoted from post at 10:41:24 05/22/23) The small ''drain'' flow from steering metering pump into that hose joins the flow going forward to the main pump and oil cooler.

As I said before IF the pressure is excessive in that area it would point to issues with the lines feeding the main pump and onward to the oil cooler and then ''lube'' circuits.

Could any rubber lines in that area have gotten ''pinched'', or POSSIBLY sometimes the lining of a hose comes apart and blocks flow.

IF something odd like that happened the front pump would be starved of oil and ''charge'' pressure would increase until the oil cooler relief valve opened. Or, the little hose popped off, LOL!
I doubt if the lining of the hose to the main pump you talk about came apart as they were all replaced when i had the tractor split for the clutch replacement.
If the main pump was starved of oil could that have caused the steering to quit ?

This post was edited by bison on 05/22/2023 at 11:19 am.
 
Thanks for the info man. i should be able to figure it out now.
first thing to check would be pump to engine coupler i guess.
 
Pump drive coupler is OK,, Oil supply hoses are pristine inside , no rubber lining blockage.I took pump apart, found nothing wrong in it but one of the plastic spacers on each side of the crankshaft roller has come of and was all ground up into little specks and fine grind. There was not much of it so most of it must be elsewhere in the system, it.s to fine to be caught in a screen but the filters will catch it.

Question , how do these pumps actually work? what causes it to de-stroke and have the pump go in stand by. does it somehow increases crankcase pressure that pushes the pistons against spring pressure and away from the crank throw?
Dealer has no clue.
 
Yes, the pump destrokes when it's ''crankcase'' is pressurized by oil from the pressure regulating valve holding the pistons away from the cam and depressing their springs.

Quite possibly there's a little bit of the plastic debris in the pressure control valve so it can't seat and cut off the flow of oil to the ''crankcase'' so the pump stays destroked.

In normal operation, the flow of ''destroke'' oil is cut off and the pressure in the ''crankcase'' is dumped to the return side when pumping is required.
 
Update, i put the pump back together after having machined 2 nylon spacers as the new (outrageous priced ($45 a piece)ones from JD did't fit and no other ones where available) Even the 0 ring kit was stupid expensive at $160 and 1/2 the 0 rings weren't even used in this pump.
Anyway the problem appeared to be solved after we put the tractor back together and fired it up. All Hydraulic functions worked again.
I let the tractor run for 1/2 hr checking for leaks and such, when nothing found i started to drive home.
After a 1/3 of a mile the clutch pressure light came on, upon investigation i noticed the dam steering return line had popped of again and this time i had pumped the entire transmission/hydraulic tank on the ground over that 1/3 of a mile. five 5 gallon pails at $140/pail worth of new oil. Now i have to buy that again.
I ain't to happy i tell ye.
 

Glad to hear you got it working!

Must have been the chewed up plastic had gotten into the stroke control valve.
 
(quoted from post at 09:24:08 07/05/23)
Glad to hear you got it working!

Must have been the chewed up plastic had gotten into the stroke control valve.
Yep, that.s exactly what happened
 

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