Tractor squeals under load after getting warm

[Soundguy]

I think i'd flush it into a bucket first.. easy enough to do a poor mans pressure and flow test at home with common tools and parts.. if a hst has failed.. the cooler will be the least of the expense or worries..

soundguy

 

[hlukeh]

Thanks for the suggestions!

The more I do myself the more I'll learn about hydraulics, and it's a field I've always wanted to learn. Three years ago I didn't know much, but I feel like I'm now learning a lot.

I'll see if there's a bypass valve next to the HST to look at and clean. The service manual shows that the tractor has to be separated to get to the high pressure relief valve, and I don't know how I'd ever get the tractor halves re-lined up if I were to separate it. It sounds like I will probably have to separate it anyways to get to the HST, but I may as well fix the flow through the cooler since I know it's blocked or bypassed somewhere.

There is definitely no fluid going through the cooler because after driving the tractor for about an hour today the cooler wasn't even warm (80F vs the 120F of most of the other hydraulic components).

Luke

 

[Soundguy]

yikes!

 

[jinman]

There is definitely no fluid going through the cooler because after driving the tractor for about an hour today the cooler wasn't even warm (80F vs the 120F of most of the other hydraulic components).

Luke

Luke, just remember when you are making comparisons that the main hydraulic system and the HST system are different. Don't compare the temperature of the HST to the main pump's temperature. Feel your HST filter and use that as a comparison. Your HST is working, so it must be getting oil. If it is not going through the cooler then it must be bypassing at the pressure bypass at the filter. Otherwise, your HST would starve for oil and self-destruct in short order. Also, one side of the HST cooler should be much warmer than the other side.

The flow of oil is as follows. The charge pump pulls oil from the reservoir and sends it through the filter and cooler before supplying it to the HST main pump. The HST pump then supplies oil to the motor based on how far the pedal is depressed. The pedal changes the amount of oil the HST pumps. The HST works the same for all transmission ranges. Only the gearing changes after the transmission when you select another range.

I think you can probably remove the HST relief valve and a couple of checkvalves from outside the transmission housing. From the parts diagram, it looks like there are round ports in the casting to allow access to the transmission valves. I'm not sure of that since I've never worked on a 1520, but you said the maintenance manual said you have to split the tractor to do that. I know for sure on my larger TC45D that the relief valve can be changed without splitting the tractor. It's worth double checking.

 

[hlukeh]

I got a gauge and tested the hydraulic pressure today.

I engaged the parking brake, put the tractor in high range, and turned up the revs to 2500rpm. I then pressed on the hydrostatic pedal to go forwards and backwards.

The service manual says to use the left test port and press reverse, but there is no pressure when I do that. If I press forward the pressure builds.

When I first started the tractor and pressed forward, the pressure built to 2600psi before squealing (I assume that's the fluid going through the high pressure bypass valve).

As the tractor continued to run and warm up (just sitting) the max pressure that the gauge would go to before squealing slowly decreased. After a few minutes the pressure would only build to 2300psi.

After 10 minutes the pressure would only go to 2000psi.

The service manual says that the pressure should build to 3839-4124

My hope is that either the relief valve just has to be adjusted and maybe replaced, and that it's not something more. The painful part is that the tractor has to be separated in order to adjust the valve, and possibly multiple times, and that means unhooking hydraulic hoses, draining fluid, unbolting the tractor halves, somehow wheeling it apart, adjusting the valve, somehow wheeling it back together and getting it lined up and back together, hooking up all the hydraulic hoses, replenishing the fluid and trying it out. Then do it again if it wasn't adjusted enough.

Luke

 

[tnewbern]

Check your charge pressure.

If the pressure is low then you may have a restiction like the oil cooler or a worn supply pump.

If it is up to spec then your pump/motor are worn and bypassing the fluid.

I'm with jinman though and think its time for an HST overahaul.

Coyote Machine funny how we both found this thread...

 

[hlukeh]

Thanks for the suggestion about the charge pressure. It's too bad New Holland didn't provide an easy test method. The manual says to remove the Banjo bolt, drill and tap it, test the pressure, and then I guess put a plug into the banjo bolt, although it doesn't say to plug the hole afterward, unless of course they want a person to buy a new Banjo bolt for $300+...

It's probably worth while to do that before separating the tractor, especially considering how dirty the fluid was and there may be a restriction in those lines.

Luke

 

[tnewbern]

Post the page with the recommended way for testing the charge pressure. If its possible post a picture or page with the hydraulic schematics. There has got to be a better way to test the charge pressure. This may even be as easy as using thew same test port for the HP relief. At the very least you should be able to put a guage before and or between the filter and HST and measure it outside the unit.

 

[hlukeh]

That's a good idea to just measure the pressure in the line instead of trying to drill and tap that bolt.

I took some pictures of some of the pages. Thanks a lot for the continued suggestions. I think I'm getting closer to the problem and haven't had to take the tractor anywhere which is great!

Luke

 

[hlukeh]

I think it might be easier to look at some pictures of the manual in pdf format rather than jpg...

 

[Coyote machine]

Check your charge pressure.

If the pressure is low then you may have a restiction like the oil cooler or a worn supply pump.

If it is up to spec then your pump/motor are worn and bypassing the fluid.

I'm with jinman though and think its time for an HST overahaul.

Coyote Machine funny how we both found this thread...

Yes it is! I had thought to mention it on the other similar thread about this kind of issue since the situations are similar to say the least.
Reading both serves to provide various views of the problem(s) and how to solve them.:thumbsup:

So let me do that here: FWIW, please see the thread "DK-40SE Squeal when moving in reverse", in the KIOTi Owning/Operating section. It is a lengthy thread, BUT it deals with some very similar issues regarding HST function/and pressure related issues. It may shed further light on this issue too. Hope it helps.

 

[hlukeh]

Thanks for the tip. I'll take a look!

http://www.tractorbynet.com/forums/...176565-dk40se-squeal-went-moving-reverse.html

 

[tnewbern]

They share a common symptom but I don't believe they are related. Judging from the age and discription I would believe your unit is worn and needs service before its to late. Reguardless I would test your charge pressure and pump pressure before rebuild. Record the values in a safe place for future use.

Luke you can read your charge pressure at the fitting as recommended. I would take the bolt and manual to a local hydraulic shop. They should be able to precision drill and tap the bolt for you. There is no issues using a plug in the end of the bolt after performing the tests.

If you are not comfortable with that you can get a spare. I don't know were you got the $300 price for the bolt I would bet $30 tops. Don't worry about purchasing a new bolt until you resolve the issue.

Another option would be to temporarily remove the hardline between the filter and HST. Bring them to the shop and get the proper fittings, tee and hose for testing. The banjo bolt is usually (npt or bpt) and can be replaced by a standard fitting and hose.

 

[jinman]

Luke, I think Soundguy had a good idea earlier. He suggested disconnecting the line at the cooler and starting the tractor to see how much fluid comes out. You could do that on both inlet and outlet side and determine if the charge pump is working. Just don't let the engine run for long so the transmission isn't damaged further due to oil starvation. That and removing and cleaning the ball-checkvalve on top of the filter assy is about all you can do before going into disassembly.

BTW: I don't think your neutral valves and relief valves are adjustable (you have one high pressure and one charge pump relief). Those neutral valves are also suspect. I think if they are clean and the springs are not broken, they will function properly. I don't think you will have to keep opening up the transmission to make "adjustments."

The problem is that this kind of troubleshooting and repair is best left to a shop with specialists with special tools. Having a drilled and tapped banjo bolt is just one example of a tool that probably most New Holland service departments have and use on a regular basis. By the time you buy all these special tools and learn the intricacies of doing an overhaul yourself, I think you will wish you had left it to somebody else. If you can find a service manager to discuss the issue, maybe he can make suggestions or agree to work on the transmission for you after you have removed it. Splitting a tractor is not that hard, but you also have to have several rolling jack platforms and it can be a huge task for a first timer. If it were me, I'd do the pressure and clog testing of the cooler and filter ball-check and then leave the rest to experts even if I had to wait until I saved enough $$$ to have the work done. Good luck, no matter what method you choose.

EDIT: What I should have said above is that I don't think your relief valve will NEED adjusting. It has an adjustment screw, but once set, it should remain constant for your tractor. I believe if it is failing, it is probably due to trash/crud build up rather than an adjustment. You have varying pressure inside your transmission as it heats up. The relief valve would always relieve at the same pressure no matter what the temperature of the fluid, so I think it is not the problem.

 

[hlukeh]

Today I drilled and tapped the banjo bolt and screwed in a 1/8" NPT pressure gauge I had (10 minute job - and free!) and checked the charge pump pressure.

At 2000rpm the pressure was 90psi, and the lowest it went was 60psi when the throttle was set to the lowest rpms. This is exactly where the service manual says the pressure should be.

After removing the gauge and before installing the plug I started the tractor and a nice solid stream of fluid started coming out of the hole in the banjo bolt. I don't think that actually tells me anything since the fluid wasn't flowing through the cooler, but it doesn't appear there is any issue with those components anyways.

I guess my next step is to separate the tractor and take a look at the high pressure relief valve and then the hydrostatic unit itself. Maybe it's something as simple as the spring in the relief valve has deteriorated.

Thanks again for the continued suggestions!

Luke

 

[hlukeh]

I separated the tractor! It was pretty easy, other than the fact that I first tried to separate it behind the steering wheel because that's where the HST is and I didn't have to remove the diesel tank or the steering wheel, but there are bolts inside holding the two haves together.

I ended up separating it between the engine and clutch at the bell housing, which is what the service manual says to do anyways.

I found that the clutch release bearing is completely seized and quite worn. Where the bearing has been rubbing on the pressure plate, the fingers are almost worn right through and there is only about 1/16" thickness left. It appears that the set screw on the rod connected to the clutch pedal that adjusts the free play is too tight and possibly wasn't ever allowing the bearing to disengage the fingers completely.

I'll have to get a new pressure plate, and I'll also have to take it off to see how the disc looks.

I'm not sure if this is the cause of the loss of hydraulic pressure (squealing) as the engine heats up, but it's more likely this than the high pressure relief valve because there is a high pressure relief valve for forwards and one for reverse and I can't see them both exhibiting the same behavior.

I'll take out the HST drive, check it, clean it and also check the high pressure relief valves while I've got it apart.

I've attached some pictures showing the clutch and some plastic and stuff around the HST and around the pressure plate. It looks like a mouse may have been living in there.

Thanks again for the inspiration and tips.

Luke

 

[hlukeh]

I now have a reason to fix the tractor - before the snow comes next winter. I spent a few hundred dollars today on some implements for the garden!

 

[Coyote machine]

OH, MAN!
The whole squeal problem was the mouse!!:laughing:
It doesn't like going backwards. Don't you know 'nothing about mice?!

The clutch bearing that rests on/ engages the pressure plate is referred to as the throwout bearing. There may be another smaller 'pilot' bearing that goes into the flywheel where the splined shaft runs through the pressure plate; but I'm a car guy so I can't say for sure they're used on tractors too. If there is one replace it too. Depending on the condition of the clutch disk and the flywheel face that it contacts you may want to have it resurfaced so you don't get chatter when you put in the new disk, etc.
Great pics; keep 'em coming with the reassembly.:thumbsup:

Wait: I'm confused?! How can you have a clutch and an HST?! You either have a manual or an HST transmission, not both!
Seems you clearly have a manual transmission; therefore you can't also have an HST.

Am I missing something?

 

[hlukeh]

It's got a HST. I've never actually used the clutch for anything, although I have pushed on the clutch pedal to see what it did but it never seemed to do anything, which it probably didn't... A friend told me that he thought the clutch was probably to allow the disengagement of the PTO, possibly for safety.

I've already ordered a new pressure plate, both bearings, etc!

The entire clutch kit cost $179 - not too bad so far!

Luke

 

[Coyote machine]

Wow! HST and a clutch?! Well that's something I was not aware of as a possibility...
Live and learn....