450C float question

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jjgurley
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450C float question

Post by jjgurley » Wed Nov 15, 2017 3:34 pm

I read the two old posts on the subject, and i'm still unclear on the way float works.

On my '81 450c, float works if you hold the lever forward but it won't hold itself in float. It appears it "should" (like my 580E backhoe), but it hasn't for the 25 years I've owned it.

My question is: is the "latch" mechanism in the spool valve or the linkage? My lever does not run into the cover (as mentioned in one of the posts), and although fairly sloppy, it works fine. I just can't see anything in the linkage that would make it hold in the forward position.

I'm not afraid of rebuilding the linkage, but I'd like to know that it will accomplish something.
1981 450C
6405 #355834

jjgurley
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Re: 450C float question

Post by jjgurley » Wed Nov 15, 2017 6:54 pm

After studying the manuals as little harder, it looks like the "latch" function occurs within the spool valve. The forward valve is unlike the other two in that it as a "detent" mechanism at it's bottom. Not sure how it works, but I guess it gives me a place to look. The discussion of sloppy linkage causing the problem must mean that the problem might be the piston just doesn't get driven far enough to reach the detent?

I should be able to test the latter by manually depressing the piston? Anyone know if the detent requires hydraulic pressure to work properly? Can it be tinkered with on the bench?
1981 450C
6405 #355834

77 Ford
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Re: 450C float question

Post by 77 Ford » Thu Nov 16, 2017 8:16 am

That's interesting, my float works "most" of the time. I'll have to check into my linkage, there is some slop in it for sure. I know that my auto leveling feature on the bucket will not work when the hydraulic fluid is very cold. Sorry I cannot help with your questions but I appreciate the follow up so we know the answer going forward!
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Re: 450C float question

Post by Lavoy » Thu Nov 16, 2017 8:42 am

The float portion is part of the valve itself, and the locking part of it is at the end of the spool. Couple different ways it might be done, but most have a couple of small "jaws" that grab the end of the spool and hold it in float. They can be removed if someone does not want it to lock in float, or they may be worn out and need replacing.
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jjgurley
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Re: 450C float question

Post by jjgurley » Thu Nov 16, 2017 10:20 am

My lever is definitely pushing the piston all the way down, so I guess my linkage isn't that bad. I'm surprised at how stiff the spring is on the piston - I can't really push it without the leverage of the linkage. So either the detent is disabled/worn out or the spring is stiffer than stock.

I'll have to remove the whole thing to progress further, so I might wait for a warmer day. Also hate leaking hydraulic all over my newly cleaned up and painted machine. I post a follow up when I get to the root of the problem.
1981 450C
6405 #355834

jjgurley
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Re: 450C float question

Post by jjgurley » Fri Nov 17, 2017 2:33 pm

I've got the thing out, and I can't figure out how the detent is supposed to work. My "detent" (#27) is actually a bunch of parts, including a body, a hex driven adjuster, a stack of four plastic (teflon or some similar material) washers, a metal shim, and a thick steel washer. When disassembled, there was a "groove" that consisted of the thick washer spaced from the inside end of the detent. The "detent plunger" (#30) has a bulge on one end, but it easily clears the detent groove. Either my detent plunger is badly worn (and the detent is metal on metal?) or there are some missing parts in the detent -like maybe a sturdy washer of sort with a diameter that would capture the plunger.

Incidentally, the technical manual and the parts manual show the plunger in alternate orientations. I think the technical manual is proper.

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1981 450C
6405 #355834

jjgurley
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Re: 450C float question

Post by jjgurley » Fri Nov 17, 2017 3:17 pm

I found a diagram on a 350C plunger, and as expected, there are a few more parts that are missing from mine.
1981 450C
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Re: 450C float question

Post by Lavoy » Sat Nov 18, 2017 10:25 am

FLoat can be defeated if desired, usually you remove parts, but possible just changing orientation is an alternative too.
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jjgurley
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Re: 450C float question

Post by jjgurley » Sat Nov 18, 2017 10:47 am

Upon recollection, I think my float did work properly before I had a bunch of work done (clutches, brakes, sprockets etc.)

The mechanic mentioned that the 6-way valve "feel apart" claiming that it was the rear piston cover, dumping a bunch of parts into the housing. He showed me a pile of washers and what looked like a broken bronze o-ring shaped object.

Now that I've had it apart on my own, I realize that it was the front piston that feel apart (the adjuster must have unscrewed), and the broken o-ring was in fact, the "jaw" that holds the piston in float. He threw the parts away after showing them to me, so I bought a new detent assembly yesterday. I'll follow up when it's fixed. I bought a "new(other)" on ebay for 1/2 price - we'll see.

I've learned a lesson about letting a home/acquaintance mechanic, no matter how impressive his shop, work on my equipment. Not much recourse when the bill goes ballistic and problems arise.
1981 450C
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jjgurley
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SOLVED Re: 450C float question

Post by jjgurley » Tue Nov 21, 2017 6:45 pm

My detent was missing the "jaws" that grab the rim of the plunger. My mechanic had found the jaws and assumed they were a broken washer - he threw them away. The "jaws" are basically a bronze o-ring that is split into quarters. It sits between two thick washers with surfaces to force the jaws towards the center. The jaws and washers are compressed by a collection of spring washers, which gives some adjustment of the grab-i-ness using the hex drive plug. My linkage was on the sloppy side, so I replaced the 1/2" bolt, which halved the amount of slop.
1981 450C
6405 #355834

jjgurley
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Posts: 18
Joined: Wed Nov 15, 2017 12:47 pm

Re: 450C float question

Post by jjgurley » Sun Nov 26, 2017 12:35 pm

In case someone else loses their detent bits, I was able to repair my old one once I understood the physics. Unfortunately, my education cost me a replacement detent.

I just took a 1/8" diameter welding rod and bent it around an appropriate socket to create a 3/4" ID o-ring (slightly spiral due to over winding it to get a good shape). That took two tries to pick the right diameter socket. If the plunger is out of the valve, you can try it to test-fit the wind - it should pass thru but just barely. Simply cut it into four quarters with a hacksaw and clean up the cuts with some sandpaper.. Assemble it as follows:

1) Hold detent body with smaller end down.
2) Install thinner of the two beveled washers, bevel up.
3) While poking a finger up from below, drop the four pieces of bronze around your finger, and stir into position.
4) Install wider beveled washer, bevel down.
5) Install spring washers, alternating orientation to create a spring
6) Screw in the plug snuggly
7) remove finger.

Once the valve is reassembled, adjust the hex drive on the plug to get the right "grab" on the float detent.
1981 450C
6405 #355834

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