Miller Bug Hitches

[Garry]

Hi guys .. got a problem with one of these. Its an auto hitch with the usual set up with a relay and solenoid on the digger, but the hitch has a check valve in it so that if the ram fails the hitch stays in the closed position.

Ive had to replace the ram but I'm wondering if there is something wrong with the check valve as its staying in the closed position and wont open

SO I have a unit sitting spare that doesnt work now .. I slaved it up to a machine and messed about with the check valve.. Ive found a faulty seal in it .. changed that to no avail. So I kinda stuck now, I think I'm gonna have to phone miller and see if I can get some data on what the check valve load pressure should be

With the new ram fitted, the hitch operates fine .. I just wand to refurb this old ram/valve so I can use it as a spare, it was £390+ VAT to replace it

[FrankB]

One of these ?

[Muz]

I know that hitch .. but Dan is the guy for them (if Frank has gone spray painting) .. nice piece of kit and well made

[Dan]

Let rip Frank if u know da problem I got 5 pence on it .. just be kind to the peeps ... and the 5p is not for negotiation

[FrankB]

Ok well my first shot is that the seals are away on the ram .. if it will presurise at all ... it'll got to maximum extension, then the check valve holds it there as a failsafe, so as not to lose any bucket attached.

Remove the check valve and plug it off and see if the ram strokes. I dont think it will, so thats your first problem IMHO. Do this with it set up in a single acting circuit, like on an auxilliary line for example, that way you can also test for holding pressure to see if the seals are allowing oil to bypass, which will confirm the problem.

The next issue is, why did that happen ?.. I'm guessing on that hitch it would be 3-5 years old, which is a bit early for seal failure

Ive heard some say there could be a defect with the ram cylinder, in that it isnt exactly true, in which case, you'll need to reseal it with oversized seals, or have the cylinder replaced .. .. still cheaper than £400 notes i'll venture

Howzat ?

[FrankB]

Forgot to say, you'll need to have the check valve retested too

[HazChem]

Bump .. so whats the deal .. I heard someone on about these the other day ?

[wee_gus]

think we have one of these lying in the yard.. with a similar problem, bosses just went and bought a new one ...

[Muz]

Well I saw it still sitting on the bench the other day with a couple of lines attached, I think its got shoved to the back of the queue .. Ive got two of em too on 8 tonners .. I'll give GAz a jag about it next time I see him

[Garry]

Well I saw it still sitting on the bench the other day with a couple of lines attached, I think its got shoved to the back of the queue .. Ive got two of em too on 8 tonners .. I'll give GAz a jag about it next time I see him

Ok boss .. its in your van now .. you sort it (plz)

[Muz]

Ok here is the offending ram c/w check valve

IMG_0823.jpg

I'm assuming the valve goes under the hex plug ?

[Dan]

Ok here is the offending ram c/w check valve

[ATTACH=CONFIG]352[/ATTACH]

I'm assuming the valve goes under the hex plug ?

In place of it .. thats just a bung IIRC

[Muz]

Well I found the check valve specs .. Had D4A020N on the head

http://www.dftcorp.com/literature/ca..._Stocklist.pdf

Go to Products - EDC Stock, then select Check Valves and scroll to Page 26 .. thats the fella with full specs, so now we can at least test the valve and work out how it holds when the pressure drops in the ram as a fail safe.

Damn those pdf's they wont let ya copy the stuff so I printed it off, then scanned it

SCAN0023.jpg

Just a bit confusing knowing what does what when you cant see the internal pipe routing inside the ram block