Dexta lift delayed reaction

This forum is about the Fordson Dexta, Super Dexta and Petrol Dexta.
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Cores
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Joined: Thu Nov 01, 2012 3:14 pm

Dexta lift delayed reaction

Post by Cores »

Hello,
I've been having a strange problem with the hydraulic lift on my '60 Dexta for a few months now and I can't seem to figure out what's wrong. So if I cold start my Dexta and pull up the quadrant lever to rise the lift arms, it takes about 30-40 seconds before the lift arms go up. Once they move the lift works absolutely normal, it has plenty of power, lifting speed is ok and nothing appears to be seized or anything like that.
Last week I took off the hydraulics cover to check if there was anything wrong to be seen. I completely cleaned and greased/oiled the internal components, replaced the return filter, cleaned the intake filter, replaced the cam follower pin (allthough there was only about 1mm of wear) and replaced the o-rings in the cover. All in all everything seemed pretty much ok, nothing clogged or worn and after I put everything back together the problem is still there. I didn't replace the piston seal as it always seemed to me it kept its pressure very well, even with a heavy load on the lift arms. So now I'm a bit disappointed and out of ideas about what could be wrong. I did not open the oil pump as to me it looks like it provides plenty of pressure.
Has anyone ever experienced this or any bright ideas please?
Many thanks,
Best regards,

bobfaecullen
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Posts: 65
Joined: Thu Apr 17, 2008 12:14 pm
Location: SW France

Re: Dexta lift delayed reaction

Post by bobfaecullen »

Hi,

Could be the unload valve, there is an O ring on the valve that deteriorates over time and glues itself to the valve bore. Sounds like your O ring might be sticky and when left for a while it sticks in the bore then frees off, sometimes they stick completely and the valve can't then move in which case the lift will not raise at all. You can remove the unload valve and discard the O ring and the lift will work perfectly well without it. It is a special O ring, don't fit any old O ring.

See my post under "vineyard dexta" from a couple of months ago, I had problems with my lift not raising at all because the unload valve was completely stuck, discarded the O ring and now no problem.
Bob

Cores
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Joined: Thu Nov 01, 2012 3:14 pm

Re: Dexta lift delayed reaction

Post by Cores »

Hi Bob,

Thanks for your thoughts. It sounds very plausible indeed, I didn't inspect the relief valve when I had it open as I couldn't figure out how to remove it... :oops: Do you happen to have any tips on how to get it out? Does it require special tools maybe?
Regards,

Martin

bobfaecullen
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Posts: 65
Joined: Thu Apr 17, 2008 12:14 pm
Location: SW France

Re: Dexta lift delayed reaction

Post by bobfaecullen »

Hi again,

Here is an extract from my previous post about my hydraulics.

Just to prove the oil pump was ok I turned the engine over on the starter with the top cover off and plenty oil came up through the port in the casing.
When I had the top cover off I didn't look at the unload valve or the check valve so set about taking them apart.

The check valve came out no problem and although the ball was a little marked I cleaned it up and put it back.

The unload valve is a little more complex, first you have to remove the plug before you get to the valve, the plug has a 3/8 UNF threaded hole in it for an extractor tool. If you don't have the proper extractor tool you need a 3/8 UNF threaded rod with suitable nut, a socket big enough to straddle the unload valve plug and a couple of washers. Screw the rod into the threaded portion of the unload valve plug, place the socket and washers over the rod, then use the nut to wind the plug out of the bore. This is where I found the unload valve was firmly stuck in the bore, the O ring had glued itself to the bore and left a deposit on it as well, so I tapped out the valve and cleaned up the bore with metal polish and a cloth. I read on the forum that the valve will work perfectly well without the O ring (Brian's advice) so I discarded it, probably less likely to stick without it.

Hope this helps, my lift working fine after this.

Bob

Cores
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Posts: 17
Joined: Thu Nov 01, 2012 3:14 pm

Re: Dexta lift delayed reaction

Post by Cores »

Hi,
Yesterday I openened the lift cover again and fabricated a pullong device for the unloading valve. I had to apply a certain amount of force to push the unloading valve out so that gave me good hope! The O-ring itself appeared to be intact but it felt rather hard, just like the other O-rings I replaced earlier in the hydraulics cover. So I removed it and put everything back together. This morning first thing I did was go get the Dexta out of the shed and guess what? It worked like a charm from the first second! I'm so happy!
Thanks a lot for your good advice!!!

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