By-pass valve removal tip

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whesbrook
Posts: 19
Joined: Sat Mar 03, 2018 7:31 pm
Location: Co Down NI

By-pass valve removal tip

Post by whesbrook » Sun Apr 28, 2019 6:10 pm

Here is a tip I discovered since owning my DB.
1. the famous stuck by-pass valve, the standard advice is to use a tapered wooden dowel which one sticks into the end of the valve and then pull it out, simples !!!!. NO
Where do you get this tapered dowel, I had a shot at making one which without a lath is nigh impossible,you can whittle for hours and then fail anyway, so the easy way out is a 8 mm plastic rawl plug, the sort that is used for heavy garden gates and a 75 mm long wood screw. Engage the screw into the end of the plug but first put a small washer onto the screw shank. Put the plug in the top of the stuck valve and screw in the screw to tighten the plug in the valve. Loop a string onto the screw under the washer which stops it coming off when you pull the valve out. If the valve is well stuck, and the plug pulls out, put it back in and tighten it more than the first time. the plug, being parallel, gets a far better grip of the inside of the valve than the tapered wooden rod does and works first or second time.
Valve cleaning is then done using 1000 grade emery paper soaked in diesel to aid the solution of the oil products that caused the sticking and lessen the chance of scoring the valve.
SIMPLES !!!!!

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ollek
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Re: By-pass valve removal tip

Post by ollek » Sun Apr 28, 2019 6:28 pm

I have made many wooden dowels using a sharp knife and trying the dowel in the valve and taking off small amounts of material from the dowel until it fits. You do not need a lath in order to make a working dowel. If someone wants to use something else, please do so, but a wooden dowel made to the correct shape and size works just fine.

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db2d
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Re: By-pass valve removal tip

Post by db2d » Sun Apr 28, 2019 7:18 pm

I would not advocate ‘ Emery Paper ‘ for use on these valves, but it is the owners decision.

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ollek
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Re: By-pass valve removal tip

Post by ollek » Sun Apr 28, 2019 7:25 pm

I have to add that there is no reason for shouting "pull it out, simples !!!!. NO". And as db2d said, do not use emery paper on these valves, it will ruin the precise fit between the valve plunger and the boring in the valve chest. Removing even a small amount of material from the valve plunger and/or the boring, will lre4sult in a gap between the two parts and oil leaking into the top part of the valve. This will in turn partly close the by-pass valve, resulting in so called ghost lift. This means that the hitch is contently lifting with a lower than the maximum pressure and this can not be repaired as the diameter of the valve plunger can not be increased.

whesbrook
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Joined: Sat Mar 03, 2018 7:31 pm
Location: Co Down NI

Re: By-pass valve removal tip

Post by whesbrook » Sun Apr 28, 2019 8:46 pm

I thought this idea worth sharing but obviously not,
the emery papers exact title is "1000 grade wet and dry".
I'm sorry my language offends the senses, but that will not be happening again.

philedge
Posts: 236
Joined: Sun Dec 03, 2006 11:27 am
Location: Chester UK

Re: By-pass valve removal tip

Post by philedge » Sun Apr 28, 2019 10:10 pm

If a dowel didnt work for you but a plastic plug and screw did, then your idea is definitely worth sharing. If it worked for you then theres every chance it will work for others.

The internet and its forums are for sharing info/ideas/veiws, a principle often overlooked. Keep posting if youve got anything to share:)
'66 880 Selectamatic rat.

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db2d
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Location: Monmouthshire

Re: By-pass valve removal tip

Post by db2d » Sun Apr 28, 2019 10:36 pm

Using the device described incurs the risk of cracking the valve. These valves were matched to the valve chest during assembly at the factory and are not available or interchangeable.

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GeoffDEAL
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Location: New Zealand

Re: By-pass valve removal tip

Post by GeoffDEAL » Mon Apr 29, 2019 12:45 am

Hi it was part of the first service on DB 1200 the valves were removed by service man and polished with fine wet and dry paper to remove any marks from the new valves slightly sticking i was told at the time, the tractor has had no valve problems to this day. I would think it would take a long time and lot of work to remove much with 1200 paper but there is finer 1500 or more it has been suggested fine Scotch Brite pads work but havnt used them myself. Whatever removes the stuck valves is necessary, there is a vidio of using an anchor bolt to remove a very stuck valve and it worked so plastic should be fine, tapered sticks to circlip pliers on normal valves, the main thing is to pack rags-foam -paper towels round the top of valve chest so you dont loose anything when removing the valves, i found paper towels as they are white and easy to pack around good and a suitable mirror makes under cab ones easier to see.

whesbrook
Posts: 19
Joined: Sat Mar 03, 2018 7:31 pm
Location: Co Down NI

Re: By-pass valve removal tip

Post by whesbrook » Mon Apr 29, 2019 2:08 pm

the chances of cracking a valve with a plastic plug and wood screw hand tightened is pretty remote, these valves were made from fine grained steel case hardened so they could grind them to the tolerance needed to work in the chest without any seals, 3 thou if I remember correctly.

If anyone is about to replace a mudguard with a new one I may have something you need to watch for.

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db2d
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Re: By-pass valve removal tip

Post by db2d » Mon Apr 29, 2019 6:07 pm

I have seen a number of these valves broken during the last fifty odd years. If the owner is aware that they can break it is their decision on the removal method. I have also seen well meaning people advise putting the valves in a drill chuck to polish them using abrasive paper, and this is definitely a No No !

Gard
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Location: Fairfax Vermont USA

Re: By-pass valve removal tip

Post by Gard » Tue Apr 30, 2019 3:32 am

I think a quick light touch with 1000 grit wet or dry "sandpaper" is really more of a polishing step than sanding, it will remove small fractions of one thou (0.001") from steel. Removing even 0.0001" takes a lot of work with 1000 grit. With tight fitting parts like this I would be very concerned about cleaning any grit or lint from the parts before reassembly. If you can get it clean enough to move freely with solvents, cloth or perhaps brass brush that is probably the safer way to go.

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GeoffDEAL
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Location: New Zealand

Re: By-pass valve removal tip

Post by GeoffDEAL » Sun Aug 25, 2019 9:46 pm

Hi moving this thread up as has information on working on DB hyd valves circlip pliers screw driver blade or tapered wood dowel usually remove them but old ones not used for a long time can be really stuck and require up to plastic or metal anchor bolts to remove taking into account possible breakage mentioned.

ALANJ
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Location: Co. Durham

Re: By-pass valve removal tip

Post by ALANJ » Mon Aug 26, 2019 10:31 am

As a general point of interest the only valve lapping material used in ,and recommended by, the factory was Jewellers Rouge. This recommendation was emphasised on the factory hydraulic service courses .Any other lapping material would result in valve skirt leakage as OLLEK has rightly said.
As for valve extraction, if a wooden/ plastic dowel will not do the trick then the safe option is to demount the valve chest , remove the circlip,plug etc from the underside and gently tap out the valve from the top with a copper drift.
This was the favoured method when such failed valve chests were returned to Meltham via service exchange.
Hope this helps, AJK.

1952CROPMASTER
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Location: Moncton NB

Re: By-pass valve removal tip

Post by 1952CROPMASTER » Thu Aug 29, 2019 1:41 am

What's wrong with removing the brass plug from inside the By-Pass-Valve then screw a 3/8 UNC bolt into the Valve & with a good flat washer & a 3/8 UNC Nut make yourself a simple puller, it works for me everytime,

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GeoffDEAL
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Re: By-pass valve removal tip

Post by GeoffDEAL » Fri Aug 30, 2019 10:29 pm

Hi 1952cropmaster it appears we have all missed the obvious including DB factory repair, provided a bolt screws in freely would work perfectly, if bolt was to tight in thread a suitable nut or threading die would soon make it a free fit,thanks for your excellent solution. cheers Geoff

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