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HT-20 CONTROL VALVE


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#1 BOLENSBOY60 OFFLINE  

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Posted December 21, 2017 - 03:42 PM

well got it off and disassembled- their is an o ring on each end of each spool and the top ones are still in the valve body- where the levers go- these should be fine as I did not get external leakage. the other ones look ok too- could a check valve be responsible for blow by? thanks in advance for your input.

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#2 29 Chev ONLINE  

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Posted December 21, 2017 - 06:22 PM

Glad you got it off - I am guessing it probably was a bit of work.  Since you have the valve apart I would recommend you replace all the o rings - they may look good but they may be stiff or not flexible enough to seal properly under pressure.  Also check the casting closely to make sure there are no hairline cracks in the bores.  I have attached the pages from the Large Frame Manual on the cylinder and valve - I assume you already have these but thought I would post them in case you didn't.  Before removing the valve did you have any luck testing it with air pressure?  You still could have a problem with the seals in the cylinder where the oil is leaking past internally which would never allow the cylinder to dead end to develop pressure - the cylinder piston would probably move until it reached the end of its travel if there was no load on it and then the oil would leak by internally to the other port and return to the valve.  You could pressurize one of the lines going to the cylinder and see how much air is coming out the other line once the cylinder is fully extended or retracted - should not be much if the seals are good in my opinion. 

 

Just thoughts that may help you - good luck

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#3 BOLENSBOY60 OFFLINE  

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Posted December 21, 2017 - 07:54 PM

nice of you to post those pages- well I had a tough time trying to apply air to the line- I still have the loader on and it`s real tight- but you may have a good point their on the lift cylinder- didn't look that close on the plumbing- but my initial problem is still my power steering is not functioning- so- if my dash control is closed- that should keep any fluid from going that way- boy- that valve is a pretty simple thing their and I was hoping to find a major problem -should not be too hard to find o rings- they aren't a special durometer or anything would you figure-?- yes- I did what wrenchinonit did and cut a 11/16" box end wrench and got down it their for that last fitting- I did remove the choke and throttle cables the dash and wiring harness


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Posted December 22, 2017 - 11:57 AM

I would think that a general purpose good quality o ring would work - you could pm Wrenchinonit to find out what he used.  I am beginning to wonder if there is a restriction in one of the lines (feed or return) that goes to the power steering or some other reason that the power steering does not offer to at least try to work but at the same time until you can get the proper pressure readings with the cylinder dead ended you cannot rule out a problem with the pump either. 


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#5 BOLENSBOY60 OFFLINE  

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Posted December 22, 2017 - 03:49 PM

just got back in- went locally and got all new o rings- put everything back together- same condition- I did put a couple shims in the implement relief valve- not much difference if any- maybe I should get the lift cylinder out to rebuild just to eliminate that possibility - at wide open throttle- I am at 100 psi now at charge pump- when I dead head the lift cylinder it jumps to almost 150 psi


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Posted December 22, 2017 - 06:57 PM

just got back in- went locally and got all new o rings- put everything back together- same condition- I did put a couple shims in the implement relief valve- not much difference if any- maybe I should get the lift cylinder out to rebuild just to eliminate that possibility - at wide open throttle- I am at 100 psi now at charge pump- when I dead head the lift cylinder it jumps to almost 150 psi

 

I was afraid that there wouldn't be any difference.  Before you go at the lift cylinder I will offer this suggestion.  While checking the pressure operate the auxiliary lever on the valve.  If there is nothing connected to the auxiliary couplers they will be closed and should have the same effect as the cylinder dead ending which should make the pressure in the circuit climb until the relief valve opens.  If the pressure climbs to the correct reading then I would suspect the cylinder but if it does not then I would suspect there is a problem in the pump or possibly the relief valve - especially now that you are only getting 100 psi.  Wish I had suggested this sooner but as I get younger the brain sometimes doesn't remember things quickly - if I remember correctly I moved the auxiliary lever on my HT23 accidently once or twice - with nothing attached to the couplers I could hear the relief valve squeal and noticed the engine rpms dropped a little bit the same as if the cylinder was dead ended. 
 


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#7 BOLENSBOY60 OFFLINE  

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Posted December 22, 2017 - 07:21 PM

holy moly- that is a good idea- yeah I really didn't think the control valve would have been the issue either anyway glad I wont need to do that again- hehe-I will try that in the morning- I guess if I cannot get that pressure up I will have to get after the charge pump - only thing I still cannot figure- on my ht23 it can be at idle and the power steering works- another thing I was considering- is just how much does that spool need to move back and forth with that drag link set-up- mine moves I would say 1/4" each way- still I had the lines connected- to bypass it and still could not get the pressure up


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Posted December 22, 2017 - 07:38 PM

holy moly- that is a good idea- yeah I really didn't think the control valve would have been the issue either anyway glad I wont need to do that again- hehe-I will try that in the morning- I guess if I cannot get that pressure up I will have to get after the charge pump - only thing I still cannot figure- on my ht23 it can be at idle and the power steering works- another thing I was considering- is just how much does that spool need to move back and forth with that drag link set-up- mine moves I would say 1/4" each way- still I had the lines connected- to bypass it and still could not get the pressure up

 

The HT23 has an Eaton hydro which may develop more pressure at idle than your HT20 with the Sundstrand does - just a thought.  


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Posted December 23, 2017 - 09:22 AM

I will suggest a few other things that you may wish to verify and double check just in case you haven't

 

Check to make sure the free wheeling valve is fully closed and not open a little bit.  You may wish to inspect the end of it and the seat to make sure it is not damaged or deformed.

 

Check the condition of the charge relief valve spring to make sure the spring is not broken.

 

Double check that the power steering unit is plumbed in correctly before the hydraulic valve - I assume you have the installation instructions but I have attached a copy just in case you don't.  Also check to make sure the lines you added are not restricted.

 

 

 

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#10 BOLENSBOY60 OFFLINE  

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Posted December 23, 2017 - 10:26 AM

I will double check the plumbing again - I did have the charge relief out several times- appears ok that spring is a lot softer than the implement relief- did not have the fre wheeling valve open but will check that out also- on th lines- I think what you mentioned is a good idea- just to make sure I will blow air thru I know I am getting some flow as I turned it over while taking off one of the hoses on the ps control valve- still appears to pressure related- this is real puzzler- thanks for your help


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