Load Sensing Valve

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12 Dec 2019 12:26 #41 by Alister McBride
Alister McBride replied the topic: Load Sensing Valve
Hi all, mine is basically out of adjustment but rear brakes are still on too much. Can someone post a pic of their rear brake proportioning valve setup so i can compare... Preferably if you've done the swap to a commodore unit. TIA ;)
Cheers, alister

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12 Dec 2019 18:06 #42 by Holmz
Holmz replied the topic: Load Sensing Valve

Alister McBride wrote: Hi all, mine is basically out of adjustment but rear brakes are still on too much. Can someone post a pic of their rear brake proportioning valve setup so i can compare... Preferably if you've done the swap to a commodore unit. TIA ;)
Cheers, alister


In general:
1) at low braking, (snow, ice, dirt, sand): then the brake force should in proportion the weight on the axel.
2) at high braking: then there is also the weight transfer... and the front always get a boost in the force that they can tolerate before lock up.

So the rears are only on too much if the rears are not the loaded axel, or there is some obvious "too much" that is not solely the measured temp.
And the fronts probably get more cooling than the rears...

Balance bars, manual proportioing valves etc are common in race cars, but the theories of the concepts apply everywhere.

I am interested in that commodore unit too.

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13 Dec 2019 05:01 #43 by Alister McBride
Alister McBride replied the topic: Load Sensing Valve
Thanks Holmz.

Has anyone got a pic of their setup, want to make sure mine is on the right way around and and piping hooked up correctly...?

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13 Dec 2019 15:30 #44 by Peter and Sandra OKA 374
Peter and Sandra OKA 374 replied the topic: Load Sensing Valve
I'll take a pic tomorrow of the standard setup on an LT if you need it.

OKA 374 LT Van, converted to camper/motorhome,
400ah Lithiums, 1100w solar, diesel cooking heating and HWS,
Cummins 6BT, Allison 6 speed auto, Nissan transfer.
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15 Dec 2019 04:51 #45 by Alister McBride
Alister McBride replied the topic: Load Sensing Valve
That'd be great Peter if you (or anyone else) could!
Cheers, alister

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15 Dec 2019 07:01 #46 by Peter and Sandra OKA 374
Peter and Sandra OKA 374 replied the topic: Load Sensing Valve
Alister here you go, if you want any more give me a yell.
The original cable between diff and arm was 130mm eye to eye and I made a new longer one at 230mm eye to eye as my springs are set at maximum "arch" (were a bugger to get back in!) as the truck is permanently loaded all of the time so needed more braking on the rear.

OKA 374 LT Van, converted to camper/motorhome,
400ah Lithiums, 1100w solar, diesel cooking heating and HWS,
Cummins 6BT, Allison 6 speed auto, Nissan transfer.
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15 Dec 2019 16:29 #47 by Peter Davis
Peter Davis replied the topic: Load Sensing Valve
Interestingly I notice your proportioning valve is mounted on to a bracket welded to the cross member. Mine is mounted directly onto cross member. The adjusting bolt at the top of the valve on yours is screwed all the way out mine is about 8mm the other way.
Mine is seized with obviously full braking to rear. Will need a new one if the anti seize doesn't work. Still to change front chassis hose as access isn't easy. Very little room for spanner to move being the middle hose under the pedals.

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15 Dec 2019 16:49 #48 by Peter and Sandra OKA 374
Peter and Sandra OKA 374 replied the topic: Load Sensing Valve
The bracket is standard from factory and I've also adjusted the bolt and locknut to fine tune the rear braking.
There isn't much inside the valve, just a floating piston and a couple of seals so if the bore isn't corroded then it should be rebuildable but given they are freely available for Holden 1 tonners probably easier to fit a new one.

OKA 374 LT Van, converted to camper/motorhome,
400ah Lithiums, 1100w solar, diesel cooking heating and HWS,
Cummins 6BT, Allison 6 speed auto, Nissan transfer.

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15 Dec 2019 18:21 #49 by Alister McBride
Alister McBride replied the topic: Load Sensing Valve
Thanks Peter x2, looks like my 'coil' spring is upside down but i don't think that explains the problem. I'll have a look at the top bolt setting tomorrow, that could definitely affect the proportioning.

Peter Davis - mine is an XT and it doesn't have the mounting bracket either. I imagine it's to avoid having the mounting bolt heads interfere with the longitudinal cross-member which holds the divorced t-case in the LT...

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15 Dec 2019 18:43 #50 by Peter Davis
Peter Davis replied the topic: Load Sensing Valve
Mine is an LT like Petes. Oka must have added that bracket in later LTs.

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15 Dec 2019 19:00 #51 by Peter and Sandra OKA 374
Peter and Sandra OKA 374 replied the topic: Load Sensing Valve
The early Lt's had a different north/south crossmember for the transfer case mount than the later ones, some of the last ones were different again.
Did yours have the sloping ends where it bolted to a flat sloping mount at each end ? 374 has right angle mounts with rubber donuts at each end

OKA 374 LT Van, converted to camper/motorhome,
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Cummins 6BT, Allison 6 speed auto, Nissan transfer.

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15 Dec 2019 19:54 #52 by Peter Davis
Peter Davis replied the topic: Load Sensing Valve
Sloping mount

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16 Dec 2019 08:32 #53 by Peter and Sandra OKA 374
Peter and Sandra OKA 374 replied the topic: Load Sensing Valve
The XT's had a removeable transmission/transfer mount that had sloping ends where it was bolted onto the chassis and some earlier LT's had similar but it ran north south, then the later ones changed to a right angle type mounting with rubber donuts.

OKA 374 LT Van, converted to camper/motorhome,
400ah Lithiums, 1100w solar, diesel cooking heating and HWS,
Cummins 6BT, Allison 6 speed auto, Nissan transfer.

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18 Dec 2019 17:05 - 18 Dec 2019 17:14 #54 by Alister McBride
Alister McBride replied the topic: Load Sensing Valve
ok, so i got under there and realised my top bolt was out too far and was basically giving full braking to the rear. So i thought that would solve the issue... but no... Doing driving tests both gravel and sealed roads i'm still locking up the rears, the rear brake proportioning valve is fully backed off. So i'm wondering if someone has previously accidentally swapped around the lines out of the front proportioning (fixed proportion) valve. Looking at the pic below would it be possible to swap the lines around between front and rear here? My fronts come out of the right hand outlet... Is that what other vehicles have?
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Last Edit: 18 Dec 2019 17:14 by Alister McBride.

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18 Dec 2019 17:22 #55 by Peter and Sandra OKA 374
Peter and Sandra OKA 374 replied the topic: Load Sensing Valve
That valve is not a proportioning valve it is a valve that operates the brake failure light in the dash if either front or rear systems lose pressure.
In that valve there is a floating piston which under normal conditions has equal pressure from both front and rear brake systems on each side, ie: one side has the front fluid and the other the rear fluid. If either system loses fluid the piston will move to that side as the pressure is higher on the "good" side which shorts the wire to ground and brings up the brake warning light on the dash.
Alister to decrease the rear braking the brake proportioning valve arm needs to drop downwards at rest. You can adjust the bolt but it is easier to shorten the cable connecting the arm to the rear diff. You can replace the cable with a piece of chain which makes it easier to get the right length by shifting from link to link to get it right.

OKA 374 LT Van, converted to camper/motorhome,
400ah Lithiums, 1100w solar, diesel cooking heating and HWS,
Cummins 6BT, Allison 6 speed auto, Nissan transfer.

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18 Dec 2019 17:36 #56 by Ralley
Ralley replied the topic: Load Sensing Valve
The valve under the dash from memory once it has blocked off one end you need to remove the switch to let the valve go back to the centre. This valve can be activated if you run the fluid too low when bleeding the brakes or obviously if there is some point of failure and you loose the fluid at one end.

Rob

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18 Dec 2019 19:27 #57 by Alister McBride
Alister McBride replied the topic: Load Sensing Valve
Thanks guys, yes both done. I have a chain already and yes it is adjusted correctly. I think it was Alan at oka years ago when i was speaking to him about the rear proportioning valve said there was a fixed proportioning valve up front as well, maybe my memory of the conversation is wrong... Will keep scratching the noggin on this one...

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19 Dec 2019 03:39 #58 by Peter and Sandra OKA 374
Peter and Sandra OKA 374 replied the topic: Load Sensing Valve
The proportioning valves can also seize in one position especially as many Oka's lived in corrosive environments in a previous life.
If corroded internally they will also not work as fluid bypasses the buggered piston seals.
Years ago I had an old Volvo which had a similar valve to the front one to operate the brake light if one circuit had failed and the seals between the front and back systems had worn to the stage where fluid freely passed between the two effectively removing any bias front to back.
I only found the problem when the plastic switch decided that it could no longer handle the hydraulic pressure and blew out making a huge mess and no brakes!

OKA 374 LT Van, converted to camper/motorhome,
400ah Lithiums, 1100w solar, diesel cooking heating and HWS,
Cummins 6BT, Allison 6 speed auto, Nissan transfer.

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19 Dec 2019 09:34 #59 by Alister McBride
Alister McBride replied the topic: Load Sensing Valve
Nah, the plunger/piston is moving freely, it's relatively new too.

That would make quite a mess in the cab... I hope it's not that! Considering it's been like that for years i doubt it's the problem. Possibly the new (second hand) rear proportioning valve is buggered, maybe moving but not proportioning... may have been sold like that. Next step, take it off and pull it apart i guess.

Thanks Peter's and Rob for the help!

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19 Dec 2019 10:05 #60 by Peter and Sandra OKA 374
Peter and Sandra OKA 374 replied the topic: Load Sensing Valve
Alister before you get carried away just try tying the arm right down close to the diff as it might work ok. You can also change the length of the arm by loosening the 6mm bolt in the middle and sliding the two halves past each other which changes the distance it has to move as well.
The bolt adjustment changes the tension on the spring which in turn changes the amount of pressure on the valve piston, you may need to screw the bolt in to lessen the pressure as well.

OKA 374 LT Van, converted to camper/motorhome,
400ah Lithiums, 1100w solar, diesel cooking heating and HWS,
Cummins 6BT, Allison 6 speed auto, Nissan transfer.

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