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Discussion Starter · #1 ·
Greetings old friends, long time no see, missed you all!

I have been consumed with my other complicated automobiles and forgot the king of them all and the most favorite, my '76 SS1.
After first drive in a while, my system is showing Bake 1 light that does not go away. Prior to that I tested my system and got 38 pedal taps before Brake 1 and 71 before Brake 2 light, so I assume that my accumulators are still usable, right? However, after that test, my brake 1 light is now on all the time and I seems to have some kind of parasitic pressure in one of the systems, which is making my brakes drag a little. I checked residual pressure and some fluid came out of left upper rear caliper, causing the brakes to release fully.
My guess is that one of the the Distribution Valves might be going, or what am I missing?

- I do have the tap coming from the rear pump and planning to rebuild both shortly.

P.S. I found absolutely great fuel pump replacement for the dreaded twin SU if there is any interest. It is very quiet, reliable and inexpensive. This design is used on my Citroen SM and seem to work well on the RR:
 

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Bleed the 2 pressure switches and your indicator lamps may go out. They can hang up and cause false readings.
 

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Discussion Starter · #4 ·
Bleed the 2 pressure switches and your indicator lamps may go out. They can hang up and cause false readings.
Thank you!
I do remember that both of my switches were stuck back in 2015 and I had to do something to make them work correctly again.
What do you think can cause that parasitic pressure to the calipers?
 

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If the condition of your flexible hoses are unknown I would change them. They can look ok from the outside but be disintegrating on the inside. Crud on the inside will act as a one way valve, preventing the brake calipers to fully release. Then I would check the brake linkage in the rat trap and make sure the distribution valves are not being held slightly open. Chapter G page 77 documents how to set the linkage.

Regards the system 1 light being on all the time, I would first check the pressure switch. You could try swapping them and seeing if the Brake 2 light illuminates instead of the brake 1 light. Or, just dismantle the switch to check it.
 

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If you have dragging brakes then it's likely a collapsed flex hose acting like a one way valve. If they release by cracking only one particular bleed screw on a caliper it will be the hose associated with that caliper. If you crack a bleed screw on any caliper and the brakes release then it's likely a sticking distribution valve. When you say you tested the brake pedal pumps prior to this fault how long ago was that?
 

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Discussion Starter · #8 ·
If you have dragging brakes then it's likely a collapsed flex hose acting like a one way valve. If they release by cracking only one particular bleed screw on a caliper it will be the hose associated with that caliper. If you crack a bleed screw on any caliper and the brakes release then it's likely a sticking distribution valve. When you say you tested the brake pedal pumps prior to this fault how long ago was that?
Thank you, scenario 2 is what I have. I opened one bleeder valve (upper left rear) and all calipers released. The whole thing happened after I did brake test (pumping pedal 70+ times) and might have pressed the pedal a bit harder than usual. My thought was that if something broke it would be in the rat trap, likely a one of the distribution valves is leaking some pressure into the system.
 

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More likely, I would start with bad rear brake hoses ( body to swing arm) and polluted rear calipers.
 

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You didn't quite understand what I was telling you. Open other bleeders like the ones on the front calipers. If they release the pressure you know the distribution valves are at fault. If the pressure releases only when you crack that one left rear upper caliper bleeder then you have determined that the fault is with the flex hose associated with that caliper bleeder. In other words, if cracking any bleeder other than the one you previously did releases the pressure, it is likely that the distribution valves or linkage is at fault. I have seen distribution valves that are rusty on the end from sitting a long time get stuck down when the brakes are applied after reviving the car.
 

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It may help to know that the outer surfaces of most old hoses have patterned finish, where newer ones have smooth surfaces. That is my experience in UK, if the situation in the USA is similar it might be useful check. The inside of the hoses can swell so that it is no longer a hose, but acts as a one-way valve when 2500 psi is squirted down it. And the crud from the disintegrating hose innards gets everywhere.

Alan D.
 

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It may help to know that the outer surfaces of most old hoses have patterned finish, where newer ones have smooth surfaces.
On my cars the original hoses had what looked like an actual woven sheath over them, though it may have just been a surface impression on the hoses. The new hoses I acquired, whether Crewe Original or aftermarket, do not and while not smooth, have a very thin linear pattern that runs the length of the hose.

There is nothing special about Crewe Original brake hoses other than the high pressure hoses from the ACV to the rest of the car, and even these can be reproduced at brake shops at a far lower price. The rest are just dirt common brake hoses that meet one of the SAE specs, the number of which I do not remember right now. I documented this extensively, with photos, on this forum in the past.
 

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Brake hoses are one of the most government regulated components on your car. Rebuilders and manufacturers must meet stringent guidelines for safety and quality control. The 2 lines are on opposite sides of the hose by regulation and will often have the "spec code" printed within the line. The lines are to visually show if installed hoses are not twisted upon installation.
 

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@Wraithman,

Definitely true, but I actually wasn't thinking about the "printed stripe" which serves precisely the purpose you mention. The hoses I've purchased look somewhat like they would have been extruded (whether they really are, or not) from an orifice with a very, very fine star pattern. It creates a series of very fine, straight ridges along the length of the hose.

They can't be seen in these photographs, but the white "make sure it wasn't twisted line" is clearly visible. This was the right front side of SRH33576, taken from front and back sides, before and after I changed out the hoses:

BEFORE:
29679


AFTER:
29680


I noted each and every hose equivalent for the SY series cars in a table dedicated to same in RR & Bentley Parts, Repair, Restoration & Other Resources Compilation, and the spec for these hoses (including the high pressure ones, but they meet additional specs as well, so you cannot use "plain old brake hoses" in that application) is EPDM brake hose, SAE J1401 - 1/8 HL spec.

This is the topic where I posted photos of the brake hoses:
SY Series Commonly Available Brake Hose Chart & Photos
 
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