Help!! Brake Flush and Bleed Instructions SZ Car - Rolls-Royce and Bentley Forums
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post #1 of 24 (permalink) Old 07-07-2014, 10:24 PM Thread Starter
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Help!! Brake Flush and Bleed Instructions SZ Car

I need to Flush and Bleed my Brakes on my 94 Turbo RL. Does someone have instruction on how to do this? I found instructions for a shadow but not the Turbo R. I was told 6 bottles of mineral oil? Is there an alternative to the mineral oil purchased from Bentley? Any help or diagrams will be appreciated.

Thanks,

Scott
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post #2 of 24 (permalink) Old 07-07-2014, 11:27 PM
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The instructions for the SY series cars are appropriate for the SZ cars as well as long as you remember:

1. You're going to use LHM+ (Liquide Hydraulique Minerale+)/HSMO+ (Hydraulic System Mineral Oil+) and not RR363.

2. You do not have height control rams, but instead have the corresponding bleed screws for the rear struts/gas springs.

You are still bleeding the system from its end points, the calipers and the rear struts/gas springs.

I have never bothered to bleed the accumulators since if you pressurize and depressurize the system several times, which typically occurs during the whole "flush and bleed process," all the air has already been expelled from the accumulators before you start working on the end points in the system: the brake calipers and rear strut/gas spring bleed points.

In all other respects it's the same as far as the bleeding process goes. You don't, of course, have the whole reservoir sludge check to deal with.

HSMO+/LHM+ is available via amazon.com. I'd still check with the local Bentley dealership as it's entirely possible that it will not be any more expensive through them. You can't know without checking. HSMO+/LHM+ is made by TRW, Pentosin, and others in addition to Castrol. Just make sure you're looking at automotive LHM+ if you go that route, since there are LHM+ types meant for bicycles. You could also check with citraulics.com or daveburnhamcitroen.com to see whether they sell LHM+ or where they source theirs from.

Brian

The opposite of a correct statement is a false statement. But the opposite of a profound truth may well be another profound truth.
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post #3 of 24 (permalink) Old 08-26-2014, 01:03 PM Thread Starter
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Brake Bleeding

Brian,

I wanted to ask your opinion on a reoccurring issue I have with my Turbo Brakes.

My brake pressure keeps going down after 45mins of driving and then once the car is parked and sits for 30 minutes the brakes work fine again.

I was told by a RR specialist via this forum that I need to have the Hydraulic system completely flushed to remove air that's in the system and if this does not fix the problem the accumulator valves need to be replaced. When the brakes go down there is no fluid to be found leaking anywhere, not even on the top of the engine. The pumps have been rebuild and sealed just last year. Do you think air in the system causes the brakes to do down? I am planning on putting the car in the shop soon but there just aren't that many RR Bentley mechanic in this area that know what they are doing. Any advice will be appreciated!

Take Care,

Scott
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post #4 of 24 (permalink) Old 08-26-2014, 04:22 PM
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Scott,

What you describe is peculiar and would require more detail to answer. I don't know what, exactly, you mean by "my brake pressure keeps going down after 45 minutes of driving." (And I'm not trying to be snotty/snarky with that comment or the following questions):

1. How do you know this? Are the System 1, System 2 or both pressure lights illuminating?

2. If the answer to question 1 is "no," then what makes you say "the brake pressure keeps going down?" Describe what symptoms you're experiencing that make you think this.

Air in the system can definitely cause the brakes to be "weirdly grabby:" they seem to do their usual thing with light application but not much more with heavier application and a second or two later, *wham*, the heavy application kicks in full force. This is usually because there's air somewhere forward of the caliper that has to be fully compressed prior to full hydraulic pressure becoming available.

It would be extremely odd, well nigh impossible, for the accumulator control valves to operate such that they flake out after a standard delay every time you drive. They should either be working or not working from the get go.

Brian

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post #5 of 24 (permalink) Old 08-26-2014, 05:00 PM Thread Starter
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Brake Pressure

I thought the same thing about the accumulator valves my self. They either worth or they don't. What happens is I am driving around town and all of a sudden the brake pressure light comes on and the stop comes on. I don't think in my car there are two lights that come on like in the shadows. I can tell there is some pressure because i can stop but i only have about 20 pumps of the brake left which i think is coming from the new brake spheres. Its almost like once the car heats up one of the lines or seals starts leaking and the pressure goes down. Or maybe the there is a leak near the pumps which causes the pressure to drop. I still have not found a leak of brake fluid when this happens. Its crazy that I can't find the problem and I don't want to change the front valves unless i have too....Its the strangest thing...
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post #6 of 24 (permalink) Old 08-26-2014, 05:46 PM
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Does your warning light cluster look like this?:



If not, can you snap a quick picture and post it?

You do not have to have an external brake fluid leak, there are many internal channels that can leak.

Given your description it sounds like the accumulator valve may be going into bypass mode once the spheres are initially charged and then staying there. If that's the case you should be able to force the error much earlier than 45 minutes just by driving around the block and applying the brakes with great frequency until your pressure light comes on.

I believe that Crewe originally intended the accumulator control valves on these cars to be replaced only as a unit. If memory serves, there are now several people who actually will rebuild them, but I've got to dig through my archives to find any details.

Brian

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post #7 of 24 (permalink) Old 08-26-2014, 06:32 PM Thread Starter
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Brake Flush and Bleed Instructions SZ Car

Mine looks different and I took a pic but I am not sure how to attach it....

[img][/img]
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post #8 of 24 (permalink) Old 08-26-2014, 07:15 PM
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Scott,

It attached just fine. Thank you for posting it. I've added this to my technical archive so I have a fully accurate warning panel from a 1994 Bentley Turbo RL.

I'm now a bit more confused because on earlier generations the "Stop" warning was usually labeled "Stop Lamp" and was to tell you one of your bulbs was out. Does your Owner's Handbook indicate that its purpose is to tell you to actually stop driving? I can't imagine how it would be related to the brake warning light in any way unless they repurposed it.

Brian, who's now trying to collect photos of these warning lamp clusters because the diagrams in the later documentation are difficult to locate and sometimes incorrect when you do
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post #9 of 24 (permalink) Old 08-26-2014, 07:35 PM Thread Starter
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Brake Flush and Bleed Instructions SZ Car

What the book stays is if the Brake light come on there is a problem with the brake system but its ok to drive. If the Brake light comes on the stop flashes then the car is not safe to drive.
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post #10 of 24 (permalink) Old 08-26-2014, 07:48 PM
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Thanks much for that bit of information as well.

I'll keep you updated on what I hear back from "my sources" on the potential to rebuild the accumulator control valves for your vintage motorcar.

Brian
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