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GabriŽl Viljoen
Frequent User
Username: gabriel

Post Number: 21
Registered: 3-2004
Posted on Saturday, 13 November, 2004 - 16:37:   Edit PostDelete PostView Post/Check IP

Good day

My 1971 Shadow makes a tapping noise on start up. When she has idled for a while, or when I have taken her for a drive, the tapping is softer, but still there. I am sure it is not a tappet.

I was told be a Rolls Royce mechanic that it is most probable the one brake pump. According to him they start tapping when they are experiencing a big load.

I have replaced all the rubber brake hoses, so there is no blockage. I have tested the accumulators - I get anything between 75 and 90 pumps. So, what else could make the pump work hard and make it tap?

Regards

Gabriel Viljoen
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whunter
Prolific User
Username: whunter

Post Number: 87
Registered: 10-2003
Posted on Saturday, 13 November, 2004 - 17:14:   Edit PostDelete PostView Post/Check IP

Hydraulic pumps loaded with sludge?
Are your reservoir sight glasses clean and clear?

Binding piston wrist pin?
The sound will come from one of the two center cylinders, right side of engine from the Driver seat.
Sad to note; I have worked on three of these this year, owners would not repair them.
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Patrick Lockyer.
Prolific User
Username: pat_lockyer

Post Number: 55
Registered: 9-2004
Posted on Saturday, 13 November, 2004 - 17:47:   Edit PostDelete PostView Post/Check IP

Use long screwdriver or dip stick on the hydraulic pumps first,note any change in sound or heavy tapping.
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Jon Rothwell
Frequent User
Username: jon_rothwell

Post Number: 16
Registered: 4-2004
Posted on Saturday, 13 November, 2004 - 22:09:   Edit PostDelete PostView Post/Check IP

Both my and my inlaws Shadows have noise from the brake pumps on startup. This only lasts for a couple of minutes and stops once the system is charged.
I had a blockage in one of the accumulator valves recently which caused one of my pumps to knock after the system was charged and the No2 system to charge very slowly, the fix was to whack the valve with a copper hammer and flush the system at the accumulator, then the wheels etc.
Once flushing the system and beating the offending accumulator valve body up a bit the problem went away and has never returned.
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Patrick Lockyer.
Prolific User
Username: pat_lockyer

Post Number: 56
Registered: 9-2004
Posted on Sunday, 14 November, 2004 - 19:51:   Edit PostDelete PostView Post/Check IP

To follow up on my brief posting,you should now know the pump in question.
As the noise from the pump transmits quieter with time it points to the pump running on open or low pressure until a slow build up of pressure is pressent.
This can be caused by the pump push rod jumping on the cam lobe but not the fault itself.
First check the filters in the reservoire.
Make sure the hoses to the pump in question are not blocked.
If ok then go to the job of checking the acumulator that is fed by that pump.
Connecting a pressure gauge that will stand a pressure of 3000lbs with the removed pressure switch and connect to the outlet.
Start the engine, the pressure should show 1000lbs
corisponding to the nitrogen sphere pressure,it should then gently rise to about 2300lbs to 2500lbs.
Stop engine.
If ok the connect a bleed pipe to the bleed nipple on the accumulator, start engine and watch gauge as the bleed nipple is opened the pressure should fall to about 1850lbs and then start to clime back to about 2500lbs.
If this is not the case with the pressure not reaching 2500lbs the accumulator is faulty or the hydralic pump itself.
Brake fluid is flamible beware.
Bill Colburn may have other intresting points as he pointed me in the correct direction some time ago With faulty sphere.
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bob UK
Unregistered guest
Posted From: 62.253.64.18
Posted on Tuesday, 18 October, 2005 - 06:40:   Edit PostDelete PostView Post/Check IP

I have just come across this posting.

I have heard this on a few Shadows and I suspect that it is because No 2 brake pump which works the suspension has to build pressure up in the accumulator while the rear suspension is pumping itself up.

On my car no 1 stays charged for ages but because I have saggy rear springs I have fitted towing rubbers to the coils. leaving the rams to jack the car up about 1/2 inch.

When I park the hydraulics try to maintain this height until the accumulator is discharged.

It will last about 4 or 5 hours then the pressure light 2 will be on when I go to start.

The pump taps as the push rod jumps on the cam and /or the push rod drops away before the pump can return due to no back pressure for about 2 seconds then the no 2 light goes out --no tapping noises. A ten second idle and I have enough charge in the accumulator to ensure that no 2 calipers on the front have adequate bite.

It has been doing this for years.

I would say that providing the tapping is not heavy and goes quick on start up that this is not a serious problem. More like a quirk.

Any air in the height control system will not help. Because air compresses the pump will have to compress the air first which takes time.

especally if there is air in the section from the accumulator to the ride valve.

The sections after the ride valve are metered by the ride valve so air here will not make so much difference.

The pumps are jerk pumps I think of them giving punches of pressure.

As the accumulator is charging the pumps pulses will not be smoothed out ( like a battery does to a generator ) so the air is being thumped by the pulses which adds to the noise.

once the accumulator has built up a charge the punches get turned into a constant push and the noise goes.

The achilles heel of the Shadow is the ride height without I suspect there would far less problems with the brakes.

I suspect that there are lots of Shadows that have air somewhere---- lurking.

SRH 17768 fast solenoid is connected to park not door switches.





(Message approved by david_gore)
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RODNEY PEACH
Experienced User
Username: rodney

Post Number: 14
Registered: 12-2003
Posted on Wednesday, 15 February, 2006 - 05:17:   Edit PostDelete PostView Post/Check IP

Hello Guys,
I have been reading your messages refering to this tapping noise I started mine today and the rear hydraulic pump makes a terrible tapping noise what shall I do first any help welcome thankyou Rodney
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Guy Boldon
New User
Username: guy_boldon

Post Number: 2
Registered: 5-2006
Posted on Monday, 14 August, 2006 - 12:06:   Edit PostDelete PostView Post/Check IP

I am still trying to get some professional help from this forum. I own a 1974 Shadow SRH 17774 which was originally registered in Australiaas AAP-48F. The car arrived here in 2000 and it worked perfectly.The quietness and smoothness of the engine was unbelievable.
I have had to replace all the brake hoses, change points, plugs ,wires,condenser etc. But I have developed a severe knock at startup which is somewhat attenuated but persists during driving.

The car shakes violently when idling and I am a loss to know how I may resolve these problems. I need to get the car back to where it is supposed to be wrt performance. Can you helpme???

Guy Boldon, Trinidad< WI.














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David Gore
Moderator
Username: david_gore

Post Number: 636
Registered: 4-2003
Posted on Monday, 14 August, 2006 - 12:45:   Edit PostDelete PostView Post/Check IP

Hi Guy,

I sent you a private email through this forum in response to your query on this problem - did you receive it?

If not, please check your email address in your membership details, update if necessary, advise when this has been done and I will resend the email.