| Author | Message | ||
     Bill Weed Yet to post message Username: oldzink Post Number: 1 Registered: 2-2005 |
Gentlemen, As a silent observer I have found great value in this forum. I've owned my 1978 T2 (SBG34264)for 10 years. As I live over 300 miles from my mechanic, we attempt to diagnose problems by telephone so that required parts can be ready when I arrive at his shop. I'm having a brake problem. In traffic, after a few stops, the pedal goes almost to the floor,with a corresponding decrease in stopping power. The hydraulics have been bled. I only get about 25 pumps of the pedal before the pressure lights come on in the accumulator test, but my mechanic wonders if this is the cause of my braking problem, as the pressure lights are not coming on as the brakes are failing. Any ideas? | ||
| Bill Coburn Grand Master Username: bill_coburn Post Number: 377 Registered: 4-2003 |
Bill/ Feel free to be a noisy observer we all do it. I would put my money on crook pressure switches and depleted accumulators. The former are easily overhauled and in a Shadow II are very accessable. There is a kit to do this and your man should test them after the overhaul. Your brakes are failing because the pumps are not keeping up with the pressure requirements to repeatedly apply the brakes in traffic that's why you have accumulators. If you want a more graphic test find a very slight down slope. Stop the car switch off the engine and turn the ignition on. Let the car roll and repeatedly apply the brakes and see how many stops you get before you go into angel gear (ie - no brakes). Can I suggest you do not do this whilst proceding towards a cliff or a major intersection - best use the bottom paddock and make sure daisy isn't grazing in front of you! Starting the engine should give you almost instant braking otherwise the handbrake should do the job. This will give you an empirical result regardless of the condiditon of the the switches! | ||
| Gordon Norris Prolific User Username: crewes_missile Post Number: 132 Registered: 2-2005 |
Bill W, As the eminently knowledgeable Bill C suggests, it is almost certainly depleted accumulators. You can't rely on the pressure switches lighting up the warning lamps as you drive as there were different types available and/or fitted at different times. Some switched at a very low pressure eg/ 100psi and the later ones at over 1000psi. If you have the early low pressure switches the brakes can fail as you describe, and the lights will not come on until there is next to no pressure left, by which time you will have either expired of a heart attack or hit something!  . New accumulators and new switches, at your option, should do the trick. GN. PS TO BILL COBURN: Finally got a reply from Crewe on the new thermostat-see the thread under Spirit/Spur section. About as useful as tits on a bull... | ||
| Bill Weed New User Username: oldzink Post Number: 2 Registered: 2-2005 |
Thank you, Bill I am indeed without brakes before the bottom of the hill. My pumps and switches were rebuilt less than 1000 miles ago.The accumulators were done 5 or 6 years ago. My tech is wondering if the accumulators have ruptured (he gave me an assignment to test this) He's also questioning the valve body on the accumulator. Because of this forum I just bought 8 litres of 363. Could having used DOT3 for the past several years be a cause of my problems? | ||
| Bill Weed New User Username: oldzink Post Number: 3 Registered: 2-2005 |
Thank you Gordon | ||
| David Gore Moderator Username: david_gore Post Number: 431 Registered: 4-2003 |
Hi Bill, Further to the information above and the fact that the diaphragms are at least 5 years old; I suggest the diaphragms have started to break down and allow the Nitrogen gas charge to diffuse into the hydraulic fluid - if the gas charge is low, the diapraghms may also have thinned locally due to stretching. A temporary fix would be to recharge the accumulators and do regular "pump-down" tests to check gas leakage and determine when overhaul is necessary. A quick check of the system working pressure with a 0-3000psi pressure gauge will reveal if the relief valve is functioning correctly - Bill Coburn has published the method for doing this on the forum previously - just use the SEARCH facility with key word "accumulator" or "accumulator valve" |
