ROAD AND WORKSHOP by Handyman
Page 46
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Be Patient—and Work to the Rules
WHEN THINKING of brakes, people do so in terms of stopping ability, placing unquestioned reliance on concealed mechanical items that are expected to function at all times in their normal fashion. The tendency is to take for granted that the familiar everyday stopping power will always be there. Yet often, in garage and workshop, the work of a brake overhaul is a rushed job. Brake shoes and wheel cylinders are hurriedly changed or serviced, and dust, grease and spilled hydraulic fluid is everywhere.
It should be appreciated at times that hydraulic-brake units are precision equipment, and as such are on a level with fuel-injection equipment, needing similar care and absolute cleanliness. Grit, dust and all oils other than the correct fluid, can be fatal to cups, seal valves and so on. Hydraulic units are often opened up on a dirty bench, littered with debris and tools, or even on the floor. And on assembly, how rare it is for the fitters to clean their hands and shake the dust from their clothes before opening the kit of valves, cups and seals for assembly.
One of the worst sights in any garage is the stripped hub and 'brake assembly, with a dangling flexible pipe siphoning out the fluid all over the place. Quite apart from the sticky mess all around the job, body paintwork can be badly scarred if brake fluid is transferred to doors and wings. Again it is quite common to see a fitter working on units under cab floors without having cleared the accumulated grit and dust invariably found on top of any unit in this position.
The correct drill is simple enough. Make it a rule that the whole working 1112
area is well cleaned before opening any underfloor item. Another rule should be adhered to as strictly as possible. Before stripping anything to do with the hydraulic side, open the line and drain or pump out all fluid from the system. Where the fluid has served for any appreciable length of time, scrap it. If in any doubt concerning the cleanliness of the storage tank or container, flush the system thoroughly with new fluid.
Cylinders or units in store should remain sealed until needed for assembly. Cylinders overhauled on site should be stripped on a clean surface, assembled with clean hands and using the correct fluid as a lubricant, or be assembled in
a fluid tank. Equally important on assembly is not to attempt brake adjustments with the system dry. Fill and bleed the system and then adjust: if a second bleed is required, do not use the fluid that has just passed through the system. Store it by all means if it is clean, but it could take days to clear of all air, and if used right away, even to top up, the brakes could be difficult to adjust without binding, and in any case would be down in efficiency. The careful exercise described will take a little banger than normal, and may be disliked by many, including the impatient customer or traffic manager. But always remember, it is the correct drill, and the extra time spent will guarantee many extra miles of safe and trouble-free operation.