"B" - is for "Brakes" By Ian Hopley
The 164 V6 12-valve braking system is a pretty straightforward conventional system with no real peculiarities to speak of. The front brakes are ventilated discs, 284mm in diameter and 22mm thick. The minimum allowable thickness is 20.2mm, which really means that they are designed to be thrown away and not re-ground. If you want to re-grind the discs, the minimum allowable thickness after a re-grind is quoted as 21.2mm. In other words, they'll let you take a whole 0.4mm off each side of the disc! Mine were about 18.5mm thick when I took them off due to a noticeable degree of vibration and harshness under braking (accompanied by a sort of faint moaning sound under heavier braking) so I decided against a re-grind! The rear discs are solid. They are supposed to be 251mm in diameter and 10mm thick. As with the front discs, you're allowed to re-grind them down to a mere 9.5mm (i.e. you're just supposed to buy new ones in reality)! The quoted minimum thickness for wear is 9.0mm. That said, rear discs don't really seem to wear much.
The callipers are Girling "single pot" items at both ends. Each calliper has only one piston - the other half of the calliper slides so as to maintain (in theory) an equal and opposite pressure on the other side of the disc. The rear callipers incorporate a handbrake mechanism and this seems to be the cause of most braking trouble on elderly 164s. I have never known a 164 brake calliper to leak, although if this happens, seal kits are relatively inexpensive and easy to fit. What does seem to be more common, however, is seizing of the handbrake mechanism. When the footbrake is applied, the hydraulic pressure forces the piston out of its housing and pushes the pad against the disc. When the pedal is released, the piston moves back fractionally to un-clamp the disc. The handbrake, however, must be purely mechanical. On the 164, the cable pulls on a little arm which actuates a shaft running into the calliper body. As this arm rotates, it turns a "screw thread" which forces the piston out as before and forces the pads against the disc. The "screw" mechanism also incorporates a ratchet so that as the pads wear, the movement is taken up.
According to the workshop manual, the handbrake should need about 3 or 4 clicks to engage it in normal use and no more than 7 when a load of 40kg is applied to the end of the handbrake lever. If the car fails its MOT either because a rear brake is seized or because the handbrake is inefficient on one or both side(s), the most likely cause of the problem is the calliper. The bad news is that they cannot be re-built as a DIY proposition and re-conditioned ones are fairly expensive. If you're going to a scrapyard to look at one, make sure the handbrake actuating lever returns FULLY under the action of its own return spring! If you have to help it with your finger, it is starting to seize.
Over the last few years I have tried packing the gap between the arm and the calliper body with water resistant grease (such as Castrol "Keenol" which is often used for boat trailer wheel bearings) to try to stop water working its way up the spindle. There's no way of telling if this works but at least it makes me feel better! Of course, the other way the mechanism could seize would be through water getting past the spindle seals from the brake fluid itself. Brake fluid absorbs water from the atmosphere with great enthusiasm. It wouldn't be a bad idea to change the brake fluid in the whole system at least every 2 years. The easiest way to do this is by bleeding some off all four wheels and replacing it at the reservoir so that it never gets low enough to expose the ports in the master cylinder. If this happens, air will be trapped and you will have to bleed it out again. NOTE: The workshop manual recommends that the set screws securing the brake callipers to their brackets (the smaller blue bolts) should be replaced every time they are removed.
Article Content and Photos
by Ian Hopley.
© Ian Hopley / alfisti.co.uk 2002