'Brake' Problems

After the disturbingly Mille Bornes-like experience of getting the car back home, (Creve!) I decided to tackle the brake problem. It had a serious effect on the drivability and safety of the car.

The problem was this: when you hit the brakes at any speed over about 35 mph, the entire car would judder violently. My theory was that there was a warped brake rotor.

The previous owner told me that he'd thought that too, but that he'd looked at the brakes, that they were fine, and that he thought the problem was elsewhere. When I applied the dial indicator to the right brake rotor, I realized that when he said he'd "looked at" the brakes, he meant just that -- he'd visually inspected them and not seen any scoring or other obvious problems. The right brake rotor showed runout of 0.030" -- thirty thousandths -- which is a lot. 0.006" is acceptable. 0.030" is more than enough to cause the problem. In any case, it's far too small a deviation to be able to see with the naked eye. It's hard to spot even when using a straightedge.

I ordered two new brake rotors and a set of pads from Mini City, put them on, and observed the same problem. I moved the rotor around, tried to see whether there were any shims involved, moved the dial indicator around to measure from different places, and kept coming up with the same 0.030" runout. On a brand-new rotor. New brake rotors will sometimes be defective. It's highly unlikely, though, that a new brake rotor will be defective by at much as 0.030". It's extremely unlikely indeed that two new brake rotors will both be defective by the same amount, and it's absurdly improbable that the two new brake rotors would happen to both be bent in exactly the same way and to the same degree as the old rotor. So something else was wrong.

The brake rotors on this car are bolted to the rear (i.e. inboard side) of the drive flanges. The drive flanges ride on the splined ends of the halfshafts, which in turn ride on the wheel bearings and are turned by the engine. The brake rotors have big holes in the middle, so the halfshafts can fit through and attach to the drive flanges. The only way the brake rotors are connected to the rest of the car is by their attachment to the drive flanges.

I observed that the deviation from flat always occurred at the same place in relation to the position of the drive flange, not in relation to the position of the rotor.

I tried measuring the drive flange, but that was impossible to do well. I wound up swapping drive flanges right to left, and sure enough, the left side now showed 0.030" of runout while the right side was fine.

So I have a bent drive flange. A bent, $195 drive flange. I figured that if the whole car was worth, by weight, what the drive flange cost, it would be worth about $200,000.

The plan is now to drop $195 on a drive flange and see if that fixes the problem. At the same time, I'll be ordering a PCV valve, radiator hoses, an intake/exhaust manifold gasket, and a carburetor damper piston (how on earth do you lose that?)

The old PCV valve, which I got in a box full of other old parts with the car (and which is missing a single crucial piece that you can't buy separately), was removed and the crankcase breather left uncorked. The whole point of the crankcase breather is to spew oil and smoke. Not having a PCV valve means that this oil and smoke gets spewed all over the engine compartment. Right now, I've got a length of heater hose diverting this to underneath the car. This is not the optimum solution, but at least it's not the pessimum solution previously employed.

The manifold gasket I need because I plan to just drop the entire exhaust system in order to repair it. It needs a little bit of welding and a new set of hangers (need to order those, too), and the car ought to be much quieter.