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I have an odd problem with my brakes.

Recently, the left front brake, periodically, would start dragging. Stop the car, let sit for 20-30 minutes and then everything is fine??

Take off the left front wheel and spin the rotor. No binding, spins absolutely freely. Pads are good and rotor is in fantastic shape. Put the left front back on, right front starts dragging???? Take right front off when car is cold, rotor turns freely. Same thing, pads are rotor are in great shape.


What gives? At first I suspected calipers that were on the verge of seizing, but I think there is more to this.

Also in the morning when I first brake, I have virtually no stopping power meaning I have to really jam the pedal down to get minimal stopping and often have to use the emergency brake to help.

The brake pedal is firm and never sinks. Could I have a problem with the proportioning valve?

Any hints/direction would be greatly appreciated.

Quick thought: Binding to me means that the calipers need to be opened up and rebuilt. Old, inflexible seals can cause binding. Replacing the rubbers helps but you may find corrosion in the pistons. I keep the ears on the pads greased and also whatever pins are involved but I don't know your specific set-up.

Second, old hoses do funny things. It is possible for them to come apart inside or swell in such a manner that pressure does not release in foot off mode. You can only find this by careful disassembly.

Poor cold performance is common with racing type pad compounds. They are great when hot but nearly dangerous when cold.

I don't know what other advice you will get here but it will be a lot more meaningful when you get the entire system apart and see what is what.

Shures,

thanks for the quick reply.

Yup, looks like I will do a complete dissassembly and rebuild on the calipers. The rest of the hoses look new, but naturally I'll check them as well.

I think the poor cold performance is exactly as you described. I found out the the pads are high performance once, so that seems to explain that. I think I will switch back to street pads in the process of the rebuild.

Cheers,

O.K,

I've taken off the right side caliper and have found that the pistons can be forced in and out by hand. It requires fairly significant thumb pressure, but it is not what I would consider, perhaps incorrectly, seized. What I find curious is that when I push one piston in, the other piston comes out. I would expect that by forcing one piston in that it would/should force fluid back into the resevoir. I compared this operation to the left side caliper, and it is idendical expcept that the pistons in the left caliper are a bit easier to push in and out.

My question is this before I rebuild my right caliper. Is this behiour typical?, or might this indicate that the reason my right caliper does not release quickly, is due to some blockage that create a sort of one way valve?

Turns out it wasn't the calipers at all. My "appear to be in good shape" rubber hoses were completely stuffed. It's a miracle I had any braking at all.

The reason the one piston was comming out while the other was forced in was because the brake fluid had no place to go.

I deduced that the high pressure created by pumping the brake pedal allowed some fluid to find it's way to the caliper but that upon releasing the brake pedal the fluid could not return to the resevoir. The result was locking up of the right front.

New hoses are on the way.

Front lines flushed and new hoses installed.

Car brakes like a champ!!

Congratulations! Went through the same thing on one of my cars, the difference is HUGE!

Well,A valuable bit of info for us all.Great stuff M.

I flush brake fluid yearly on my street cars to preserve the calipers. A yearly change minimizes moisture related corrosion which is important in light of the cost of replacement calipers. My Alfa sees some track time and so gets a flush more often, before each event. I am currently using ATE fluid and alternating between Blue and Gold which gives an indication when the fluid is completely flushed. I don't like to see hoses go too many years but have found a bad hose by noticing a difference in flow rate between calipers.