What would cause a clutch master cylinder to go bad?

Question

I have a 1980 Honda Prelude and have only driven it a few hundred miles per year for the 10 years I've owned it. Redid the clutch when I got it, with new cylinders and everything.

Last week I got in it having not driven the car for several months, and the clutch was just dead. No hydraulic pressure at all. Two days ago I bled the line and put in new fluid. It was working again although the pedal still was only coming up half-way.

Today I was driving and with my foot, I pulled the pedal all the way up. Then when I pushed it back down, no pressure again -- somehow air got in the line from me lifting up the pedal all the way like that.

I looked at the master cylinder and it has yellowish residue on it. Is that a sign that it's got a leak? There is also what looks like red mold or rust on the shafts of the pedals, since the car has been leaking moisture into the interior (I live in a city where it rains a lot).

My question is, firstly, what would cause the clutch hydraulics to leak and get air inside if the car wasn't even being driven? I probably didn't add clutch fluid in several years so I'm assuming it just evaporates slowly over time, but my brakes haven't had the same problem so I wonder if it's something else.

What could cause the master clutch cylinder to leak after not many miles? Defect? Maybe from freezing repeatedly over several winters?

I'm just wondering if it's worth bleeding again or if I'm likely to run into the same issue.

Answer 1

Your best (easiest/cleanest) bet is to replace the master/slave cylinder assembly. The main part of play here is lack of use. What happens is seals dry out and when you then subsequently use the clutch, extra wear is put on the seal, which allows it to wear much quicker. You can avoid this situation by driving the car at least once a month until the entire vehicle is warmed up (engine, transmission, coolant, wheel bearings ... everything). Take it out for a weekend drive for an hour and you should be golden. With that, you should also start the vehicle about once a week. Also, put some type of fuel stabilizer in your tank and keep the tank as full as possible. Also, even though you are not driving the vehicle much, you still want to change the oil once a year as well.

As far as the pedals go, you need to take them apart, clean, then grease them. There may be nylon or plastic bushings at the top which might need to be replaced as well. You are getting rid of the "red mold" (which is rust, most likely) which has invaded.

When all of this is said and done, if you want to keep the car, invest in a car cover. If you don't, you are just allowing nature to reclaim the vehicle.

Answer 2

most likely it because of wear and tear.sitting unused for long periods is also another cause. the rubber seals must have dried up. i bet its time to replace your slave and master cylinders.