The brake pedal has a strange symptom which I am trying to identify. The pedal at times is long and at other items is short. When the pedal is long the car takes longer to stop. When the pedal is short it stops promptly.
I am trying to find out if this a master cylinder issue, brake line issue or something else.

In the past I had a 760 volvo and had to replace the master cylinder. The symptoms were different tho. The pedal would go to the floor. Pumping the pedal would make it firm again. This is not the case with the 740 I presently own. Pumping the brake when the pedal is long does not change the quality of the pedal.

 

I had the same issue with my 240. I had brakes fail on me in the middle of Chicago and ended up changing the master cylinder in a parking lot

Check the booster and valve on it. If there's no leakage, then it is most probably the master cylinder. The symptoms you have right now are going to worsen and become just like your 760.

 

thanks for the reply. How complicated is the master cylinder replacement job? Do you know any resource to become familiar with the replacement procedure? I would like to do the repair myself.

 

How hard is a mater: Well, I've been working on cars for years and there simple to me.

Depending on your skill level and tools moderate to difficult. The master should be bleed as well as the entire system afterwords. The fitting could be hard to remove, system hasn't been bleed in a long time things can be gummed up and a pain to bleed.

 

Many thanks, I will keep it in mind.

 

I did it in a parking lot with just my wrenches. So pretty easy. Take care that you clean stuff and dont dirty them when you put in on the ground. If you dont have the "brake" nut wrenches, use the regular ones. The lines are 11 mm if i remember correctly Be gentle and dont strip the threads, You will be fine. Also try not to spill the brake fluid - it will take out the paint. Good luck!