I had my car in for service last month and had the fuel system relay replaced. Afterwards I noticed something odd - when waiting at a traffic light the car has a tendency to creep forward a bit, until I push down a little harder on the brake pedal.

My questions:
1. For those of you who know what would be involved in replacing the fuel pump relay, is there any way that the mechanic could have accidentally "bumped something" that could cause this? I'm guessing probably not, and that this is a coincidence, but can't help but wonder, due to the exact timing...
2. My recollection is that the previous owner replaced either the master or the slave cylinder. Is it normal, after 30+ years, to have to replace these items, so I should simply replace whichever unit hasn't been replaced yet?
3. Any advice about what should be replaced or serviced?

Thanks,

Naimnut
--
'85 240 DL with 48K miles

1) No
2) Only slave cylinder on a Volvo 2/7/9 series is is if you have a hydraulic clutch actuator...in that case you have TWO master cylinders. One for the clutch and one for the brakes
3) Most likely it is a failing brake master cylinder master cylinder

A thirty year old master cylinder does not owe you anything. It is likely that it is corroded on the cylinder walls outside the normal sweep of the piston. This is especial true if you and the PO drove gingerly and politely to church on Sunday and never had to slam on the brakes.

Then one day...you do have to panic stop (or you bleed your brakes with the pump, pump, hold method and let the pedal sink further toward the floor that it normally travels). In very short order you will begin to notice the sinking pedal.

Moral of the story is, sometimes you should just drive the snot out of your car.

Press hard on the brake pedal while at a stop, if the pedal gradually goes to the floor you need to replace the master cylinder.
Dan