MGB: Front brake problem driving me crazy!

For the last 4 years, about this time of year after one or two longer drives than usual (i.e. 4-7 hrs constant driving at varying 40-70 mph speeds vs the usual 1/2 hr to 1 hr slow to mid (30-60mph) speed putts around town), I suddenly start getting significant pulsating from the front brakes that I feel through the steering wheel and brake pedal. No discernible pull to either side but pedal feels slightly softer than usual.

Year one over winter I replaced the rotors (properly torqued) and pads. Bled to good reasonably firm pedal. Okay til next year same time etc.

Year two same thing. To be safe over winter I replaced both calipers, rotors and pads. Also redid both front wheel bearings as right front one was going. Bled to good reasonably firm pedal. Okay til next year same time etc.

Year three same thing. I found a stuck right hand caliper piston. Over winter, replaced with two new (not remanned) calipers, slotted rotors and new V8 pads. Bled to good reasonably firm pedal.

Year four (this year). Replaced brake fluid this spring. Bled to even firmer pedal. Okay until today. Same thing just arose.

Have not replaced the ss front brake hoses that are 10 years old.

Left rear brake will lock up in panic stop.

Dual line braking system with booster. No fluid loss.

Right front wheel hub always needs to be torqued to 80lbs to get the cotter pin in but end float always seems fine. No binding either.

Any suggestions/ideas on what's going on or to try next?

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Cost's about $30. and would be my first suspect.

then wheel straighteness/runout out of round. possibly tire issue

Might try an experiment before you buy new lines. If you can get it to do it again, pull over and feel the rotor/caliper on both sides. Careful, it may be very hot! If it is hot, then I'd suspect hoses that are "ballooning" perhaps with ambient temperature and then the residual pressure from the ballooning holds pistons/pads against the rotor. Stainless hoses not as inclined to balloon as the pure rubber/reinforced ones...but you never know.

Left rear locking up sounds to me like you may have a bad axle seal and are getting grease on the drum. I don't see any connection between the two problems.

also with the other suggestions...look to that big brass proportioning valve on the driver's inner fender just below the brake box...it may be sick and they make a kit for it, otherwise the thing is about 400 dollars, I don't know why.

David,
It sound suspiciously like "pad knock off" where driving long distances allows the bearings to heat up a little more than usual.

A good discussion on this site below:

http://www.bmsc.com.au/forums/rallying-technical/507-brake-pad-knock-off.html

but be aware it is an Australian rally car discussion group board.

Cheers , Pete.