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Discussion Starter #1
After riding my 2000 Xpedition 425 for 15-20 minutes at the start of the day the front and rear brakes lock up hard. I know it's both front and rear since the rotors are all hot when this happens. This happens even when I have not applied the brakes. After setting for an hour or so everything goes back to normal for the remainder of the day. Any suggestions on what I might check?
 

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13 years is a long time on brake fluid. Just a guess but I would think a system flush, new pistons and fluid would be in order.
 

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13 years is a long time on brake fluid. Just a guess but I would think a system flush, new pistons and fluid would be in order.
^^this. And check your lines. Even tho they may look ok from the outside, they can be swelling and/or collapsing on themselves internally not allowing the fluid to escape out of the piston(s).

Another thing is make sure your rotors aren't bent or warped
 

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Discussion Starter #5
Kme743;350695^^this. And check your lines. Even tho they may look ok from the outside said:
I've heard of the collapsing brake hoses with Chevy brakes in years past. Any suggestions on how to diagnose this issue.

Since this issue seems to occur regardless of whether the brakes are used and since it seems to occur only when the bike sits overnight and warms up I tend to believe the brake lines that run above the engine are picking up heat and expanding the fluid and the return path to the brake reservoir is blocked. This could be due to either internally collapsing hoses or a master cylinder with a fluid return port blocked. I don't have a good explanation for why it occurs only with the first ride of the day and does not persist.
 

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Discussion Starter #6
OK, I finally finished the repairs today. Thought I would share what I found with the group.

1) The compensation port on this bike is really small and was plugged so when things heated up there was no place for the fluid to expand.
2) All of the brake lines were plugged solidly. As in they would not pass 100 psi air. Probing with a small stiff wire indicated that the obstructions were at the fittings where the hard line transitioned to hose. When I cleared the blockages it appeared to be rust and corrosion products. I was able to clear all of the lines by putting them in an ultrasonic cleaner for about a half hour with distilled water and vinegar. After the blockages were cleared the lines were filled with a phosphoric acid solution to treat the corrossion.
3) All of the slave cylinders and master cylinder were rebuilt with new soft goods.

I tried several techniques to bleed the brakes. At the end of the day backfeeding fluid from the slave cylinders to the master cylinder seemed to work best.

This could all have been avoided by changing brake fluid every few years.
 
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