Possible brake issue

[JimVette]

I took the Z out for some exercise yesterday and had a problem. After 20 minutes on the road it started to bog down in 5th gear at 60 mph, I down shifted and still bogged down, power key on. I pulled off the road clutch in and when I applied the brake the pedal was all the way up and stiff with no cushion, rock hard. I backed up about 50' and everything seemed normal. The brake pedal felt normal also. No stored codes in any system.

I drove about another 10 miles gassed up and was on the way home and the same thing happened again. I backed up with the same results. Either time it did not pull to either side. I spent the rest of the afternoon reading up in the service manual. The only thing I could figure out is that the master cyclinder is failing or the proportioning valve is going bad and appyling pressure to the rear.

This is probably just a C4 issue

Any thoughts.

Thanks!

Jim

[Hib Halverson]

I'm a little unclear on the last part of the post...did you determine conclusively that the rear brakes are dragging or are partially applied?

[JimVette]

No, not for sure. Just reading what the proportioning valve does. I would like to know for sure. I don't like just changing parts til the problem is fixed. RPM didn't seem to fall off. What would cause the brake pedal to be full up and rock solid, no cushoin what so ever and during this the nose never dropped like appling the brakes (all 4)?