Scary brake problem

[chrisvmax]

Hi Guys'n'Gals,
driving to work this morning... all's well. Everything working (except my fingers after scraping the ice of the windscreen!)
After about a mile or two I needed to stop at some traffic lights and brake power drastically reduced!! managed to stop before hitting the car in front by using the handbrake as well.
The brake pedal feels hard to press, doesn't seem to move far and brake power is greatly reduced.
I had to keep driving as I couldn't turn round where I was, I drove very cautiously, the next time I used the brakes they were working as normal, before I got home the brakes went scary again, then when I parked they were OK.

Anyone got any ideas. it's not something that's ever happened to me before and I'd rather it didn't happen again.

Regards,
Chris

[FredTransit]

Sound like a servo problem, or pipes associated with it (you have a Di in your amby right?). It could also be the servo pump on the dodge, which is attached to the back of your alternator. Hope it's the pipes or the pump, cos the servo itself is no longer available, and the best bet is to fit a Mk3 servo and master (the Mk2 master won't fit the Mk3 servo)

[John Grove]

Certainly sounds like the servo isn't boosting intermittently for some reason. It can't be the main diaphragm split cos then it wouldn't work at all. I seem to remember there was a valve fitted to the servo? Could be sticky? Icing? WD40? Not sure. Worth a look before you start stripping it down. Check the hoses too. Can't see it being an intermittent problem with the pump - I think they either work or they don't

[baconsdozen]

Fluid leaking into the servo over the years can get to the point where it reduces the boost the servo gives.Pull the vacuum pipe off ad wiggle a bit of flexible pipe into it,see if it comes out wet.

[chrisvmax]

Thanks for the replies.

I'll check it out over the weekend and let you know how I get on.

Regards,
Chris