Random brake pedal travel issue

[Laird Scooby]

Originally Posted by CNGBiFuel

OK, I must admit I've never had need to change a P80 MC. Changed MCs on quite a few vehicles over the years, and never needed to bleed anything. Pour fluid back in thru' the top and be done. Air comes back up thru' MC. Worst case, I've a MityVac. Force fluid in from the the bottom and as it rises, see it pop out the MC.

Back in the day you could get coloured brake-fluids, red/blue or Green. That helped.

I've got the original MC on one 290K car. Should last the life of the car. Or replace 3-4 times more often than fluid, 'you pays your money'. See jammin's pix.

Unless a P80 is somehow different, the only reason I've ever done a bleed with an MC change,is because a flush is good practice... because we're on...

You've obviously been very lucky. Every MC i've ever changed has had upwards-pointing outlet ports so air will be present in the brake lines immediately after the MC and as you know, you should never reverse bleed them by pushing the brake pads away from the disc to expel the air into the MC as you force dirt backwards up the line to the ABS modulator and/or the MC which causes problems for the seals.

It is, as you hint at, best practice to always renew the fluid, especially when fitting a new MC as the warranty will probably be void if you don't renew the fluid. Same goes for new PAS racks and i wonder when anybody last changed their PAS fluid?

Just a thought - why are we even having this conversation? This is our safety and that of others, not to mention our cars that we've probably invested a lot of time, money and care in over the years in varying proportions.

We're pontifficating on the paltry amount of money to renew the fluid to preserve the braking system, why are we piffing about like this? It shouldn't need a discussion, we should just be changing the brake fluid at regular intervals instead. I recently bought a simple tester for about a fiver on ebay, it's a simple go/no-go tester with half a dozen LEDs, first shows it's working, next few show from 0% to 5% in 1% stages of contamination (presumably water as that will alter the intrinsic resistance of the fluid) and by the time it's reading 5% the last two LEDs are red - red for danger and the "suggestion" in the instructions is that 2% or more, change the fluid!

When i last checked my Volvo a few months ago it was 1-2% depending exactly where in the the reservoir i poked it in.

On my Rover last year it was off the scale - no surprise really, the plan was to change it immediately after getting it back from the MoT and i still adhered to that plan.

Thanks to the sheer incompetence of the garage doing the MoT it took 6 months to get it back and by then it had been sitting so the corrosion had time to take hold.

During changing the fluid, the MC popped but luckily i had a spare and plenty of fluid. I'd also managed to create a bespoke cap to fit the reservoir to use the Gunsons Easibleed thankfully so it took about 45 minutes in total to renew the pads and fluid all round after changing the MC and then readjust the handbrake.