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Excessive brake pedal travel and "bench bleeding"?


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The car in question is a mark 2 Ford Focus.

I fitted a new brake master cylinder to this car and new back brake hoses, then bled the brakes.
The brake pedal is rock solid with very little movement, however,
on starting the engine and trying the brakes, there is now a lot of travel.
Pumping the pedal effected no change.

To remedy this,
I am going to, weather permitting, fit new front hoses and try the brakes again.

Out of curiousity, I tried a Google search and found myself on a U.S. Ford forum 
where it was stated that you need to "bench bleed" the master cylinder before fitting.
I have never heard of this procedure and the Haynes manual makes no mention of such.
Over the years I have replaced a few BMCs and always just bled the brakes at the calipers and/or wheel cylinders.

Any thoughts?

Thanks,
Ian

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I typically bench bleed my MCs, but I do it on the car on install.  It just involves filling the reservoir(s), and installing temporary tube(s) on the MC outlets which divert fluid back to the reservoirs.  Pump the brake pedal until there are no more bubbles.  

I don't think it is necessary to bench bleed, but it seems to make the system bleed go a little quicker.

Ed

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As Ed says........

Only time I’ve ever done it was on the PI clutch because Lockheed M/Cs are rubbish.

Does the car have ABS? If so, the pump may need bleeding. You can generally get away without if you have been in the system downstream of the pump, but upstream, probably not. Pump bleeding usually needs a scan tool.

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Thanks for the replies.

Yes this car has ABS.
The Haynes manual states bleeding after replacing the ABS unit, is at the calipers.

On other cars, eg Peugeot 307 or Citroen Picasso I didn’t encounter problems 
when bleeding the brakes despite both having ABS.
I think I removed the bleed nipples and allowed gravity to run it’s course.

Having previously run T2500s I have a Gunson’s Easibleed, 
which I acquired purely for bleeding their clutch hydraulics.
I am thinking I should try this tool here.....

 

Ian 

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Agree that in most cases, on most cars, there should be no need do a bleed routine on the ABS pump with a scan tool. Indeed I have done so many times. But the ones I have done have always been disturbed after the abs pump and kept full of fluid, so the abs pump will not have got air in it.

Obviously, when doing a master cylinder swap it is inevitable that air gets into the lines upstream of the abs pump and will have to pass through it to be evicted.  I hope you are right that it can be bled through in the usual way and some form of pressure or vacuum bleeder should certainly help.

However, if it just won’t come right, it may be necessary to do a bleed routine on the pump.

Good luck!

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  • 4 months later...

A solution to the problem.....

It was the front flexible hoses that were to blame.

 

As we were in a “stay at home” lockdown I left the car until now.

I had already replaced the back ones last year with some difficulty (had to also renew
two brake pipes which in turn involved removing heat shields..) so wasn’t much
fancying tackling the front hoses, but as it turned out this was really easy.

 

thanks
Ian

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