940 master cylinder refurb

[vickyg]

Originally Posted by NI_Volvo_Nut

I've a used one off a 95 940, worked fine when removed. £30 posted if interested.

Not on here very often so drop me an email AndyD345@btinternet.com

Much appreciated Andy but I think I have found one, fingers crossed!

[vickyg]

This isn't going entirely well. New rears all done and the master cylinder on. Lots of bleeding and the car stops well enough but the pedal has a bit too much travel for my liking and some softness. I'm reading that 940s don't bleed well and there could be air trapped in the MC or ABS despite doing a thorough bleed on MC and all wheels. I could buy locally a pressure bleeder of the type that goes on the reservoir. Unsure if I'm being OTT or if this pedal feel is "normal"

[Dippydog]

Obviously I can't say whether the pedal you have now[I take it it's an improvement over what you had before?]is normal or not and I don't say for definite that a pressure bleeder would solve the problem but after purchasing one my self this year I'd say a pressure bleeder is well worth the investment.

[Laird Scooby]

Originally Posted by vickyg

This isn't going entirely well. New rears all done and the master cylinder on. Lots of bleeding and the car stops well enough but the pedal has a bit too much travel for my liking and some softness. I'm reading that 940s don't bleed well and there could be air trapped in the MC or ABS despite doing a thorough bleed on MC and all wheels. I could buy locally a pressure bleeder of the type that goes on the reservoir. Unsure if I'm being OTT or if this pedal feel is "normal"

The pedal feel should be short and firm. Are you following the correct bleeding order?

A Gunsons Easibleed is worth its weight in gold in terms of time saving and ease of use. A little tip that might help is to release the bleed nipple 1/4-1/2 a turn with the bleed tube fitted then push the pads/piston in and hold it there either with a G-clamp or similar device used to retract the piston into the caliper. Now bleed that caliper, close the bleed nipple and refit things as they should be, move on to the next caliper in the sequence.

Doing it this way helps eliminate any air that might be trapped in the calipers which can cause a long pedal travel.

Also worth checking the brake pedal to pushrod clearance and also the pedal shaft for wear at the point the fulcrum pin goes through to join the pushrod to it.

[vickyg]

Originally Posted by Dippydog

Obviously I can't say whether the pedal you have now[I take it it's an improvement over what you had before?]is normal or not and I don't say for definite that a pressure bleeder would solve the problem but after purchasing one my self this year I'd say a pressure bleeder is well worth the investment.

It's a bit better but not the improvement I hoped for. In an emergency stop there is no sense of being flung through the windscreen. It does stop but it's a little unnerving!

[Ian21401]

Definitely agree with using a pressure bleeder. It is soooooo much easier. I cannot comment about pushing the pads back into the caliper as I have never done it. However, on the very infrequent occasions when I have needed to bleed the entire brake system I have found that after the initial bleed the pedal was not as hard as I would like, so after a day or two of use I pressure bled the system again and this gave me the harder pedal that I was used to.
Regarding the bleeding order. Depending on the particular car, it is not always obvious which brake is farthest from the master cylinder. Depending on how the brake piping is routed, the length of brake pipe from the master cylinder to the brake may mean that a brake which is physically nearer the master cylinder, ie the offside rear, may actually have a longer pipe run than the nearside rear, similarly the front brakes.

[ukvolvo]

I used to borrow a friends mac tools bleeder that linked on the reservoir and ran off 12v. You just turned it on and cracked every nipple off one by one starting furthest away or all at once. As long as the tank on the bleeder was kept full it worked brilliant.

Just push so much fluid through its all new and any air is pushed out with old That's the advantage of any pressure assisted bleeder and why they work so well. You're not really bleeding your flushing under pressure with a side effect of bleeding.

After a quick google it seems there is lots of pneumatic style ones out there now

[Laird Scooby]

Originally Posted by ukvolvo

I used to borrow a friends mac tools bleeder that linked on the reservoir and ran off 12v. You just turned it on and cracked every nipple off one by one starting furthest away or all at once. As long as the tank on the bleeder was kept full it worked brilliant.

Just push so much fluid through its all new and any air is pushed out with old That's the advantage of any pressure assisted bleeder and why they work so well. You're not really bleeding your flushing under pressure with a side effect of bleeding.

After a quick google it seems there is lots of pneumatic style ones out there now

Gunsons was the original AFAIK and even comes with the right cap for the Volv M/Cyl making life easier. I had to make a cap for my Rover to use the Gunsons but it made life much easier!

Also one point to mention, on cars with ABS on NO ACCOUNT WHATSOEVER have the ignition on while bleeding. This is known as "live bleeding" and can cause serious damage to the system.

[ukvolvo]

Originally Posted by Laird Scooby

Gunsons was the original AFAIK and even comes with the right cap for the Volv M/Cyl making life easier. I had to make a cap for my Rover to use the Gunsons but it made life much easier!

Also one point to mention, on cars with ABS on NO ACCOUNT WHATSOEVER have the ignition on while bleeding. This is known as "live bleeding" and can cause serious damage to the system.

Never knew that thankyou

Can you modify a gunson unit to run off a air feed? As in proper air feed over tyre.

[Laird Scooby]

Originally Posted by ukvolvo

Never knew that thankyou

Can you modify a gunson unit to run off a air feed? As in proper air feed over tyre.

It would be possible to modify a Gunsons Easibleed as long as your pressure regulator goes down to 20-25psi but i've always found it just as easy to use a spare wheel (tyre doesn't even need to be legal) and just top it up from the airline.