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[terry paget]

Haynes is concerned I shall push grit back to the ABS valves when pushing back brake pistons to replace brake pads. He recommends clamping the brake flexible hoses and opening the bleed nipples to avoid this. I have been changing brake pads on cars with ABS for 30 years without problem. Are Astra ABS valves peculiarly sensitlve to grit, or is Haynes being very cautious?

[Doctor Gollum]

They're perhaps ass covering, but clamping the flexi and opening the bleed nipples is the 'correct' method regardless of car. Followed by a final clamp free bleed once finished each wheel

This actually results in much better pedal feel even if you don't change the fluid...

[Marks DTM Calib]

I have always advised this, for a number of reasons:

1) You get the ancient brake fluid flushed from the calliper (this si rarely achieved with just a fluid change)
2) It makes pressing the piston back dead easy
3) No risk to any ABS component
4) No risk to inverting the seals in the master cylinder  (and I have seen this happen!)
5) You don't risk the fluid reservoir overflowing

[TheBoy]

Yes, always clamp the hoses, irrespective of whether it has ABS or not.

[terry paget]

Thank you gentlemen, I shall clamp and bleed henceforth, for the reasons you give, not Haynes. I have suffered many an ABS failure, but none caused by grit in valves. Most were electronic unit failures, 2 were sensor, 2 were sensor ring splits, and one was front wheel cable failure.

[Shackeng]

It was much easier, back in the day, to rivet new linings to old brake shoes -not!

[JasonH]

I think Astras in particular have a nasty habit of inverting their master cylinder seals if you don't open the nipple. I'm fairly sure I've heard it happen a few times, but only on Astras for some reason.

[Andy H]

Am I the only person who is concerned about the possibility of damaging the flexible hoses by crushing them with a clamp

Opening the bleed nipples without crushing the hoses seems to work just fine

[Andy B]

Am I the only person who is concerned about the possibility of damaging the flexible hoses by crushing them with a clamp

Opening the bleed nipples without crushing the hoses seems to work just fine

As their suggests ..... they're flexible and easily cope with being squashed. Obviously you don't try to crush the life out of them. 

[dave the builder]

Am I the only person who is concerned about the possibility of damaging the flexible hoses by crushing them with a clamp

Opening the bleed nipples without crushing the hoses seems to work just fine

my thoughts exactly 
not that the flexi hose is expensive , but you won't see the inside damage of the hose until it becomes outside damage
5L of brake fluid £20 ,i just bleed the lot through because brake fluid does not get better with age like wine 

[terry paget]

They're perhaps ass covering, but clamping the flexi and opening the bleed nipples is the 'correct' method regardless of car. Followed by a final clamp free bleed once finished each wheel

This actually results in much better pedal feel even if you don't change the fluid...

Interesting that this practice improves pedal feel. I suppose a little air can leak in on each brake actuation, which accumulates over time, making the brake spongy.

[Andy H]

They're perhaps ass covering, but clamping the flexi and opening the bleed nipples is the 'correct' method regardless of car. Followed by a final clamp free bleed once finished each wheel

This actually results in much better pedal feel even if you don't change the fluid...

Interesting that this practice improves pedal feel. I suppose a little air can leak in on each brake actuation, which accumulates over time, making the brake spongy.

brake fluid absorbs water and becomes slightly compressible as it ages. The old dirty looking fluid will give a spongy feel even without any air bubbles in the system.

[Nick W]

Am I the only person who is concerned about the possibility of damaging the flexible hoses by crushing them with a clamp

Opening the bleed nipples without crushing the hoses seems to work just fine

No, I find the idea of clamping hose much worse than any possibility of turning seals or worrying about fluid in calipers/opening bleed nipples. It's one less thing to do while doing a simple job.


And I do have the clamps, that I was given by a friend who had also never used them.

[Viral_Jim]

As their suggests ..... they're flexible and easily cope with being squashed. Obviously you don't try to crush the life out of them. 

Andy (and anyone else who does this regularly), can you do the same with braded hoses, or are they more susceptible to being squashed?

I must admit that this is a totally new one on me.

[Nick W]

Am I the only person who is concerned about the possibility of damaging the flexible hoses by crushing them with a clamp

Opening the bleed nipples without crushing the hoses seems to work just fine

As their suggests ..... they're flexible and easily cope with being squashed. Obviously you don't try to crush the life out of them. 

But clamping them so they can't pass fluid is just like tightly bending them over at 180 degrees, which is way past their flexibility.


Clamping a braided hose is something you should never do: those use a nylon pipe inside the external braid. The pipe won't return to round once it's been crushed(which is what the clamp is actually doing)


The procedure listed strikes me as a stack of possible what ifs rather than anything to actually worry about. So I do not, and will not be following it. That is my opinion based on over 30years of this sort of work, and is worth exactly what you paid for it.