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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.

[Sir Tigger KC]

I've never clamped the hoses when changing brake pads either, but seeing the advice in Haynes when I changed the Mondeos rear pads last year I thought I'd give it a go.   

What a faff! I ended up juggling the caliper and the wind in tool. The tube kept falling off the nipple and I manged to knock over the jar that the brake fluid was going into!   

I'm sure it's easy when you know how! 

[henryd]

I always release breed nipple when doing Vauxhall pads,had a set of seals turn on an Astra years ago and been wary ever since

[TheBoy]

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.

On the bike (never had a car with braided hoses), I actually dismantled the calipers to get all the crap fluid out.  But that had no ABS, so letting it all drain completely didn't result in a huge faff.

[Viral_Jim]

TBH I'll probably end up just going the middle route and opening the nipples without clamping the hoses and take my chances. 

Next stupid brake related question (thought about it while wrestling the Volvo calipers the other week). What can you use to stop the nipples seizing in the calipers? Luckily a couple of doses of penetrating fluid and a proper spanner freed off the Volvo ones but it did make me think...

Copper slip maybe? 

[Andy H]

All the standard black rubber brake hoses that I have seen cut open had fabric braid in their construction  (covered over with an outer rubber sheath )

The only time the braid was obvious (without cutting it open) was when I bought Aeroquip hoses with the stainless steel braid  on the outside.

[Doctor Gollum]

Regular servicing... ie changing the fluid as per manufacturer specs rather than when a hose bursts

[Viral_Jim]

Regular servicing... ie changing the fluid as per manufacturer specs rather than when a hose bursts

What a novel idea *makes a note*   

[terry paget]

Regular servicing... ie changing the fluid as per manufacturer specs rather than when a hose bursts

It was while changing the fluid I discovered that the pads were worn out, probably original and been there 10 years and 110,000 miles. I ordered new pads front and back, should be here Tuesday. The brake hoses look like simple rubber, not braided, but I think I will  skip the clamping and just open the bleed nipples while pressing back the pistons, then bleed. Thanks to all for advice.

[Marks DTM Calib]

I should add, I don't clamp the flexi in this case, the back pressure is huge compared to that of the open bleed nipple, so its not essential.

Also it wont damage them if you are sensible, you can get special tools for this (which have been around for decades so far from a new concept)