406oc.co.uk

Ive been reading lately that on some cars you should open the bleed nipple when retracting the caliper piston to avoid damage to the ABS unit is this necessary is it it advised that i do this

It's not essential, but if you are worried about it, do it.

To be honest ive never been bothered before but wasnt sure as some people say that it can damage the ABS unit just wondered if this is true or just people being over cautious

You'll be fine on the 406.

If you had a Vauxhall or a Golf TDi I would maybe be a little more careful, but most cars I just push back the pistons without undoing the bleed screw....unless the pistons are a little tight.

Electronic handbrake and other braking systems controlled by the ECU are a different story

I would do it just in case.

You'll be replacing the brake fluid when changing pads anyway, so there's no reason to push it back into the system, only to push it back out again.

I don't think he was replacing the brake fluid...it isn't essential to replace the fluid if you are changing brake pads.

It's perfectly fine to push the pistons back on the 406 without undoing the bleed screw!

I never heard of doing it before until I went to change the brakes on my Mondeo just before Christmas. I could not get the rear calipers to wind in smoothly. I was having to put my serious force on them to wind them in. I consulted the haynes manual who said it will not retract without pinching the brake hose and opening the bleed nipple, it also warned that damage could be done to the ABS module if you were to force the fluid back. Pinched the hose and opened the nipple and it went back like a piece of cake

Bailes1992 wrote: I could not get the rear calipers to wind in smoothly.

If you read my previous post I said ....

"If you had a Vauxhall or a Golf TDi I would maybe be a little more careful, but most cars I just push back the pistons without undoing the bleed screw....UNLESS THE PISTONS ARE A LITTLE TIGHT"

I've pushed hundreds of caliper pistons back without undoing the bleed screw over the last 43 years and only had one single problem.....which was with a Vauxhall Astra back in 1992 when they brought out a new model that had weak brake master cylinders...the rubbers in the cylinders would fold back as you pushed the driver's side piston back causing loss of pressure in the master cylinder.

If anyone is any doubt then use a brake hose clamp on the rubber hose and undo the bleed screw before pushing the pistons back.....the down sides to doing this are....

1) You could possibly break off the bleed screw if it gets rusted in.

2) You need to bleed the brake afterwards.

I agree that if you were thinking of replacing the brake fluid then you might as well do it now....BUT...a novice may let too much fluid out and cause problems with the ABS or by not being able to bleed the system properly.

You pay your money and take your choice

I worked at a vauxhall main dealers in the early nineties and I remember the same scenario with the astra master cylinders...........changed loads!! I personally wouldnt bother undoing bleed nipples when pushing pistons back in callipers as its highly unlikely that it will damage the abs unit or master cylinder.

jasper5 wrote:I don't think he was replacing the brake fluid...it isn't essential to replace the fluid if you are changing brake pads.

No, but it's a damn good idea. Brake pads usually last 3-5 years depending on driving style, and the normal recommendation is to replace the brake fluid every 2-3 years.

If you've done any panic braking, you may have heated the brake fluid beyond its boiling temperature, which will severely impede the performance of your brakes. In addition to this, brake fluid is hygroscopic and it readily absorbs moisture from the air, again impeding the performance of your brakes, mostly by lowering its boiling point.

Brake fluid is inexpensive, even the cheapest DOT4 is good enough for everything but track-driven cars. Never ever skimp on brakes.

I never skimp on brakes and have not and would not advise anyone to do so. I know all about the properties of brake fluid and the renewal intervals. I also possess a tool for measuring the water content of brake fluid so can easily check the state of the fluid.
As you have yourself agreed, it isn't essential to replace the brake fluid when you change the brake pads.

Obviously if the replacement interval of the brake fluid is close to the pad renewal then that would be a good time to replace the brake fluid.

I have to agree with jasper5 & crackpoterpig, in my 28 years of working on cars, truck & motorbikes I have never had to undo a bleed nipple to push the piston back unless there has been an underlying problem .
On quite a lot of modern cars you have to use a windback tool to push the piston back, but this is nornmaly on the rears only & you can tell because there will be a locating lump on the back of the pads & four cut out's in the piston for the locating lump to go in.
I have in the past had to let out / drain out brake fluid because the master cylinder / reservoir has been topped up before new pads / shoes have been fitted .
Like jasper said changing your fluid is a good idea, but the question was do I need to undo a bleed nipple to push my pistons back ? .
Well the answer is no, unless there is an underlying problem