Help with brake issue

[bhm1712]

Hi All,

As an experienced engineer and hobbyist mechanic ( been doing classic American cars up for years) I am struggling with an issue with my Vauxhall Astra's brakes. The problem is brake squeal from the front disc brakes. When it started to get worse, i stripped them down and replaced the discs as they were borderline on minimum thickness. At the same time i lubricated various moving components on the calliper with copper slip grease, and put new chamfered pads on. This usually gets rid of squeal, but this time it has not! any ideas? They only squeal under light application of the brakes when travelling below 30 mph. Of course, i cleaned up everything at the same time with decent brake cleaner and wire brush. Cant think of anything else. Brake fluid is only 8 months old.

Its definitely not the rear drums.

 

[Burnerman]

Here's teaching granny to suck eggs
You've done everything possible to prevent squeal - presumably the caliper pins were free to slide.....try pressing the brake pedal really hard - do the brakes fully release?
How easy was it to push back the caliper pistons? Could they be sticking a bit due to swollen seals within, or maybe the front flexy pipes collapsing internally a little?
Presumably you have used standard quality components, and not uprated stuff like Green Pad materials which seem to have a mind of their own?
At this point I could have suggested glazed front discs, but you've replaced them. I do think the pads aren't retracting fully though.
John

 

[bhm1712]

Calliper pins were not bad but they received a dose of cleaning and copper slip.

Standard quality OEM parts used. The calliper pistons were free to move.

The only thing i have not checked is the flexi pipes. The brakes do seem to fully release, and if not i would have expected to hear squeaks under no braking and going round corners. I will double check this as its now annoying!

 

[libby lou lou]

Dust or lack of anti squeal pads in my days on the astra mk2.

 

[bhm1712]

No dust...they are brand spanking and clean as hell. Brake cleaner has been used generously at times! The pads are genuine GM pads for the astra. I have never purchased pads marketed as anti squeal, as i always buy OEM.

The sqeual was apparent on the old pads and discs and the new ones.

 

[Burnerman]

So, if the fault was there before and after, it indicates that the problem lies elsewhere in an area thats been untouched for now.....
I'd have to say go for the flexi's - I've replaced loads due to internal collapse (but this particular fault hasn't been one of them). Usually the system is difficult to bleed if they are below par.
John