Lubricating Brake Pistons

[grubby mits]

I have a really annoying and loud creak from my front O/S brake caliper (2008 V70). The caliper has been apart twice and all the usual parts lubricated with brake grease but the noise persists. I now think the source is the piston itself and I have read that injecting a specialist fluid (Kluber) behind the dust boot may cure the problem. Does anyone have any experience of this remedy? I can't find the Kluber fluid suggested but would have thought that silicone spray would have been just as effective?

GM

[Tannaton]

I would be surprised if it was the pistons - they hardly move at all when applying braking force, but if it does turn out to be the pistons then its likely water has got under the seal and there is corrosion between the piston and the bore - in which case the callipers should stripped, cleaned and reassembled (or replaced).

Apologies if you've been through it all already but are you sure it's not suspension bushes? Also what discs/pads have you fitted - some pattern parts like Apec are more prone to squealing and creaking.

Does the caliper creak when you apply the brakes when the car is stationary?

[grubby mits]

Thanks for reply Tannaton.

This is the link to a description of the issue and the suggested remedy https://www.brakeandfrontend.com/bra...speed-braking/

My symptoms are the same/very similar. I can feel the vibration caused by the creaking noise by holding my hand against the caliper whilst an assistant presses on the brake pedal and therefore yes, this occurs with the car stationary. I'm 101% sure it is nothing to do with the suspension/steering.

At my MOT/service last week I asked the tester to look for the cause - he couldn't find it (and passed the car without any advisories). Pagid discs and pads were fitted a couple of years ago.

I am also sceptical about the piston being the cause and as you say, it implies wear/corrosion/defects in the piston - but as yet no evidence of any fluid seepage. Squirting a blast of silicone spray behind the dust boot can't do any harm I suppose - at the worst I am in for an exchange caliper anyway.

GM

[Ian21401]

Check for free movement of the caliper pistons by removing the brake pads and replacing them with a piece of plywood or similar which is thinner than the pads but still thick enough to prevent the pistons popping out completely. Press the pistons back into the caliper (crack the bleed nipple open to allow some fluid to escape whilst you push them back. This lessens the chances of damaging seals in the master cylinder ) Then close the bleed nipple and have assistant press brake pedal whilst you observe/feel. Whilst pistons are in the pushed out position spray some silicone lubricant in behind the dust seal. You may have to do this more than once to achieve a desirable result.

[Tannaton]

Sounds like your testing and diagnosis is well advanced...

Personally I would remove the calliper and strip it down to examine the piston and bore, if I was a betting man I would say water has got in there and now you have some corrosion - in that case squirting in some lubricant may only be a temporary relief of symptoms.

The callipers are quite simple and not difficult to strip. If you do confirm a problem with it you can re-assemble it with the original seals etc. and still use it whilst you source replacement parts.

[Ian21401]

My suggestion as at post #4 avoids the need to remove the caliper and hence bleed the brake system afterwards. If it achieves the desired result that’s good. If it doesn’t work or works for a while then the problem returns then move on to further strip down or caliper replacement.
I serviced the brakes on my car shortly after I first acquired it in 2005. It has single piston front calipers. . I found that the rubber dust seal on one of the calipers was badly split but I did not have time to deal with it properly so resorted to the silicone lubricant spray to hopefully prevent any corrosion developing. This proved to be adequate until I later dealt with it properly by replacing the dust seal. That job was not as straight forward as I had found on my previous cars. On my previous Marina the edges of the seal were located over a lip on the caliper and within a groove on the exposed end of the piston which meant that it was simple to flip off the old seal and fit the new one. On the Volvo the seal is fitted slightly differently.
The outer edge of the seal fits into a groove in the wall of the bore so it is necessary to remove the piston to remove the old one and fit the new one then manoeuvre the piston back in through the seal and locate the inner edge of the seal onto the piston. This proved to be rather difficult but was eventually achieved. Then reassemble and bleed brakes as normal.

[Montana]

Like Ian says, I also have successfully used silicon spray to remedy sticking pistons in the past like mentioned.

[Ian21401]

I’ve deleted my section regarding the fitting of the new seal as it incorrect and added corrected version.

[Tannaton]

A bit of spray might alleviate the symptoms, but I would personally want to understand the root cause and be sure that the pistons are acting evenly to avoid uneven brake wear and disc corrosion.

[grubby mits]

Thanks to all for your helpful input. I have another car in the workshop at the moment but will get to the V70s caliper again shortly. What I end up doing will depend largely on what I find - I will post the outcome in due course.

GM