S60 Brakes: soft pedal, weak brakes. No one able to diagnose.

[suchy101]

Hello,

First and foremost - I am a complete idiot when it comes to car mechanics. Zero experience, zero knowledge, zero skill. With that out the way - please help !

I have a 2005 2.0T petrol S60 with brakes issues. I think it happened quite suddenly but it is hard to say as the car was used very infrequently, sometimes sitting on the driveway for weeks.

One day I noticed the brake pedal is very soft, the usual stiff point is not there anymore, and keeps going down really, really deep. The braking power was very small, but still there to some degree, able to stop the car, but I would not want to end up in emergency braking situation. Pumping the pedal kind of worked (made it stiffer) but then when I held the pressure on the pedal, it would start sinking anyway.

Took it to local independent who replaced one of the callipers some time ago on it. They said they cannot find anything wrong with the car but they bled the brakes and said there was air in the system. After bleeding, the brakes worked perfectly.

Within days, the problem slowly returned. At this point I did some google searches and found someone suggesting it could be faulty caliper that is leaking, but in those cars a leaking caliper instead of actually leaking fluid - sucks air in. I mentioned this to the shop but they said they cannot confirm.

The car needed a service anyway (overdue by 2 years) so took it to a different shop that I had good experience with and asked them to look into it. They tested the brake fluid and said it was fine. Sadly it turned out they were not equipped to perform investigations at the level it required but said they "think" they found a lead "somewhere between servo and master cylinder", but are unable to either confirm or fix.

Then I took it to a Volvo dealer, with a very friendly Service Manager where I received over-and-above service every time I used them over the years (and different volvos). The car spent 4 weeks there, and came back with a list of issues they identified, most to do with suspension, however there was no 100% diagnosis on the brakes. They said they cannot find anything visibly wrong with any component (no leaks) and they have to rely on their expertise and experience and said it most likely will be the master cylinder, adding that if it is not, then the only other possible cause would be Brake Control Module (ABS/DTSC) Hydraulic Unit which is £1,500 for the part alone...

Took the car back to have a good think what to do with it next. After a few weeks wife without consultation with me found another supposedly "good" local independent to see just how cheaply can the work be done, in case it will not solve the issue so we would not burn a ton of cash for nothing. She was quoted less than 1/3 of the price to get everything listed done and she took it there.

That place, once again said they have no idea what the problem is. They do deal with lots of Sweds, plenty Saabs and seem to know their stuff. They said they put the MOT brake tester on in and "it passed". The pedal despite being soft and sinking, would not sink further after its final point, overnight. They also tested the calipers and said no lazy calipers found. Based on "their experience" they started quoting maybe brake servo, maybe master cylinder, maybe ABS control module ... but would not commit to any work and wanted me to take the car back.

Any help would be greatly appreciated. Thank you in advance.

P.S. I am from UK, Staffordshire. is there any recommended place I could take the car to for yet another look ?

[stuart bowes]

total shot to nothing but an unrelated problem I had with mine was the brake pedal travel sensor failed which stopped my cruise control working

when I took it out i left a gaping hole in the servo and of course you lose all pressure (I heard a rush of air on removing it) I think I was supposed to pump my brake pedal first.. oh well

yours will look a bit different but it's this bit, easily located



so that makes me think.. amongst various other possibilities this does sound a bit like a slow leak on the vacuum in the servo

is it possible the seal (rubber O ring) on that sensor is failing?

may be a total red herring but wouldn't be very hard or expensive to try

https://www.matthewsvolvosite.com/fo...ic.php?t=59173

getting it out can be a bit of a sod, you need to pry off a C shaped metal ring from the outside and not drop it into the engine bay. refitting required warming up the new O ring in a cup of boiling water to get it to squeeze in (reassuringly tight) then holding the sensor in tight while popping the clip back on

maybe you could get someone to pump the brakes while you listen for any hissing noises but with the engine running in the other ear it might not be obvious

--

others may be along with better suggestions, good luck

[stuart bowes]

sorry edited there Im getting my master cylinders and servos mixed up duh

while testing / listening for hissing you could try pushing the sensor in a bit tighter and see if that changes anything

might be nothing to do with it of course like I say

[barrybritcher]

I would start with a good manual bleed about 200ml at each wheel is good.
But sounds like failed seals to me

[suchy101]

Which seals would that be please ?

Does replacing the Brake Master Cylinder sound like a good place to start ? Or is it a case of "it could be anything ..." ?

The biggest issue is so far no one can tell me which bit has failed.

[Brianhill]

I have found
Squire automotive in Burntwood a very helpful and knowledgeable Volvo specialist 01543 672247

[Willber]

I'd check and tighten or replace (with hose clips) any clips on the large vacuum hose that comes from the brake servo.

It runs right to the front of the engine and forms part of the vacuum system.

Replacing the rear discs and pads on my car increased power also quite significantly. I'd already replaced the front discs and pads to eliminate some judder, but doing the rears made bigger improvement to brake power.

[richmac]

Hi,

I can't be 100% sure remotely but the symtoms you decribe are pretty much text book master cylinder internal seal(s) failure:

No warnings
No leaks
Long brake pedal
Brake pedal sinks under constant pressure after being pumped to harden.

You can have the seals replaced or the whole master cylinder. Both are simple procedures for a competent mechanic, particularly replacement, and about an hours work, most of which is spent bleeding the system afterwards. It's worth trying to save your Volvo/ATE master cylinder if possible as they're very good units.

Best of luck with it,

Rich.

[XC90Mk1]

Your issue is that if the garage starts to replace items part by part it could cost a fortune.

I would re-bleed the brakes and if the brakes then work well you can rule out mechanical failure. At this point it is now quite simply a leak. Air in the system is what would cause those symptoms.

You will need to start at the master cylinder in the engine bay and manually check every pipe and connection for leaks.

It sounds to me as though this is not ‘one for the experts’, the Volvo dealership you took it to should never have required more than 4 hours.

I would suggest taking it to a proper old school mechanic, explaining the problem to them and using their ramp to manually chase each and every brake line and joint through.

Of course, if you replace the fluid and it makes no difference then you can jumk all of the above and it may well be mechanical.

[ASt85]

Originally Posted by suchy101

Which seals would that be please ?

Does replacing the Brake Master Cylinder sound like a good place to start ? Or is it a case of "it could be anything ..." ?

The biggest issue is so far no one can tell me which bit has failed.

Take barrybritcher's recommendation into serious consideration - he knows what he's talking about

If the car has sat for some weeks unused, it could just be down to either moisture in the brake fluid or heavily rusted discs - try the "Italian tune up" method, repeated acceleration followed heavy breaking to clear the crud of the discs and the pad faces.