The front calipers are aluminium alloy so the issue is galvanic corrosion. 2012 TDV8 Vogue (L322)

anythin can be done to prevent? Its actually a sport

Not anymore, 4.4 TDV8 now

Ease the bleed nipples off every year and retighten and the apply a liberal coating of grease to each nipple as protection. Works for me.

ah okays, i did that so hopefully they dont snap.

one of mine was impressively blocked with road salt i had to drill through haha Its actually a sport

Not anymore, 4.4 TDV8 now

You can also buy alloy 'racing' bleed nipples which would avoid the galvanic corrosion. 2012 TDV8 Vogue (L322)

Can you clarify when you get your sinking pedal ?
Is only immediately after starting the engine ?
Or anytime after the engine is started ?

If you're holding the pedal down while the engine is starting or immediately after starting, you may not have a "real" problem - as when the engine starts the vacuum pump immediately starts building / restoring vacuum in the brake booster - adding assistance to the effort from your foot and causing the pedal to go down further. Once the vacuum is stable, there won't be further assistance so the pedal won't sink again.

If the sinking is minutes after the engine has started, but does stop after a while, it suggests you may have a vacuum leak that the vacuum pump is having to compensate for when the engine starts, but after a while the pump is "coping" with the leak.
If it is a vacuum leak, it could be the brake booster vacuum pipe connection grommet or Non Return Valve - which are also known to fail.

If the sinking is at any time after engine start up it's more likely to be a mastercylinder internal leak past the main pressure seals or maybe an internal leak within the ABS unit.

From what I've seen on this and other RR forums, internal mastercylinder leaks are not uncommon - especially on the older, higher mileage cars.

It's highly unlikely air is being sucked into the mastercylinder and causing a sinking pedal - despite what any "expert" tells you. There is no chance of air getting into the pressure generating side of the mastercylinder without the brake pipe nuts being loose. Paul,
2001 Discovery 2 TD5, 211,000 miles & climbing
2006 FFRR TDV8 Vogue 151,000 miles & now sold
Member of Midland (Land) Rover Owners Club, www.mroc.co.uk

Pawl, for me its every time when the engine is running.

I didn't notice it when I bought the car - and I only had a quick test drive up the road.

However last weekend, I was sat in it on the drive with the engine running. And I moved the car a foot or so and thought 'hmm the pedals a bit soft' so stopped and them pressed pedal bit harder, and that's when I noticed it started to sink to the floor.

With a lot of pressure (more than you would ever use when driving) it will sink from the top all the way to the floor in about 5 seconds. It then requires about 2 pumps on the pedal to get it to go back to normal (hard at the top, and not spongey feeling). But again, if you pump the pedal, and then hold pressure on it, it will sink again.

I don't think its a vacuum boost issue. I am going to whip off the master cylinder and strip it down to see if there is anything obvious wrong, however that will be next week now when I get chance.

Based on when it happens, I agree with you, it's very likely to be the mastercylinder.
Have you found a supplier for the internal seals to replace them or will you take it apart to "just" confirm the diagnosis and then replace the cylinder.
Paul Paul,
2001 Discovery 2 TD5, 211,000 miles & climbing
2006 FFRR TDV8 Vogue 151,000 miles & now sold
Member of Midland (Land) Rover Owners Club, www.mroc.co.uk

Tested mine today and can get the pedal to slowly sink to the floor with the engine running if I press hard enough.- way harder than I would press it even in an emergency. 2012 TDV8 Vogue (L322)

[quote="Pawl”] If you're holding the pedal down while the engine is starting or immediately after starting, you may not have a "real" problem - as when the engine starts the vacuum pump immediately starts building / restoring vacuum in the brake booster - adding assistance to the effort from your foot and causing the pedal to go down further. Once the vacuum is stable, there won't be further assistance so the pedal won't sink again. [/quote]

I think this is what I experience. On starting the engine, with a foot on the brake of course, the pedal will travel to the floor. With a couple of pumps (or if you simply move off) the the pressure seems to be in the system and it’s rock solid.

I’ll keep a careful eye on it but I’m happy there’s no issue with the MC as far as I can tell.

J

Pawl wrote:

Based on when it happens, I agree with you, it's very likely to be the mastercylinder.
Have you found a supplier for the internal seals to replace them or will you take it apart to "just" confirm the diagnosis and then replace the cylinder.
Paul

No I've not found a supplier so its mainly just to visually confirm. Might see if I get chance later today.

I have my brake fluid replaced every MOT, F1 Autocentres do a deal for £45 to replace your brake fluid at the same time as the MOT.

So if they break anything.......

For £45, I'll go with the peace of mind. Quite how they do I really don't care to be honest.

Andy Fuji White / Jet 2012 4.4 TDV8 Westminster

It's very likley that there is nothing wrong. Before you take it apart get under the dash to check for leakage out of the piston. If it's leaking here or somewhere else the brake fluid level will be dropping also so check this. If it's not leaking at the MC seals it's 'possible' the ABS is accumulating some fluid or needs purging. 2012 TDV8 Vogue (L322)

Hi All, Bit of an update!

I managed to remove the master cylinder today (at last!).

I stripped it down (the circlip had no holes in it as not designed to be removed - but 'grabbing' with some small side cutters managed to pinch it and pull it out. ) and couldn't see anything wrong. It looked brand new almost. I did take some photos of the insides (if anyone is interested). I will upload these when I get chance.

Anyways, as I couldn't see anything wrong, I gave it all a good clean with brake cleaner and put it all back together and refitted it to the car. I left the 2x brake pipes disconnected as I wanted to try and run some new fluid through it all to rinse out any leftover brake cleaner etc.

I then wanted to start the car to raise up the suspension to give me better access (note to self: do this before!) ... AGHHH it wouldn't start... no click or anything. The dash lit up for couple of seconds, something whirred / buzzed under the bonnet for about a second, then everything went off... I thought the battery at first, so out comes the charger... no difference. I also noticed that the lights etc didn't dim when trying to start so that also rules out (to an extent) the battery... so out comes multi meter… No 'crank' feed to starter motor. Swapped relays... nothing. Hmmm.... Long story short, they WONT crank if the system can't detect any brake pressure!!! Obviously there’s no pressure as the lines from the master cylinder are still undone! Thankfully the no start was just a false alarm. However, no start = never did get suspension raised!

I bled the fluid through the MC into a old rag the best I could. I reattached the 2x brake lines and then (thankfully) it fired right up. Pumped the pedal a couple of times and apart from a tiny bit of air which I had inevitably got in, it felt okish – but more importantly, no sinking pedal! I then raised the suspension to full height to make access for bleeding easier.

Plugged in the laptop and ran through the bleeding process in SDD. Now the brakes feel like they should. Firm, with no sinking at all. So, I’ve no idea what the issue was, or what I’ve done really… but it all seems fine (for now at least!).
Ian

Glad it's sorted and a nice cheap fix...  Pete
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2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Parchment over Navy Interior. Sold
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand, Jet Interior. Sold
2002 L322 Vogue 4.4 V8 Epson Green, Ivory over Aspen Interior (Fatty Offroader) Sold
-Click for Project Fatty off roader-