Brakes gone soft, need new master cylinder?

[phil_bennett]

I've been mulling over how to handle this situation for a while now. Was due to attend the Yorkshire Supercar & Superhero day back in September and after getting car out for a polish realised the brake pedal had gone soft with no travel. I checked the fluid levels which were low, so it needs brake fluid flush and bleed. Can't see any obvious leaks around the master cylinder or dripping on the garage floor. So looking at the master cylinder I wonder if the seal is a bit perished and the fluid has just leaked out.

I'll attach some pictures, but just after some thoughts really. I'm not competent enough to rebuild or replace. The plan would be to get a new master cylinder from Scott, find suitable garage that would do the work, then get RAC out to then transport this to the garage.

Does this look like a master cylinder which has been leaked on and needs replacing?

 

[Roscobbc]

Have you been around to the individual calipers and followed brake lines and check for leaks? - presumably power brakes? Master cylinder external corrosion is perhaps indicative of storing car in a damp location?. Logic says that perhaps you should consider overhaul of calipers too......perhaps?

 

[Mad4slalom]

I've been mulling over how to handle this situation for a while now. Was due to attend the Yorkshire Supercar & Superhero day back in September and after getting car out for a polish realised the brake pedal had gone soft with no travel. I checked the fluid levels which were low, so it needs brake fluid flush and bleed. Can't see any obvious leaks around the master cylinder or dripping on the garage floor. So looking at the master cylinder I wonder if the seal is a bit perished and the fluid has just leaked out.

I'll attach some pictures, but just after some thoughts really. I'm not competent enough to rebuild or replace. The plan would be to get a new master cylinder from Scott, find suitable garage that would do the work, then get RAC out to then transport this to the garage.

Does this look like a master cylinder which has been leaked on and needs replacing?

Touch wood , I havent had to touch my brakes yet but I have read a couple of times that after lack of use the vette pedal can go soft but can also return with use or with a quick bleed and is then fine again? If there are no signs of leaks it may just be that. Good luck

 

[phil_bennett]

Yep, power brakes, got a brake booster assembly. The cars kept in a garage, so shouldn't be too damp in there. Only time its ever outside overnight is on trips to Isle of Man, Le Mans or Spa, rest of the time its in the garage. I've not had a look at the calipers, will have to wait for dry weather and take a look on the drive. Not got space to do anything the garage, have to get window down to climb out!!

 

[Roscobbc]

Yep, power brakes, got a brake booster assembly. The cars kept in a garage, so shouldn't be too damp in there. Only time its ever outside overnight is on trips to Isle of Man, Le Mans or Spa, rest of the time its in the garage. I've not had a look at the calipers, will have to wait for dry weather and take a look on the drive. Not got space to do anything the garage, have to get window down to climb out!!

Have you used coloured brake fluid?(or is it contamination from internal brake corrosion) - its the front compartment that has run-out of fluid? - Food for thought.......see the condition of the master cylinder exterior?........the car has been (or currently) being kept in a damp enviroment (hence the corrosion) all four brake calipers are made from the same material and if water or moisture is present will also rust to a far lesser degree internally, but present a rough surface for the piston seal to rub over (causing one or more seals to eventually fail).
Old brake fluid is usually the culprit here (being hygroscopic) and its ability to absorb water from condensation. In addition to the internal corrosion to parts of the braking system the moisture content lowers the boiling point of the brake fluid causing the trapped moisure to boil and create brake fade. Some will say use silicon brake fluid - which is not hygroscopic.......however any moisture present in the brake fluid will form small globules.......under heavy braking conditions will potentially boil and 'gas-off' again reducing brake efficiency. If the vehicle is being stored in less than ideal conditions the brake fluid should be ideally changed annually.

 

[phil_bennett]

In all my years of owning the car (17 now) I don't remember ever touching the brakes. I'll have to go through the receipts from Scott as the car has been with him for some major work over the years (engine rebuild, new gearbox, post Le Mans Classic breakdown '08, body mounts etc) but I don't recall anything about calipers. The cars stored in a garage so I wouldn't have thought this was considered a damp environment. I can't say whether this is an original master cylinder or what condition it was in when I bought it, so it could be that its always been a bit corroded and has just got worse. The brakes have always just worked, I'm not one for heavy braking in the Vette as they're not like modern ABS so I'm naturally cautious, especially when dropping into Mulsanne Corner with a Ferrari on my outside. I get this MOT'd at Nick Rydens and they do the engine oil and filter at the same time, I'll start getting the brake fluid done at the same time just for peace of mind.

 

[phil_bennett]

Bit of progress made on this issue. I've spoken to Scott and will be checking to see if I can identify whether the fluid leak is from the back of the master cylinder, or from the calipers. As mentioned, it's the front reservoir which is noticeably lower so the front calipers are the obvious candidate, but will have a look and check. Just need the rain and wind to stop as all this is done outside on the drive, how I'd wish for a nice double garage!! In the mean time I've also booked this in to the local garage down the road for next Thursday to get the brake fluid replaced. They MOT and service our daily drivers and are happy to have a crack at this, they've just asked I give the bleed screws a dose of WD40 over the next few days to try and loosen them up.

At least if the master cylinder is full and the system bled it might help identify the source of whatever the issue is. And if it needs a replacement master cylinder, plus anything else, I'll get it shipped over to Norfolk for some TLC. Now I just need to decide whether I drive it the 1 mile to the garage, or get the RAC to transport it......

 

[Emc]

If the MC has slowly emptied then there is a leak I have found that its normally a caliper with a slow leak and the fluid leaking out can get into the pads and even burns off on the rotor, we always replace the old lip seals ,which are useless anyway, with O ring conversions, once done, you can forget leaking calipers.

 

[Roscobbc]

If the MC has slowly emptied then there is a leak I have found that its normally a caliper with a slow leak and the fluid leaking out can get into the pads and even burns off on the rotor, we always replace the old lip seals ,which are useless anyway, with O ring conversions, once done, you can forget leaking calipers.

Gavin is 100% correct - did mine with 'O' ring seals and very carefully and thoroughly cleaned out the calipers removing any 'high' spots and corrosion with fine wet 'n' dry. Did this once about 15 years ago and its been fine ever since. Do it 'right' first time and you hopefully won't need to do it again!

 

[phil_bennett]

Thanks for the replies. I'll get the car out tomorrow and check out the calipers and MC to try and identify a possible leak. Its good to know about the O ring conversion, something I'll definitely get done if needed. With any luck the local garage will make the car driveable so I can carry on checking for leaks after local trips. At the moment there's such little travel on the brakes, but at least I only have 1 mile to go next Thursday. Then if needed get it booked in with Scott for an overhaul. I need to make sure its all ready for Le Mans and potentially a trip to Spa in April.

 

[Roscobbc]

Thanks for the replies. I'll get the car out tomorrow and check out the calipers and MC to try and identify a possible leak. Its good to know about the O ring conversion, something I'll definitely get done if needed. With any luck the local garage will make the car driveable so I can carry on checking for leaks after local trips. At the moment there's such little travel on the brakes, but at least I only have 1 mile to go next Thursday. Then if needed get it booked in with Scott for an overhaul. I need to make sure its all ready for Le Mans and potentially a trip to Spa in April.

Just remember Phil its a waste of time doing the job if you don't prepare the caliper cylinders properly and make sure they are perfectly clean, smooth and unmarked.

 

[phild]

It may also be worthwhile changing the flexi hoses while the other items are being attended to. I was getting 'spongy' brakes on my daily driver last year and a fluid and flexi hose change gave back a nice solid pedal.

 

[Emc]

It may also be worthwhile changing the flexi hoses while the other items are being attended to. I was getting 'spongy' brakes on my daily driver last year and a fluid and flexi hose change gave back a nice solid pedal.

I have just got 50 sets of O ring caliper conversion kits in @ £60 each they are the best way to go, give me a call if you need any advice. I rebuild all my cars calipers weather they are leaking or not.

 

[phil_bennett]

I've had each wheel off and been spraying the bleed screws with WD40 at request of garage which is doing fluid change on Thursday. No obvious signs of leakage that I could see. Lots of bits I think might need replacing after the 18 years I've owned the car.

I also took off master cylinder after chatting to Scott. There was a hint of a drip, which could be coming from the MC. Attached some more pics.