Brake Question

[Northernpar]

Came out from work tonight jumped in car and started to drive out of car park. As I came to the end of a lane doing 10-15mph applied brakes and.........nothing!! And I mean nothing, pedal hard against the floor and the car still moving. Applied a few times and feel came back. This is the second time this has happended, the last being a couple of months or so ago, and it's pretty unnerving. These are the AP big brakes and although it had been raining through the day this shouldn't be happening. The pedal feels spongy and it doesn't take much to get the pedal against the stop. Brakes haven't been worked on so there should be no air in the system and its the braided hoses so shouldn't be any issues with 'bulging'. Which leads me to my questions:

1. 7.5k on the clock, no track days although some spirited road driving. From what I can make out Pagid RS14 pads as standard. What would be the expected lifespan of the pads/minimum recomended thickness?

2. Any other suggestions for symptoms if not due to pad wear?

3. If due to pad wear then what type pads are recommended (4 pot type)?

4. And finally best place to buy?

Thanks in advance
Graeme

[Rich H]

Bleed them anyway, sounds like air in the system somewhere....

[Mikie711]

Have you checked the brake fluid level and is it OK. Agree that you need to bleed the brakes and if still the same then probably the master cylinder is goosed. What car is it BTW as in does it have ABS.

[Northernpar]

Have you checked the brake fluid level and is it OK. Agree that you need to bleed the brakes and if still the same then probably the master cylinder is goosed. What car is it BTW as in does it have ABS.

Not checked the brake fluid level yet, plan to do that at the weekend with some daylight and probably do a quick system bleed.

Car is MY08 S PP so has servo-assist, ABS, AP Racing 308mm front discs and uprated pads front and rear. As you can see, with the system as listed this thing should be stopping on its nose. I've ruled out pad contamination/glazing at this stage due to the fact that I can bottom the pedal out so this can only mean an issue with the fluid or something more sinister with the system. Car is still under warranty so might just get MMC to come take it away and fix it and save any hassle, needs serviced as well so they could get that done at the same time.

[Mikie711]

Nothing that could happen to your pads would cause those kind of symptoms, other than boiling your brake fluid. But you would notice the drop in performance if you had a sticking/binding caliper. You need to check you have the correct amount of fluid before using the car again. It may be that you have a leak that only occurs during braking and have used up almost all your fluid, however I would expect your dash warning light to be on if that were the case. ABS complicates things somewhat as it could be a fault in the ABS unit as well as anything else that's been mentioned. For me it has to be one of two things assuming no fluid loss, master cylinder or ABS unit.

[robin]

The pedal should not go to the floor when cold. Even if the fluid is totally knackered, when cold it will still act like hydraulic fluid (once hot, the water content in the fluid boils and then you get vapour which can compress, but when cold you cannot compress water any better than hydraulic oil, so the pedal would be at least as solid as when you parked up).

Without doubt there is something very wrong with your brakes, so much so that I would say you should not even be driving the car on the road. Given that the car is in warranty and the brake pedal went to the floor I don't think you'll have any problem persuading the dealer to collect the car and work out what's wrong with it.

In a MY08 car the pedal should be rock solid - early (i.e. 55) servo'd Elises had a crappy pedal setup and the pedal was rubbish compared to pre-servo cars. Modern cars have a proper pedal once more.

If the pedal is always spongy I would say air in the brakes; however other causes of this can be binding brakes (the brake disk and pad heats while you're driving; when you park up the brake cools and contracts meaning you need to pump it back up before it works; also this cooks your fluid which will make the pedal worse all the time).

The fact that the pedal gets worse once parked up for a while feels like some sort of leak or seepage - so it could be a servo or master cylinder fault (not clear in my mind what that fault would be).

Like I say, don't drive it!

Cheers,
Robin

P.S. What kind of Elise is an S PP?

[Peter76]

P.S. What kind of Elise is an S PP?

An Exige kind!!

[robin]

So that's Exige Supercharged Performance Pack then?

I had another thought - if the braided hoses were not fitted by the dealer (or at least a dealer) you're going to struggle with the warranty if it turns out that the fault was caused by either a hose being damaged or badly fitted.

If they're badly fitted they can rub through and burst - though usually that's a catastrophic failure rather than spongy pedal!

Cheers,
Robin

[Northernpar]

So that's Exige Supercharged Performance Pack then?

I had another thought - if the braided hoses were not fitted by the dealer (or at least a dealer) you're going to struggle with the warranty if it turns out that the fault was caused by either a hose being damaged or badly fitted.

If they're badly fitted they can rub through and burst - though usually that's a catastrophic failure rather than spongy pedal!

Cheers,
Robin

It's all dealer fit so it's off back down to Edinburgh via Lotus Assist. Spoke with Keith over the phone and he seems to think it's probably an issue with the master cyclinder. I'll keep you posted once I find out what went wrong.

Cheers
Graeme

[Northernpar]

Update on the brake situation.

Car finally got transported to MMC on Saturday and managed to speak with Keith today. Turns out the brake fluid was brown/black so the system was flushed, replenished and they will be testing the brake efficiency on a rolling road. Whilst that will undoubdtedly cure the brake issue it doesn't explain why the fluid boiled/became contaminated. The car has done 7.5k miles since April 08, no trackdays and although there has been some spirited road driving this has been well within the capabilities of the car so the fluid should not have boiled. I think the brake usage can be demonstrated by the pad wear over this time with a good 10-11of original pad on the front. Keith suggested air in the system which I guess could have been left over from production or during the clam repair the brake system was broken into and not bled. Guess I'm going to have to keep a very close eye on it from now on.

Another issue was performance which seemed more sluggish than usual and also I had felt that fuel consumption had got worse even though driving style hadn't changed. Also noted that exhaust tip showing lots of carbon build up both on the standard/2Bular. On investigation they think that there is an issue with the fuel pump although I can't see how that would produce the above symptoms as there must also be a regulator in the system unless it's integral with the pump?

All being well I should get her back on Fri/Sat with a clean bill of health and fully serviced.

[robin]

Brake fluid goes black when it mixes with water - it is hygroscopic (meaning it absorbs moisture from the air), so you don't have to actively pour water in it, just exposing it to the air will get you there.

Trapped air in the system will result in a spongy pedal, but assuming it's a fixed quantity of air that was trapped once upon a time, it will not make the fluid black (the little moisture in that little bit of air will be absorbed, the air will be dry and that will be that).

The reservoir lid should have a seal on it, not air tight, but limits the flow of air (and thus moisture) to the reservoir.

I didn't realise the brake system had to be broken open to remove the front clam on an exige ... if that is the case, maybe they used contaminated fluid when refilling?

Make sure the pedal is rock solid before you take the car back - you can save yourself a wasted journey by asking the garage to confirm that the pedal is at least as hard as some of the cars that are currently in the show room - if it isn't they can keep it until they can get it so.

If there really is no explanation offered, and given the fact that the braking system has been apart to repair clams/replace brake hoses at some point, I would tend to accept the car back and keep an eye on it, like you suggest.

I cannot help you on the engine, but I would guess that if it's running rich, the ECU will know and should spill the beans when the code reader is hooked up. Be worth asking what that said when it was hooked up. Would also be worth getting an emissions test done somewhere ...

Cheers,
Robin