What Brake fluid does the 4.6 use?

[james8whippy]

Hey Guys,

I want to improve my brakes as my standard discs warped and faded big time when going round the ring last year so I've just bought some EBC Ultimax Slotted Discs, Yellowstuff pads and goodridge braided hoses.

I've also been told I should upgraded the brake fluid to Dot .1

Silly question but do I need to get Dot 4.1 or 5.1? Is there a difference too?

Thank you!
James

[IanP]

I understand DOT5.1 does not have the problems with corrosion that DOT5 had and is also compatible with DOT4. It is also supposed to have a higher boiling point than DOT4 so you might find it better on the track. Is it possible that part of your fading problem was slightly worn pads transmitting heat into the fluid?

[Greydog]

Most "normal" drivers would never need 4.1 let alone and wouldn't know the difference.

4.1 has a far higher boiling point than standard Fluid and 5.1 higher yet again one thing you must not do is mix them. Not with standard fluid or each other you will end up in a ditch for sure.
With a big heavy beast like the X and trying your luck around the Ring go for 5.1 to be sure you have the best chance of making it without cooking everything.
Been there and done that in an upgraded V70 and one of the E55's addictive isn't it.

[james8whippy]

Thats great thanks. I will go for the 5.1 then. You mentioned they can't be mixed? Do you know what they come with from BMW would it be DOT 4? So if that is the case I need to make sure I totally remove all the fluid when changing it. I read somewhere about a ABS reservoir that you can't remove all the fluid unless you plug it in via the OBDII port.

Do you know if this is true and is changing the fluid a PITA?

Ian it wouldn't surprise me if my worn pads were transmitting the heat into the fluid as they were pretty shot.  Sometimes even when going for a hoon about in the lanes I get brake fade. I am hoping once I've gone for uprated pads, discs, braided hoses & then the high boiling point fluid It should resolve this but I suppose I will see if not I don't know what else to try. Yes I agree Greydog! I love it there I know the X is no way in a million years a racing car but it's still good fun having a blast around there.

[IanP]

Regarding mixing the fluids, I have just been reading comments about using 5.1 in racing motorcycles, and the technical advice was  that 5.1 is compatible with DOT4. I would get in touch with manufacturer of the fluid and ask their advice.

[Greydog]

Hi James all the Volvo T5's I have owned I had ECU tuned to 300+ BHP the standard brakes just couldn't cope fortunately Volvo have a police spec Brake upgrade off the shelf which used 4.1 so that went with the ECU upgrades. The T5 I took round the ring showed 287 bhp at the wheels on a rolling road, insane on a front wheel drive car but great fun. The E55 had an ECU upgrade and Black Exhaust power delivery was brutal with out doubt the fastest dog mover I ever owned, 5.1 was the standard AMG fluid. Neither car cooked brakes at the ring mind you two reasons spring to mind (1) neither are any where near as heavy as an X (2) my sense of self preservation might just be kicking in before yours!!!
I have read that you need someone who has the right kit and knowledge to bleed the brakes or change fluid on the X others here probably know a lot more about that. Good luck with the Brake upgrade and if you go back to the Ring special luck and don't bend it.
By the way the German version of the AA will recover cars from the Track at the Ring the contractors used by the AA etc wont. When I was there with the E55 a Brit lad stuffed his Subaru he had to pay to get it recovered from the track before the recovery contractor would collect it. I gave him a lift back to the UK he rang me a couple of weeks later to tell me this in case I was going back!

[james8whippy]

Thanks for the feedback. Sounds like great fun Greydog can you remember what sort of times you were getting round there? Corr bet that E55 went like stink! bet it was juicy too especially around the Ring

Does anyone know what kit I need to buy for the fluid changes? Is it a automatic vacuum bleeder? Also does anyone know anything about this ABS reservoir that I've heard can be a pain to flush completely?

Thanks
James

[amacman]

The best kit for bleeding brakes is a helper to push the brake pedal the old fashioned way
Pressure bleeders can introduce tiny air bubbles
Vacuum bleeders do work but air can be drawn through the threads on the caliper bleed valve
The abs reservoir does not need any special attention unless you get air into the system

[Greydog]

Morning James
My timing slip for the Volvo (best brown trousers tucked into my socks) for the Nordschleife 12.37.53. It took 5 laps to get there and by then I had run out nerve (the talent jumped ship on the first try) To much power, massive oversteer and tyre smoke at almost every corner plus being passed twice by a guy in a Corsa!!
The E55 was a completely different experience, first it was an AMG organised day, second we all got some tuition (own personal Stig) for 3 laps just left it in auto and low 10's straight away (it does help when you have someone who knows where they are going). Last 2 laps using manual in the 9's best lap 9.44.20 and out dragged a Porker (no strange smell in the car either)
I don't think I would have the nerve to go at it in an X5 though, you are a hero young man ENJOY.

With regards to mixing 4.1 and 5.1 Fluids I talked to one of my son's (Chemical Engineer) He rolled his eyes and looked skywards then said " Dad if you mix them you straight away reduce performance to the lower rated fluid" Logical when you think about it.
Good luck with the Brake upgrade.

[Nat]

Hi,

A 4.6 ( or any X5 ) was not really designed for the track. If your disks and calipers are anything but perfect and or your pads are near the end of life you will warp the disks. If you have ever changed the disks you will note that they are huge. Personally I think the calipers have the clamping force required, its the pads that are the weak point. I would use ferodo DS2500 pads.  Braided hoses will give you a firmer pedal, especially now the car is more than a few years old. I am not a fan of ECB pads myself. The big issue is heat. Thise big disks are easy to warp with 2 tonnes being stood on its nose all the time. One thing that helps is when you come to a complete stop, dont sit with your foot on the brake , use the handbrake. Otherwise you super heat just a pad sized area on your disks ( creating a heat spot ) and that encourages warping. Obv if you can just keep rolling and have a slow down lap thats even better. Ive changed a few pads on X5's in my time, they dont age well and if you have a slightly sticky caliper or one with lots of crud on it , ( they seem to store crud on them )this will make the issue worse. Just make sure its all 100 % .  Given all the posts about gear boxes id make sure both the gearbox and transfer box have some nice clean fluid. Also use plenty of engine breaking.

Regards,

Nat.

[james8whippy]

Ok thanks Amacman I'll get an extra pair of feet round to help pump the pedal if that’s the best method.

Greydog - That’s some nice times you got there! That's excellent you had your own personal Stig that must of made all the difference. Cheers I wouldn't say I was a hero at all maybe foolish as X5's aren't meant for the track!
The hardest thing I found though was learning the track, It's soooo long its impossible to learn after a few laps and a few of the common nasty corners caught me out first time round. Hope to get out there twice this year if I can. My personal best was 9m30s but since I now have the LPG conversion I think I will struggle to get near that now with all the extra weight. Still I hope my brakes won't fade this time!

What your son say's makes perfect sense so I really need to make sure I drain it completely!

Nat - I agree the discs are huge I believe the fronts are 14". My friend runs Ferodo pads in his Evo VII and highly recommends them too. I will give the EBC discs and pads a go and if they are pants I will upgrade them at a later stage. Thanks for the tips! I was told about not holding the brakes on once stopped and Someone once told me after leaving the ring to carry on driving normally without using the brakes to allow the air to cool down the disc. Didn't work on my car but then again the discs were glowing red so maybe the damage was already done  ) Great I look forward to the sticky callipers then as mine no doubt have loads of crud in there  ::) Funnily enough I had the lock up clutch replaced in the torque convertor 10k miles ago @70k so luckily the fluid was changed then. I drive the car in manual most of the time anyway as I prefer the engine braking.

Appreciate the help and tips guys.

Best
James

[Raj]

4.1 is fine tbh for the odd Ring trip and majority normal driving. I'd only really run 5.1 for a dedicated track toy but its person opinion. Definitely just use proper discs and pads and the brakes will be fine again for their use o odd track day. Even BBKs will start to fade somewhere like the Ring when used on an X5 weighing some 2.3 tonnes LOL.

When coming off a lap at the Ring, just put it in park and remove your foot from the brake as has been suggested just to allow them to cool. Certainly don't keep your foot on the brake for too long.

[Greydog]

Hell's teeth 9.30 in an X5 no wonder you ran out of brakes!!!

AMG had a Nav disc just for the Ring several of the other owners brought copies, from my perspective that disc would useless for anything other than talking about in the Pub. Knowing what the corner looks like on a map at the ring doesn't show the evil adverse camber and change of surface.

You have my respect don't break it.

[james8whippy]

Thank you sir!