Question about changing brake fluid

[mjgreen81]

Hi all,

I'm new here . I tried searching for this but couldn't find an answer.

I just bought a Leon and want to change the brake fluid. I have a pressure bleeder and have done it on my other cars several times in the past.

I have just been looking for instructions for the Leon to make sure there is nothing unusual and I keep coming across mentions about this not really being a DIY job as the car needs to be plugged in to a diagnostic machine and something to do with the ABS needs to be enabled during the process.

However, on the other hand I have seen YouTube videos of people doing the brake flush on VWs and Audi's (which presumably are the same) and they are doing it themselves without plugging it in. I have also done it myself on other cars with ABS and have never seen this extra step mentioned.

Any advice/opinions on this please? Is it a DIY job?

I did ask this question on the Leon mk3 Facebook group and someone posted up the instructions from the SEAT workshop maintenance guide and although they use a fancy filling/bleeding machine I see no mention of a requirement to plug the car into a diagnostic machine and activate the ABS.

This suggests to me that even if I took it to a garage, they wouldn't do this step anyway.

Thank you in advance

 

[RUM4MO]

I know that to do this job properly and replace as much of the old brake fluid as possible, you should run the ABS pump etc as there will always be some old and so "wet" fluid still in the ABS block, but so far, I've never bothered doing that as the volume of fluid held within the ABS block, at a a guess, will only be 5% of the total system fluid volume, and from my way of thinking, as long as I replace the fluid with newly bought sealed tins of fluid every other year, then the moisture level in the system fluid will always be low enough.

Where/when you can't really avoid running the ABS pump etc, is when you have lost all the fluid due to another failure, or you didn't quite keep an eye on the fluid level.

I've found that Gunson's Ezibleed kits are okay as long as you replace them every few years due to the seals hardening etc, I have a new kit for this year's fluid changes!

Edit:- oh, sorry, and welcome to this forum, not much shouting and falling out happens here!

 

[mjgreen81]

I know that to do this job properly and replace as much of the old brake fluid as possible, you should run the ABS pump etc as there will always be some old and so "wet" fluid still in the ABS block, but so far, I've never bothered doing that as the volume of fluid held within the ABS block, at a a guess, will only be 5% of the total system fluid volume, and from my way of thinking, as long as I replace the fluid with newly bought sealed tins of fluid every other year, then the moisture level in the system fluid will always be low enough.

Where/when you can't really avoid running the ABS pump etc, is when you have lost all the fluid due to another failure, or you didn't quite keep an eye on the fluid level.

I've found that Gunson's Ezibleed kits are okay as long as you replace them every few years due to the seals hardening etc, I have a new kit for this year's fluid changes!

Edit:- oh, sorry, and welcome to this forum, not much shouting and falling out happens here!

Thank you so much, this is exactly the answer I wanted to hear. As mentioned previously, looking at the workshop manual I believe that if I took it to a garage they wouldnt bother running the ABS pump so I may as well do it myself as I have the equipment.

If you are investing in new equipment this year, I can't recommend the Sealey VS820 pressure bleeder enough. It's a brilliant bit of kit (although I am yet to check that the standard cap fits on the reservoir in the Leon, but I expect it will).

Out of interest, what brake fluid do you use and how much do you use?

Do you have a manual? If yes, do you bleed the clutch as well?

...and thanks for the welcome

 

[SuperV8]

Hi all,

I'm new here . I tried searching for this but couldn't find an answer.

I just bought a Leon and want to change the brake fluid. I have a pressure bleeder and have done it on my other cars several times in the past.

I have just been looking for instructions for the Leon to make sure there is nothing unusual and I keep coming across mentions about this not really being a DIY job as the car needs to be plugged in to a diagnostic machine and something to do with the ABS needs to be enabled during the process.

However, on the other hand I have seen YouTube videos of people doing the brake flush on VWs and Audi's (which presumably are the same) and they are doing it themselves without plugging it in. I have also done it myself on other cars with ABS and have never seen this extra step mentioned.

Any advice/opinions on this please? Is it a DIY job?

I did ask this question on the Leon mk3 Facebook group and someone posted up the instructions from the SEAT workshop maintenance guide and although they use a fancy filling/bleeding machine I see no mention of a requirement to plug the car into a diagnostic machine and activate the ABS.

This suggests to me that even if I took it to a garage, they wouldn't do this step anyway.

Thank you in advance

Hi and welcome,
I believe you only need to activate the ABS module if any of the module chambers have run dry following a leak for example.
There is a comment following pressure bleeding process in the manual to 2zero compensation for brake pressure sendor 1 - G201 must be performed after bleeding the brake system" this would obviously need a diagnostic tool - but I think this is only after pressure bleeding so the pressure sensor is correctly calibrated - and I don't think this need to be done if using a manual bleed process.

Personally I just use gravity when bleeding my brake fluid - start at the wheel nearest your master cylinder, clear tube on the bleed nipple - looped up slightly then down into the jar. Crack the nipple and go make a cup of tea and wait for nice clean fluid!

I personally don't like the pump brake pedal method as there is a chance that stroking the master cylinder its full stroke that the seal can pick up crap further down the bore when it never normally travels, which can then leak. Less of a chance on more modern cars vs classics but still no need when gravity works fine.

 

[mjgreen81]

Hi and welcome,
I believe you only need to activate the ABS module if any of the module chambers have run dry following a leak for example.
There is a comment following pressure bleeding process in the manual to 2zero compensation for brake pressure sendor 1 - G201 must be performed after bleeding the brake system" this would obviously need a diagnostic tool - but I think this is only after pressure bleeding so the pressure sensor is correctly calibrated - and I don't think this need to be done if using a manual bleed process.

Personally I just use gravity when bleeding my brake fluid - start at the wheel nearest your master cylinder, clear tube on the bleed nipple - looped up slightly then down into the jar. Crack the nipple and go make a cup of tea and wait for nice clean fluid!

I personally don't like the pump brake pedal method as there is a chance that stroking the master cylinder its full stroke that the seal can pick up crap further down the bore when it never normally travels, which can then leak. Less of a chance on more modern cars vs classics but still no need when gravity works fine.

Thank you.

That raises another query you have reminded me of.

I saw it mentioned in the workshop guide that you start at the front wheels. That surprised me as I have always understood you should start at the furthest caliper from the reservoir.

Do you know the reason for starting at the front?

 

[SuperV8]

From the Seat workshop manual:

There are many different ways to do brake bleeding, if your just flushing clean fluid through as long as you are getting clean bubble free fluid out of each caliper i'm sure it will be fine.
If you have air in the system and you are activating the ABS module then I suspect the sequence is more important.

 

[mjgreen81]

From the Seat workshop manual:

View attachment 32700

There are many different ways to do brake bleeding, if your just flushing clean fluid through as long as you are getting clean bubble free fluid out of each caliper i'm sure it will be fine.
If you have air in the system and you are activating the ABS module then I suspect the sequence is more important.

Thanks for that. I do however notice that there appears to be a note in the workshop manual that on right hand drive cars, you should start with Front Right caliper ( I presume it then goes FR, FL, RR, RL)

 

[RUM4MO]

I've always and will continue to start at the longest pipe, then the second longest and so on, from my way of thinking, that means that you have flushed through the reservoir and longest lines first, but I'd doubt if it makes too much difference.
Remember VW Group and no doubt other marques, word their official service and repair instructions to best suit a commercial workshop on a time/convenience prioritising way, that is something that us DIYer don't need to both doing.

I am still using VW Group brake though that it seems can be tricky to buy from VW Group dealerships as the workshops now tend to use bulk deliveries of brake fluid - but there is no reason to try to find that brand, just my way of working as I can pick it up on ebay, well within date for very little money and have it delivered to my door.

I looked into "which type" of brake fluid that you should use on these cars, and found that while the brake reservoir cap states DOT4 and the VW Group correct product states DOT4, it is actually something more like "DOT4+" in as much as it has a different spec to basic DOT4 and as yet no newer dot spec exists for that type of brake fluid. It is down to viscosity of the fluid as in modern cars it needs to be able to react quicker in the system now that cars have ESP etc etc, will using ordinary DOT4 cause you any big problems, I'd doubt it, but why put that to the test when there are many more suitable brake fluids out there.

TRW DOT4 ESP brake fluid PFB440 1litre, Comma brake fluid BF4ESP1L 1litre, Febi brake fluid DOT4 PLUS 1litre 23930, ATE brake fluid SL6 DOT4 ESP 1ltr, Pagid DOT4 PRO (available in 1ltr and 5ltr containers), Mobil DOT 4 ESP (normally available in 1ltr containers).

The above are just some examples of brands that I would have considered from when I made that list a few years ago, but as I say I'm still using VW Group branded brake fluid.

Quantity, going by the official workshop manuals, without flushing the clutch you should get away with 1litre, I've always been a bit hesitant to flush the clutch system due to the fact that the bleed valve is or was plastic, and originally if you broke it, then either a new cylinder was needed, although now I think that only a new bleed section of pipe is needed - if replacing that is always possible without needing to "go further back" I can't say, as I said, I'm just being cautious.

Unfortunately, I've already bought my next Gunsons easzibleed kit, for years I've been using these kits with a modified garden sprayer - using the sprayer as a pressurise air source. I've also bough a cheap vacuum bleeder from China, just to try it out, if nothing else it will be useful for removing as much fluid from the reservoir at the beginning instead of using a dedicated turkey baster and/or a large syringe - so belt and braces and more!

For once in my life, if only using the pressure bleeder, I might apply a ring of brake grease around the top of the bleed valve threads to prevent annoying micro bubbles appearing in the pipe, I've got a quite heavy schott glass bottle to collect the waste fluid in and I've marked it up, or it is already marked up with "volumes" so that I know when I've reached my target quantity of fluid per calliper - every container that I've used in the past has attempted to annoy me by tipping over, having this heavy one and and having it placed securely in a wooden stand (made to jack up the rear of old Ford Fiestas),really stops that nonsense! That bottle cap is complete with a long section of stiff tubing for the incoming waste fluid and a short section of stiff tubing as a vent - again massive overkill, but it suits me.

Disposal of waste brake fluid - what do you do about that? I just buy wood shavings and dump that into an old oven tray thing and pour the waste brake fluid into it, then when it has all been soaked up, I double bag it and put in the general waste house bin, that, it seems is an acceptable way to dispose of it.

 

[Lozzy15]

Hi @mjgreen81, t'was me who replied to you on facebook. I'd have elaborated abit more but I was out and about at the time.

As other have already discussed you'll get away without cycling the ABS pump to change out the fluid. It's actually a job I'm considering doing myself soon so it would be awesome if you could give your afterthoughts on the bleeder you used as I'll be purchasing one to do it.

If you want access to the workshop manuals by the way they're hosted on this site right here:

General maintenance - Leon Mk3 Official Seat Workshop Manuals Link

Hi All! I obtained these a few months ago, and they've been a great use so far. Here's a link to all of the Seat Workshop manuals for the Leon Mk3 3dr/5dr. https://drive.google.com/drive/folders/1M4ofxxMgsFjE7hNWg6l4KuifelmdMUu0?usp=sharing...

www.seatcupra.net

The images I posted for you on FB are in one of these documents (D3E804FD4C3-Maintenance in particular)

 

[mjgreen81]

Thank you for all your help guys. I've planned everything out, ordered the fluid and will get the job done soon.

 

[martin j.]

I worked in a Kia main dealer and saw nothing during brake fluid changes that suggested anything was done with the abs unit, we had one auto bleeder machine so If two techs were doing at the same time I could be roped into “pump the pedal” routine, even using the auto bleeder machine nothing was done other than couple the machine the master cylinder and bleed nipples, Kia may be different but brake systems are pretty much the same all over?

 

[SuperV8]

Unfortunately, I've already bought my next Gunsons easzibleed kit, for years I've been using these kits with a modified garden sprayer - using the sprayer as a pressurise air source. I've also bough a cheap vacuum bleeder from China, just to try it out, if nothing else it will be useful for removing as much fluid from the reservoir at the beginning instead of using a dedicated turkey baster and/or a large syringe - so belt and braces and more!

For once in my life, if only using the pressure bleeder, I might apply a ring of brake grease around the top of the bleed valve threads to prevent annoying micro bubbles appearing in the pipe, I've got a quite heavy schott glass bottle to collect the waste fluid in and I've marked it up, or it is already marked up with "volumes" so that I know when I've reached my target quantity of fluid per calliper - every container that I've used in the past has attempted to annoy me by tipping over, having this heavy one and and having it placed securely in a wooden stand (made to jack up the rear of old Ford Fiestas),really stops that nonsense! That bottle cap is complete with a long section of stiff tubing for the incoming waste fluid and a short section of stiff tubing as a vent - again massive overkill, but it suits me.

If you are only doing a fluid flush to replace old with new and you're not under any time pressure or trying to evacuate any pesky trapped air then try the 'gravity' method.
So easy. Collect something like 200-250ml at each corner - more for the rear, less for the front and you're done.

I have a 'cheap chinese' vacuum bleeder kit but I could never get it to hold a vacuum!
Also have the gunsons bleeder, and also an expensive pressure bleeder machine - and now I only ever use the vacuum method.

 

[RUM4MO]

My cheap Chinese vacuum bleeder is powered by compressed air and has a venturi to develop a vacuum, I was more interested in how it worked in general for drawing/sucking fluids than its original intended use as a brake fluid bleeding tool - I had already bought a bigger version for refilling coolant systems, which many modern cars seem to need to speed up coolant changing without ending up with trapped air - and it worked well. I've also got the "standard brand" of small vacuum handpump, but I've found it to be a bit small for bleeding the brakes on 2 cars in a row/day.

For the record, the VW Group official workshop manuals quote 0.20ltrs for each front calliper, 0.30ltr for each rear calliper and 0.15ltr for the clutch, I think that when I start at the rear/long callipers first, I aim to remove 0.35ltr from the first rear calliper as that includes what old fluid remained in the reservoir, 0.25ltr from the other rear calliper and 0.15ltr from each front calliper, which all adds up to 0.90ltr so still within the "range" of a single 1ltr container of new fluid - and that includes starting with removing as much old fluid from the reservoir first.

Edited to change the quantity of fluid being taken out from the individual rear callipers.

 

[SuperV8]

My cheap Chinese vacuum bleeder is powered by compressed air and has a venturi to develop a vacuum, I was more interested in how it worked in general for drawing/sucking fluids than its original intended use as a brake fluid bleeding tool - I had already bought a bigger version for refilling coolant systems, which many modern cars seem to need to speed up coolant changing without ending up with trapped air - and it worked well. I've also got the "standard brand" of small vacuum handpump, but I've found it to be a bit small for bleeding the brakes on 2 cars in a row/day.

For the record, the VW Group official workshop manuals quote 0.20ltrs for each front calliper, 0.30ltr for each rear calliper and 0.15ltr for the clutch, I think that when I start at the rear/long callipers first, I aim to remove 0.35ltr from the first rear calliper as that includes what old fluid remained in the reservoir, 0.25ltr from the other rear calliper and 0.15ltr from each front calliper, which all adds up to 0.90ltr so still within the "range" of a single 1ltr container of new fluid - and that includes starting with removing as much old fluid from the reservoir first.

Edited to change the quantity of fluid being taken out from the individual rear callipers.

Interesting data on qtys. Thanks.

Mine was a small hand pump type - like a 'cheap' mityvac. The actual hand pump worked fine - but when bleeding brakes you use a sealed reservoir/catch can to collect the fluid - but I couldn't get this to seal.
I also found issues of the bleed nipple leaking air around its thread.

Since spending hours figuring out where phantom bubbles were coming from, a VW/BMW master-tech mate suggested to just use the gravity method - and haven't looked back.

 

[RUM4MO]

Mityvac, that's the one!

I've been changing the brake fluid in all our cars for over 40 years, and it is only now that I've noticed that the official VW Group workshop manuals instruct you to coat the threaded section of the bleed valves in lithium paste to VW spec G 052 150 A2 - now that should stop the micro bubbles and hold back rusting on the threaded section of the bleed valves, but I had always considered that you could only use certain greases in areas where they might make contact with brake fluid - ie to avoid contamination and possible damage to system seals. So, digging deeper I found that while the official VW Group product is a bit expensive at roughly £35, Febi Bilstein market their own version that complies with that VW spec, and the Febi Bilstein number for that is 31942 and can be bought for £13.55 - so last night I jumped and bought a tube of that to use this year when changing brake fluid in 2 or 3 VW Group cars!

Normally I tend to replace brake bleed valves at the 9 year point as by that time the tapered base which seals the corresponding tapered section in the calliper body has been crushed and is now ledge/ridge and so more torque is needed to get a proper seal, okay doing that just continues to crush the bleed valve more. These bleed valves, I think, are made from softer material than the calliper body so if they are or needed to be abused, this will always happen - though maybe a bit less if the threads are now greased using that Lithium paste that VW Group suggest we use.

Edit:- 10Nm is the recommended torque for the bleed valves by the way.

 

[SuperV8]

Normally I tend to replace brake bleed valves at the 9 year point as by that time the tapered base which seals the corresponding tapered section in the calliper body has been crushed and is now ledge/ridge and so more torque is needed to get a proper seal, okay doing that just continues to crush the bleed valve more. These bleed valves, I think, are made from softer material than the calliper body so if they are or needed to be abused, this will always happen - though maybe a bit less if the threads are now greased using that Lithium paste that VW Group suggest we use.

Calipers can be either cast iron or alloy.
Bleed nibbles are steel.
You could argue depending on iron and steel spec which is the harder - but I'm sure the steel nipple would slightly deform the alloy seat.

 

[RUM4MO]

That would be a bit annoying, have you ever fully removed a brake bleed valve and checked the state/condition of it where it meets the calliper, I've never ever seen one that has not been deformed at that point, ie a ledge/ridge formed on it with repeated tightening - well that only covers VW Group callipers.

 

[SuperV8]

That would be a bit annoying, have you ever fully removed a brake bleed valve and checked the state/condition of it where it meets the calliper, I've never ever seen one that has not been deformed at that point, ie a ledge/ridge formed on it with repeated tightening - well that only covers VW Group callipers.

Car manufactures generally don't make their own hydraulic systems including calipers. VAG for example mainly use TRW/Bosch/ATE/ hydraulics inc calipers/wheel cylinders/masters/slaves etc.. So you will find commonality between calipers from the same manufacturer spread over different car manufactures.
I believe (don't quote me haha) bleed screw seat angle is usually slightly different angle to the caliper seat angle - so you get more of a narrow point contact and much higher contact pressure and a better hydraulic seal. This would explain the deformed ridge you see.
This wouldn't worry me, as the next tightening it will microscopically deform again as long as it is not heavily deformed or corroded.

 

[RUM4MO]

Yes, my "well that only covers VW Group callipers" was written to indicate which "selection" of brake calliper brands I had noticed this happening to, so for me that means Lucas/TRW and ATE.

 

[bahyr]

Don't forget to bleed the clutch pump.