[David.m]

I'll shortly be changing from oem brake fluid to some racing fluid in preparation for track days. I obviously have a RHD car and just noticed that the ABS unit is on left side (my passenger), same as LHD cars. The reservoir is of course on the right side with the 2 lines running across the firewall to the ABS unit, otherwise I would assume all the brake lines outwards from the ABS unit are identical for both LHD & RHD cars.

As such am I right in assuming the procedure/order of wheels for bleeding my RHD car will be the same as LHD cars?

[5.M0NSTER]

Yes, order would be the same since the distribution of fluid to individual wheels happens after the ABS unit. Good luck! I just did this with mine using Castrol SRF.

[GasBurnlife(landapanda)]

Originally Posted by 5.M0NSTER

Yes, order would be the same since the distribution of fluid to individual wheels happens after the ABS unit. Good luck! I just did this with mine using Castrol SRF.

Make sure you also flush the ABS unit. I had my shop do the first flush from oem fluid to SRF, and I now do my own flush 2x year.

[MR RIZK]

Generally you always start from the furthest corner to the shortest corner from the abs unit.

[Megator]

Originally Posted by landapanda

Make sure you also flush the ABS unit. I had my shop do the first flush from oem fluid to SRF, and I now do my own flush 2x year.

How do you flush the ABS unit? just use a pressure bleeder?

[GasBurnlife(landapanda)]

Originally Posted by Megator

How do you flush the ABS unit? just use a pressure bleeder?

I plan to do it once a year. Since I don't think any air would generally enter it anyway, I just do a full manual flush once mid season. I compensate for this also by using the Castrol SRF, which has the highest wet boiling point.

[Megator]

What do you mean manual flush? like pumping the brakes?

My point is that you can flush the lines but not he ABS unit, if you then cycle the ABS unit you get "old" fluid in your lines.

I have heard that pressure bleeding forces all of the valves in the ABS unit open flushing it at the same time.

I have also heard that you need to cycle the ABS unit using some BMW software/diagnostics in order to flush the ABS unit properly.

Just trying to find out what is true

[Caduceus]

Originally Posted by Megator

What do you mean manual flush? like pumping the brakes?

My point is that you can flush the lines but not he ABS unit, if you then cycle the ABS unit you get "old" fluid in your lines.

I have heard that pressure bleeding forces all of the valves in the ABS unit open flushing it at the same time.

I have also heard that you need to cycle the ABS unit using some BMW software/diagnostics in order to flush the ABS unit properly.

Just trying to find out what is true

I think the need to do this is over-rated. What matters is what fluid is in contact with the back of the pistons inside the brake calipers. This is what boils under heavy use and leads to vapour in the lines and a soft pedal. Brake fluid is not a recirculating system. There’s no return line from the caliper. So boiling fluid and vapour inside the caliper doesn’t end up in the ABS unit, or the master cylinder and it isn’t conductive enough to transfer the heat along a considerable length of brake line.

In a perfect world, the entire system would be full with clean, fresh SRF. But for all practical purposes, as long as that’s what is coming out of your caliper bleed nipples and there isn’t air trapped in the system further upstream (which would be soft all the time, not just when hot), you will be fine.

[MR RIZK]

Go with what Caduceus said.

Otherwise here is the book detail https://www.newtis.info/tisv2/a/en/f...-lines/E26nU3b

[5.M0NSTER]

Originally Posted by landapanda

I plan to do it once a year. Since I don't think any air would generally enter it anyway, I just do a full manual flush once mid season. I compensate for this also by using the Castrol SRF, which has the highest wet boiling point.

Actually there are higher dry boiling point fluids out there. Motul RBF 660 has a dry boiling point of over 650F, about 50 higher than Castrol. The biggest appeal of SRF is that it’s wet boiling point is almost as high as it’s dry boiling point. Most other fluids boil 250 sooner when they absorb air moisture.

[5.M0NSTER]

Originally Posted by Caduceus

I think the need to do this is over-rated. What matters is what fluid is in contact with the back of the pistons inside the brake calipers. This is what boils under heavy use and leads to vapour in the lines and a soft pedal. Brake fluid is not a recirculating system. There’s no return line from the caliper. So boiling fluid and vapour inside the caliper doesn’t end up in the ABS unit, or the master cylinder and it isn’t conductive enough to transfer the heat along a considerable length of brake line.

In a perfect world, the entire system would be full with clean, fresh SRF. But for all practical purposes, as long as that’s what is coming out of your caliper bleed nipples and there isn’t air trapped in the system further upstream (which would be soft all the time, not just when hot), you will be fine.

Yeah, I would generally also agree. The reservoir holds 250cc if fluid. The ABS unit has accumulators which hold about 4-6cc. Calipers and lines hold about 50 CCs. The only way you get contaminants or boiled fluid into the accumulators is under ABS pressure decreases from the calipers. And it’s a lot harder to get into ABS when the pedal gets soft. Then from there the boiled fluid would go back up to the master cylinder when the driver releases the brake. But the bottom line is the few CC’s in the ABS unit are not that much

[Megator]

Guys thanks a lot for the info!

Intuitively I figured this was the case but with brakes I would rather be overly cautions.

I used RBF 600 in my RS and never got any fade. Its cheaper than RBF 660 but has very similar specs. 312C vs 328C dry boiling point and 204C vs 204C wet boiling point.

https://d23zpyj32c5wn3.cloudfront.ne...pdf?1492016152

https://d23zpyj32c5wn3.cloudfront.ne...pdf?1492016152

I will use my Gunson pressure bleeder to do the brakes

BTW its the inside nipple first and then the outside one for the front calipers?

[5.M0NSTER]

Yes, that is correct. Have fun and I wish you a firm pedal and fade free brakes.

[David.m]

Originally Posted by MR RIZK

Go with what Caduceus said.

Otherwise here is the book detail https://www.newtis.info/tisv2/a/en/f...-lines/E26nU3b

Actually that link in the repair manual relates to bleeding following a repair in the brake system when use of the ISID software if required.

A normal maintenance full flush is here and doesn't involve anything special for the ABS system though they use a pressure bleeding system and not the old 2 person method:

https://www.newtis.info/tisv2/a/en/f...ion/1VnXDR6doh

NOTE also that for the callipers with 2 valves (nipples) the manual says the 'outer' valve is done first followed by the 'inner' valve.

[David.m]

Originally Posted by Megator

Guys thanks a lot for the info!

Intuitively I figured this was the case but with brakes I would rather be overly cautions.

I used RBF 600 in my RS and never got any fade. Its cheaper than RBF 660 but has very similar specs. 312C vs 328C dry boiling point and 204C vs 204C wet boiling point.

https://d23zpyj32c5wn3.cloudfront.ne...pdf?1492016152

https://d23zpyj32c5wn3.cloudfront.ne...pdf?1492016152

I will use my Gunson pressure bleeder to do the brakes

BTW its the inside nipple first and then the outside one for the front calipers?

As I mention above the Repair manual says the outer nipple first followed by the inner. It would be consistent with the general idea of starting furthest from the ABS unit and working inwards.