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Old 6th April 2020, 20:20   #11
grout20
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Quote:
Originally Posted by Synchromesh View Post
Was it obvious from the colour change when the new fluid had reached each caliper?
How much new fluid did you use?
Hi,

I was using a clear piece of tubing but it wasn't blindingly obvious looking at it when the fresh fluid started coming through.

However, on the rear calipers I did notice a slight increase in the rate of the drips. So when I noticed that I dripped some drips into another (empty) glass jar for comparison, and that fluid did appear a bit lighter than the stuff in my main "catch container". Does that sentence make sense?

The O/S rear bleeding seemed to turn clear quicker than the (first one) N/S rear, and the N/S front and O/S front went quicker too. Fairly obvious perhaps, as the pipes/hoses to flush through are shorter length as you work your way round the system.

Volume of fluid overall? I only needed one litre. I'd estimate the amount bled at each wheel before it appeared fresher was (...ish...)

N/S rear - 400ml
O/S rear - 250ml
N/S front - 150ml
O/S front - 100ml

(If someone knows how much fluid you should aim to bleed out of all four corners ... ignoring any ABS related bit .. then please let us know)

Of course, when I state above the drips got "quicker" please be aware that using this gravity-only method you should plan on 3 hours, copious cups of tea and have another couple of jobs to get on with at the same time....

.. and if someone responds to say "you should flush 3 litres of fresh fluid through, mate" I think I'll save up for one of those pressure bleeders!

Another long post .... sorry ... but hope it's useful.

Good luck

John
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Old 6th April 2020, 20:43   #12
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John, I shall be trying this method tomorrow. All 4 bleed nipples have been loosened.
Is that 3 hours to do all 4 wheels. Did you have your car on the ground when you bled or did you jack up and remove each wheel in turn for better access?

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Old 6th April 2020, 20:56   #13
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Originally Posted by macafee2 View Post
John, I shall be trying this method tomorrow. All 4 bleed nipples have been loosened.
Is that 3 hours to do all 4 wheels. Did you have your car on the ground when you bled or did you jack up and remove each wheel in turn for better access?

macafee2
Hello Ian

The 3 hours included me loosening off each bleed nipple (carefully does it as I guess you know! ) so you hopefully have saved some time.

I jacked up each wheel, removed it and put an axle stand under each corner as I needed clear access to the nipples. If yours are already sorted you could try without removing wheels if you have flexible enough wrists!?

Good luck and let us know how you get on

Stay safe

John
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Old 6th April 2020, 21:04   #14
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Quote:
Originally Posted by macafee2 View Post
John, I shall be trying this method tomorrow. All 4 bleed nipples have been loosened.
Is that 3 hours to do all 4 wheels. Did you have your car on the ground when you bled or did you jack up and remove each wheel in turn for better access?

macafee2
Jack up the back end, put it on stands, and remove the wheels,bleed NSR, then OSR, put the wheels back on, then jack up the front, remove the wheels, bleed NSF, then OSF.

It will take no more than a litre to completely change the fluid in the entire circuit

Brian
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Old 7th April 2020, 15:47   #15
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I did a brake fluid change today.
I was sceptical that the gravity method would work and even more sceptical when told to jack the car up when doing the rears.
I should have had more faith and so I apologise for being sceptical.
The rears were slow and I did not settle doing anything else while waiting. It was very noticeable once new fluid came out of the bleed nipple, old fluid very golden, new fluid very light and I was amazed by how little fluid was required.

I am a bit worried however I have the sinking pedal, it does go down and can be felt sill going down but then does stay firm and has not hit the floor.

I think one of my rear dampers is now leaking but I have spares.
This method is easy... very easy and will be my method of choice from now on.

thank you for the thread

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Old 8th April 2020, 10:39   #16
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A factor to consider here is the situation where there may be air bubbles in the system. I doubt 'gravity' will provide enough flow rate to encourage air bubbles to be expelled.

Another feature noted when brake bleeding is the sinking pedal phenomenon. It's not been discussed for a long time and it's surprising that relatively few members have observed it. After a bleed, it's natural to press and hold down the brake pedal to confirm the hydraulic lock. So, when you do that, keep your pedal hard down for several minutes and observe if it very slowly sinks. It's a well known effect that many car makes exhibit (including Jaguar) and is not an MOT nor a safety issue. The effect doesn't happen with the engine running. There are several old threads discussing it (search for 'SPP' for some of them). It's reported that SPP is not observed when a T4 is used to bleed the brakes. (This is the basis of my query in Post 6). If that's a real effect and not simply experimental variance/operator bias, then what's the difference in the state of the brakes after each process? I'd love to find a convincing answer.

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Old 8th April 2020, 11:47   #17
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I will try it when I get the chance, nothing ventured nothing gained. thank you

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Old 8th April 2020, 13:41   #18
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The ABS "wheeze" is actuating the ABS pump on the secondary circuit, which is what T4 does but under controlled conditions, both in primary and secondary circuits.

However assuming the ignition is not turned on during the bleed process, the valve block within the ABS pump remains shut, and no air can enter.

It is not that any air will be introduced to the system in any event when a fluid change is taking place unless the fluid level is allowed to drop sufficiently in the master cylinder reservoir.

If you didn't have SPS before you started, and you bleed the system in the correct order, you won't have it once you finish.

Brian
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Old 8th April 2020, 13:58   #19
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Quote:
Originally Posted by T-Cut View Post
The effect doesn't happen with the engine running. There are several old threads discussing it (search for 'SPP' for some of them). It's reported that SPP is not observed when a T4 is used to bleed the brakes. (This is the basis of my query in Post 6). If that's a real effect and not simply experimental variance/operator bias, then what's the difference in the state of the brakes after each process? I'd love to find a convincing answer.

TC

I ended up with SPP after the rear brake line burst on my way home from work. Once replaced I had several goes at conventional bleeding myself, plus pressure bleeding at a local independent garage.
That all made the SPP better but still present, so it had a T4 bleed and air did come out of the secondary ABS circuit.

Was enough to convince me that SPP is caused by trapped air in the ABS modulator, but you shouldn't get it if you bleed with the ignition off.
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Old 8th April 2020, 14:13   #20
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Quote:
Originally Posted by marinabrian View Post
....
However assuming the ignition is not turned on during the bleed process, the valve block within the ABS pump remains shut, and no air can enter.

It is not that any air will be introduced to the system in any event when a fluid change is taking place unless the fluid level is allowed to drop sufficiently in the master cylinder reservoir.

If you didn't have SPS before you started, and you bleed the system in the correct order, you won't have it once you finish.

Brian
I'd picked up these tips beforehand from previous threads, but just to confirm ....

.... during my gravity bleed marathon I left the ignition alone, made sure the Master Cylinder level went nowhere near the neck of the cylinder, never touched the brake pedal and the brake pedal is as hard after as it was before I started.

I also understood the fluid in the ABS would not be flushed by gravity method (40ml I think Brian had mentioned before)

I'd heard of Sinking Pedal but thankfully it didn't make an appearance for me. Sorry to read it did for you. Hope you sort it out ok macafee2.

Good luck and kind regards

John
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