Gotta love LR service charges - Brake flush

[SHS14]

I have the luxury of 3 different LR franchises within 1 to 1:15 hours. So, I always call around to compare prices. Last time I caught one speeding on a wheel alignment. They wanted $350 for $140 job.


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[spawnywhippet]

Finished my brake flush yesterday, took around 30 mins excluding jacking up the car and removing the wheels. (I had already done that in order to install the upgraded transmission pan and change transmission fluid and filter.)

How any shop can charge more than $20 in parts and 1 hour labor is practically theft, if a home DIYer can do it in less time.

 

[RBA]

Finished my brake flush yesterday, took around 30 mins excluding jacking up the car and removing the wheels. (I had already done that in order to install the upgraded transmission pan and change transmission fluid and filter.)

How any shop can charge more than $20 in parts and 1 hour labor is practically theft, if a home DIYer can do it in less time.

Whoa, whoa, whoa....upgraded transmission pan?? Tell me more...

How hard was the tranny fluid change and filter? It seems to be a major job on the LR3, so I assumed it was the same for the LR4.

 

[spawnywhippet]

It's the same job as the LR3, but this time I used a replacement pan with no built-in filter, so I just dropped the fluid, unbolted the pan and hacksawed the old filter neck off.
Then I inserted the new separate filter, bolted on the new transmission pan and filled with around 5 quarts of Lifeguard 6 fluid. (keep adding fluid with the engine running and the transmission temp around 85F until it starts to trickle out the filler hole on the right side of the transmission.) I measured the amount of fluid I removed and it was about the same as I put back in.

No need to mess around with removing exhausts, unbolting engine mounts or any of that. The trickiest part was removing and replacing the bolts at the front and rear of the pan, as the cross members were in the way. I used a small wrench on a T30 torx socket to get to them. Probably quicker to remove the rear cross member though, only 5 bolts.

Total time was around 4 hours, but next time it would take under 3.

 

[Davidinseattle]

I think it depends a lot on where you live. Brake fluid being hydroscopic, it will eventually absorb enough moisture to rust your brake lines, etc.
If you live in the desert with 10% humidity as we do, you can go for years without a flush. On the other hand, if you're in the UK...

They gave me this same BS about flushing the system on my porsche. So, you know what I did, I bought the OEM brake fluid and took a turkey baster and pulled fluid out of the reservoir and replaced it with new fluid. I did this once a month until the new fluid was empty. Never had any issues.

My porsche was 11 years old when I finally sold it. It was a Cayenne S and comparable in weight to the LR4.

my two cents on the issue.

 

[Quijote]

They gave me this same BS about flushing the system on my porsche. So, you know what I did, I bought the OEM brake fluid and took a turkey baster and pulled fluid out of the reservoir and replaced it with new fluid. I did this once a month until the new fluid was empty. Never had any issues.

My porsche was 11 years old when I finally sold it. It was a Cayenne S and comparable in weight to the LR4.

my two cents on the issue.

This is not a good approach. It will help some but not completely. The brake fluid doesn't recirculate. It gets pushed to a dead end (your calipers) and it will be stuck there. Sure. changing out the reservoir will help because inevitably the concentration will change some, but it is likely that near the calipers you will have fairly old fluid.

I've done brake bleed where the initial few table spoons of fluid off each caliper looked like hell, and afterwards looked pretty good.

You really need a proper bleed from the calipers.

 

[Davidinseattle]

This is not a good approach. It will help some but not completely. The brake fluid doesn't recirculate. It gets pushed to a dead end (your calipers) and it will be stuck there. Sure. changing out the reservoir will help because inevitably the concentration will change some, but it is likely that near the calipers you will have fairly old fluid.

I've done brake bleed where the initial few table spoons of fluid off each caliper looked like hell, and afterwards looked pretty good.

You really need a proper bleed from the calipers.

Let's just agree to disagree on this one. A couple of points to make:

1) The preferred natural state is equilibrium. The brake fluid will mix, otherwise you wouldn't add new brake fluid to old brake fluid as you'd have a system with multiple states.

2) Pull out your fluid mechanics manuals and you'll see that since their is an up and down piston action against a barrier/closed end, it should follow normal internal flow properties. The fluid velocity at the barrier is obviously zero and the fluid velocity in the circumference of the line is <0 at some point through the circumference the line. So, the fluid is going to move with each depression and release in opposite direction to the piston.

3) I believe the laws of diffusion apply here as well.

All of that said, yeah bleeding the lines makes sense, I don't disagree, especially if you've heated things up a bit.

One other thought too, if there was no circulation and the only point of entry is the reservoir, then how does water make its way to your calipers?

 

[Quijote]

Let's just agree to disagree on this one. A couple of points to make:

1) The preferred natural state is equilibrium. The brake fluid will mix, otherwise you wouldn't add new brake fluid to old brake fluid as you'd have a system with multiple states.

2) Pull out your fluid mechanics manuals and you'll see that since their is an up and down piston action against a barrier/closed end, it should follow normal internal flow properties. The fluid velocity at the barrier is obviously zero and the fluid velocity in the circumference of the line is <0 at some point through the circumference the line. So, the fluid is going to move with each depression and release in opposite direction to the piston.

3) I believe the laws of diffusion apply here as well.

All of that said, yeah bleeding the lines makes sense, I don't disagree, especially if you've heated things up a bit.

One other thought too, if there was no circulation and the only point of entry is the reservoir, then how does water make its way to your calipers?

It's been some time since I took fluids, but there is no need to brush up on my Navier-Stokes. Your application of the principle you mention is highly idealized. You are talking about a very small amount of fluid displacement every time you hit the brakes. Also, the conduit has a, what, 1/8" diameter? and a length of many dozen to a couple of hundred inches in length. You think your piston moving a tiny fraction of an inch is going to circulate fluid much?

Anyhow. I get your approach. I've done it on a coolant system on a previous car where getting the last 10% out was a PITA, so I drained 90% and filled it with good coolant, and a few weeks later did the same. Still not ideal, but mostly there. The difference being that there is a water pump circulating the coolant. That doesn't happen on brake lines.

Also, brake fluid doesn't mix so easily. There is a reason people successfully put new fluid and let it push the old fluid out.

Finally, water doesn't make it into you lines all that easily - air does. Water is incompressible and would not affect the feel of your brakes. It is air, with much smaller molecule size (why Gore Tex works) that can find its way in, and it being compressible will make the pedal feel spongy, thus requiring a brake fluid flush.

Maybe this all explains why I have never heard of anyone just replacing brake fluid at the reservoir and hoping it will all mix nicely as a way to avoid a proper bleed/flush.

But yeah, let's agree to disagree.