bleeding front brakes only?

[GGR]

I'm swapping the front axle on my W111 Coupe and I have disconnected the front calipers in the process. I've always bleeded brakes starting from the farthest wheel to the closest to the master cylinder. But given this car has two different circuits, one for the front wheels and one for the rear ones, I'm wondering if I can bleed only the front ones? Brake fluid has gone down in only one of the tank's compartments.

[MattBelliveau]

I think you would be OK if you were using a power bleeder or something. I would think that if you were using the pump method, the air would eventually work its way up to the master cyl, and distribuite itself amoung all the calipers. You might be OK if you gravity-bleed first. Someone else can chime in if I'm totally offbase.

[Billybob]

Originally Posted by GGR

I'm swapping the front axle on my W111 Coupe and I have disconnected the front calipers in the process. I've always bleeded brakes starting from the farthest wheel to the closest to the master cylinder. But given this car has two different circuits, one for the front wheels and one for the rear ones, I'm wondering if I can bleed only the front ones? Brake fluid has gone down in only one of the tank's compartments.

Assuming that the rear circuit didn't run dry or in the interim was pumped where it could injest air into it, just bleeding the fronts should be fine.

[wbain5280]

Gael, as you wrote, start at the farthest from the master cyl first, that would be the front passenger side and then the drivers side.

What's wrong, or going on, with the front suspension that it needs to be changed?

[Tomguy]

I would assume he's swapping the 111 front subframe with a 108 one with vented discs so he doesn't need to remove & swap hubs (and calipers, since the vented ones are probably bigger). If his donor has all good rubber bits & bushings it would probably be faster than doing just the hubs & replacing the other bits later on.

BTDT, only need to bleed the fronts on a dual-circuit setup if only the fronts have been drained.

[GGR]

My front axle had developed a bit of play in the kingpins, so I have rebuilt a front axle (out of that green W108 at Crazy Ray's) last winter with new bushings all round and am now fitting it on the car. In the process I have also removed both front fenders and am rustproofing the front of the chassis. I already did that in the back when I swapped the rear axle with the 3.27 one and a 27 gallons fuel tank out of a 6.3.

[sokoloff]

For the extra ten minutes it will take to bleed the backs too, why not just do it? They are supposed to be done every year anyway.

[GGR]

I did it in the back when I swapped the rear axle. In my case I don't have a lift so it means jacking the car up, removing the wheel, bleeding, putting back the wheel, jack the car back down, and repeat the operation on the other side. I may see if there is a way to bleed the brakes just by reaching behind the wheel.

[JiveTurkey]

Originally Posted by GGR

I did it in the back when I swapped the rear axle. In my case I don't have a lift so it means jacking the car up, removing the wheel, bleeding, putting back the wheel, jack the car back down, and repeat the operation on the other side. I may see if there is a way to bleed the brakes just by reaching behind the wheel.

I just jack the back half of the car up and support both sides on safety jacks, that way you don't have to go up down up down up down.

[230/8]

With respect to your original question, you are seldom wrong to bleed the entire brake system...you can never be certain the extent to which air can/will migrate into the system when any part is opened to the atmosphere. In addition, it gives you the opportunity to flush the old fluid, remove contaminants and thereby extend the life of the expensive parts like master cylinder, calipers and lines. Decent quality brake fluid is cheap, $10-$12/liter at the most and you should only need a liter to do the job. Flush regularly, using a $50 power bleeder, like the Motive-Power units, which is a useful addition to any car guy's garage, and the job is a simple easy 2-hour Saturday morning job that can permit brake calipers and master cylinders to last almost indefinitely because they will not corrode.

My 2-cents...