StratfordShark

I want to change all the flexible brake hoses this year, as well as replace pads and discs. The existing hoses are fine but original.

This will involve opening the system at various points, whether cutting the old lines or undoing at union to hard lines and caliper end.

I have various plugs to prevent fluid leaking out, but I was intrigued to read a tip - I think here - about effectively isolating the fluid reservoir from system by pressing the pedal down, and using an extendable rod to hold it down.

I have a telescopic rod that could do this, but I'm thinking that if I keep the pedal depressed, this will force pads against discs and make it hard to remove calipers and/or take old pads out.

Is this correct, and if so what is advice for changing all the flex lines and minimising risk of getting air trapped in parts of the system which may be difficult to bleed subsequently?

Thanks

GlenL

That sounds like an interesting idea. With the brake pressed the fluid won't run in from the reservoir. You'll still have air in the new hoses.

Suggestion: bleed each corner as you change the hose.

James Bailey

unscrew the reservoir cap put a piece of plastic wrap and replace the cap.....the now airtight cap will not let all the fluid drain out...greatly reducing the amount of bleeding.

dr bob

Interesting idea. To make it work, have your trusted assistant press the pedal gently while you bleed a little fluid from one front and one rear caliper. You only need to push the pedal down a couple inches to block the ports from the reservoir, and this will also keep you from getting the cups into unknown and possibly corroded or debris-filled territory in the master cylinder. Leave the pedal there with your brace or a stick of wood, wedged gracefully between the front of the seat and the pedal.

----

To keep the fluids in the steel lines while changing hoses, I slipped a short section of rubber vacuum tubing over the end of the steel flare, and piched the hose with a handy hemostat. These are medical pliers used for pinching off blood vessels to prevent excessive bleeding and loss of fluid. Except for the color of the fluid, these are designed for this task it seems. Or... fold the rubber hose over tight so it's pinched at the fold, secure the fold with a cable tie or a rubber-band.

On installation of the calipers and the new hose, you can either vacuum-bleed the caliper and hose from the bleeder end, hose end siting in a cup of brake fluid, or push fluid with your powe bleeder from the caliper end until fluid runs out the hose end. The first option clears air from the caliper if it's slready mounted. Second option is great if you can invert the caliper so the hose connection is at the top, letting you push the air out of the high points and up through the hose.

Once the air is out, you'll connect the line to the hose, secure with the metal clip, and eventully do a whole-system bleed once all four hoses are replaced.

Other things: Before you attch the hoses to the calipers but after the old hoses are removed and the steel lines blocked, test-fit the ends of the new hoses into the support brackets on the car. The Goodridge hoses I got were close to a perfect fit, but still took a little fiddling with a round file in the bracket to get the fit just right. You'll want to do that fiddling and filing and fitting with the little plug and cap still in the hose end, without the caliper dangling from the other end.

mark kibort

this thread might have been better entitled, "how to get the air out when changing the lines".

StratfordShark

Thanks for whole raft of useful tips and suggestions.

I'll be printing this thread out for when I start the project.

James Bailey

I think hoses is an accurate description of a hose....brake line is a more accurate description of the hard flared metal tubing that the hoses connect to. But many do refer to the braided stainless shielded hoses as "Brake lines" . Just not nearly as clear.

GregBBRD

The biggest problem with changing 928 brake hoses is getting the flexible hose separated from the steel line. The design of the nut on the metal line trapped water....and the nut and line are frequently fused together.

Start spraying your favorite rust solvent at these junctions about a week ahead....and be prepared to replace the steel lines also.

dr bob

The OP's original title is much more appropriate for the work he is getting into. Keeping the air out, especially in ABS cars, is a much easier strategy than letting the fluid drain out, air take its place, then trying to get the air out.

upstate bob

the more brake fluid pours out the better. good opp for refreshment.

dr bob

Better to flush than to drain and refill. There are some places that air hides out in the system, making removal a challenge.

More than several listers have reported problems getting air out completely after a service that included draining the brake system of fluid. Bill Ball helped Nicole with this problem, which was serious enough to keep her from driving the car. Bill was DQ'd from an event when his instructor felt his pedal was too soft and low.

I casually chased a soft pedal for a while after accidentally getting air in the system. Normal bleeding and power flushing didn't help. Ultimately, a combination of vacuum- and pressure-bleeding each section of the system was what it took to restore the brakes to new operating condition with high/hard pedal. Nicole ended up doing a similar exercise on her car to make it safe again.

mike77

I did mine last year. Perhaps I got lucky but I just let mine drain and then used a gunson eezibleed.

The big problems for me were. Stuck bleed nipples. Lost a front caliper to that and had to replace it.

Also the connections on both the rear hard lines where the flexi hos connects were completely corroded and literally disintegrated when I attempted to remove them. I had to replace the rear hardlines. You are in the UK like me you may find the roads have done something similar to yours.

Eurocarparts sell pagid discs, pads, hoses and sensors at a decent price. Think they sell a bit cheaper through their ebay shop.

DuncanF

So, for the sake of argument , let's just say that the flexible hoses are fused to your hard lines, as Greg has described, and despite soaking the connections in rust remover and penetrating fluid on and off for the last three weeks and using decent flare nut spanners you are still struggling to open the connection. How difficult is it to replace the hard lines? Can that be done with the engine in place?

I'm talking about the front lines on an 87 S4.

Thanks
Duncan