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F to R + across brake lines... DIYable?


Yas Marina
1 Sep 2003
I need to replace my 4Ss front to rear and transverse brake lines at some point, and wondered if it was something that can be DIYd. I have a talented friend with a four-post lift and decent tools who knows his way round vintage cars who's offered help.

- firstly, is this practical, or does a world of pain await...?
- is there a how-to anywhere? All I've found online are just about the flexi pipes from the caliper.
- I would like to use Cunifer rather than the OE ones. Does this pose additional problems?
- I am worried about the rear pipe that goes over the 'box. Is there any way of threading a pipe over without dropping engine/box as I'd rather not do that until it needs clutch/RMS?
- any particular pratfalls... I'm guessing seized/sheared bleed nipples, anything else to consider?

I'm annoyed that my indy did not recommend replacement of the rear line when the thing was in bits having the AOS done, but that's water under the bridge...
Coincidentally I heard recently from RPM Technic regarding the line that goes over the box, which apparently is prone to fail and a pain to replace, and they just replace with a long braided hose (like a long braided brake hose). May be something you could therefore fit yourself...
I was wondering whether a braided hose would work, but then I read that an unsecured hose like that would be an MOT fail, or at worst could rub on something and split. Perhaps I'll give RPM a call and see if they have a particular plan.

My thinking was to route it safely and securely below the 'box until such time as it all needed to come out anyway.

I did the transverse rear line myself last year. I have a lift at home and was able to drop the gearbox and do the line on my own - its not paricularly complicated (similar to other cars I have worked on).

There are guides in various books, showing how to drop the gearbox. Then its just a brake-line.
I used cunifer for mine. It was pretty easy, but you do have to bend the lines yourself, whereas the OEM lines come pre-shaped (but will rust again).
I have heard of people threading the line over the box, but I think that would be pretty tricky.
You mentioned seized bleed nipples as a risk - that was the issue I had, sort-of....one of mine bleed nipples wouldnt reseal properly, as the seat was damaged. Pro-callipers were brilliant, they installed a new seat and threads into the calliper.

I took my time doing the job and used it as an opportunity to really inspect the underside of the car etc. Was a real sense of satisfaction when I had finished.
If you are comfortable working with cunifer / doing your own brakelines (which it sounds like your friend is), the 911 is just another car. The only real downside of Cunifer is cost (slightly more expensive than steel) and it is a bit softer so you need to be a little more careful not to additionally bend /kink/ work harden the lines as they are installed. Lots of advantages to it, one is that it doesnt rust.

The line over the gearbox - I wouldnt accept a flexi hose (much more likely to have a little expansion and give a spongier pedal). Plenty of folks with boxsters have routed a replacement under the gearbox/engine till it is dropped and replaced above fine. The other option would be to place a union in the middle somewhere above the gearbox that would make it much easier to get the line in.
Basic rule of thumb .. if a brake line is insecure or routed dangerously then its an mot failure .. how dangerous is at the discretion of the mot tester .

I have seen a pipe run from the n/s and a pipe run from the o/s with a connection in the middle .. as long as the pipes are in the locating brackets then this to me seems the best , quick , alternative , i suspect you could do this with box in situ .. never tried so cant say for certain though .

I'm not a fan of running a brake line under the gearbox and making it one of the lowest items on the car i'm afraid ... safety first ... cost second Imho.


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Sounds like it's doable, but I'd better get my big boy pants on and do a proper job by dropping the box!

That pic is really helpful to make a plan, thanks DeMort.

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