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Discussion in 'Technical Q&A' started by NC348, Jul 13, 2004.
how does a line under hydraulic pressure "collapse"?
The rubber becomes kind of semi porous and the fluid becomes absorbed into it, this then causes the rubber to collapse under it's own pressure when the brake is applied....if you look inside one that has had it happen, it looks like a cats arse.....
The diagnosis is very easy yet often overlooked.
A binding brake (or pulling to one side) will be the symptom. To prove it to be the hose and not a caliper simply crack open the bleed screw (with a drain hose connected)....the wheel will still drag if the caliper is binding, or spin freely if it's the hose.
This only happens after 20 years or more, or if you use non compatible fluid in the system.
i have the symptom. now i need to find the solution.
i will investigate per your instructions...
is it best to buy new lines, or to have them rebuilt using the old ends?
Consider stainless steel lines (Goodridge, etc)...
Agreed. Goodridge will firm up your brake feel and be very reliable over the aged (multi-decade!) lines.
having trouble with sourcing. either wrong country or do not have listing for my car, a 90 TS
anyone with a 348 been down this path already?
thanks in advance
I agree with the explanation of what happens to old rubber hoses. Its true they end up working like a valve. They let fluid get pushed to the caliper but don't let it pass back upon release of the pedal.
Regarding braided lines, the caveat here is that the braiding prevents visual inspections for cracks and other damage. Plan on changing braided lines regularly for safety in exchange for the benefit of the firmer pedal you get when using them.
As you mentioned in post #3, I once had some Lancia flexible brake hoses rebuilt using Aeroquip high pressure line spliced into the old Lancia fittings. This was done locally at the industrial hose supply store, took only a day or two, cost very little. It can be done if replacement hoses are not available or are ridiculously expensive.
I have seen a few cases of old rubber hoses collapsing internally and acting as "one way valves", and the hose in question can look fine on the outside. But I'd be surprised to see it happen on a 1990 Ferrari. For the benefit of the rest of us, please take some pictures if you do indeed find a rotten hose!!
i will post pictures of what i find. all indicators are that i got me a "one way" renegrade hose. there is a tractor place next door that i believe specializes in hydraulic lines rebuilding (i live in Land O' Tobacco). i will give the results of that conversation as well.
I got my Goodridge lines from www.demon-tweeks.co.uk less than $100 delivered, to the USA. Had them installed by a local shop, no leaks, no problems. Big improvement over the 17 yo rubber lines on my 328.
i went to the page, but they do not have pre builts for my 348.
i talked to the local hydraulic lines guy. he said he can make anything and everything. gave a ball park of about $75. each (this is ROM without him looking at them).
i will continue. any other 348 guys out there know of a source?
Also do a "google" and "froogle" search for "Goodridge brake lines" or something like that....