!!! WARNING!!! Flexi brake pipe failures. Naturally aspirated models.

[J44EAG]

Guys,

I received an email from Mike H this morning which included a copy mail from a friend and fellow JEC member. It concerned the failure of a front flexible rubber brake pipe on a "small brake" model X350. Fortunately, the failure of the flexi pipe occurred whilst the car was on the rollers for an MOT. The naturally aspirated cars have the small brakes. "Big brake" XJR and Super V8 models are unaffected by this issue. Below is an extract from the mail I sent Mike H by return.

"This failure of rubber flexi brake pipes on "small brake" models is indeed disconcerting to say the least. The fact that the car in question has covered just 67K miles makes it even more of an issue. I`ll flag up the problem on the Club web site. Inspection at yearly intervals would be prudent.

The flexi issue highlighted on "small brake" naturally aspirated cars does not exist on "big brake supercharged cars ie XJR and Super V8 models. Dependent on model year, these cars have either Brembo or Teves four piston calipers together with stainless steel braided, thin wall flexi pipes. This is highly advantageous as it affords the pipes with abrasion protection and also contains the thin wall rubber pipe within. It is an excellent "big brake" modification which also helps control pipe expansion under heavy braking application. I have it in mind that it may well be possible to retro fit these XJR type pipes to small brake models.

The pipe comes with a mounting bracket which fixes to the horizontal chassis leg. The steel brake pipe from the modulator unit screws into the end of the bracket. At the caliper end of the braided end, I recall there is a typical pipe banjo with copper washers either side. A hollow hex headed trunion fitted through the washers and banjo affords brake fluid flow to the caliper. I see no reason why the XJR braided hoses could not be retro-fitted to "small brake" models although anyone considering such a conversion should check end fitting suitability before buying XJR type pipes for conversion".

So a heads up here for owners of small brake vehicles which includes S-type and XF models which also have identical brake components.

Mike K

[PaulGover]

FWIW, an MOT tester I talked to once did not like braided hoses, as the braiding could hide defects in the hose, such as broken reinforcement, which would otherwise be detected when the hose swelled during the MOT test.

Personally, on my older cars which I maintain myself, I try to follow Jaguar's (well hidden, I really don't recall where I found it) to replace brake fluid every couple of years, and hoses every 4 years,

[J44EAG]

Indeed sensible advice, Paul... the trouble is that few of us ever replace flexi brake hoses unless our own inspection or the MOT man picks up the defect. Therein perhaps lays the problem.

I`d agree that braided hoses are much more difficult to inspect and to find localised faults. In principle I agree with your points. The thing about the Jaguar braided hoses is that they are only about 6mm in diameter...and that includes the braiding which constricts expansion under pressure and indeed perhaps physically contains some of the problems which we all know about with conventional rubber only flexi pipes.

I recall from my marine industry days when I was involved in getting often decrepit leisure craft through an Inland Waterways inspection. It could often be a nightmare and take many hours to fix. I would often find genuine, in date, flex rubber but braided gas pipe fitted from a bottled gas regulator to the gas feed pipe on the boat. Although the hose was in date and perhaps previously passed by an inspector, the boat would later come up for its four year compliance inspection. On would come a new inspector, look in the gas locker, see the braided gas pipe and fail the boat on the spot! I`d then have to fit conventional flexi pipe to get the boat through inspection. Next time I went on the boat, I`d find the owner had removed the rubber pipe and re-installed the braided pipe!! I could never win!!!

Good points indeed, Paul and so nicely presented as well.

Mike

[greyhair]

At my annual service at Chris The Jag specialist at Doncaster , replacement of the flexi pipes at the front was an advisory and he has since completed the work. Better safe than sorry

[J44EAG]

The principles of good PREVENTATIVE maintenance.

Catching issues like this is what its all about. As a former licensed aircraft maintenance engineer, my job at an annual inspection (ie an aircraft MOT) was to specifically go looking to find troubles. Any perishable item would come under intense scrutiny. On the Piper Cherokee and other similar series aircraft, it was necessary to replace two fuel tank breather hoses. If they failed, a full tank of fuel would push fuel up the breather pipe which if perished would the disgorge fuel into the wing structure. Having dihedral, (angled wings with the lowest point being under the cockpit) fuel from any defective breather pipe would run down the wings and settle under the "dummy at the front". The aircraft would fill with petrol fumes and risk of explosion became huge.

The idea of maintenance was to catch the problem before such an event occurred. Taken further, the Star Annual inspection occurred every three years. That inspection required the aircraft to be ripped down to bare bones and rebuilt. Even the starter motor was stripped to check for a cracked pinion housing. This standard of maintenance reduced the possibilities of failure to the minimum and kept aircraft safe. A similar level of inspection and replacement needs to be applied to our flexi car brake hoses on a regular basis. The MOT should catch that issue but often a potential failure issue gets missed.

So it comes back to decent regular inspection and we perhaps need to change attitude to flexi brake pipe issues. If we were all made to replace those hoses every three or four years by Law and regardless of mileage covered, then we would probably never see brake pipe failures and we wouldn`t be flagging this issue up at all. Forced replacement would see the events of failure gone for ever.

Mike