Rear brake pipe

[howard m]

The car concerned is a 2008 model Jaguar XJ Sovereign and my rear offside brake pipe gets extremely hot and melts the pipe allowing the brake fluid to leak and then catch fire. It would appear that the fault is connected in some way to an electrical supply as I have to disconnect the battery to prevent the fire re-igniting. Any ideas on what is causing this problem?

Edited by howard m on Saturday 9th June 18:03

[LarJammer]

Are you saying the battery is somehow shorting out through the brake pipe?

[GreenV8S]

howard m said:

my rear offside brake pipe gets extremely hot and melts the pipe allowing the brake fluid to leak and then catch fire

What material is the 'pipe' made from?

[howard m]

It would appear that could be an option. All I know is that there must be some sort of electrical presence getting to the shrouded brake pipe as the only way of stopping the hose from smoking and then bursting into flames is to disconnect the battery.

[Dave Brand]

Looks like you need to check all the earth points in the surrounding area.

[stevieturbo]

howard m said:

The car concerned is a 2008 model Jaguar XJ Sovereign and my rear offside brake pipe gets extremely hot and melts the pipe allowing the brake fluid to leak and then catch fire. It would appear that the fault is connected in some way to an electrical supply as I have to disconnect the battery to prevent the fire re-igniting. Any ideas on what is causing this problem?

Edited by howard m on Saturday 9th June 18:03

Are you saying a metal pipe or rubber pipe melts ?

either way, sounds impressive !

[howard m]

I believe the pipe is made of rubber with an outer steel braiding.

[howard m]

The rubber pipe appears to be melting as a direct result of there being some sort of electrical presence in the braiding which in turn leads to the loss of brake fluid which eventually catches fire.

[GreenV8S]

I'd refer to that as a brake hose to avoid confusing people.

A braided rubber hose would conduct electricity reasonably well and not take a lot of heat to damage. This is very different to melting a brake pipe.

It is quite likely this is the only electrical path from the hub to the main vehicle ground so any electrical supply reaching the caliper would try to earth itself through that.

Does this problem occur when you connect the battery even with all the vehicle systems switched off?

With the battery ground terminal disconnected, measure continuity between the battery positive and the brake caliper. I suspect you'll find there is a connection.

Look for any wires going to the hub or anything connected directly to it, such as ABS sensors.

Does the problem still occur with these disconnected?

[howard m]

Thanks very much for that information, I will do the checks you suggested but I can't do it for a few days as the car is not currently with me.

[E-bmw]

I suspect the battery earth is missing & the battery/fuse box is using the pipe as an earth (laws of physics/path of least resistance etc) causing the heat.

[GreenV8S]

I've seen engines earthed via throttle cables and clutch pipes and so on, but I'd have thought the brake hose would normally be mounted to the chassis/suspension and nominally grounded so no obvious way for either end to become live. But the hub may be being fed power from damaged wiring at the hub or via the handbrake cable etc, and if that happened the brake hose may be the only thing completing the path back to the chassis.

[tapkaJohnD]

Dear, dear Howard,
If you have to refer to " an electrical prescence" in the brake pipe, then I respectfully suggest you urgently seek the assistance of an electrician.
John