Complete and instant brake failure !

[Shayne]

Before i phone roughtrax i need to get my head around this . These stainless lines are maybe a year old and my brakes are/were brilliant when i drove half a mile 2 hours ago , but just now going out and less than a minute from the house i was half over a stop sign before i caught it with the handbrake !?!

I drove home in first gear using the handbrake but it still didn't take a full 5 minutes and there is no evidence of a leak on the ground where i was parked earlier .

I got the mrs to apply the brakes so i could see where the spray was coming from and it's like someone drilled straight through the centre of the stainless line , What you see in the pic is the plastic outer sheaf split and burnt .

So any theories or indeed points i should raise with Roughtrax before i call them ?

 

[Towpack]

Any heat high enough to melt the plastic outer will probably melt the inner but where is the heat coming from? How close to the line is the nearest heat source?

 

[Shayne]

It's the drivers front caliper and brake heat is the only source .

The outer sheaf just keeps the stainless clean i think and so even normally heated fluid would likely melt it as it is never supposed to come into direct contact .

Roughtrax are sending me a new kit asap saying this is a first and they are keen to have the broken line back for investigation .

 

[frank rabbets]

Shayne I hate to say this but is that vandalism ? Looks like a flame was involved to me. In braking heat fluid would boil and you would lose brakes temporarily before the rubber would melt and fail.

 

[clivehorridge]

There's no visible heat source, the only thing I can possibly think of (which would be a complete outsider, knowing Shayne's approach to mechanics) would be the line rubbing on the inside of the tyre, causing friction heat.

Even if it was (which I'd find hard to believe) that's a complete meltdown in the photo, not a localised hot spot....

 

[Shayne]

Passenger side front is the same but not yet leaking

And fluid doesn't look terrible ?

 

[Shayne]

There's no visible heat source, the only thing I can possibly think of (which would be a complete outsider, knowing Shayne's approach to mechanics) would be the line rubbing on the inside of the tyre, causing friction heat.

Even if it was (which I'd find hard to believe) that's a complete meltdown in the photo, not a localised hot spot....

.

That might be nearly almost a compliment Clive , perhaps you should see a doctor

It's not rubbing though there is a solid line from caliper to steering arm and the stainless runs from the arm to the chassis , i couldn't make it touch anything else even if i used a crowbar for leverage .

 

[Trevor]

What fluid did you use? The only 2 you can't mix is Dot 5 and DOT 5.1 as they are Glycol and Silicon. When mixed they can lead to component failure (never seen it myself) but wondering if this is a chemical reaction going on.

 

[StarCruiser]

I'm with Frank on this one.

1, Friction burn, rubbing on tyre = worn and split plastic, no melting or discolouration.
2, heat or anything fluid related = melted plastic away from the braid, no discolouration.

That has had heat applied that has caused the plastic to catch fire. First thought, the brake fluid has ignited in contact with the hot disc (as brake fluid can do) No, as you then said the other side is like it without brake fluid.

I think I have the answer but I'm not sure how it occurred. I've seen that before on water cooled welding leads that lost water and caught fire.

Shayne, you were welding your bumper the other day. Where did you attach the earth lead? Was it to the axle by any chance?

 

[Shayne]

You could be on to something there Rich the bumper has been on off tacked welded cut and altered several times in the past few months and the bumper is attached to the frame - as are the brake line brackets

Not sure what fluid i used Trev but it would have been what the book said , the calipers were off for a week allowing old fluid to drain and it was flushed with new fluid as well .

 

[frank rabbets]

Solved by Rich in my opinion.

 

[Towpack]

Aha! Welding. A good call there SC. The axle will be earthed to the frame through the springs (you would think) as everything else is bush mounted but throw in some paint or corrosion and suddenly a SS braided line nicely crimped at each end looks like the easiest path to earth.

 

[Shayne]

If we are all in agreement that welding killed the lines i guess i better phone Roughtrax and give them some card details tomorrow then and i will do it happily because i don't mind replacing with the same if the failure was my fault .

 

[AndyCook]

GREAT detective work guys

 

[StarCruiser]

Sorry Shayne, it would have to have been part of the circuit. As TP says, all but springs are rubber bushed but the springs will have poor contact. It all depends where the Earth clamp was as without it being somewhere on the suspension the brake lines would not be in circuit.

With your setup axle, Is there a rubber in each of the front driveshafts? Hope there is.

 

[Shayne]

No rubber in the driveshafts Rich but the brake line passes through a bracket that is i think welded to the chassis , could it be because the brake line itself is conductive stainless ?

 

[stumog]

I don't understand how this could be caused by welding.

If you were welding the front bumper the earth would be somewhere near what you are doing.

This would melt if you were welding the chassis for example and you put the earth on the chassis.

The make up of these lines are ptfe tube with a braded ss outer.

It has to have got extremely hot to.melt like this. Such as fire not even hot brake fluid would cause this damage.

 

[StarCruiser]

No rubber in the driveshafts Rich but the brake line passes through a bracket that is i think welded to the chassis , could it be because the brake line itself is conductive stainless ?

Exactly Shayne. The brake line will be the path of least resistance. It all depends on where you had the welder Earth clamp attached. If as Stu says, you had it close by on the chassis then my theory doesn't hold water. It would need to be on the suspension or running gear to do that I think. And even then there's a path through the driveshafts but not so good as the stainless brake lines. The thing is, if I'm right there may be some pitting and partial welding of components in the driveline due to other paths. Hope not.

 

[Shayne]

These bolt to the chassis where Toyota originally mounted the hidden crash bumper , the brake line bracket is welded to the other side of the chassis tube . I'm thinking my earth clamp jaws are weak so maybe i propped it against something on the wheel side of things ?

 

[Towpack]

Isn't the transmission mounted on rubber bushes/mounts? It all comes down to resistances and the easiest path to earth. Testing with a multi meter you may well get close to 0 ohms between axle and body/frame but trying to push welding current through the same path is a different story and the resistance, effectively, goes up. The braid of the brake lines act like effective earth straps, they're just not of sufficient gauge to handle the high current involved. I think the fact that both lines are shot backs up SC's theory.