How to undo seized brake-line to hose nuts? Any ideas?
 

Hi all,

I'm at my wits' end with this one!

I've had to replace the rear calipers on my 740 estate. All went well until trying to remove the old hoses from the brake lines. The nuts are absolutely solid, having been on there for 32 years.

They also appear to be brass and even the use of a proper split-ring brake spanner resulted in turning over the corners.

I've since bought a special locking wrench (4LW size - https://www.irwin.com/tools/locking-...cking-wrenches) which is designed to clamp on to the alternate triangular faces of the nut so as to avoid slipping over the corners and it doesn't slip but I still can't shift them.

I've tried heating the metal ends of the hoses to try to break any rust seal and tried to get some 'plus gas A' up there (though tricky because of the angle - hose pointing downwards) but to no avail. Even putting a lever between the grips and the 14mm spanner on the hose just ended up trying to twist the bracket.

I had a similar problem with one of the O/S/F pipes when replacing calipers there a year or two back, so I had to dismantle back to the master cylinder and take it into my local motor factor who made up a complete new pipe. It wasn't too bad there, as it was the shortest run. However, that's absolutely the final resort on the rear as, with split diagonal circuits, both pipes individually run the entire length of the car and would be a nightmare to remove and replace.

Does anyone have any ideas?

Ta,
David.

I know very little about hydraulic lines on cars but would one option be to cut off a section of the hard line, install a fresh union, and extend the flexi to meet it?

Unfortunately not - the hose fits through the bracket and has a stepped end that stops it from going beyond the normal position. Additionally, I have no method of creating the required flared end for the metal pipe (though I think my cousin might have a tool for that ... but I'm not sure whether it's the right version as there are many different types of flare, I gather).

I am wondering whether I'll have to cut through the metal section of hose to be able to get some plus gas up from the 'inside' and try to shift it that way ... but it's high risk.

Thanks anyway.

Heat and reheat, interspersed with application of penetrant. Also try and tighten the connection, then loosen, sometimes that will break up the corrosion and allow penetrant to enter.
Many swear by a mix of ATF and Acetone as a penetrant, more effective than off the shelf products.

Yes I suspect I'll have to try more of what I've already been doing, though it hasn't done much, so far. The snag is that the female end points downward (and the bracket and spring clip are in the way too) so it's pretty much impossible to get anything up there into the threads.

Thanks for the thought.

Be very careful when heating brake lines as they can explode in a big way.

It's not good practice to cut lines and join them either.

Yes - I've heard of that happening but I've already drained the fluid out completely and the caliper end of the hose is open, so it shouldn't build up any pressure... but good advice, nonetheless.

Ta.

D.

Use a razor blade to cut the old rubber off to the union and there's no chance of exploding molten rubber then :)

The 50/50 acetone/ATF mix is the way i would go as well. Use one of the following, Carlube ATF-U or NAPA MV ATF and if you can't find pure acetone locally, buy some nail varnish remover that says' it pure acetone (some have oils in for the fingernails apparently) and mix in 50/50 proportion.
Shake well in a sealed container then brush, dribble or spray on and leave to soak, repeat a few times overnight with another dose shortly before trying to shift it.

Make sure you keep the container sealed to prevent the acetone evaporating and shake before each use as they two separate easily. With this mix, it will eventually shift.

If using any sort of tool with a movable jaw (locking wrench as you linked to, adjustable spanner etc) make sure the movable jaw is in the leading position for turning as it reduces slip and increases grip. For example, an adjustable spanner trying to undo (anticlockwise as viewed) a nut, the movable jaw will be underneath the nut and the fixed jaw above the nut as you look at it. As you try to turn the nut anticlockwise, the handle will help push the movable jaw onto the nut. Same goes for Mole Grips, Vise Grips, the Irwin Grips you linked to and so on.

*** EDIT *** This YT video puts my words into (not very) pretty moving pictures : https://youtu.be/qsHomDTTRXo

Thanks for that. Yes, I agree about the direction of rotation. Mind you, I've already found that space is very limited and I can only really get the locking grips to fit in one orientation as the closure of the handle fouls the backplate on the wheel. I tried rotating 60 degrees to get on the next flat but then it fouls the wheelarch. I'll have another look when I get to it, assuming the weather holds.

I'm not sure what I've got in the garage re:ATF. Does the brand really make that much difference? Surely they should all be to the same spec as ATF anyway shouldn't they? If I have to order in a specific one then that's going to delay the job yet again.

I suspect that the main problem, however, is that the female metal end of the hose points downwards, with the pipe nut going up into it and the interface of the two is difficult to reach because of the spring clip and bracket completely blocking access. How on earth do you manage to run the dismantling fluid upwards into there (short of turning the car on its roof! :rolleyes:) I know it's supposed to 'creep' (up to a point) but that seems a bit ... er... 'optimistic' in this case. I thought that about the PlusGas but at least I was able to spray that in vaguely the right direction.