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

[AllHailKingVolvo]

I had a nightmare with this when replacing the front brake hoses on my petrol 940 for its last MOT-but-one. One side was stuck fast, the union absolutely seemingly welded solid. I tried everything, heat, cold, every spray and fluid imaginable, flare ring spanners and allsorts. Eventually I had to admit defeat, purchase a flare tool, cut the union off and remake the joint. Surprisingly not particularly difficult and has been 100% trouble free since. I did purchase a reel of brake pipe in case I had to remake the entire hard line, but it wasn’t required in the end.

[eeedelli]

Originally Posted by AllHailKingVolvo

I had a nightmare with this when replacing the front brake hoses on my petrol 940 for its last MOT-but-one. One side was stuck fast, the union absolutely seemingly welded solid. I tried everything, heat, cold, every spray and fluid imaginable, flare ring spanners and allsorts. Eventually I had to admit defeat, purchase a flare tool, cut the union off and remake the joint. Surprisingly not particularly difficult and has been 100% trouble free since. I did purchase a reel of brake pipe in case I had to remake the entire hard line, but it wasn’t required in the end.

I suspect it might well come to that but the snag is that I'm not sure there's enough 'spare' pipe to do that. It's pretty straight from the body to the bracket and the alternative of having to replace it right back to the front of the car on both sides would be a nightmare, as I'm trying to do it outdoors with only the back on stands in a yard that tends to pool to a couple of inches near the front half of the car when it rains!

Do you remember which flare type it was, though? I gather there are loads of different types it could be.

[griston64]

Originally Posted by eeedelli

I suspect it might well come to that but the snag is that I'm not sure there's enough 'spare' pipe to do that. It's pretty straight from the body to the bracket and the alternative of having to replace it right back to the front of the car on both sides would be a nightmare, as I'm trying to do it outdoors with only the back on stands in a yard that tends to pool to a couple of inches near the front half of the car when it rains!

Do you remember which flare type it was, though? I gather there are loads of different types it could be.

It should be this type https://www.skandix.de/en/spare-part...-left/1057845/

[eeedelli]

Originally Posted by griston64

It should be this type https://www.skandix.de/en/spare-part...-left/1057845/

Ah ha. Yes - thanks for that. Just been looking at the different types. It looks as though those are DIN/ISO bubble flares. Would they also be 10mm x 1mm pitch nuts? This site seems quite comprehensive re: different styles, btw. http://racetrackdriving.com/tech/bra...verted-bubble/

The weird thing, looking at that Skandix page, is that the little coil of pipe and the weight of 40g doesn't seem anything like enough to reach all the way to the front wing.

When I looked underneath, I saw the pipes going off by a pretty circuitous route around the rear jacking point and fuel tank protecting flap etc but I didn't see any connectors near the back ... and even if there were, I suspect they'd be just as seized, so not necessarily helping the situation if I decided to just replace the pipes from there to each wheel arch.

Have I missed some joins that are actually there? If so, I might have another look to see whether it's just going to be easier to replace back to the joins.

Edit: I suspect I might have been right, as the ones listed there are for ABS models, which mine isn't. I assume it's still a DIN/ISO bubble flare though.

[Forrest]

There is quite a bit in the FAQ about how to tackle this, including the type of flare joint, the complexity of replicating it and the likelihood that you will end up replacing your brake lines.

https://www.volvoclub.org.uk/faq/Bra...andReplacement

I must admit my own policy has always been to leave brake work to the professionals. Quite apart from being much easier with a proper lift the results of getting something wrong are likely to be bad.

If I were in this position I would probably be tempted to try the suggestion in the FAQ of cutting the rubber pipe and getting a decent socket on that side. I think my last resort before replacing the lines would be to try an impact wrench. However, the latter did not go well for me dismantling rusted banjo fittings on a fuel line so use at your own risk.

[eeedelli]

Good grief! How did I manage to miss that in the FAQs!? I know I looked in there when I was looking at putting new seals in, before I found the calipers were scrap (on which more at another date - quite an interestingly hairy story!)

Thanks for that.

[Laird Scooby]

Originally Posted by eeedelli

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! ) 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.

I was specific about the ATF as there are lots of different types. Both those i mentioned are synthetic with a viscosity of SAE 32 so it can be used as jack oil as well if you have a hydraulic jack but also can be used in your auto box and PAS system. Being synthetic, the molecules are smaller so the creep effect is better. Mineral ATF such as Dexron II-D does not work anywhere near as well. I've not tried Dexron-III but that may work, the two i mentioned i have tried and know they work.

Once you've got it mixed 50/50 with the acetone, spray, brush or dribble it on the top of the union. Think about it - the pipe is flared and the flare meets a "cone" in the union and they form a pressure tight seal. There is no such seal from the body of the nut to the brake pipe so the WMP (Weapon of Mass Penetration = 50/50 acetone/ATF) can run downwards past the seal to where you need it, inside the threads.

As for Plus-Gas, it was ok 30 years ago but not so good these days, ditto for WD40 and many others.

[kiloran]

On the 940 there's a central manifold which the L & R rear brake line connect to - see https://weblisher.textalk.se/gcp/201...0&noConflict=1 (page 1126 if that direct link doesn't work). Possibly it's similar for the 740 as the rear brakes are the same? So it wouldn't necessarily be a big run of brake pipe that's needed. Of course, no guarantee that the unions on the manifold aren't similarly corroded to hell and back.

[Laird Scooby]

Originally Posted by kiloran

On the 940 there's a central manifold which the L & R rear brake line connect to - see https://weblisher.textalk.se/gcp/201...0&noConflict=1 (page 1126 if that direct link doesn't work). Possibly it's similar for the 740 as the rear brakes are the same? So it wouldn't necessarily be a big run of brake pipe that's needed. Of course, no guarantee that the unions on the manifold aren't similarly corroded to hell and back.

That's not just a manifold Alan, if it's non-ABS it's a brake pressure reducing valve for the rear circuits and if it is ABS, it's a copy valve. The system is essentially the same between the 7 and 9 series cars but the problem of getting the rubber flexi hose disconnected from the hard metal line in the wheelarch still remains because they meet in a bracket that holds things in place.

[darroch]

You will get many a union nut off with proper vise grips when a flare spanner fails. Atf/Acetone Freeze type sprays and heat are your friend.
If all fails and you have to cut anything, then cut close to nut and use a flat type hex socket, which gives more puchase than ring spanner. Grinding past can help under the socket and over the union nut for even more grip.