850 rear flexi-brake hoses. How to replace?

Redneck · Post by **Redneck** » 23 Oct 2018, 15:49

Has anyone ever seen or heard about the rear brake line hose (the one impossible to get to) burst or fail in Volvo 850? I replaced other 3 brake line hoses 6 years ago, but this one is still there and it is the original Volvo now 22 years old. Should I be worried? I am worried. Can I wait 5 more years? The problem is, I don't have a suitable repair place to do this quite problematic repair right now. Where the car has been driven for the past 22 years, there were no salty roads and it was parked in a building garage, so this should help extend the life of the rubber hose I hope. What do you guys think? If I really needed to, I would try to find a place to replace it.

What will happen if the rear rubber brake hose fails? Does the braking fail in all wheels, or just the rear? How to rescue myself from that situation in case of hose failure? I read that in some cars the master cylinder has two chambers, one for the front and another for the rear brakes, so if the rear brakes fail, there is still enough pressure in the front calipers to apply front brakes. I am not sure if what I read is true because when I bleed the brakes, the pedal goes to the floor immediately after opening the bleeding valve at each caliper.

Post by **misha** » 23 Oct 2018, 16:29

I doubt that it will fail...there is no stress on it like on front wheels(they don't move) and plus....that what you see is just a rubber shield,the main line is under it.
I tried to cut one of these from old 244 caliper we had in the family long time ago just for curiosity....and i barely managed to cut it.
There were few examples where they can be clogged,but very rarely and that was on front lines.
Mine are still original too.

Redneck · Post by **Redneck** » 23 Oct 2018, 16:42

Misha, thank you for that assurance. This rear hose has been on my mind for the past 6 years since I started the repair hobby. I replaced and rebuilt nearly everything in this car except for replacing this hose. One day, I will get to it. I don't know why Volvo put it there.

Post by **misha** » 23 Oct 2018, 17:02

I don't even think about them.

I really don't see how they could break unless they don't become physically damaged.

Post by **erikv11** » 23 Oct 2018, 17:17

I've replaced a couple of those because I was in there already, but I've never seen (maybe never heard of?) one of them fail.

Post by **mecheng** » 24 Oct 2018, 17:55

I’m in the same boat, original hose and no desire/will to tackle it. They will probably be seized to hell. Yes you are correct there is a proportioning valve. And yes the hose you see is just a shield. If the inner hose leaks the outer hose should contain the fluid I believe.

I’ve replaced my front hoses. I’ve had a brake line fail on my old Acura but that’s because they used cheap steel. I was able to drive home with fluid I bought from the gas station

Redneck · Post by **Redneck** » 24 Oct 2018, 20:00

I hope Volvo 850 has such proportioning Valve. I read that the proportioning valve is only used in systems where front brakes are discs/rotors and rear brakes are drums. This valve is needed to ensure that both front and rear brakes engage at the same time. But I see that such proportioning valve is available for purchase for Volvo 850, so It may have it.

Post by **mecheng** » 25 Oct 2018, 10:56

Maybe it doesn't have the prop valve, however I believe all cars built since the 70s or 80s have a dual circuit master cylinder like this:

https://www.thoughtco.com/symptoms-of-m ... re-4154925

Post by **abscate** » 25 Oct 2018, 11:16

I think ABS did away with proportioning valves, since brake pressure can be independently controlled from brake pedal pressure by design

Post by **JimBee** » 25 Oct 2018, 21:55

There are 2 problems with the rear brakes that eventually cause hair loss on the frustrated P80 owner. The main one is the seized brake line fitting at the rear wheel calipers. Sometimes you can get the left side fitting to loosen, the right side is almost always extremely hard to impossible to crack loose.

So, what to do? When I ran into this problem for the second time, I decided to replace the system of rear brake lines with new ones. As you acknowledge, the brake line for the rear, right side has a flex hose that cross over the suspension arms. The fittings on that hose are seized worse than the fittings at the caliper.

There is some good news. One hard line brings fluid to the rear of the car. It goes into a flex hose and that hose goes into a splitter that exits into 2 hard lines—one to each rear wheel. On the P80's, those hard line fittings, on the exit side of the splitter, always seem to crack loose quite easily with an 11mm open end wrench or small vice grip or the "v-jaw" locking plier linked below. (I'm really glad I have that tool. I have the 4" which is the handiest and the next size up which is helpful on the front lines.) And with the left rear wheel off, the splitter fittings are pretty easy to get to.

So, disconnecting the hard lines, you can take the left side rear caliper right off the car with the hard line attached. Take it to your work bench and maybe with some heat on the caliper while holding force with a wrench on the fitting, you can break it loose. With the line off, you can slip a box wrench over the free end and down to the caliper. Or, better, use the v-jaw pliers.

The second problem: You can disconnect the hard line for the right side at the splitter, also quite easily. But that line goes into the flex hose and I've found it impossible to crack the hard line fittings loose at the flex hose. Even if you could (possible on a garaged vehicle? Maybe), you still have the fitting at the right rear caliper to deal with.

I gave up and just replaced the hard lines and the flex hose. I've been meaning to post a writeup of this. The hardest part of the replacement is the 2 mounts that hold either end of the flex hose. Again, on a garaged car, those might not be too hard to remove.
Each mount is held to the transverse suspension arms by one T-25 screw.

I changed those lines out on 3 850's, which I plan to keep for a long time, so I wouldn't have any more headaches with seized fittings. Total cost for the lines is only around $30.00 if you use the Centrics brand flex hose.

If it doesn't rain here tomorrow I'll post some pictures and specs on what you need to do the job. It's doable.

To get at the cross over flex hose mounts, I jacked up the rear, supported with blocks and removed the shock absorbers to get the longest drop on the suspension arms. You don't need to completely remove the shocks, just loosen the top nut at the mount and pull them off the bottom stud. If your shocks are original they'll be seized on the stud (even replacements seem to seize fairly quickly because of the tapered bushing). I used a 3-claw puller (free rental from O'reilly) to break them loose.

If you're going to tackle this project, the part to begin with is the flex hose mounts. Once you get those 2 screws out, (assuming you have the replacement parts ready to go), things bolt together real easily. If for some reason you can't remove the screws in the flex hose mounts, that's a project stopper. Working on the ground I was able to do it. If you can get the car on a lift it would be easier. Use a small 1/4" ratchet and a NEW T-25 bit (applied firmly but patiently to avoid rounding out the head in an awkward place).

Plug the splitter: Pick up a couple of short 10mm x 1 bolts and wrap the threads with teflon tape and screw them into the splitter to limit fluid loss (you don't want air in the ABS block).

V-jaw vice grip:
https://www.zoro.com/irwin-vise-grip-lo ... &gclsrc=ds

850 rear flexi-brake hoses. How to replace?

Re: 850 rear flexi-brake hoses. How to replace?