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seized brake line union??

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Old Apr 16th, 2018, 20:48   #21
Laird Scooby
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Did you bleed the front calipers as well Ted?

Sometimes it's worth undoing the lower caliper slide so the caliper can be lifted up so the bleed nipple is uppermost, this helps get the air in the caliper to the top of the piston in the caliper and out through the nipple.

As for the back end where you changed the pipe, had it blocked up inside? I'm wondering if the secondary piston in the master cylinder has become stuck due to not being able to move because of a blockage.

The ABS system can be tricky to bleed, some are easy, others can be a right royal, ocean-going pain in the ar5e though.

If it's any help, Pg17 onwards in this pdf might be useful :

http://www.myvolvolibrary.info/Tech_...es_service.pdf

Whatever you do, don't be tempted to "live bleed" it with the engine running, i've heard tales of FUBAR modulators and similar horror stories as a result.
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Old Apr 16th, 2018, 22:19   #22
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Thanks Dave, the pdf was informative they say 29-44psi I was only using 10psi! totally forgot you said go up to 40 on a previous post! So that's why the fluid was only dribbling out from the back brakes. Doh!!
I replaced the hose to the front left side not the back end but bled from all four corners!
I did think of live bleeding but something told me not to!
Will have another go tomorrow at higher pressure!!
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Old Apr 16th, 2018, 23:44   #23
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Good luck Myron! Hopefully higher pressure will improve matters. The "clicking" from near the master cylinder might be the brake pressure reducing valve in the rear lines, apparently there's a pressure differential switch built into it (if one side pressure is lower it slides an internal spool which operates a switch) that operates a warning light on the dash, might be that's a clue to where the sponginess is coming from as well.
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Old Apr 17th, 2018, 19:00   #24
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No luck here! ran through a bleed as per the instructions @35-40psi, flow was stronger but no bubbles. I let each corner run out about 250ml, still the squish before the brakes harden when the engine is running.
They stop the car fine on a test drive, can't really say it's any worse than it was before except a lot smoother due to new discs and pads.
Maybe it was like that before and I'd gotten used to it? maybe I'm looking too hard for problems?
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Old Apr 17th, 2018, 20:10   #25
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Silly question but have you checked the adjustment on the pushrood between the brake pedal and master cylinder via the servo?
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Old Apr 17th, 2018, 23:43   #26
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Hi Dave, no I haven't cant see how that would account for the squish?
One thing that has come to mind is that before doing any work I noticed that when stopped at the lights say, and holding the car with the brake, the pedal would hold position for a while then slowly sink a bit, hold that position then sink again. Master cylinder??
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Old Apr 17th, 2018, 23:56   #27
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Quote:
Originally Posted by Greybeard View Post
Hi Dave, no I haven't cant see how that would account for the squish?
One thing that has come to mind is that before doing any work I noticed that when stopped at the lights say, and holding the car with the brake, the pedal would hold position for a while then slowly sink a bit, hold that position then sink again. Master cylinder??
I think you've just found the problem Myron! That's fairly typical of a going/gone master cylinder.

As for why the pushrod out of adjustment accounting for the squish, inside the master cylinder there are two pistons, connected mechanically by a spring but hydraulically as well. If the first piston can't move through its full range of travel because of incorrect adjustment/wear in the mechanism between the pedal and pushrod, there's a chance the spring is the only connection between the front (primary) and rear (secondary) pistons with the front piston being nearest the driver. Usually when the secondary piston moves, besides moving brake fluid down the pioework, it displaces fluid into the void between the two pistons.

I'm not explaining it very well but i think you see where i'm going with this?
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Old Apr 18th, 2018, 00:49   #28
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Thanks Dave your description makes sense! Given the age of the car there may be corrosion in the bore, repair or replace?? Maybe source a repair kit and rip it apart to see?
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Old Apr 18th, 2018, 11:15   #29
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When i first read your post (in my slightly gormless, just woken up state) i thought "Yeah, that'll work!"

Difficult one to call, with the age of the car it's often easier to just replace the M/Cyl with another known good secondhand unit. Rebuilds aren't always as successful as we'd like to think.

That said, many have been rebuilt over the years very successfully. I think you'll have to do it on a "suck it and see" basis, get a rebuild kit, strip and clean the M/C and evaluate it. If it's all good, polish the bores and then fit the seals and give it a whirl on the car.

If it turns out to be horribly corroded then obviously you'll have to go for a new or reconditioned unit.

Some light corrosion of the bore can be polished out using this stuff :

http://www.halfords.com/motoring/pai...bbing-compound

If you can get a long bolt, piece of stud bar or similar in the drill and wrap a lint-free polishing/cleaning cloth round it (microfibre cloths are good) and smear some of this on it, stick it down the M/C and turn the drill on it should clean, smooth and then polish the bore to a highly smooth surface.

It's what's known as a "diminishing abrasive" so starts off relatively coarse and gets smoother the more it's worked. I've used it in suspension hub knuckles to polish the bearing housing prior to fitting the new bearing.

From this :



to this :



It removed all the score marks from removing the old bearing, cleaned up the surface and then polished the surface to almost a mirror shine in about 30 seconds.

Use some meths, brake or carb cleaner or similar to clean it through after to make sure the compound is completely removed. Use some fresh brake fluid to lube the seals as you fit them to the M/C piston and a little more to help them slide into the M/C when it's ready to be refitted.

It's possible it won't get rid of the longer brake pedal travel, that might still be down to the pushrod adjustment between the pedal and M/C but at least you'll know the M/C is sound after. It should get rid of the squelching sound and that "sinking feeling" though.
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Old Apr 18th, 2018, 15:50   #30
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Wonderful stuff Dave! I'll give it a try and see!
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