delboy

Ok, i know this isnt toy related but its close ot my heart. My GF's brakes pedal is going to the floor on her volvo. Checked the back brakes and they were in bad shape. Put on new shoes, new cylinders and cleaned and greased all the right places. Bled the system and still the same problem. Both front brakes and the rear left brake are working but not the rear right brake. I have naroowed it down to either the master cylinder or a blocked line. If anyone has any suggestions i'd be v. grateful. It's 240 euro for a new cylinder and cant find an aftermarket one!
Delboy:pat:

keisur

I would think if a line were blocked it would get stiff when depressed since the pressure would build up. Your problem sounds like you are losing pressure somewhere. does that car have an LSPV? if so, that may be the culprit and just needs to be bled. but maybe when you said you bled the system you did that thing too. Is there any fluid leaking around the master cylinder or in the cab where the brake pedal shaft dealy goes through the friewall? that would indicate a leaking or bad master cyl. the maybe it's the wheel cylinder in the stated wheel. is there fluid leaking there, wait, on that, are the rears disc or drum?

Yoda

Just a few ?? to try to narrow it down:

What year and model Volvo is it? Does it have antilock brakes? When you bled the system, did you get fluid/air coming out of all 4 wheels? Did the rear brakes get adjusted after the install? Does the park brake seem to function at both rear wheels?

Victor

Sounds like a bad master cylinder - the seals are worn inside the bore and fluid is escaping around the seals and not being pushed into the brakelines.

delboy

Yoda, It's a 1990 volvo 440 si. No ABS! Got both air then fluid out of all four wheels. Park brake works perfectly and adjusting screw seems to be ok! Can you bleed the master cylinder? Bloody Haynes manual doesnt tell you anything and hasnt got any pic of the MC!

I'm hoping you are wrong Victor. A new MC would probably cost more than the car is worth!
:pat:

Victor

As long as its only the o-rings and the bore isn't scored you can buy new o-rings.

Yoda

You can bleed the master cylinder by pushing down on brake, and crack open the brake tubes coming from the master cylinder (just like at the wheel cylinders bleeder valve. Do you have 2 or 4 tubes? Seems odd you would only loose 1 wheel braking.

The US versions do not list a 440 series car, we show 240, then 740 in the parts book

This web site has lots of troubleshooting info:
http://www.mpbrakes.com/troubleshooting.htm

delboy

Thanks Guys! Think i'm gonna have to dismantle the MS. Which is a pain in the ass, cause there is absolutely no room in the to do anything. Everything seems to be packed into one corner. Gues i'm just used to having lots of room under the hood and not having th jack the vehicle up to climb underneath.

Victor

Whenever you buy a master cylinder it comes with 2 hoses and fittings to bleed the MC. You hook up the fittings and hoses, slip the hoses back in the fluid area of the MC, and compress the piston in with a screwdriver. I wonder if you can buy that kit somewhere to see if it is air in your MC.

delboy

I've never seen one of those Kits victor, so i'd say they're hard to find here! I found something in the link Yoda posted about troubleshooting. You can disconnect the pipes from the MC and block them with plugs. Press the brake and if its ok, then its one of the lines, so just reconnect the lines in turn to see which one is bad! Might give it a go tomorrow! Too dark now. Tired.
Thanks again.

Biohazard

FYI - I've had issues with master cylinders. If you let 'em leak too long, they'll eat out the diaphragm in you power brake booster (depending on where the leak is). And I'll tell you right now, if you think replacing the MC is a pain, try your brake booster -- O!!M!!G!! Great (but maybe destructive) way to find out if you got a leak, pump the pedal and if you lose fluid, you got a leak. Granted it has to be a bad one to notice it this way.

Also, make sure you bleeding the brakes properly. Not to second guess your auto skills, but if you don't close the bleeder before you lift the pedal, you suck air right back into the line.

My .02

delboy

Took the drums off yesterday and checked to see whats working. The cyliner on the RHS rear seems to be getting a little fluid but not enough to push the shoes . Disconnected the shoes just to make sure and still very little movement. If its getting some could it still be the MS or could it be a blocked line? Getting tired of it now and it keeps raining so i cant do anything with it!
:pat:

Biohazard

My vote would be "no" concerning a blockage in your line. KEISUR is correct in that if you had a blockage in your main line, your peddle would be stiff (as in wouldn't go down much at all). If you had a blockage in a specific line such as your RHS rear brake, your brake peddle would work fine, but your vehicle would pull to the opposite side of the blockage. No pressure would be applied to that brake. Also, if you had a blockage, you would know because you wouldn't be able to bleed the brakes.

When you press the brake pedal, you push the brake fluid forward in the lines which pushes the the pistons out in the rear wheel cylinders which in turn pushes the shoes against the drum. In the case of disc brakes, the movement of the fluid forward forces the calipers to pinch down on the brake disc. Having said that, if you have air in the line, when you depress the pedal, instead of forcing the brake fluid forward, you compress the air in the line (which compresses easier than the brake fluid). This is why the pedal goes to the floor if you haven't bled the brake lines.

I hope that maybe explains things a little bit. Another .02, I guess that makes .04.

delboy

What you said Bio makes perfect sense. You know when you've analysed something so much it becomes even more confusing than it actually is. Even when i pump the brakes they dont get any harder which would dispell the air in the lines theory wouldn't it. Guess it must be the master cylinder. Bad news for the GF. I'll still take it apart though, just to check! This is good practice though for if i ever have trouble with my own brakes again. Touch wood, i don't! I'll do it tomorrow. Off to the pub soon!
Cheers!

(hic!)

delboy

Well now! Doesnt that just beat all! I'd totally given up on fixing the brakes myself because of all the rain lately and no room under the hood. So today we took the car slowly down to a car wash with underbody wash so it would be clean for the volvo garage. Anyway, the GF said th ebrakes felt slightly better, so i got in and they were perfect. Well the shoes need to wear in a bit. Jacked up the offending side and checked the wheel with the brakes pressed. Not a budge. I guess there must have been air in the system which worked its way out. Not gonna think about it. Anyway thanks for all your help guys!
Long live Toyota!

Delboy