How to Bleed Brakes correctly and other brake info

[Johnno]

I've just spent the past week plus sorting out the brakes on my 740.

I replaced a faulty right front Bendix caliper (exchange unit) and master cylinder (2nd hand); the big problem was 'bleeding' the system so all would work properly and feel like 'Volvo brakes' again.

Now I have it all working correctly, I thought I'd post to the forum for others that may have some brake work to do.

I did a fair amount of trawling the web for info and came across one very useful site in the UK
http://www.volvoclub.org.uk/faq/Brakes.html
I also converted their webpage into a Acrobat file for download here (I even got all bookmarks working)

'Dual Line Brake Circuits' have been standard fitment on vehicles for several decades now; the idea is that if one circuit fails, then the vehicle continues using the remaining circuit.

There are two different 'Dual Line Brake Circuits' used on Volvos;

• 'Dual Triangulating Brake Circuit' as fitted to the earlier 7 series Volvo's (and earlier model Volvo's).
• 'Front/Rear Dual Line Brake Circuit' as fitted to later model 7 series (with ABS, and later models) and follows a fairly standard brake bleed method.

My car is an '85 model and has the 'Dual Triangulating Brake Circuit'  fitted; so below is the bleeding procedure I eventually used to get it all working correctly.

With the 'Dual Triangulating Brake Circuit' system, there are 2 circuits with each controlling '3' of the 4 wheels;

• Upper Circuit controls right and left upper brake cylinders on the front callipers, and the left rear calliper, with fluid coming from the rear chamber/reservoir of the Master Cylinder.
• Lower Circuit controls right and left lower brake cylinders on the front callipers, and the right rear calliper, with fluid coming from the front chamber/reservoir of the Master Cylinder.

You'll need - approximately a litre of new Brake Fluid (DOT 3 or 4, not 5), 2 glass bottles, and 2 x 1mtr lengths of approx 1/4" (6mm) ID clear vinyl/plastic tubing to fit over bleed nipple and collect 'waste' brake fluid (also makes less mess); plus an 11 and 9 mm open-end spanners (advisable to use a ring spanner to initially crack the bleed nipples). And with this system you really do need a helper to 'pump' the brakes whilst you do the actual bleeding.

Due to the way the Master Cylinder actuates; it is necessary to bleed the "Lower Circuit' first in the following sequence, and it is also absolutely imperative that one bleed nipple on the Upper Circuit is 'cracked open' in order to bleed the Lower Circuit correctly - if you don't crack one upper bleed nipple, then you spend hours 'not bleeding' the lower circuit 

Must do - Fit a length of tube over one upper bleed nipple (either will do) and 'crack' the bleed nipple open just a touch so that pressure isn't contained in the upper circuit, but not so much that fluid gushes out when bleeding the lower circuit; put the other end of tube in glass bottle/jar and put some brake fluid in so that the end of tube is immersed (this'll stop air getting back in the upper line).

Remember to keep an eye on the fluid level in the Master Cylinder - keep topping it up!

Lower Circuit bleed order - right rear, left front lower and then right front lower. Fit the tube over the relevant bleed nipple and place other end in the bottle/jar.

Have your assistant 'pump' the brake pedal a couple of times, and then 'hold' pressure whilst you open the bleed nipple; once the pedal has 'gone to the floor', close it and repeat pump, hold and bleed procedure until fluid is clean and free of 'air bubbles', then close off the bleed nipple, remove tube and move to next wheel in sequence.

Once you have bled the 3 lower circuit cylinders; close off the upper bleed nipple you cracked to relieve upper circuit pressure. Remove tube and bottle from the upper circuit nipple and put it aside (you only need the second tube and bottle for Lower Circuit bleeding, not for the Upper Circuit bleeding).

Upper Circuit bleed order - left rear, left front upper and then right front upper. Fit the tube over the relevant bleed nipple with the other end in the bottle/jar.

Repeat the 'pump, hold and bleed sequence for each of the Upper Circuit cylinders until fluid is clean and free of air bubbles.

Remember to close of each nipple in turn before removing tube and going to next wheel (you don't want any air sneaking back into the line).

That's it; if you followed the sequence you should have a solid feeling brake pedal, and awesome Volvo brakes again.

Clean up is easy; just rinse off brake callipers, wheels and ground with water - don't forget to replace the dust caps on each nipple.


Above applies to Right Hand Drive vehicles.

2 weeks after getting it all right, the increase in pressure due to the lack of air bubbles in the system resulted in the left rear caliper 'blowing' its seal - inconvenient, but easily fixed by taking both left and right rear calipers to Perth Brake Parts for reconditioning $125 each - should be ok for another 20+ years 

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