I replaced the right rear caliper because it was leaking and braking was getting poor. I bled all 4 wheels until no more bubbles. After all that the brake pedal is softer yet, and now the brake failure light is on. Where did I go wrong? The master cylinder was a rebuilt put on last August with no problems.

Help!

You don't say how you bled your brakes (pressure? pedal?) But on the off chance that you didn't bleed in the recommended sequence, the following is from a "canned response" I use for these questions.

Since the 240 has two separate hydraulic systems, the recommended sequence bleeds each system separately.

The upper two piston chambers on the front calipers form an inverted "U", with a single bleeder at the highest point. The lower two piston chambers form an upright "U", with bleeders at the two high points.
(See illustrations in Bentley, p 500-1 and Haynes, p 9-13)

Either A or B can be done first:

System A:
1) Left rear
2) Left front - Upper piston chambers (single bleeder, top)
3) Right front - Upper piston chambers (single bleeder, top)

System B:
4) Right rear
5) Right front - Lower piston chambers (inner and outer bleeders, either first)
6) Left front - Lower piston chambers (inner and outer bleeders, either first)

P.S. You also don't give your car's year ( it's an easy pull-down), but this sequence is for non-ABS 240s.

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Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.

Excellent information in the other posts.

Some trivia to add - If the pressure bleeder comes with two cap gaskets for the round cap, you may need to use BOTH of them. The cap was deeper than the reservoir threads on my '91, so the cap hit the top of my reservoir before sealing. I had a pint of brake fluid on my garage floor before I realized what was going on.

If you have air in the pressure limiting switch, aggressive use of a pressure bleeder is your only hope, and it may take several attempts to get it all out.

I don't know if this is the case for Volvos, but I have heard that on some cars, once the brake failure light comes on, you have to manually re-center, or replace, the pressure differential switch to get the light to turn off.

I don't know if this is the case for Volvos, but I have heard that on some cars, once the brake failure light comes on, you have to manually re-center, or replace, the pressure differential switch to get the light to turn off.

This was the case for older/vintage Volvos, until they started using a non-locking electrical piston switch in the pressure differential switch (aka Junction Block). I believe the change was made to the non-locking switch in 1975 with the start of the 240 production. All of our 200/700/900 and newer vehicles should re-center and reset themselves during a firm applicaiton of the brakes once all air has been removed from the lines. The prior vehicles had a detent in the sliding piston that would catch on the spring loaded electrical switch contact. Resetting the brake failure light required unscrewing the electrical switch where it mounted into the pressure differential switch, recentering the piston (press on the brake pedal and hope you've got all the air out), and then screwing it back in. For a picture of the older Junction Block and the switch system used in it, check out a previous post: here.

I'm glad my brake line metal composition error was pointed out. It's also further testimony of Volvo's commitment to the longevity of their vehicles. However it's still a good idea to flush the system every two years since there are steel components in contact with the brake fluid (the largest ones probably being the caliper channels, and in close proximity to the pistons). Just think of a brake fluid flush as being the final maintance step after you've changed your engine coolant (since both are supposed to be done at 2 year intervals).

God bless,
Fitz Fitzgerald.
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'87 Blue 240 Wagon, 251k miles.

You still have air in the brake system. When I changed my first 240 rear caliper, I went through 2 quarts of brake fluid trying to get the last pocket of air out. I got it to the point where the pedal was hard, but there was still enough air in the system to illuminate the Brake Failure light. -then I drove on it for a few weeks, bled the system again, and the last of the air finally came out.

The Brake Failure sensor is simply a pressure differential switch. Since you have two seperate hydraulic brake systems on the car, it looks to see if one system has more pressure than the other (the circuit with less pressure is due to the air compressing). When there's more pressure in one circuit, it slides a pressure switch left or right and closes an electrical connection.

Personally I find "bleeding" the brakes on a Volvo to be a frustrating task, -especially on the non-ABS models which have 8 or 10 bleed screws. I spent the $50 for a Motive Pressure Bleeder (available from IPD or FCP Groton). Now, I toss in a quart of DOT 4 into the power bleeder, pump it up and open the bleeder screws one at a time until clear fluid comes out. By the time I'm done, I've used almost the full quart and I've got clean fluid in the lines and no air bubbles. I can't tell you how many hours this device has saved me. Worth every penny!!! -and no more Brake Failure lights.

FYI, a brake caliper will last almost indefinately, provided the brake fluid is clean. The auto manufacturers, including Volvo, advise flushing the brake fluid ever 2 years (not just bleeding it but flushing it clean). DOT 3 and DOT 4 brake fluid is almost chemically identical to Alcohol and it disolves moisture (it literally sucks the humidity right out of the air and disolves it in the brake fluid). The water is still chemically active and it begins to rust the steel brake lines from the inside out. The rust particles brake free of the lines and become suspended in the fluid, -thus changing color and causing the calipers to lock up (they're precision components and assembled in a clean room).

Additional information for anybody who is changing a brake caliper in the future:
If push the brake pedal down about 2 inches and brace it there so that it can't return upwards, you'll move the Master Cylinder forwards in the bore past the two resivouir ports and effectively "close" the brake system. This removes the atmospheric pressure from the system on the Master Cylinder end, and thus keeps the brake fluid from running out the open line when you disconnect a caliper. Think of it like you are dipping a straw in a glass of water. If you put your finger over the top, you can lift it up without the water running out of the straw. After you've got the new caliper installed, you only have to bleed a little bit of air instead of a lot. This also helps prevent air pockets getting trapped in the distribution block and the pressure limiting gates.

God bless,
Fitz Fitzgerald.
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'87 Blue 240 Wagon, 251k miles.

Good post, but an error (lucky for us) in the 4th paragraph—
", . . .and it begins to rust the steel brake lines from the..."

We are lucky because our brake lines have been made of a copper-nickel alloy starting with the first 240s. I googled the following some time ago, but have since lost the URL.

>>Efforts to achieve a metallurgical solution to the corrosion problem continued. Volvo began the use of 90-10 copper-nickel ("Cunifer Alloy") tube in their 1976 model vehicles and have been using it since. Figure 1 shows the installation at the master cylinder in a 1990 model Volvo. Audi began using this material in 1990. The other European cars using this material are Porsche and Aston Martin.2

Users of copper-nickel brake tubing in addition to Volvo include world-class vehicle manufacturers like Rolls Royce, Lotus, Aston Martin, Porsche and, most recently, Audi. Copper-nickel is also used in military, fire fighting and other heavy vehicles.

Properties of Copper-Nickel Brake Tubing

The copper-nickel alloy used for brake tubing typically contains 10% nickel, with iron and manganese additions of 1.4% and 0.8% respectively. The product conforms to ASTM B466 (American Society for Testing and Materials), which specifies dimensions, tensile strength and yield strength. Formability and internal cleanliness conform to specifications SAE J527, ASTM A254 and SMMT C5B (Society of Motor Manufacturers and Traders). Also, the alloy meets the requirements for pressure containment, fabrication and corrosion resistance for ISO 4038 (International Standards Organization) and SAE J1047. <<
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Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.

I second the recommendation on the Motive bleeder. eEuroparts has it for $39.90 shipped (to the lower 48 states). Best $40 I've spent so far. It brought a bit of firmness to the brake pedal of my 760. Of course it turned FLUSHING the brakes on a non-ABS 240 (8 bleeder screws: 3 screws X 2 front calipers + 1 screw x 2 rear calipers) a breeze.

The only thing I'd really want to add to your post on bleeding is that you need to bleed the non-ABS brakes in a specific order. By the time I got to the last lower chambers on the front calipers I was getting clear fluid almost as soon as I opened the bleeder screw.

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alex