Rear Right brake problem

[DanielPeeters]

Hello Thanks for letting me in this forum

Just new to volvo brand but already had some long way past experience in "car" mechanics.

Having had company cars for the last 20 years I had no need to get may own hands dirty in getting my cars on the road.

Last year i got myself a 2004 XC90 2.5D to use for some towing and holiday use because we are a family of 6 this car was just ok for the job, with new emission regulations in Belgium these cars are getting cheap....

so last year the garage sold me the car with no real apparent troubles exept the front wheel triangles and inner tie rods that where worn.... i discoverd later - always surprised to see how garage sellers can get thru technical inspection with cars in this conditions "almost a danger on the road"

so to make the intro and the story short. this year I replaced all the worn parts, wheel hanging and inner tie rods and rear brakes + parking brake. The car is only used very rarely and before doing all these replacements i noticed that after driving a few km, one disk brake was still rusty and the car pulling to one side when barking. I was thinking stuck caliper and i will look at it /fix it when i replace the brakes.
i used a c-clamp to put back the caliper that moved quite correctly i also cleaned the complete brake unit so al could be moved "freely" - after als the works where done and some test driving the disk brake was still rusty and car still pulling to one side. That break doesn't seem to work. I can rotate and pull out the caliper so it's not stuck and when I press the pedal it is not coming out.
i removed the bleeding valve and tried braking but no oil comes out not even a drop....

so what might i need to look at? all ideas are welcome. thx

[pgill]

Daniel,

Welcome to MVS

Based on your post it looks like something is blocked.

Possible causes

1. Flexible brake hose that attaches to the caliper has collapsed and needs to be replaced (not expensive to fix)

2. Hard brake line is damaged (crushed) and not allowing the fluid to pass

3. ABS module is broken for this circuit (this will be expensive to fix)

4. Master cylinder is broken (this is unlikely because it should affect two brakes (Rear Right and Front Left)


Questions

Q1. when you compressed the piston did you open the bleed screw or push the fluid back into the master cylinder?

Q2. if you go for a short drive (about 2 KM) and check the front brakes are they about the same temperature, spray some water on the rotors, the rotors should be over 100C and at the same temperature (if one side is hotter post here which side)

Q3. have you replaced brake hoses before? if yes I would start there. If no then contact a mechanic to replace the hoses

Good luck

Paul

[DanielPeeters]

Hello Paul, thx for your reply,

Did some More checks today.
But in andere to your question about opening bleeder valves before pushing the piston back? No I didn’t. But I noticed the problem before servicing the parts…. So it was present before I did anything on the brakes….
My further investigation took me to the next conclusions.
I checked by removing the flexible tube to the brakes and pushing the brake - no oil and no spongy pedal…
Did the same on both connections on the master cylinder unscrew slightly and push the pedal - oil comes out…
Did the same on the 4 outlets of the brake control module one of the 4 has no oil coming out….
Took the BCM out and blew som pressurised air in it the all seem to let thru some amount of air…. Not sure if the one that was clogged did not al of a sudden unclog…. I can try tomorrow to put it back…. The aluminium part seems not to be serviceable…. But no idea what can go wrong in there…. Hopefully it is unclogged and it wil work again… to be continued

[pgill]

Daniel,

The Brake control module that you identified is the ABS module.

As I wrote above this will be expensive to replace. (see item #3)

The approach that you took to find the blockage makes sense.

Note: you will need to carefully bleed the brakes because you introduced air into they system by removing the lines at the ABS pump. Make sure the brakes work before you go for a test drive. Air doesn't work well as a substitute for brake fluid.

Let me know if you can bleed the right rear now that you cleared the blockage.

Good luck

Paul

[DanielPeeters]

Just for information,
Blowing the Aluminum ABS valve bloc resulted in getting oil to all the brakes so this is rather a good start...
now comes the bleeding, because yesterday late this was not a big success :/ it kept feeling spongy and no braking ...
to be continued...

[pgill]

Daniel,

I pressure bleed my brakes to solve the problem that you are having

https://www.amazon.com/Motive-Products- ... 519&sr=8-4

Good luck

Paul

[DanielPeeters]

Problem solved!
So after decently bleeding manually "thank you to my son who was pressing the pedal"
the spongy feel is gone and the car breaks in a clean straight line at different speeds.

just as a small info, because of what i read about air being trapped in the ABS manifold and the need to get the ABS valves tripping to empty all the air, i did following:
with the ABS unit out i poured oil in the manifold in/outs so the got filled up. then i put the ABS unit bakc in the car without spoiling too much of the fluid and reconnect the pipings...
so in a general way, problem is solved.
thank you guys for the support and see you...not too soon i hope however
Daniel