Any Volvo techs on here? re: brakes

[Shappy]

Possibility #4 - Are you getting any ABS warning lights?
( Just to make sure, does the ABS warning light come on
in self check mode just before you crank the engine over? )

No ABS warning or other lights. Will double check if ABS light comes on prior to cranking but I'm pretty sure it does. Once when climbing a very long hill I got a warning light that disappeared after the next stop/start cycle.

[Shappy]

Are you losing brake fluid?

No fluid loss. Brakes work well most of the time.

[Shappy]

The brake vacuum hose can chafe on the rear engine mount and bleed vacuum. Have a good look at the hose by removing it. There is an ejector pump which makes vacuum even under boost ( if you have a turbo) which ca also leak

Check valves and ejectors are available, I believe the brake boosters are not

I have two spares though, and traverse GTO quarterly

Do you mean you traverse the GTA (Greater Toronto Area)? If so let me know next time and maybe we can meet up? I'm in Caledon just north-west of Toronto. BTW it's non-turbo.

[Shappy]

Today I pulled the vacuum hose off and tried to blow through it. Could not blow through. I could create a vacuum no problem but the booster would not hold it, or maybe my lung capacity is insufficient. Should it hold a vacuum?

[abscate]

You can make about 1-2 psi pressure with good lungs and I suspect not much more vacuum than that, that’s about 70-100 millibar

The eng8ne makes about 20 inches of vacuum or about 670 millibar

The test of the booster is to give several cycles of assist with the engine off

[Shappy]

Still trying to sort things out. I've replaced all 4 calipers, left front flex brake hose and check valve. Want to do the other hose but found it very difficult to loosen the flare nut without rounding it. Damn things are very soft! What were they thinking? I have both metric and SAE flare nut wrench sets and the closest to fitting the flare nuts is the SAE 7/16". Seems odd for a European car. Is there some sort of special tool that fits perfectly. I don't want to resort to vice grips again or install a new hard pipe. What tricks have you used? Also can anyone explain what the 'brake position sensor' on the booster does? How does it work? Does it fail? Symptoms? THANKS!

[erikv11]

The flare nuts are all metric, force the right size flare nut wrench on there and it should give. Maybe it si 11mm? I don't remember ... Also flare nuts are always soft. Really important to not round them, if you do then you can abandon saving the nut and resort to vice grips but you really shouldn't have to on the front ones. A little heat can help tremendously but don't cook the rubber hose and watch for boiling brake fluid.

[scot850]

Erik is correct it is an 11mm nut, same as many European manufacturers. A good quality flare nut wrench is required. I tried various cheaper ones as I have difficulty find an 11mm wrench locally. All of them just try to round the nuts as they flexed too much. There are good brands out there and this is one where I splashed out for a good tool. It was a Snap-on on and was about $40 CDN about 5 years ago. It worked really well, but even so, I carefully soaked the joint in Deep Creep (or likes) penetrating oil (and not WD40) for a couple of days and wire brushed it thoroughly in between applications. I also carefully cleaned any scale around top of the flare nut with fine emery or wet/dry paper to try to prevent the nut grabbing on the pipe and damaging it. All came off in spite of the heavy rust. I wish you luck.

Neil.

[dalel]

I've heard that squeezing the flare wrench with a vice grips can be helpful to prevent rounding. Done while wrench is already on the nut.

(hope this wasn't already suggested. Sorry if it was.)

Dale L

[Shappy]

THANK YOU! I have a quality set of wrenches and the 11mm fits nicely. Now does anyone know what the brake position sensor does?