No front brakes after jumbo conversion on 740

Hi folks. I finally got around to installing the donor strut towers
with the
jumbo brakes from a 92 960 with ABS.

This was installed on an 86 740 turbo that had the dual piston girlings.

I did everything described at brickboard, and now I have little to no
front brakes. This included disconnecting unused brake lines, and
blocking those ports with ATE plugs.

I fully flushed and bled the entire system. I have a good hard pedal,
but
very little brake action.

I did see a note on swedishbricks where someone said that you can't put
an ABS caliper on a non ABS system. I can't see why not, the ABS stuff
is separate from the caliper, isn't it?

I need help with this, I'm down to this one car, and I would like to be
able to
stop..... (so would the folks in front of me....8*)))

thanks for the help, /glenn

 

Are you sure you used the correct ports in the calipers, and that the
calipers are not plugged up? I had thought the pressures were the same
whether ABS or not, but I don't really know. Not really sure what the
point in upgrading the brakes is, Volvo used very good brakes right from
the factory, I've never found them to be inadequate, even when towing a
boat.

 

Glenn has already given us the answer (use of calipers designed for
ABS).

Antilock brake systems can, and frequently do, operate under *extremely*
high pressures (much more than non-ABS).

I can only hazard a guess that this is the case for the Volvo in
question, but I sure as hell *wouldn't* recommend the mixing and
matching of ABS/non-ABS brake components on any car I drove.

Can only suggest either getting the correct components (which
unfortunately may involve replacing both the calipers *and* the rotors)
and fitting them to the car, or re-fitting the original 86 spec brake
components as soon as possible.

Cheers,
Andy.

 

Hi guys, a bit later than the fix, but here's what I did..... (sorry for
the
length.........8*)

I had 2 goals, one was to end up with 2 piece hub/rotor setups, and
to upgrade to jumbo brakes. What started this is that the original
setup
on the 86 740 was starting to act up, pullling, and pedal pulsating, and
I didn't want to spend money on the 1 piece rotor/hub.

I had obtained the strut towers with brakes from a 92 960. I installed
that with the jumbo brake setup per the brickboard. The 'yard calipers
were frozen, so I stole the calipers from my 940 which had recently
died. These were known good calipers, less than 6 months old. After
bleeding, etc. I had a very stiff pedal and no front caliper action.

I did drive it a couple of days that way, with careful planning for
stops.
Braking did get better as things settled, but it wasn't right. After my
last
post, I went and found a pair of rotors (2 piece, 10.25") for that car,
thinking that if the orig. caliper and bracket and this rotor didn't
work on
the 92 strut and hub, then I'd get the conversion hubs and use them
there.

It worked!!!!!!!!! I pulled the 960 stuff, and put on the new rotor,
with
the original bracket and 2 piston caliper. It all lined up, and fit
right. I was
hoping that volvo had maintained a standard distance for everything, and
they had. In the process, I found that all 4 pistons worked correctly,
and
the problem was that the pads weren't sliding, ie were frozen to the
brackets.
So, after cleaning that, and lubing things, it's back to normal. (this
is on the
960 strut towers which bolted right in!)

James:

Yes, I used the ports as pictured on the brickboard. If you go to
'brakes'
on the first pulldown, in that section is the upgrade section. In there,
there is
a specific paragraph that tells about using ABS calipers on a NON ABS
system. I guess that's the part that I don't understand. Everything else
that
I've found on the brickboard has been spot on, so I still think that there
might
be something amiss on my particular car.

There is one slight possible clue to this. My BRAKE light is on. Last
night
I did the procedure to reset it, and it didn't work. There is a bit of
corrosion
where the switch sits, and I'm wondering if lack of movement of the piston
could affect things.

Pressure. I had heard warnings over the years to be careful of opening
up
ABS brake systems as they held pressure until relieved and were dangerous
because folks were getting brake fluid forcefully injected under their skin
when
they opened a system. Along with that was the news that volvo didn't work
that way, that the pressure got relieved. (?) So, maybe the systems do
operate
at higher pressures, there is a pump that does the pulsing.....

As to good brakes, yes, they are ok, but the jumbo setup fixed a lot of
things that I thought caused problems with the 2 piston setup, plus larger
pads and rotor surface, not to mention a thicker rotor. I've had both 740's
and a 940, and found the 940 brakes to be a bit better.

Andy:
Thanks for the reply, your last words about restoring the original 86
stuff
helped me realize that the 2 pc rotors just might work on the new hubs. As
to mixing and matching, it's been going on for years, and can result in a
better
setup. Look at what the hot rodders have done for years.

I'm not done. If I do find the answer, and find that it can work, I
have the
parts to put the jumbo setup back on. For now, it's keeping the 86 running
reliably until I can find a replacement for the recently deceased 91 940.
And
if I don't find the answer, I'm happy with where the 740 is now, and I have
spare parts for my next 940.

Sorry for the extreme length. I do ramble on a bit............

drive safe, /glenn