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Handbrake adjuster |
This
is a stressful time for the motorist; it is where you hand over
your pride and joy to a third party to be poked, prodded and shaken
into revealing those profitable faults for the garage. If you are an
owner maintainer you should be able to minimize these unexpected
failures because you regularly service and put right problems as they
show up. I know in practice this is not always the case. But it is
better and more cost effective if you do, than to be thrown in at the
deep end when you are at your busiest.
MOT
testers are human and have pet hates. As an ex-tester mine were
lights not working and torn wipers. To me this indicated that it may
have other MOT issues which proved to be the case on many occasions.
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Brake fluid |
I
am not immune from the unexpected. Having checked the van over and
put right the sticking hand brake again, I was confident that it
should pass its MOT. The van and tester had other ideas. It failed!
I was expecting him to say it was a ball joint but no it was that
damned hand brake again. Apparently, the brake machine showed that its
effectiveness was outside the permitted balance parameters - (MOT
speak), and it was the offside that was less effective or put another
way the nearside was still sticking.
With
the vans 'back end' in the air and the wheels off, I started to check
everything again. But this time more thoroughly than before. I
started by loosening the hand brake cable at the adjustment in the
middle of the van. Then removed each cable from the calliper first
checking to see if the handbrake lever was at rest. They were both
holding off by a fingernails width even though the cable was very
slack.
Surprisingly with this
poxy system this small amount can make
the brake bind badly. I freed off the arms as described in a previous post. Then checked to see how free the movement was on each hand
brake cable that ran from the calliper. The OS one was very rough and
stiff as the cable moved back and forth in the sleeve. The NS one was
less so but on the way. I changed both to be on the safe side. what's next? The brake pads are not that old, but I checked them
anyway. The near side looked OK, and the piston moved freely the same
for the offside, but the pads had an unusual wear pattern. It looked
like the centre of the pad had crumbled away meaning that only the
outer portion was in contact with the disc; could this be the
problem? I checked the brake disc carefully; the surface was
reasonably flat, and I could not see any reason for the centre wearing
faster than the outer edge. The only way to be sure is to replace
them. I know! more expense!
Now
to fit them. I started by winding the piston back into the calliper.
This needs a special tool but if you do not have one you can get away
with using an adjustable wrench (the type that bites your fingers if
it slips off - ochhh!!) and a G clamp. It is slow and a pain but
saves on the price of the tool. Basically, you wind in the adjuster
several turns and then use the G clamp to push the piston back.
Before you start this, you should pop the hood and take the cap of the
brake fluid reservoir and place a cloth over the top to stop the
brake fluid pouring all over the engine bay. This may happen if the
fluid has been topped up. Once it is wound back clean the mounting
bracket area where the brake pad sits and then put a little copper
grease on the edges of the pad that sit on the bracket, this prevents
sticking. Push the calliper into place, always use the new guide pin
bolt provided with the brake pads and tighten to 35 newton meters (26
lbf ft). You should only remove one pair of pads at a time this
allows you to reset the piston for the new pads by pumping the brake
pedal also reducing the chance of the fluid reservoir overflowing.
Spin the disc to make sure it is free and then apply the hand brake
with your hand on the lever to make sure it works and releases
properly. Then do the same to the other side.
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Adjustment settings |
Now
attach the hand brake cable to each side and adjust the cable. I
usually put a bit of copper grease on the adjuster thread to stop it
freezing. Wind the adjustment nut up until you obtain a clearance of
between 0.1 and 0.5 mm between the operating lever and the stop on
the back of the calliper body. You can check this by using a feeler
gauge. Now spin the discs, if it feels like it is binding then back
the adjustment off until it stops. Hop in the cab and pull on the
hand brake several times checking how many notches it come up - one
or two is about right but not set in stone. Then check again to see
if the discs are binding now the cable has been settled in. If OK,
it's time to box it up.
It
is a tense time back at the MOT station as they check the hand brake
on the brake machine. Has it passed? it looks to me as it's within
parameters. Yes! A 'thumbs up,' great news! back to the day job.
Update to post 18/8/13.
The handbrake is still working properly with no sticking to date. I have noticed that the mpg has increased since sorting out the brakes by as much as ten miles to the gallon which is astounding. So, all those bits I replaced will have payed for themselves.