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Alfa Boxer Cambelt Replacement |
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Written by Evan Bottcher
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Wednesday, 24 November 2004 |
I wrote the following article for "Cross and Serpent", the magazine of the Alfa Romeo Owners Club of Australia Victorian Division.
First of all an introduction - my wife Fiona and I spent the last 4
years living overseas, during which time our little red Alfasud has
sulked in a family shed up in the country. At least it was dry -
I doubt there was a drop of rain in that time and the car was covered
in a half inch of red dust. Now that I've been foolish
enough to take up the position of club secretary, it's definitely time
to dust off an Alfa. This'll be a slow process as life is busy,
but while I'm here I'll try to contribute a couple of technical
articles. I'm a mechanical simpleton and this article is targeted
at members just like me.
ALFA BOXER CAM BELT AND TENSIONER REPLACEMENT
While we lived in the UK we drove a '91 33 16V Sportswagon, bought for
?600 and providing more than 3 years of generally reliable
touring. At this price, I could not bring myself to do more than
the minimum of servicing - the car wasn't meant to last long.
Unfortunately one cold spring morning we broke a cam belt in a spirited
drive in Essex, and bent four valves. I learnt the hard way the
importance of those rubber bands that keep your cams going round and
round.
Replacing the cam belts and tensioners is not particularly difficult,
but it is fiddly and time consuming so a good one to DIY and save some
dollars.
Step 1. First I needed to clear access to everything, so I
removed the twin carb air filter assembly, alternator, radiator and
thermo fan. It's not strictly necessary, but there's not much
space with everything hooked up. To remove the radiator, drain
the cooling system by removing the drain plugs on each side of the
underside of the block. Remove all hoses and then undo the single
bolt at the top of the radiator and it will simply lift out.
Step 2. You need to rotate the engine until piston no.1 is
at "top dead centre" (TDC) on its compression stroke. Remove the
plastic plug exposing the flywheel at the rear of the block. Turn
the engine by hand until the TDC mark on the flywheel lines up with the
marker. On my flywheel this is a small T as highlighted in the
photo below.
I've highlighted the TDC mark on the flywheel here in white.
Now remove the cam covers on both sides, so you can view the cam lobes
and the timing marks on the rear of the camshaft and housing.
When cylinder 1 is at TDC on compression, the timing marks on the rear
face of each camshaft will line up with the marks on the camshaft
housing.
Here is a view of the exposed right hand camshaft, the timing mark is visible on the housing to the left.
Step 3: With all the timing marks lined up, slacken the bolts on
the tensioners themselves, and push the tensioners against their spring
tension. Tighten the bolts again to lock the tensioners in this
?loose' position. The belts can both now be removed. The
tensioners can also now be removed at this point, if you are going to
replace them.
Why replace the tensioners? I've seen some debate on Internet
forums on the merits of replacing the belt tensioners. Some say
to definitely replace the tensioners every time you change the
belts. Certainly if a tensioner bearing WAS to fail and seize I
expect the consequence would be as fatal as a broken belt. I
chose to replace both tensioners this time as the cost is not
exorbitant and I know they are very old.
As it turned out the left hand tensioner was fairly well worn, with a
decent rumble when turned by hand, so I feel happy about changing them
both.
Another consideration is whether to replace the water pump at this
point, while you've got all the belts and radiator out of the
way. In my case the water pump is not very old and feels and
sounds smooth when spun by hand, so I've left it in there.
Step 4: Fitting the new tensioners and belts. Bolt the new
tensioners in place, tightening them in the loose position against the
spring tension, so you can fit the belts over them. The parts of
the tensioner assemble in this order: tensioner pulley body, the
spring, a large washer, small washer, and lock nut. The spring
keys into a hole in the block and a slot in the tensioner body, and
it's a little fiddly to assemble, as the spring is quite strong.
Shiny new left-hand tensioner in place.
Ensure the flywheel and camshaft timing marks are still all lined
up. Fit the left-hand belt first, ensuring the driving side of
the belt is held taut as you key the belt teeth onto the camshaft
pulley. The driving side of the belt is the side opposite the
tensioner. While fitting the belt ensure the timing marks remain
aligned - the crankshaft at TDC and the camshaft marks lined up on the
side you are working on.
If you find the belt a very tight fit and you want to ?stretch' the
belt to fit, ensure the belt is keyed properly onto the crankshaft
pulley teeth. The belt slips on fairly easily when the teeth
match up correctly. Now release the tensioner nut on that side,
allowing the spring to tighten the belt up, and then tighten the
tensioner in position again. Check that the timing marks all line
up still. Repeat the procedure on the right hand bank.
Left hand belt fitted
Step 5: Now we need to set the correct belt tension. Turn
the crankshaft over by hand until all the cam lobes on one cylinder
head are not touching their tappets, and then slacken the tensioner
bolt to allow the tensioner to re-tension the belt. Tighten the
tensioner in this position. Repeat this procedure for the other
cylinder head.
Turn the crankshaft in the normal direction for 2 or 3 whole rotations,
and then repeat the procedure (from step 5) on both sides - this time
tightening the tensioner bolts to the specified torque (27.4-33.8
lb/ft). Turn the engine to TDC once more for a final check that
all the timing marks align exactly.
Step 6: Job done! Now just refit the radiator and hoses,
alternator and drive belt, and air filter assembly. The new cam
belts are meant to last for another 60,000km.
Disclaimer: Follow these instructions at your own risk -
if you have any doubts, please get a professional to work on your
car. If you have a correction/suggestion, please write to myself
or
This email address is being protected from spam bots, you need Javascript enabled to view it
and have it published.
References:
Haynes Alfasud/Sprint Owners Workshop Manual (revised edition 1991)
Autobooks Alfasud Owners Workshop Manual (published 1976) |
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Last Updated ( Thursday, 25 November 2004 )
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