When to change cambelt?

Andrew H · Post by **Andrew H** » Fri May 24, 2002 12:23 am

I bought a 1990 import about 6 months ago that had just arrived from Japan.

From the condition the 50K km looks about right.

When does the cambelt need changing? I don't know the history of the car and
as it did well in an AA check I have
only changed the oil and 2 tyres.

Any advice would be appreciated.

Andrew H

Graeme Naisbitt · Post by **Graeme Naisbitt** » Fri May 24, 2002 12:43 am

G'day and welcome to the list,

My Haynes manual recommends every 60,000 miles which is erm something in
Km's (I'm an ex pom so I don't know how to convert, anyway don't want ot
make it too easy for you...)

Graeme
D4NGER

Fletcher Blades · Post by **Fletcher Blades** » Fri May 24, 2002 7:42 am

100,000km or every five years... many people ignore that second
bit...

The cam-belt itself is approx $60, you should probably also replace
the cam-shaft and crankshaft oil-seals (3 x $5-$10), some people also
replace the water-pump ($120-ish). You'll also need to replace the
old dried out cam-cover gasket. ($30-$40?? )

I can do a timing belt change without any gaskets/seals in my
drive-way, with hand-tools in 1.5 hours.
Allow an extra hour for the water-pump, or half an hour for the
oil-seals...

Multiply by your repair-shop's hourly rate, and see if they are
ripping you off or not...

Fletch.

P.S. There are special issues with working on all '89-'90s and some
early '91s which have a poorly designed crankshaft nose. You owe it
to yourself to investigate this, if you plan to do the work yourself.

Delich, Martin · Post by **Delich, Martin** » Fri May 24, 2002 9:47 am

Fletcher.
I'm aware of the early 1.6 crankshaft design short comings (something to do
with the nose of the crankshaft being a smaller diameter than optimum, thus
strength is compromised - the 1.8 engine has a larger crank nose so doesn't
have the same problem of breaking).
Do you know of any actions that can be carried out to minimise this problem
(besides correct installation torque of the crankshaft pulley bolt and
correct tensioning of the accessory drive belts)?
Cheers.
MD.

Gary Morrison · Post by **Gary Morrison** » Fri May 24, 2002 10:11 am

Yeah, what colour eyes his as yet unborn child will have... eh Fletch?

Fletcher Blades · Post by **Fletcher Blades** » Sat May 25, 2002 8:51 am

The bit in the middle will be black!

Fletch.

Fletcher Blades · Post by **Fletcher Blades** » Sat May 25, 2002 8:59 am

The main problem is that the bolt itself is too small, and it gets
stretched over time...

Replace the bolt with a new one. (You'll have to get it from Mazda),
and put loc-tite on it so it doesnt come loose. The correct torque
for the early bolt is 80ft-lb. DO NOT use the later design's higher
torque rating (120ft-lb) as you'll just start the stretching early.

Read all of http://www.miata.net/garage/crankshaft.html as the latest
info is at the bottom.

Originally, Mazda (USA) blamed poor re-assembly after work on the
area... and it was thought that simply leaving it alone was the best
idea. Now that more cars have gone higher mileages... This theory
has been dis-proved, by a number of "un-touched" crankshafts
breaking...

Mine broke at about 150,000km.

Fletch.

Biff [Paradise 2] · Post by **Biff [Paradise 2]** » Sat May 25, 2002 12:47 pm

I don't suppose Mazda accept any sort of liability???
B

Michael Donovan · Post by **Michael Donovan** » Sat May 25, 2002 6:59 pm

Hey Fletch,
What did you do when your pulley failed? Get another engine or were you able
to get the crank repaired or what?

Planning for the future as they now say they'll all break sometime...

mike
On Sat, 25 May 2002 08:59, you wrote:
[...]

Michael Donovan · Post by **Michael Donovan** » Sat May 25, 2002 11:45 pm

O.K thanks Fletch, when I first got mine, I was also very new to
Auckland, and I drove around a few wreckers in south Auckland to have a
look at getting a cheap spare motor...
Every engine I looked at (maybe 4) had it's crank bolt finger tight, and
once unscrewed, they all had knackered or broken keyways. Some had had
two keys put in at about 120 degrees, I guess this cant upset the
balance tooo much... Oh well I suppose one of these days I'll have to
get to mine and try changing the bolt, I brought a new bolt a while back
but as I'd already changed the cam belt, I didn't feel like taking
everything apart again...but...
Cheers
MIke

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