Mazda MX5 - cambelt failure=no damage?  
Mazda MX5 - cambelt failure=no damage? - Ian D
I own a 1990 H UK Mazda MX5 1.6 which has done 30000 miles and has always been garaged, I have been asking my local dealers the highly technical (?) questions of whether:

i) the cambelt needs replacing
ii) the tensioner needs replacing
iii) whether if the cambelt fails damage will result

I have read elsewhere that the engine is 'non-interference' i.e. if the cambelt fails all that happens is the car breaks down and no damage is done to the valves etc...

Does anyone out there know categorically the answer to the above
questions

many thanks
Ian

Tags: technical issues repairs classic cars cam belt

Mazda MX5 - cambelt failure=no damage? - M.M
Ian,

If you are talking about the 1.6 DOHC engine then yes it *is* an interference type.

Belt change about a two hour job in the trade and no special tools needed.

If your belt has never been changed in 30K but is over ten years old do it soon. Personally I would examine the tensioner and guide roller...as long as they are not the plastic pulley type, and the bearings are smooth they should be OK for another 30K+. Having said that I would take any reasonable sounding advice the Mazda dealers may give you on the tensioner/roller, I see too few Mazdas to know if they have any issues in this area.

MM
Mazda MX5 - cambelt failure=no damage? - Paul Mykatz-Tinks
"yes it *is* an interference type"

How the heck does that work?
Mazda MX5 - cambelt failure=no damage? - M.M
Paul,

Which bit puzzles you?

MM
Mazda MX5 - cambelt failure=no damage? - T Lucas
I had a 1990 1.6 cambelt break on the trip back from the docks,very luckily it did not cause any other damage.
Mazda MX5 - cambelt failure=no damage? - Paul Mykatz-Tinks
It's Ok, MM, just read Martint123 below. Now I understand. Why aren't all engines thus designed??
Mazda MX5 - cambelt failure=no damage? - TrevorP
"If you are talking about the 1.6 DOHC engine then yes it *is* an interference type."

1.8 also.

Mazda quote 60k - no time limit -

BUT, as above, I would agree that 10 years is enough.

Mazda MX5 - cambelt failure=no damage? - martint123
The 1.6 is not an interference engine. Cambelt failure will stop the car but not wreck the engine.

www.miata.net/garage/timingbelt.html

"The Miata timing belt must be changed every 60,000 miles. Although the California Owner's Manual says 105,000 miles, this is just to satisfy a state requirement that says timing belts should last 100,000 miles or more. Still, it should be done at 60,000 miles. The Miata engine is a non-interference engine, meaning that the pistons will not crash into the valves. However, if you neglect this major service, you risk being stranded due to a belt break.
"


www.mx5parts.co.uk/product_info.php/products_id/216
is a kit of parts, belt, idler and tension pulleys anc cam cover gasket.

Martin
Mazda MX5 - cambelt failure=no damage? - M.M
Martin123,

OK this is important enough to know the information source.

My reference is the trade "bible", the Autodata timing belt book. They may err on the side of caution but I would have to go with their comments if advising a customer.

They actually say the engine has been identified as an interference type where damage is most likely in the event of belt breakage.

With respect you quote from a website with the following disclaimer...

"We make every effort to ensure accuracy and quality of the information provided on Miata.net. However, except where specifically noted, the information on this site is not factory approved by Mazda .

The information presented on this web site represent the opinions of the individual contributors. No representation is made regarding the accuracy or reliability of any information contained on any of these pages"


They may be right but I wouldn't risk £1000 on it.

MM
Mazda MX5 - cambelt failure=no damage? - John S
Whether it's an interference engine or not, ask yourself the following:

Do I want engine failure in the fast lane of the motorway?

Do I want to be stuck on the hard shoulder on a wet night?

What other damage might the ends of the broken belt cause?

I'd change it


Regards

John S
Mazda MX5 - cambelt failure=no damage? - JL
John S,

You are right of course regarding each of the points you make, and I would respond similarly.

I do find it frustrating however, when sources representing accuracy and fact provide instead ambiguity, omissions and sometimes error. Employees of car main agencies are also not immune to this. The assumption that technical info supplied by them to me in support of the new car they have sold is correct, has later been found to be only partially accurate when cross referenced.

The impact of flawed info re the original cam belt subject could of course be potentially catastrophic and expensive.

Regards

Julian Lindley
Mazda MX5 - cambelt failure=no damage? - martint123
Curses on this board and it logging me out!
I just found about 10 links pointing to them being non-interference and it's all gone.
Search google for interference mazda and you'll find many references to this subject.

Martin
(disgruntled and off for tea)
Mazda MX5 - cambelt failure=no damage? - martint123
MM - some links from a Google search. Some may well be copies but I didn't spot one that said the 1.6 mx5 was interference.

www.skillcentre.com/mazda.html
www.ourautoshop.com/TBeltChart.html#MAZDA
www.rovatune.com/tbelt.html
www.theautoshop.com/timing.html
www.batauto.com/tbelt/mazdatb.shtml
www.webcars.net/roadster.htm
www.connieanddicks.com/tbelt.html#MAZDA
www.rpmrons.com/mazdatiming.html
autorepair.about.com/library/diy/bl_timing_belts-4...m
www.tremontstreetgarage.com/timing_belt_chart_for_...m
www.autoref.com/mazda01.html


I'd certainly agree though the belt is well worth changing at or before the recommended mileage limit. I'm not happy with them not stating a time limit as belts deteriorate as much with time as with use.

Martin
Mazda MX5 - cambelt failure=no damage? - M.M
Martin,

OK OK but there are 200,000+ internet search returns for Elvis being alive and 1,000,000+ for the earth being flat.

;-)

It's no big deal but I'll always go with UK info published by a respected trade source....and always always err on the side of caution where DOHC timing belts are concerned.

Perhaps that is why over some ten years no car I've worked on, where the customer has followed my advice, has suffered belt or tensioner failure.

I do appreciate you are trying to offer help.

MM
Mazda MX5 - cambelt failure=no damage? - dirtrocker
To clarify on the source of info of at least one of those listed by martint123.
The source of info for at least one of those sites was Alldata, Mitchell and the manufacturer.
I know for a fact that at least one of those sites used information from Alldata and Mitchell, who's information came directly from the manufacturer and are the leading information sources for aftermarket automotive repair in the U.S.
Mazda MX5 - cambelt failure=no damage? - martint123
Sorry to bring this up again MM, but as I knew the MX5 was non-interference, but you insisted it wasn't, I went to the source of your quote and got the following reply today.
Hope this clarifies things.

(now how many owners have been ripped off for head work after a cambelt failue on this engine from data in this book???)


Martin,

Thank you for contacting us and bringing this to our attention. The latest
edition of the Timing Belts book does indeed quote the Mazda MX-5 as being
an interference type engine. However, recent information we have received
from our operations in the USA, where this model is very popular, and
further research in the UK has revealed that it is in fact a freewheeling
type engine. The Mazda workshop manual information is very ambiguous in
this respect and in these cases we always default to quoting "interference".

We have made a note of this and the next edition of the Timing Belts manual
will reflect this changed information.

Regards

xxxxxx xxxxx
Technical Origination Manager
Autodata Limited"

(name removed for privacy)

Martin
Mazda MX5 - cambelt failure=no damage? - M.M
Martin,

I'm sorry this irritated you to the point where you didn't actually read my posts.

I didn't *insist* this was an interference engine, my insistance was that I had to treat it as such to be safe when the main UK trade data source was of that opinion. The only time I really asserted the interference/non-interference issue was when first helping the questioner with third-party information I trusted.

Actually I commented...

Of Mazdas (tensioners) I said..."I see too few Mazdas to know if they have any issues in this area".

Of Autodata I said..."They may err on the side of caution but I would have to go with their comments if advising a customer.

Of your website links I said..."They may be right but I wouldn't risk £1000 on it".

Taking a responsible attitude to timing belt issues I said..."It's no big deal but I'll always go with UK info published by a respected trade source....and always always err on the side of caution where DOHC timing belts are concerned".

Any responsible Motor Engineer mindful of claims from a customer, and perhaps involving his third party liability insurance, would perhaps need to show he'd used appropriate sources for his information to be giving best advice/practice.

Following Autodata would, I'm sure, be deemed to be a responsible course...... taking information from private/small commercial websites would hardly stand up in the case of disaster.

The reason I took this seriously in the first place, and am doing so now, is that these type of tech help forums are only of any use when the tech' data offered on them is accurate. There is so much spoofing going on folks can be badly misled and it could cost them dear.

I appreciate you taking the trouble to get the *actual* answer from a properly respected source.

Thanks,


MM

Mazda MX5 - cambelt failure=no damage? - Maz
I appreciate you taking the trouble to get the *actual* answer
from a properly respected source.


Martin

Let me second that and add 3 more words - You Da Man.

What are the chances of putting that dearstalker on one more time to look at Eunos rust-proofing? Some of the opinions expressed in an earlier thread and the CBC breakdown don't agree.

Sorry I'm too much of a technophobe to include a link to the earlier thread, but a search under Eunos will bring it to your attention.

Cheers, ta, thanks a lot.
Mazda MX5 - cambelt failure=no damage? - martint123
Hi Maz, I did reply on that thread (discussions) near the bottom
www.honestjohn.co.uk/forum/post/index.htm?f=2&t=86...4

One of the importers put up some pictures of the underneath of a 12 year old import www.spmotor.co.uk/eunospic1.htm
and its looks brand new (I've no connection etc with them).
I think the CBC breakdown is wrong saying imports have no rustproofing - I think it's a myth put around when imports were a problem to main dealers. I think an import will be better underneath than an equivalent UK car that has been used on salty roads.

I've no axe to grind on this as mine is a UK car.

regards
Martin
Mazda MX5 - cambelt failure=no damage? - Maz
Thanks Martin, very kind.

I did read your original thread, but didn't appreciate the full implications. I am in full agreement, but as often happens this myth has spread - leading no less an authority than Top Gear Magazine to say avoid early imports.
Mazda MX5 - cambelt failure=no damage? - Ian D
Thanks for help, it is good to get a definitive answer that the engine is non interference (the answer I wanted), although I wasn't quite expecting such a bun fight - thanks again...
Ian
Mazda MX5 - cambelt failure=no damage? - skipperstu
wot a tossa, I know where the words cranky old b****** come from now!
Stu

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