Cam belt stress

[pernod]

Hi guys,

Today we had a cam belt snap (I think). Genuine mistake where we both thought we had changed it when we got the car but our records show different, by the time we discovered this a few months ago we were already planning to sell her so planned to sell as overdue for the cam belt - Murphys law thought otherwise.

The "stress question" now is the likely damage? I thought it had a non-interference motor in it but I've had a concerning number of "car people" today seem skeptical (including two mechanics) as to whether this would guarantee no damage. I'm now starting to doubt my own knowledge on this and getting a bit stressed - I'm hoping you guys can give some thoughts:

• First thing this morning, I tried to start her. A second later, just as she caught and I released the key, she stopped (without ever really catching properly).
• I tried cranking her over twice more, to quickly realise it was just the starter motor free spinning (without any real cranking to it like it had the first time).

She is a 2004, Mk 2.5 1.8l.

Any thoughts to calm (or shatter) the nerves?

[rovermorris999]

I think it'll be fine. Worry not.

[MX-5 Lazza]

That doesn't sound like a broken cam belt to me. If the starter is spinning freely and not turning the engine over then it sounds like a broken starter or starter ring.

[GC8]

Its certainly the time of year for a broken cam belt, and when youre starting the engine is a likely time too. If it does turn out to be the cam belt then I dont think that you need worry: at 6,000rpm Id be concerned until it was checked, but at 600rpm itll be fine - it is a non-interference engine as you believed.

[Steffan]

GC8 said:

Its certainly the time of year for a broken cam belt, and when youre starting the engine is a likely time too. If it does turn out to be the cam belt then I dont think that you need worry: at 6,000rpm Id be concerned until it was checked, but at 600rpm itll be fine - it is a non-interference engine as you believed.

Good advice.

A non interference engine should be safe at `any speed because the vales cannot hit the pistons.

But as GBC says better a few hundred revs than a few thousand for any failure. My daughter suffered Cam belt failure on an early VW Polo. I expected complete disaster because she was zonking along at eighty MPH at the time.

In fact it just required a new belt and a service as a precaution.

Car lasted another three years without problems. Sleep well!!

[pernod]

MX-5 Lazza said:

That doesn't sound like a broken cam belt to me. If the starter is spinning freely and not turning the engine over then it sounds like a broken starter or starter ring.

Interesting, hadn't thought of that. Can you think of any way to diagnose if it's a Cam or something else?

Thanks guys - I'll sleep a bit easier tonight. We'll be getting it fixed (and then unfortunately it has to be sold due to a baby... I'm more than a bit guttered!)

[MX-5 Lazza]

Is the engine actually turning over when you crank it?

It's easy to check the cam belt. Just take the cam cover off and have a look. It's a pretty easy DIY job to look, it just takes a bit more work to do the swap.

[pernod]

MX-5 Lazza said:

Is the engine actually turning over when you crank it?

It's easy to check the cam belt. Just take the cam cover off and have a look. It's a pretty easy DIY job to look, it just takes a bit more work to do the swap.

Just rechecked... It's turning the engine over but no sign life, so cam is still me best guess (won't get a chance to take the cam cover off until the weekend when there is some daylight).

[JSquaredJim]

Take the oil filler cap off and you will see the cam shaft directly under the hole. Crank the engine while observing the cam. If it spins it's not the cam belt. If it remains stationary don't panic. The engines are non interferance and I've seen hundreds with snapped cam belts, (ex Mazda tech). Mostly imports with unknown history. Just get it changed and bobs your uncle. Hope that helps.
Interestingly the UK service interval is 3 years by time, yet in the States the same belt "lasts" 10 years! Weired

[pernod]

JSquaredJim said:

Take the oil filler cap off and you will see the cam shaft directly under the hole. Crank the engine while observing the cam. If it spins it's not the cam belt. If it remains stationary don't panic. The engines are non interferance and I've seen hundreds with snapped cam belts, (ex Mazda tech). Mostly imports with unknown history. Just get it changed and bobs your uncle. Hope that helps.
Interestingly the UK service interval is 3 years by time, yet in the States the same belt "lasts" 10 years! Weired

You're a star mate. Simple and Clever.
I'll have a check tomorrow in the day light.

We both swore it had been changed, but can't find a record of it. I have a horrible suspicion that we couldn't get it booked in to be done at the same time as it's first MOT when we got it. I'll bet we thought 'we'll do it next month' and then 'forgot' it had never actually been done

[GC8]

JSquaredJim said:

Take the oil filler cap off and you will see the cam shaft directly under the hole. Crank the engine while observing the cam. If it spins it's not the cam belt. If it remains stationary don't panic. The engines are non interferance and I've seen hundreds with snapped cam belts, (ex Mazda tech). Mostly imports with unknown history. Just get it changed and bobs your uncle. Hope that helps.
Interestingly the UK service interval is 3 years by time, yet in the States the same belt "lasts" 10 years! Weired

California state law requires the longer service interval Jim.

Small thread hijack - how many NB 1.8s did you see with bottom end failures caused by the oil pressure relief valve? I understand that the oil control rings caused an issue too, that was fixed in the NB2 VVT engine?

[Richyvrlimited]

GC8 said:

California state law requires the longer service interval Jim.

Small thread hijack - how many NB 1.8s did you see with bottom end failures caused by the oil pressure relief valve? I understand that the oil control rings caused an issue too, that was fixed in the NB2 VVT engine?

FWIW the NB2 has a different oil pump to the NB, this is to cope with the added oil requirements of the VVT mechanism

[pernod]

JSquaredJim said:

Take the oil filler cap off and you will see the cam shaft directly under the hole. Crank the engine while observing the cam. If it spins it's not the cam belt. If it remains stationary don't panic. The engines are non interferance and I've seen hundreds with snapped cam belts, (ex Mazda tech). Mostly imports with unknown history. Just get it changed and bobs your uncle. Hope that helps.
Interestingly the UK service interval is 3 years by time, yet in the States the same belt "lasts" 10 years! Weired

Daylight confirmed that the cam is still turning.

This suggests the problem is going to be Spark or Fuel (or timing belt slipped), time for some more investigation...

Thanks for the help guys!

[Steffan]

GC8 said:

JSquaredJim said:

Take the oil filler cap off and you will see the cam shaft directly under the hole. Crank the engine while observing the cam. If it spins it's not the cam belt. If it remains stationary don't panic. The engines are non interferance and I've seen hundreds with snapped cam belts, (ex Mazda tech). Mostly imports with unknown history. Just get it changed and bobs your uncle. Hope that helps.
Interestingly the UK service interval is 3 years by time, yet in the States the same belt "lasts" 10 years! Weired

California state law requires the longer service interval Jim.

Small thread hijack - how many NB 1.8s did you see with bottom end failures caused by the oil pressure relief valve? I understand that the oil control rings caused an issue too, that was fixed in the NB2 VVT engine?

This interests me.

Does this mean that a different cambelt is used in california capable of ten years wear? If so I would really be interested. Changing cam belts is an unwelcome expense.

If it does not mean this, how on earth do Toyota tget round the problem?

Ta.

[GC8]

As far as Im aware it involves little more than a reprint of the owners handbook.

[Steffan]

GC8 said:

As far as Im aware it involves little more than a reprint of the owners handbook.

I appreciate your advice.

Which presumably means either the cam belt change is unnecessary or the cars in California regularly break belts.

Simply reprinting the handbook is an interesting approach. Saves the owner three cam belt changes. It does seem odd to me.

[MX-5 Lazza]

I believe the rule in California is 10 years or 100k miles, whichever is sooner. Still a lot more than over here but realistically, a cam belt should be able to last 100k miles without a problem.
The belt itself is the same item regardless of the market.

[Richyvrlimited]

warmer climes and much longer commutes in Cali no doubt aid in the lonegivity of the belt.

[pernod]

Given mine isn't the cam, anyone know of a good troubleshooting list for the MX5 I should be working through?

[GC8]

If youre saying that the engine is spinning more quickly than usual, as it would when the belt is broken, then Id suspect a slipped belt. This will allow the engine to spin more quickly due to the lack of compression, although itll not be as quick as if the belt had broken, as the camshaft is still being turned.

You need to take the cambelt cover off and identify the static timing marks. Youll need a .pdf of a workshop manual for an NB or NB2 - unfortunately Im not sure where to find one. Ive been told that theres one on MX5Nutz, although Im yet to find it.