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?

[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!)

[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).

[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

[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!

[pernod]

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

[pernod]

Right, after a fair bit of diagnosis I've actually tracked it back to a dodgy spark lead.

Lesson - the easiest solution is generally the right one

[pernod]

Lesson #2 - follow the advise on the forum thread from an identical car with identical problem on the same day... http://www.pistonheads.com/gassing/topic.asp?h=0&a...