Series 2.5 Sport, 2004

I had just written a lengthy dissertation regarding my problems removing the alternator, lower mounting bolt. Coming almost to the end, I inadvertently hit a key on my laptop which deleted all the text, so here goes with a much shortened version!

Whilst replacing both the alternator and P/S drive belts, I had intended to remove the alternator to give it a clean. However, I was thwarted by the rectangular, plastic , terminal connector, which would not yield to my efforts. Mazda appear to have employed many and varied positive connectors; I have, so far, managed to disengage all that I have encountered, but not this one. What is the secret? Is there a special tool, or was I just so exhausted by tackling the task of undoing the lower mounting bolt and all that that embodied, ( mine is the type that has the fastener fitted from the rear and necessitates the removal of the inlet manifold support bracket) that my fitting skills and rational thought process had evaporated?

Answers greatly appreciated, as there will be a ‘next time’!


The rectangular connector has a thumb tab on the end furthest away from the pulley, nearest the butt end of the alternator.

Quite difficult to get to whilst alternator in situ. I usually free off the alternator before disconnecting the electrical connections, battery disconnected first of course:-)

If you have managed to get the 14mm nut on the bottom bolt undone, everything else is very easy.     

Many thanks rhino666 - Did I reply before? I fully understand what you are explaining. I managed to rotate/invert the alternator, so the connector was ‘end on’; despite al my efforts I could not locate a ‘thumb tab’. I just wonder if it had been damaged/broken at some stage? I am the only owner, so somehow doubt that. More on that alternator belt. Despite kicking off with a relatively loose belt tension, then increasing it to , ‘blimey, that’s tight’ and spraying with Ambrosil belt dressing, the new belt is prone to slipping, especially just post start up, obviously when the alternator load is at it’s maximum. I purchased the belt from MX5 Spares and my next step is to obtain a genuine Mazda product from my local dealer, Do you know if this is a common problem? All pulleys are clean and in good mechanical order, as is belt alignment.

I presume you mean MX5Parts for the new belt but thats not the problem. Any belt should not squeal , even on start up. Did you leave the bottom bolt loose while tensioning the belt as alternator needs to rotate slightly as belt is adjusted. Then tighten the bottom bolt. Or belt is still too loose and needs adjusting more


Another thought , although unlikely, i seen it about twice on 25 years of mx5. The damper on the front crank pulley has seperated from the inner pulley causing the pulley to rotate somewhat  on the inner .Its called harmonic damper and its rubber so rot away maybe.Lots of other brands of cars do this but not so much mx5 bar the odd 1 or 2.I remember only last year selling a new pulley to lad for this exact reason

Seized water pump?


That’s what crossed my mind.

Perhaps an Alternator bearings.

Pure conjecture on my part.

MX5 123,

Many thanks for taking the time to respond to my question regarding the slipping Alternator Drive Belt. In reply;
Yes, on all occasions of adjustment, the lower 14mm A/F mounting bolt has been slackened. The slippage is very intermittent and 90% of start up the belt does not ‘squeal’ at all. You were not to know, but I am a past, time served motor vehicle apprentice and additionally, worked at the highest level of motorsport engine supply for over thirty years. We are all guilty, at times, of ‘finger trouble’, but I am quite happy that the component parts are sound, i.e. the water pump , alternator and the harmonic crankshaft damper, as is the belt tension; that is why I am considering that the drive belt specification / quality may be an issue. It may be worth adding that I only changed to drive belt because it had completed 28,000 miles and/or 14 years of service; up until the belt change, there had never been an issue with slippage and/ or squeal.
Thank-you once again for your reply.


Many thanks for your time and suggestion. With the belt removed , the alternator and water pump bearings were checked. All components were free running and sound.
Thanks again,

Steve G,

Thanks for your suggestion. Both the Alternator and Water Pump were checked when the belt was replaced, both components were satisfactory. Prior to changing the belt, (which had completed 28,000 miles and fourteen years) there had been no problems with belt slippage and/or belt slippage.
Thanks again for your time,

tyton, old chap

Given your experience of motorcars you will be aware of the cause of a drive belt squealing. Quite simply is it the movement of the belt over a pulley or guide where there is no associated movement or reduced associated movement by said pulley(s) and/or guide(s)

Causes are…

  1. belt too loose causing the belt to slip over rather than drive pulley(s) and guide(s).

  2. Pulley(s) and guide(s) seized or partially seized leading to correctly tensioned belt failing to rotate it/them effectively.

Here endeth the lesson my learned friend:-)       


May the blessing of The Lord be upon you, rhino666!
Agree, in entirety with your prognosis - Velocity delta! The only problem being that the belt tension is on the tight side of satisfactory and all component parts are in good order. Plus any slippage is transient, i.e. when it occurs, if it’s convenient, I switch off the engine, restart and all is fixed, until the next event.
There has to be a reason though and even a spray with a propriety, belt dressing aerosol has not really done anything. However, took the car out this morning, (in the wet) and not a squeak from the belt! Even loaded the alternator by switching on headlights and heater blower. I’m as mystified as other contributors.
As you may have picked up, my head is full of front rail issues right now and from positive comments, plan to call Thrussington Garage on Monday morning to discuss / book.
I do plan to purchase a genuine Mazda belt, just to be on the safe side. As I’ve said to others, all was ‘tickety boo’ before I fitted new drive belts. The change only due to potential time / mileage expired parts.
I really do appreciate the giving up of your time to discuss this issue.

Couple of thoughts, going back to my Engineering studies on belt drives.  Don’t forget a vee belt is designed to be pulled in to the vee of the pulleys and therefore ‘wedge’ in place under tension to transmit the power.  The belt will be pulled further into the pulley as load increases.  Initial belt tension has only to be sufficient to ensure the belt is pulled in to the pulleys once the system starts to move so as to start it to be ‘wedged’ into the pulleys. If the belt (or pulleys) are worn to the point where the belt ‘bottoms out’ then it will still slip even with a very high belt tension.  Maybe the pulleys are worn or the new belt is the wrong specification and too slim.  It is quite possible that during the wet drive you describe the belt was still slipping, but water spray was getting on it and acting as a lubricant so preventing the squeal. 


Your input is greatly appreciated. I agree with your philosophy on belt drives - as everything was ‘fine’ before I changed the drive belts and the alternator and it’s drive pulley , water pump , ditto and crank damper/pulley are unchanged, then by deduction, the replacement belt specification, (MX5 Parts ‘aftermarket’ - tooth profile and material)has to be in question. As mentioned, once I get the chassis rail issue dealt with, then my plan is to purchase and fit a genuine Mazda part.
Thanks once again for your interest and contribution.

I’ve had this issue on my Mk 2.5 both with its original (quiet) belt and a new continental one.  In the end I slackened off the alternator leaving all the bolts just loose enough to allow me to rotate it Having slackened the belt off very slightly I started the car with max load (lights, HRW, radio, fan etc) and it started squealing - the din was awful so wear ear defenders. I then gradually tightened the belt until it ran quietly - the noise stops very suddenly.  Checked it was quiet at various revs and re-tensioned as necessary. I was surprised at how tight it needs to be - perhaps that’s why these multi V belts have a screwed adjuster unlike the “just lever or pull on the alternator” method of older cars with a single V belt.


I thank you for your response to my post regarding the Alternator Drive Belt issue. There is a similarity, in that I have fitted a ‘Continental’ belt.
Yesterday, I drove my car to East Tressington, in order for chassis rail ‘surgery’ to be performed. The journey was fifty-three miles and included a couple of ‘stop and starts’. Throughout, there was not the slightest ‘squeal’ from the belt, which was most rewarding! I understand that the following makes no engineering sense, but it is almost as if the multi-vee belt and pulley interface required a period of ‘bedding in’, as I had not increased the tension since a previous event of transient ‘squeal’.
Hopefully this issue is now resolved? Collecting the car on Tuesday of next week, so fingers crossed! Many thanks, once again, for your suggestions.


Tyton, glad to help.  I found that after a while it started squealing again but a quick nip up using the method above seems to have sorted it.  When people refer to manufactures original parts for things like belts there is no such thing - they are made by OE manufacturers to set specifications.  Conti are a well known and respected brand and its probably just coincidence we had the same one fitted , in fact the one I took off was Gates and that squealed occasionally as well.