HOW TO... Fit an al­ter­na­tor belt

It’s the squeal deal… That nasty screech­ing sound from un­der the bon­net prob­a­bly means it’s time to re­place your al­ter­na­tor drive belt. Here’s a quick step-by-step guide on how to go about do­ing it on a non-air­con mk1.

Total MX-5 - - CONTENTS -

Kill that dread­ful screech­ing sound by re­plac­ing your aler­na­tor drive belt: we show you how

1 You’re go­ing to need unim­peded ac­cess to the front of the engine, so the in­duc­tion pipe has to be cleared out of the way. Start the process by loos­en­ing the ju­bilee clip hold­ing the pipe to the air­box and throt­tle body us­ing a crosshead screw­driver.

4 This is where a torch comes in handy, be­cause the al­ter­na­tor is buried away low in the bay. Al­ter­na­tors are ex­posed to wa­ter and road grime, and their mount­ing bolts can rust and stiffen. Soak them with oil to loosen them a lit­tle be­fore get­ting busy with the 12mm span­ner.

3 Wrig­gle the in­duc­tion pipe free of its fix­ings and place it on top of the engine, out of the way. By the way, if your air­box doesn’t look like the one in the pic­ture, that’s sim­ply be­cause our pho­to­graphic car is fit­ted with a Dave­fab cold air in­duc­tion kit.

2 At the other end of the in­duc­tion pipe, use your long-nosed pli­ers to squeeze and loosen the clip that holds it to the con­trol valve air by­pass pipe.

6 Us­ing a 12mm ring span­ner, slacken off the bolt on the ten­sioner suf­fi­ciently that the old al­ter­na­tor drive belt can be slid off the pul­leys. That done, check the con­di­tion of the wa­ter pump and al­ter­na­tor bear­ings by ro­tat­ing them – they should turn smoothly.

10 Check the ten­sion – there should be about 10mm de­flec­tion on the long­est part of the belt run. Tighten the al­ter­na­tor mount­ing bolts, re­fit the in­duc­tion pipe, and run the engine: too tight and the belt will whir, too loose and it will squeal. Ex­pect to re-ten­sion after 100 miles.

5 Undo the up­per and lower al­ter­na­tor mount­ing bolts. The lower bolt is hid­den from view on the back of the al­ter­na­tor and you’ll have to lo­cate it by feel. If it’s seized you’ll have to get the car on a ramp, re­move the plas­tic un­der­tray, and at­tack the bolt from be­low.

8 Slip the new belt over the pul­leys, start­ing with the crankshaft pul­ley, seen at the bot­tom of the pic­ture. En­sure that it is seated prop­erly in the grooves of the pul­leys.

9 Tighten up the ten­sioner bolt again, un­til you can feel that the belt is stiff­en­ing on the pul­leys.

7 Old belt on the right still has some life left in it, but the deeper grooves of the new belt will help it seat bet­ter on the pul­leys.

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