Tech­ni­cal is­sues solved

Michael Clev­er­ley of Clev­er­ley Re­paired Cars, ex­pert on all things MX-5, an­swers your ques­tions

Total MX-5 - - CONTENTS -

Fix­ing leaky roofs, noisy clutches, stiff gearchanges, and in­ves­ti­gat­ing a nasty coolant prob­lem

CLUTCH BUZZ

QMy mk2 has just had its clutch re­placed and now there’s a buzzing, rat­tling sound on the over­run. Any idea why, as it didn’t do it be­fore?

AIt’s a prob­lem we see quite a lot. The sound seems to come from the bell­hous­ing and can be loud. Some say that the gear­box has been bolted into the PPF (power plant frame) at a dif­fer­ent an­gle when the clutch is changed. The PPF bolts to the back of the gear­box and has elon­gated holes giv­ing quite a lot of ad­just­ment, al­low­ing the rear of the box to be raised and low­ered.

Ad­just­ing this can re­duce the noise a lit­tle but I can’t re­ally see why it has any ef­fect at all. The real prob­lem seems to be the fit of the clutch fric­tion plate’s splined cen­tre on the gear­box in­put shaft. Many af­ter­mar­ket fric­tion plates are a slop­pier fit than the orig­i­nal, al­low­ing the splines to chat­ter and res­onate on the in­put shaft. This is am­pli­fied through the bell­hous­ing. The cure is a good fit­ting clutch fric­tion plate such as those made by Exedy (fit­ted from new by Mazda). While you are in there, grease the clutch fork pivot as this com­monly squeaks!

THE DREADED DROOP…

QMy mk2 some­times suf­fers with an un­even tick­over and stalling at junc­tions. I have cleaned the in­take but the prob­lem is still there. Any sug­ges­tions for a cure?

AThe dreaded idle droop seems to be a bit of an is­sue on some MX-5S, par­tic­u­larly mk2s and mk3s – un­for­tu­nately there is no blue pill to over­come this mal­ady!

You have to go back to ba­sics and en­sure the throt­tle but­ter­fly is cor­rectly set (base idle), crank or cam an­gle sen­sors are in good con­di­tion and ad­justed cor­rectly, and clean the idle con­trol valve, etc. How­ever, on the last car we looked at with this fault, the prob­lem was caused by a loose crankshaft pul­ley caus­ing wear in the crankshaft nose and key­way; the cam and ig­ni­tion timing was shift­ing by more than 10 de­grees at idle, caus­ing stalling and the tick­over to be quite un­pre­dictable. The en­gine was the im­proved long nose de­sign, so I pre­sume the crankshaft bolt was torqued in­cor­rectly af­ter a cam belt change. Un­for­tu­nately the repair in this case was ei­ther a new crankshaft and pul­leys, or the cho­sen op­tion of a good sec­ond­hand en­gine. Hope­fully you car’s fault will be less dra­matic.

PS: mk3s can suf­fer with un­even idle af­ter a bat­tery dis­con­nect as the ECU has to re-learn the idle valve

op­er­a­tion. It should sort it­self out af­ter a few miles’ driv­ing.

HOT AND BOTH­ERED

QMy mk1 is over­heat­ing when I drive quickly. It’s OK in nor­mal con­di­tions but gets re­ally hot when pushed harder. Have you any idea why?

AThe cool­ing sys­tem and en­gine on the mk1 is very ro­bust and re­li­able. How­ever, the cars are quite old now and prob­lems can oc­cur be­cause of in­cor­rect main­te­nance or poor repair. We had one in this week with a good demon­stra­tion of this: it was be­hav­ing like yours.

In the en­gine bay there was rust stain­ing at the rear of the head and one of the heater hoses had been re­placed. The coolant in the ra­di­a­tor and header tank was brick red in colour. This usu­ally sug­gests ei­ther a blown head gas­ket (com­bus­tion gases make the coolant acidic and cor­ro­sion takes place caus­ing the colour), or overzeal­ous use of some kind of Rad­weld-type prod­uct. The head gas­kets on these cars are very tough and will usu­ally only fail be­cause of ex­treme over­heat­ing caused by coolant loss or sim­i­lar.

In the case of this car, I sus­pect lots of ra­di­a­tor sealant had been added to the coolant in an at­tempt to cure a wa­ter leak (that heater hose maybe). This had par­tially blocked the ra­di­a­tor (with the car up to tem­per­a­ture, care­fully check the core for cold ar­eas). Also, the ther­mo­stat was blocked. We removed the ra­di­a­tor and ther­mo­stat, flushed the en­gine and heater ma­trix with a hose, cleaned and tested the ther­mo­stat and fit­ted a new rad. Fresh an­tifreeze mix and the car seems fine now. Left much longer and the head gas­ket would surely have blown.

WET, WET, WET…

QAfter a down­pour last night my car is wet in the footwells. Why?

With most MX-5S there are a few things to check. But first it must be noted that these roofs are re­ally well de­signed, but even the best will let a bit of wa­ter in dur­ing ex­treme cir­cum­stances, for ex­am­ple, pres­sure wash­ers or hard driv­ing rain hit­ting the side win­dows.

The rear sec­tion of the roof is de­signed to let wa­ter drain into a plas­tic gut­ter be­low the rear deck. This gut­ter leads the wa­ter to a drain ei­ther side of the car just be­hind where the hood frame bolts to the Bposts. These block with leaves and soil. We clear these with a slim plas­tic rod dur­ing a rou­tine ser­vice. You can rod them from above or un­der­neath (just in­board of the rear lower sills).

The hood can also leak from the cor­ners of the front rail near the latches. The an­swer here is to prise the plas­tic locks from the latch ad­just­ing rods and, us­ing a 10mm span­ner, shorten the threaded rod. This in­creases the clamp­ing force of the front hood rail to the wind­screen frame seal.

Fi­nally, the rub­bers that seal onto the side win­dows can be pulled off and the stain­less re­tain­ing strips mount­ing screws loos­ened; next push the strips to­wards the win­dow, tighten the screws and fit the rub­bers. With the hood set cor­rectly, leaks should be re­duced.

SWEET SHIFTIN’

QThe gearchange on my mk1 Eunos is quite stiff – can this be im­proved?

It’s im­por­tant to re­mem­ber that Mazda de­signed these cars with a short throw, pre­cise gearchange, much like sports cars of old. As a re­sult they feel firmer than the foot-long lever in your av­er­age Eurobox.

But there are a few things to check. Start­ing at the top, the gear­lever gaiter can shrink and be too tight, thus re­strict­ing the stick’s move­ment. Next, take the gaiter off and re­move the gear­stick (three bolts), watch­ing you don’t drip gear oil on your seats! There should be a small quan­tity of gear oil around the bot­tom of the lever where the gear se­lec­tor rods slide. If dry, pour on some gear oil.

With the gear­lever out, check the white ny­lon ball-socket on the base of the lever. If this is worn or bro­ken the gearchange will be sloppy: just snap a new one into po­si­tion to re­ally sharpen up the se­lec­tion.

Fi­nally, it’s im­por­tant to know that both the clutch mas­ter and slave cylin­ders are in good con­di­tion. Look up in the footwell where the pedal con­nects to the mas­ter cylin­der; it should be dry. Re­place it if in doubt. Also peel back the rub­ber boot on the slave cylin­der and re­place if it’s leak­ing. Now fill the mas­ter cylin­der and bleed a lit­tle fluid from the slave cylin­der to en­sure it’s free of air. With these is­sues ad­dressed, your car will have a very sweet shift again.

A pos­si­ble source of buzzing af­ter a clutch change is a sloppy fit of an af­ter­mar­ket fric­tion plate on the splined cen­tre of the gear­box in­put shaft: as it moves slightly it cre­ates an an­noy­ing res­o­nance and chat­ter

The brown stain­ing and goo are signs that some­one has over-used a ra­di­a­tor sealant in­stead of hunt­ing down the source of a coolant leak. Here, the whole coolant sys­tem was flushed and the ra­di­a­tor re­placed be­fore re­fill­ing with fresh an­tifreeze

This 10mm nut on your hood’s latches can be tight­ened to in­crease the force with which they clamp to the wind­screen’s header rail

Grease (above) and a new ny­lon ball-socket, im­prove the shift

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