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Tech­ni­cal prob­lems solved

I was mildly con­cerned, hav­ing signed off last month’s how-to story (pages 88–91), that I might have given the wrong im­pres­sion about the best method of re­plac­ing the ex­haust-gas re­cir­cu­la­tion valve in a Cayenne Diesel. To put it an­other way, that la­bo­ri­ously (and ex­pen­sively) re­mov­ing the en­tire as­sem­bly – that is, both the EGR valve and its associated heat-ex­changer – was the only way of tack­ling the job.

My doubts were based on the fact that, while Porsche seems to pre­fer to sell the two items as one unit (for £654.09 in­clud­ing VAT), the valve it­self – the bit that does the work, and thus (pre­sum­ably) seizes up and causes the prob­lems – is avail­able sep­a­rately for ‘only’ £265.81 in­clud­ing VAT, plus about £3 for an ‘O’-ring. And in which case the labour cost would prob­a­bly be for no more than three hours’ work in­stead of more like seven.

I sug­gested in the piece that I would be car­ry­ing out some sort of ba­sic foren­sic ex­am­i­na­tion of the first EGR valve that had come off this very same car, back in 2014 – pri­mar­ily to try to find out pre­cisely what was wrong with it, but also to as­sess whether or not it could be cleaned and used again. I can now re­port, then, that at­tempt­ing to re­move the valve alone, with the heat-ex­changer still in situ on the en­gine, would prob­a­bly be just as time-con­sum­ing, and ar­guably im­pos­si­ble with­out caus­ing sig­nif­i­cant dam­age to the part you want to keep.

The EGR valve is se­cured to the heat-ex­changer by three Torx screws. Hav­ing re­moved those from the old unit, I not un­nat­u­rally ex­pected the valve to pull rea­son­ably smoothly out of its hous­ing, but even care­fully tap­ping the for­mer with a cop­per ham­mer – which would have been im­pos­si­ble with the as­sem­bly still in the car – shifted it no more than a frac­tion of a mil­lime­tre. Soak­ing the valve with heavy-duty car­bu­ret­tor cleaner, sprayed in through one of the ports, made no dif­fer­ence, ei­ther, and in the end I re­sorted, with the aid of a heavy brass drift and a big­ger ham­mer, to sim­ply hit­ting it a lot harder.

Whether that will have achieved any­thing, or even ir­repara­bly dam­aged the del­i­cate elec­tri­cal com­po­nents in­side the valve’s ac­tu­at­ing mech­a­nism, I hon­estly don’t know. I sus­pect, though, that how­ever care­fully the de­vice is re­moved and sub­se­quently cleaned, it nei­ther can nor will ever be quite as good as new. And that while your ef­forts might con­ceiv­ably get the ve­hi­cle go­ing again with­out the basilisk stare of the CEL, or Check En­gine Light (which is an Mot-test fail­ure), the light will soon come back on again. Don’t they al­ways?

Hav­ing said that, at least I now know that the valve can – in the­ory, any­way – be ex­tracted on its own; and that, since it can phys­i­cally ro­tate within its hous­ing, al­beit through only a few de­grees, a com­bi­na­tion of de­ter­mined twist­ing and pulling, per­haps plus co­pi­ous amounts of pen­e­trat­ing fluid, might just get it mov­ing. I sin­cerely hope that nei­ther Robin Mcken­zie nor Terry Parker at Auto Um­bau have to do this job again – and I’m sure they do, too – but I have a feel­ing that if it does crop up they might be will­ing to give this method a go.

When is what might look like a clas­sic so-called bodge most def­i­nitely not a bodge? An­swer: when in prac­ti­cal en­gi­neer­ing terms it is the equal or even the bet­ter of what it re­places. And which was in this par­tic­u­lar ex­am­ple de­signed purely for easy and cheap au­to­mated as­sem­bly, rather than for any se­cu­rity or longevity it might of­fer.

In right-hand-drive 996model Car­reras, and the me­chan­i­cally al­most iden­ti­cal 986 Boxsters, there is a seem­ingly ever-in­creas­ing like­li­hood of an an­nual MOTtest ‘advisory’, or even the dreaded fail­ure, due to the now per­haps in­evitable cor­ro­sion of part of one of the power-steer­ing pipes, vis­i­ble in­side the right-hand front whee­larch. (With the wheel off, any­way, or per­haps turned to full right-hand lock.) The pipe lay­out in the equiv­a­lent left-hand-drive cars is such that, so far, they ap­pear to be un­af­fected – as, too, seems to be the fer­rule on the larger-di­am­e­ter line in right-hook­ers, even though it is only a few inches away from the one that does rot.

Un­sur­pris­ingly the ‘fac­tory’ way of do­ing the job, and which we showed in our howto fea­ture in Novem­ber 2014, is to re­place the en­tire pipe. And that means not only rais­ing the ve­hi­cle on a lift, but also then low­er­ing the front sub­frame a few inches. You – or your cho­sen spe­cial­ist – will then have the joy­less task of sep­a­rat­ing the pipe from the steer­ing rack (and also the con­nec­tion half­way down the left-hand sill mem­ber) and, who­ever ends up do­ing the work, of pay­ing for it all. The pipe alone costs well over £200 – and in our ex­pe­ri­ence you might find it quite dif­fi­cult to ob­tain from Porsche those re­quired for cer­tain mod­els – and you are prob­a­bly look­ing at a min­i­mum of around four hours’ labour. Call it around £600–£700 in to­tal.

The way I would now do it, how­ever, hav­ing watched an­other spe­cial­ist’s prag­matic ap­proach on be­half of a cus­tomer who, jus­ti­fi­ably in my view, wasn’t pre­pared to spend that much on a car that does only a few thou­sand miles a year, is shown in the ac­com­pa­ny­ing pho­to­graphs. Tools re­quired: a trol­ley jack and an axle­stand, plus a small pick and a screw­driver. Parts: two wor­m­drive hose clips. Time and cost: about half an hour (at most) and, if do­ing it your­self, all of about £5. Or noth­ing at all if, like many of us, you have ‘Ju­bilee’ clips be­yond num­ber stashed away in the garage. For cos­metic rea­sons alone do try to use two iden­ti­cal clips, how­ever, and in size terms suit­able for the roughly 15–20mm hose.

The tech­nique is made pos­si­ble by the fact that the alu­minium fer­rule where the flex­i­ble rubber hose meets the rigid steel pipe is it­self noth­ing more so­phis­ti­cated than a clamping de­vice that, rather than re­quir­ing la­bo­ri­ously to be tight­ened by hand, can be closed up by a ma­chine in a fac­tory in just one swift op­er­a­tion. You could also use the so-called Oetiker clips favoured by Porsche for many other ap­pli­ca­tions, but they too are used purely for ease of orig­i­nal as­sem­bly and, as in the Cayenne Egr-valve job that was the sub­ject of last month’s how-to, might here be dif­fi­cult to tighten in situ. They also re­quire spe­cial pli­ers to in­stall – and even with those are by no means easy to get right ev­ery time.

EGR valve is se­cured to heat dis­si­pa­tor by three Torx screws, but un­do­ing those to sep­a­rate the two items had no ef­fect, and tap­ping and lev­er­ing was go­ing to do more harm than good. A lib­eral squirt of heavy-duty car­bu­ret­tor cleaner into both sides of the dis­si­pa­tor made no dif­fer­ence, and ul­ti­mately the only so­lu­tion was to se­cure the cast­ing in a large vice, and care­fully but res­o­lutely tap the un­der­side of the valve with a heavy ham­mer via a non-dam­ag­ing brass drift – which would have been im­pos­si­ble had the as­sem­bly still been mounted on the en­gine. Most ob­vi­ous cul­prit is the car­bon build-up that is, of course, go­ing to be the rea­son why you want to sep­a­rate the two items in the first place, but even with­out that they are al­most an in­ter­fer­ence fit – and note rubber ‘O’-ring (mid­dle). And still there re­mains a flap valve in­side the main body (above)

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Photograph top left is a com­mon sight un­der the right-hand front wing of a right­hand-drive 996 or 986 Boxster, and the cor­roded and split alu­minium fer­rule will likely earn the car an MOT advisory or even a fail­ure. The fac­tory way of re­pair­ing it is to re­place the en­tire pipe – as we showed in the Novem­ber 2014 edi­tion – but nat­u­rally that is both time-con­sum­ing and quite ex­pen­sive. Fact of the mat­ter is, though, that the fer­rule is noth­ing more than a cheap and sim­ple hose clip, de­signed to al­low it to be fit­ted in one swift mo­tion by a ma­chine in a fac­tory – rather than la­bo­ri­ously tight­ened by hand – and it is per­fectly per­mis­si­ble to re­place it with two or­di­nary worm-drive clips; or, in dire emer­gency, by just one. All you need do is pull away the re­mains of the alu­minium sleeve – which won’t be too dif­fi­cult – and, af­ter clean­ing up the rubber, per­haps, open up and then tighten the new clips. Job done. Photo on the far right shows an air-con hose with one of these fer­rules be­fore it has been crimped and thus tight­ened – and how even here it is per­mis­si­ble to use so-called Oetiker clips in­stead, al­though those won’t be par­tic­u­larly suit­able for the PAS pipe be­cause of re­stricted ac­cess

The same car had been taken to this in­de­pen­dent spe­cial­ist’s work­shop for an air-con check/re­gas, and pos­si­ble re­place­ment of the con­densers. The lat­ter were long in the skip by the time I got there with my cam­era, but the state of the main en­gine-cool­ing ra­di­a­tors (left) gives you an idea how bad they were. And this in a car with barely 40,000 miles on the clock

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