FAQ: Common faults/design irks/questions on Mk5 GTIs (and related PQ35 cars)

Discussion in 'Mk5' started by Teutonic_Tamer, Aug 9, 2010.

  1. Teutonic_Tamer New Member

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    OK - a few common 'issues', primarily regarding the Mk5 GTI and Edition 30, but may also afflict other 'A5' generation cars which use the PQ35 platform cars, such as the Jetta Mk5, Tiguan, Touran, TT2, Mk2 A3/S3, Leon 2, Octavia 2.




    POWERTRAIN (engine, transmission, driveline)
    • Engine & transmission mounts - known to be very soft and 'soggy'. Indications of excessively worn mounts: air filter intake trunking regularly dislodging (be careful of this, the top part can wedge into one of the cooling fans, and potentially bu&&er either the fan or radiator, or both); knocking in footwell area under hard acceleration, particularly under loss of traction (wheelspin); broken front exhaust mount (especially after fitting aftermarket item such as Milltek); excessive wobble from gear lever (mainly affects manual, rather than DSG) during hard accel or deceleration. Remedy - either modify existing mounts (fill with high temp black RTV silicone [but then you need to leave car standing for at least 7 days for silicone to cure]); use a poly insert for the rear bottom mount (such as Powerflex - these are supplied with Millteks - but arn't 100% ideal); install a 'fast road' lower rear mount from someone like Vibra-Technics (supplied exclusively through Volkswagen Racing) or VF Engineering; install full set of three 'fast road' mounts (from same suppliers).
    • 'Diesely' noise on idle - this is a very common concern, but is totally normal. Caused by the considerably higher pressures in the fuel lines for the Fuel Stratified Injection (FSI) direct injection fuel injectors. Remedy - learn to live with it!
    • Heatsoak - mainly affects GTIs and Edition 30s, and even more apparent on 'tuned' engines, rather than TDIs or lower spec Golfs etc. Basically, the OEM intercooler on the GTI and Ed30 isn't particularly efficent - both in terms of general internal flow rate, but also in terms of physical siting (it is sandwiched between the air con condensor and the engine coolant radiator). Remedy - a number of possible solutions, in various permutations are available. To keep it strictly OEM, replace standard intercooler with genuine Audi 8P S3 (this has about a 40% improved internal flow rate, and uses an all alloy construction, rather than the alloy/plastic hybrid on the standard GTI/Ed30) - this is a fairly big job to do though. If you want to retain the standard GTI/Ed30 cooler, you can add an additional lower front mounted intercooler from someone like Forge - the 'Twintercooler' - which essentially supplements the OEM sited cooler. Or for the best possible solution - use an S3 cooler AND the Forge Twintertcooler - as this particular combination overcomes weaknesses in OEM design with regard to siting of standard cooler (be that the normal GTI/Ed30, or the S3 cooler).
    • Loss of turbo boost - generally only affects the early GTIs with the AXX engine, later BWA variants seem immune-ish. Caused by faulty turbo cut-off valve (N249 - also known as turbo divert valve, and sometimes incorrectly referred as a 'dump valve'). The original valves had a poor quality black diaphragm which was prone to spliting (especially on remaped motors); later valves (from 06F 145 710 C, and upto 06F 145 710 G) which have an orange diaphragm are considerably more reliable. The latest valves (06H 145 710 D - originally designed for the EA888 TSI engine) have a piston rather than a diaphragm, and can be retro-fitted to the EA113 Mk5 engines.
    BRAKES (inc ABS/ESP)
    • Faulty ABS/ESP unit - All PQ35 cars use a cheaper Teves Mk60 unit (rather than the more durable and reliable Bosch units). Whilst not yet a reported problem on Golfs, there are alarming numbers of Touran owners reporting failures of ABS/ESP units (identical spec to Golfs/Leans/A3s/TTs/Octavias/etc) - at a cost of around 1500 to replace. My research would indicate these fail on Tourans due to two issues - the first being the failure to change the brake fluid every 2 years, and the second probably due to the ABS/ESP not being 'exercised' (Touran owners, with their little 'darlings' strapped in the back seats are considerably less likely to activate ABS, traction control, or ESP functions - whilst performance cars such as GTIs, Octy vRS, Cupra owners are considerably more likely to activate those systems - especially traction control[:$]). Remedy - do NOT skip the 2-yearly brake fluid change - and ONLY use the genuine VW brake fluid. From 2006 model year, ONLY brake fluid which meets VW 501.14 is permitted (generic DOT4, and even DOT5.1 are no longer permitted) - basically, the 501.14 standard is for a special 'low viscosity' fluid, designed to cope with the miniscule bores and passages within ESP modulators. The genuine VW brake fluid also out performs many so-called high performance 5.1 fluids too.
    • 'Weak' brakes - a very subjective issue, and depends entirely how you drive and use your brakes. But if you are particularly heavy on your brakes, or have a remap, or other performance enhancing mods, then the standard brakes can feel a little weak. On the standard GTI, the Edition 30, and the Octavia vRS, the front brakes have a disc size of 312x25mm (radially vented) and use a single-pot sliding caliper with a 54mm dia piston. Remedy - obviously, the first and most important solution is to make sure your standard brakes are in A1 condition (discs within min thickness with no 'pick-up', pads with pleanty of meat, calipers free from rust in pad slides and appropriately protected with a decent anti-seize paste [and NOT plastilube], and caliper slides [those shiny bolts removed with a 7mm allen key]) and bushes appropriately lubed with a proper silicone grease. Next would be to consider uprated brake pads (Ferodo DS2500 seem to get good feedback). Or you can consider 'big brake' upgrades. To keep it strictly OEM, the Audi 8P S3, Golf 5 R32, and Leon 2 Cupra all use larger front brakes (with the S3 and R32 also using larger rears) which are sized at 345x30mm with a caliper containing a 57mm dia piston (do NOT use the visually idential caliper from the B6/B7 Audi S4, as this has a 60mm dia piston, and will seriously mess up the hydraulic biasing). The Leon 2 Cupra uses an identical red paint as the GTI/Ed30/Octy2 vRS (this is ideal if you wish to retain your standard rears, and can't be bothered painting calipers to match). The S3 and R32 are coloured differently to the GTI, being black or blue respectively - and these would be ideal if upgrading to the larger rears as found on the S3 and R32. Or for the non-OEM aftermarket options: any quality big brake kits, from the likes of quality manufacturers such as Alcon, Brembo, AP Racing, or lesser quality makes such as Tarox, ECS, Movit etc could be considered. However, from feedback from users who have gone down this aftermarket route (which often use much larger diameter discs), it is strongly recommended to upgrade the rears to the larger S3/R32 ones, otherwise braking instability between front and rear occurs.
    CHASSIS (inc steering, suspension, wheels)
    • Uneven rear tyre wear - on the GTI & Edition 30, the rear wheel alignment is set up as standard with quite a large camber. This is to give excellent handling from the rear axle, particularly under hard cornering. However, if a GTI is mainly used for 'straight line' motorway or dual carriageway crusing, some uses have reported excessive wear on the inner shoulders of the rear tyres. Remedy - start hooning it around the twisties. Or alternatively, VW released a modified range of settings for the rear geometery (basically much less rear camber), so opt for this (but whilst this will even out the rear tyre wear, it will also lessen the rear end handling - your choice!)
    • Steering rack knocking - this was prevalent in very early Mk5 cars (of all specs). A modified 'generation 2' steering rack was factory fitted (from around 2006-ish) and this was fitted under warranty to those early affected cars. However, many Mk5 owners still occasionally complain of knocking or clunking from the steering. This was discussed at length on the GolfGTIforum.co.uk - www.GolfGTIforum.co.uk/index.php?topic=32092 - and is probably best to look there for answers. Ultimately, most just 'put up with it', as some kind of design trait!
    • 'White worm' on 18" Monza II alloys - an exceeding common (and irritating) problem with the factory fitted optional 18" alloys (the standard 17" Monza alloys are not affected). Basically, the Monza IIs, rather than being grey painted like conventional alloys, have a clear lacquer applied over a diamond-cut finish. If there is any imperfection in the lacquer, then a white powdery corrosion (typical of unprotected aluminium alloys) burrows its way in a worm like fashion under the clear lacquer. Many owners have had many wheels replaced under warranty, but the issue remains even outside the warranty period. Remedy - get the wheels refurbed at a known 'Monza II' specialist such as Spit and Polish or Pristine Wheels. This issue also affects the black plastic centre caps too!
    ELECTRICS
    • Poor halogen headlamps - another subjective issue, but some owners report poor headlamp performance with the standard halogen headlamps. Remedy - firstly, make sure you have the driver-adjustable aim (the wheel to the left of the main rotary light switch, next to the dash light dimmer) set to the highest setting (obviously, if you have some pie-eaters in the back seats, or bags of cement in the boot - then adjust said headlamp level wheel accordingly). Next, make sure the beams are actually correctly aligned (just because it may have passed a recent MoT, does'nt mean they are at their 'optimum' setting). Finally, consider some high performance uprated H7 bulbs such as Philips Vision Plus (or whatever they are called these days) from somewhere like the very highly regarded and reputable www.PowerBulbs.com.
    • 'Tyre Pressure Warning System' - dispite what it may say in the brochure/handbook - the system is definately NOT a proper system (it does NOT measure the actual pressure in individual wheels). It is utter shyte, and exceedingly misleading (to the point that VW now call it a mere 'flat tyre warning'). Do NOT rely on this system, because some (though not all) owners have reported that it just does NOT work. Remedy - get yourself an old skool pencil-type tyre pressure guage, and use it once a month (and before long journeys, etc).
    BODYWORK
    • Tailgate badge corrosion - another 'white worm' issue, similar to the 18" Monza II alloys, on certain variants of the VW badge used for the tailgate release, white worm corrosion can affect these. Remedy - get it replaced, either with a new OEM one, or a matt black one, or an expensive carbon fibre one!
    If there are any other issues that I, or anyone else think of, then post below and I'll add them to this first post of the thread.
     
    Last edited: Aug 12, 2010

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