I've just read the used hot hatch article in February's CAR. They have consulted Jabbasport and VAGTECH to comment on buying a used MK5 GTI. I'm sure there is nothing here that you guys don't already know about, but I thought it would be worth posting for those who are about to buy, or have recently bought a MK5 GTI. there are at least 2 additional things I have learnt that I'm getting checked at my cars major service on thursday. Main points are as follows:
1) The OEM turbo dump valve has a rubber diaphragm which can split, and lead to a loss of that turbocharger surge of power delivery at 2000rpm. Jabbasport replace this with a plastic piston from the S3, but if you are sticking with OEM, get it checked at service. DOES ANYONE KNOW IF THIS DIAPHRAGM CAN BE REPLACED ON ITS OWN?
2) More serious is the fuel pump follower, which is prone to early wear and tear, especially if the car has been on long-life servicing. GET THIS CHECKED IF YOUR VEHICLE IS 40,000 MILES PLUS, AS FAILURE CAN RESULT IN SERIOUS TOP-END DAMAGE. Jabbasport usually change them every 20,000 miles as a precaution, as they are only 28 quid a pop.
3) If the car is a DSG and lurches when you pull away, it's likely to be a failure of the Mechatronic ECU. Should be super-smooth when you pull away.
4) As it's direct injection, fuel goes straight into the cylinder, so therefore the back of the valves can get coked up leading to high oil consumption. However, VW says loss of 1Litre per 1k miles is normal, so check oil level regularly.
5) Check the inner wear on the rear tyres. The outsides can look fine, but the inner edge can be down to the canvas if the rear shocks are weakened. You should hear a droning noise similar to a shot wheel bearing if this has happened.
6) And finally, CAR recommend swerving the DSG and going for a basic spec with cloth seats and manual for one of the best hot hatches ever made!