You just bought a high mileage car? Here are some tips
Congratulations, you bought a new car (or at least new to you)! Hopefully it's in decent condition. Here are some ways to get the most out of your car. What is considered high mileage? A car more than 15 years old or with more than 175,000 miles is what I would consider high mileage because parts start to fail more frequently past this point. The target lifespan for automotive engineers is about this, although with proper care and proactive maintenance, cars will gladly go longer. A TDI engine tends to last longer because diesel fuel is an oil and doesn't wash the engine oil off the cylinder walls like gasoline might, lower rpm operation, more robust construction, and cooler operation. See 1000q: how a diesel engine works for more details.
First, make sure all maintenance is up to date. Do not attempt to add power mods unless the car is in proper running order. Mileage isn't the factor when adding power mods, engine condition and maintenance is. Second, detail the car to make it look its best. Third, take proactive maintenance steps if you want to avoid any problems. From a financial perspective, it might not be worth it to spend money doing proactive maintenance if the value of the maintenance exceeds the value of the car. On the other hand, since newer cars depreciate more than older cars, driving your old car and keeping it reliable will save you money in the long run and help prevent break downs.
Here are the general new owner checklists for mk3 and mk4 cars.
mk3 new owner checklist
mk4 new owner checklist
Basic maintenance: refer to the FAQ section 1000q for more details and "how to" for your car, see above for more details
Timing belt - if you don't have proof of when the timing belt was last changed, change it as soon as possible. Not as soon as practical, as soon as possible. It doesn't need to break completely, it could just slip and cause thousands of dollars of damage to the cylinder head and engine. Replacement costs range from $300 if you do it yourself to $600 or more if you take it to a mechanic.
Fluid change - oil, coolant, power steering, and brake fluid. Manual transmission gear oil or automatic transmission fluid and differential gear oil will result in smoother shifting and longer transmission life. Note that most manual transmissions share gear oil with the differential, automatic transmissions use fluid for the transmission, gear oil for the differential.
Detailing: refer to 1000q: car detailing index for tips on how to polish the paint, wash and wax your car, and detail the interior and exterior. There may be paint chips or wax stains on the car that you can fix with those techniques. Polishing the paint will also remove or lessen the appearance of scratches.
Proactive maintenance and other inspection items: refer to 1000q for more details and "how to" for your car.
Vacuum hose replacement - After many years or miles, the rubber vacuum hoses that regulate the engine and turbo will get worn out. They tend to rub through anywhere they make contact or crack near the ends. Vacuum leaks rob the engine of both power and efficiency, so this is probably the most basic proactive maintenance step.
Rust - Rust is a killer of cars. If you see a some rust here and there, it means that there is rust everywhere that you cannot see. Even if the car is mechanically in good shape, rust on the body will cause the wiring harness to be exposed, the car to lose resale value, and it looks bad too. Rust will make maintenance on the exhaust, suspension, brakes, etc., twice as hard as it needs to be due to corroded bolts and nuts. You can cut rust out, burn it out, or seal it with chemical sealers. Once rust starts, it keeps feeding itself, so the best way to fix rust is to cut it out, weld in new metal, grind it down, and repaint the affected area.
If you can't do that, there are rust "stoppers" available at auto parts stores that use chemicals to temporarily seal rust and prevent it's growth. Just thoroughly clean the area, apply the rust stopper, and paint over it. It won't look perfect, but it's a long lasting- temporary solution. If you live in an area where they salt the roads, wash the underside of the car every spring and during the winter. VW has a warranty against rust but it only covers rusted holes that fully penetrate the sheet metal from the inside out and was not caused by damage.
Alternator - Alternators also tend to fail after many years. Soaking engine degreaser or letting oil or power steering fluid drip onto the alternator will also kill them. Alternator failure will cause the car to be stranded because your battery cannot supply all of the electrical power needed to keep the car running. Luckily, earlier TDIs have pretty low electrical demands as long as the headlights are off. This is because the car has a large battery for cranking the high compression diesel engine. They can be easily replaced and are usually under $100 for rebuilds, so a new or rebuilt alternator every 150,000-175,000 miles is not unreasonable. It could last as long as 300,000 miles but there are brushes in the alternator that wear down and have to be replaced and it can be more economical to also replace the bearings, etc., with a rebuilt alternator.
Battery - the battery should last a long time if it is properly maintained. Overheating or draining a car battery all the way and then charging it up will also shorten the battery's lifespan. You would need a "deep cycle" battery for those demands. Keep the terminals clean, as seen in 1000q: tips for the mechanic, and it should provide a stable electrical supply for the car. Also check the water level occasionally. Many batteries have indicators for the water level. If you don't know how to safely check the water level, take it to a mechanic!
CV boots - these are the rubber boots that seal the CV, or constant velocity joints. They are located on the drive axle ends. They wear out over time, especially if they are exposed to heat or salt. The inner CV boots are exposed to the heat from the engine and the outer CV boots are exposed to salt and other road wear. As a result, they can crack and throw grease around. If there is grease splattered on the inside of the wheel or transmission flange, immediately remove and regrease the CV joint and put a new boot on. If there is noise, the CV joint is bad and must be replaced. Once they are replaced, they should last many years before they need replacement again. The grease inside also tends to get a little dried out past 10 years so you may want to regrease the bearings if it's convenient. If not then I would just leave them alone.
Clutch life and adjustment - if the clutch is engaging close to the floor, it could mean that the clutch pedal (non TDI) needs adjustment or that the clutch is worn out if it's engaging at the top. If it is slipping, it doesn't necessarily mean that the clutch is worn out, it may just need adjustment or fresh clutch fluid. The TDI clutch pedal is hydraulic and is not adjustable. There is also an inspection port on the bellhousing of the transmission that lets you view the flywheel, pressure plate, and clutch. Depending on the car, it may be on the bottom, top, or side of the bellhousing, always next to the engine block, as this is where the flywheel is located. See 1000q: clutch FAQ for more info on how a TDI clutch works.
Replacement is expensive for a new pressure plate, resurfaced flywheel, master and slave clutch cylinders, clutch fork and springs, clutch pivot point, etc., but a reasonable proactive replacement interval would be after about 17-20 years and 300,000 miles with normal use of the various components. Again, this is a proactive replacement interval and is normally not needed if you don't suspect a problem, but many of these components will be worn down or close to it at this point. In theory, these components could last forever, but past a certain wear point, things just begin to break. I would not expect the clutch master and slave cylinders to last past that since the seals will be worn out. A clutch could in theory, last forever but in practice the pressure plate springs get worn out and other stuff just starts to fatigue. Metal fatigue sets in and could cause the fork/ball or springs to break or get weak. Regular changing of the clutch fluid will help prevent rust and seal failure but wear and tear take their toll on the seals.
If you have an mk4 or newer (1998+), you also have a dual mass flywheel (DMF) which is a wear item. See 1000q: clutch FAQ for more technical information. If you remove the transmission and have over 100,000 miles, I suggest a new DMF or a compatible solid flywheel. Early replacement of a DMF will help absorb engine vibrations but the difference is so small that I would leave it alone unless there's another reason for replacement.
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