mk3 VW Jetta-Passat TDI buying guide

Nov 29, 2015
mk3 VW Jetta-Passat TDI buying guide
  • Mk3 jetta and passat new owner/buyer's checklist (1996-1997 passat TDI, 1996-1999 jetta TDI)

    Congratulations! You just bought a VW Jetta TDI or VW Passat TDI or are looking to buy one. Here is a maintenance checklist to bring your car up to good running order, list of common problems, and other things to know.

    You can view a full list of "how to" repair instructions for the mk3 TDI at: 1000q: mk3 turbodiesel FAQ and "how to" index, this page is organized to show new owner issues and info.

    Mk3 or mkIII means mark 3 or 3rd generation VW and includes the years of Jetta and Passat listed above. A3 is the 3rd generation jetta. B4 is the 4th passat and is also a mk3 car.

    For immediate inspection

    Check for any error codes
    Autozone and many other auto parts stores give free error code scans. See if there are any error codes in the car computer's memory. This will let you know of any problems. If you plan on working on the car yourself, get the VW/Audi specific VCDS ross tech car diagnostic cable. It used to be called VAG-COM.

    Do you have constant low power or rev limiter or the car suddenly loses power? See 1000q: constant low power or 1000q: limp mode diagnosis.

    Vacuum hoses:
    The ECU (car computer) has a vacuum hose inside that will need replacement. All mk3 VW TDI have had or will have this problem. If you have a check engine light and an error code showing "65535 - Internal Control Module Memory Error" this is an indication that the ecu hose or another vacuum hose is leaking. Since ECU failure is rare, most bad ECU can be fixed by replacing this hose. See 1000q: ecu hose replacement for this procedure. The vacuum hose ends get dried out, rub through, or crack, causing running problems. They're mostly 3.5mm and 4mm hoses which you can buy silicone hose at Mcmaster.

    Timing belt replacement interval
    = 60,000 mile replacement - this must be serviced immediately if there is no recent record of changing it. If this part fails, the cylinder head will be damaged and in severe cases you will need a new engine. This is because the TDI is an interference engine. If the timing belt or timing belt roller/tensioner fails, the valves will hit the pistons and cause damage. Mk4 cars can use a long life timing belt, the Mk3 must stick to the 60,000 mile maximum replacement interval. See 1000q: timing belt removal or check for more details.

    Note - if you just purchased this car, many sellers will have the timing belt changed to add value to the car. Many don't know how to properly index the tight tolerances that a diesel engine needs or the procedures for replacing the timing belt on a TDI or have a mechanic who is used to gasoline cars and then does the work on a TDI engine. At least remove the timing belt cover and inspect the parts to see if they look new as some sellers will outright lie or be lied to by a 3rd party. If you have any doubt about the timing belt, have it changed as soon as possible not as soon as practical!

    Engine oil change:
    = 10,000 mile change w/filter if you are using synthetic diesel engine oil. See 1000q: diesel engine oil for a list of oils you can use in this TDI. Note that it is normal for the oil to be black, even when new. It is also normal for the engine to consume a little oil between engine oil changes. See the engine oil list for more details.

    Plastic belly splash shield present? - While you are under the hood, see if the plastic belly pan is there. It's a black plastic splash shield with sound absorbing squares in it. It keeps water and dirt off the bottom of the engine and belts, reduces sound, and improves aerodynamics. If you can see the ground through the engine bay, it's not there - replacement is suggested.

    Tire air pressure = as specified by the manufacturer. There is a sticker inside the fuel door, on the inside of the driver's side door, or in the trunk which will specify an appropriate cold tire air pressure. Check the pressure only when the tire is cool or you haven't driven the car in at least 5 hours. A generic tire pressure you can use is 32 psi, never exceed the cold tire pressure listed on the side of the tire.

    Engine coolant = lifetime coolant should be changed as necessary. VW/Audi G12 (G12+) or Pentosin coolant is red, pink, or purple. Do not mix G12/G12+ or any VW compatible coolant with other colors (green, blue, orange) otherwise it will damage the coolant. If it has to be topped off, use distilled water. See 1000q: coolant flush to see a how to article on this. Note that the Jetta came with G12, some early Passat came from the factory with blue colored G11 which is not compatible with G12/G12+/G12++.

    Diesel fuel filter change:
    = 10,000 mile drain water, 20,000 mile replacement. If you plan on using high percentages of biodiesel, you should change it as soon as practical because biodiesel can loosen up deposits. See 1000q: fuel filter change for more details. See 1000q: intro to biodiesel for more info on biodiesel.

    Diesel injection pump leaks: Due to age and fuel issues, the seals on the injection pump can leak. The diesel fuel will corrode the timing belt and coolant hoses and even a small leak should be cleaned up ASAP. The top cover, middle quantity adjuster section, and head o-ring can be replaced on the car, most of the other seals should ideally be done off the car and might need a rebuild with all new seals. The pump should not be totally removed without locking the timing belt with VW timing belt tools. See 1000q: injection pump top cover replacement for more details on top seal replacement. Warning: only the top cover seal can be easily replaced, the other seals require a VAG-COM and/or at least basic mechanical sense. See 1000q: injection pump removal for more details on removal.

    Replace relay 109: Some cars have a relay 109 that can fail, shutting the engine off without explanation. Relay 109 controls the ECU and since the ECU controls fueling, failure of relay 109 causes the engine to suddenly shut off. The old relay is black and marked "109" and is under the dashboard in the relay box. The redesigned relay to fix this problem is gray and is also marked "109". If you have a black relay 109, get it replaced ASAP with a gray relay 109. A common symptom is the glow plug light not turning on. Sometimes the relay will cool down, letting you start the car a few minutes after suddenly shutting off.

    If the engine ever suddenly races and accelerates on its own, it may be having a runaway. An engine malfunction could cause the engine to eat its own engine oil. Since diesels are throttled by fuel and not air, this causes a feedback cycle where the engine races higher and higher. If the car is in gear it will also accelerate. Read more about a diesel engine runaway at 1000q: runaway engine FAQ.

    Service areas that can wait and common problems
    You may have noticed a chirping noise on cold starts that gets worse on cold days. Disabling the daytime running lights and misc. electrical load will help reduce this tendency but a likely solution is to replace the harmonic balancer/crankshaft pulley and maybe the serpentine belt tensioner. If you have a Jetta, the chirping noise could also be the one-way clutch on the alternator pulley slipping (not used on the Passat). The alternator pulley clutch is designed to increase the life of the alternator by letting it freewheel in one direction.

    The instrument cluster on Passat often burn out and need to be replaced. Be wary of a Passat with low mileage because it may have a replacement instrument cluster which will not reflect the true mileage. If you take off some of the instrument panel trim, there's red paint on the original screws holding the instrument cluster. If the paint is disturbed the cluster may not be original. The problem comes from cranking the engine with low battery. The voltage drop from using the starter discharges the memory in the dashboard - extended starting attempts can cause permanent damage. If you drain the battery down, do not try to start it without fully charging the battery! If you play with the ignition key, hear a buzzing sound from the dashboard, and the trip meter resets to zero, this means that you are in the danger zone. If you have a low battery, STOP and get it fully charged.

    Passat odometers reset back to 0 at 300,000 so if the car shows unusually low mileage it's possible that the odometer has flipped over. (Jetta don't have this issue)

    There's a fuse on the firewall next to the coolant tank that is commonly burnt out. This is the coolant glow plug fuse. The coolant glow plugs are separate from the engine cylinder glow plugs. Coolant glow plugs heat up the coolant and should help in faster engine warm up. Unlike the cylinder glow plugs, it won't affect engine starting. Clean the contacts of corrosion to help prevent future damage and replace the fuse.

    Check the fuel injection quantity through VCDS. Some cars tend to have running problems or smoke due to poorly calibrated fuel injection quantity. See 1000q: injection quantity adjustment and testing for more details.

    The door handles tend to stick or become hard to open with wear. If the back doors open easily but the driver's side is hard, it can be easily adjusted. See 1000q: passat jetta door handle adjustment/repair FAQ.

    Apply the parking brake when parking! It's good practice with any car but it is important on VWs because this sets the rear caliper self adjusters. It's best to apply the brake before going into park (auto trans) or first/reverse gear (manual trans) to put stress on the brake instead of the transmission internals.

    After scanning with a VCDS you may notice airbag error codes. The Mk3 airbag sensors are sensitive and will often set off a false alarm code. Clear the code and see if it comes back, it is very common due to overly sensitive sensors. If the code comes back soon, there is probably a real problem. Check the heater core for leaks, as it can leak coolant onto the electrical connectors below it and corrode the system. Also note that the Mk4 cars had a problem with VCDS damaging the airbag controller, this does not apply to mk3 cars.

    The car might go into limp mode due to a broken vacuum line or sticking solenoid. If you are applying power and all of a sudden it feels like you hit a huge headwind and power is taken away, this is limp mode. See 1000q: limp mode for some easy fixes.

    Due to age, mileage, and possibly the switch to ultra low sulfur fuel, some people experience leaking seals on the fuel injection pump. This may also be caused by heavy biodiesel use and then switching to petrol diesel. This will cause a no or hard start condition due to the fuel pump losing it's prime. The dealership will not fix it, their only option is to replace the entire pump at great expense. It's easy to change a few of the seals on the car as long as you have the right tools. Do NOT remove the center section, the quantity adjuster, without first indexing it with a VCDS. The diesel fuel injection pump can have the fuel temperature sensor malfunction, if you go to the dealership, they will try to sell you a new injection pump. Are you using biodiesel? Make sure the fuel is water free!

    The center console HVAC light often burns out. Just pull the center knob straight out to reveal the light bulb.

    Misc VW quirks and maintenance, non priority
    The ignition switch replacement should be done on all mk3 TDI. It was an extended warranty item for the 1996-1997 jetta/passat but only for 8 years and 100,000 miles so the coverage is probably worthless now (worth it to ask the dealer for a discount anyways). A bad ignition switch can cause the car to have flaky electrical symptoms, shut off the car, or result in a no/hard start. If the car starts when you jiggle the key up, down, in, out, etc., while holding it to start, the ignition switch is causing the issue.

    It's normal for the speedometer to read slightly higher than actual speed. German cars tend to have fast speedometers to account for car variations and so that they don't read lower than actual speed. The odometer reading should be correct and is a separate display from the speedometer.

    Jetta odometers reset at 300,000 miles to 0.

    Don't add a cold air intake filter because it already has a cold air intake and it won't be effective. If you want effective power upgrades, get a chip tune or chip tune + nozzle upgrade. Further upgrades would include a bigger turbo and a supporting mod like a stronger clutch. Check out KermaTDI for chip tuning for TDI engines. Also see the basic power upgrades article in the FAQ for more details.

    Holding the door key in "unlock" will open the power windows. If this happens even when you're not holding it in unlock, the microswitch inside the door handle is faulty and is making the ignition switch think you are holding the key to unlock.

    The mk3 TDI were usually sold in base trim so the car probably doesn't have remote keyless entry. See 1000q: adding OEM VW remote keyless entry for the procedure.

    The power door locks are vacuum actuated. Some Audi did this too because it moves the door locks smoothly instead of an electric solenoid thunking them up and down. The problem is that a faulty door microswitch, vacuum leak due to a worn line in the door hinges, and other issues can cause problems. See 1000q: central vacuum locking repair.

    It's common for the valve cover or EGR to seep oil. None of these will affect engine function but it can cause smoke and a big oily mess. The valve cover seal can be easily replaced but the EGR is part of the intake manifold and has to be replaced as one piece.

    Stepping on the brake and accelerator at the same time will cause the drive by wire throttle to reduce power. The Audi R8 exotic sports car also does it too; it's a byproduct of drive by wire.

    You can add an aspherical driver's side mirror to give a wider field of view. The part number is VW# 1h1 857 521 c. There is no writeup for this exact model but see 1000q: a4 blind spot mirror to see pictures and a description of this on a similar VW.

    Is there wax like tar dripping from the bottom of the doors? It is the wax sealant that VW uses to prevent corrosion. It helps to prevent rust but it melts, coming out of the door vents. Just use Goo Gone or some other paint-safe solvent and wipe clean with a microfiber towel and lots of water. Why microfiber instead of a paper towel? Microfiber is non-scratch and paper towels will scratch the paint. The tar also has lots of dirt stuck to it so using a microfiber towel will help avoid scratches. Follow up with soap and water, then wax.

    Get the car detailed. You will be amazed at what a good paint polish and interior cleaning can do. See 1000q: car detailing index for more tips.

    The front fenders will rust due to soundproofing that VW put between the metal fender and plastic wheel well liner. You can prevent this from occurring by removing the plastic wheel well liner and trimming the foam. There'll also be a lot of dirt behind the wheel well liners - clean it out to prevent moisture from building there. Also check for rust in general.

    You may also notice that the headlight plastic is oxidized. Polish and seal the headlights as seen in 1000q: headlight polishing. The VW Jetta TDI have glass headlights so they are not prone to this problem but Passat are old enough so that they will need a good polish. Passat TDI headlights are also pretty dim and dark. You can modify brighter bulbs to fit, see 1000q: 9005 9006 headlight bulb mod for details, but make sure the headlights are cleared or else it will just create glare.

    If you don't open the driver's side door within 30 seconds of unlocking the car, it will relock itself. If the car does it even if you open the door, the door module, handle, or wiring may be bad.

    Brake and clutch fluid should be changed every 2 years with DOT 4 fluid. See 1000q: brake / clutch fluid flush for some tips. Refer to your owner's manual for the general maintenance schedule.

    The exhaust gas recirculation (EGR) system lets in exhaust which mixes with the oily crankcase vapors. It forms a carbon buildup which will clog the intake. The intake must be removed from the car for cleaning or replacement, do NOT try to clean it while it's still attached to the engine. See 1000q: intake cleaning for the procedure. Some people suggest turning down the EGR with a VCDS but the ECU will adapt and the result is lower fuel economy. The EGR solenoid or valve can also leak or stick. This is due to broken vacuum lines or a bad solenoid.

    The EGR can also leak oil out the outside of the valve. This causes an oily mess but it can also be a fire hazard if the leak is bad and a lot of oil gets onto the exhaust. Your TDIs has the EGR and intake manifold as one piece, the mk4 cars have the EGR and intake manifold as two separate pieces. EGR/intake manifold replacement or diverting the leak is suggested. See the above paragraph for the removal procedure and parts lists.

    The parking brake cables may freeze the rear calipers in the "engaged" position in freezing moist weather. If the rear wheels stick on cold freezing mornings, that is the most likely cause of the problem. The boots crack due to age and let water in.

    If the shifter is difficult getting into 1st gear, it may be because of a worn shifter linkage or it may need a simple adjustment. See 1000q: shifter adjustment for details. New gear oil may also help.

    Most 1996 passat have a metal ECU case that was replaced under a recall. Those which were not replaced had black plastic case. If the 5th fuel injector (only for emissions) has not been disabled (it doesn't work anyways, wastes fuel, and creates unnecessary smoke), fix it now. I think it might have been a recall item. See 1000q: 5th injector disable for more details and a "how to".

    The heater door uses a foam covered door. If the foam breaks up you'll only get a little bit of heat. If you see bits of grey foam coming out of the air vents you know it's falling apart. You can use any adhesive foam to repair the blend door.

    Clean the engine air filter (for all) and change the cabin air filter (for Passat only). The snowscreen for the air intake should also be cleaned. See that procedure at 1000q: intake air filter and snowscreen service.

    Do the front strut mounts have a lot of play between the mount and it's seat? Does the strut top stick up and does the strut fall down a little when you raise the car? This is normal because some play is needed to allow the front wheels to turn. As the suspension ages, this gap may get larger because the weight of the car and use/age has caused the springs to sag and bushings to compress.

    The Passat center console glove box has a weak door hinge and tends to break. It costs $75 for a replacement, available from the dealership.