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Thread: Z3 Pre-Purchase Advice

  1. #1
    Join Date
    Jul 2006
    Reston, VA
    My Cars
    '06 Z4M Roadster

    Z3 Pre-Purchase Advice

    Before purchasing a Z3, you should make all of your normal inspections. This is simply a list of common Z3 issues that you should keep in mind.

    Water Pump:
    The water pumps on Z3s fail like clock work around 60k. If the car is over 50k, and hasn't had the water pump replaced, expect to replace it. Part costs ~$150 and labor is 2 hours.

    Differential Mount and Trunk Floor Welds:
    The Z3's differential mount and rear trunk floor welds are prone to tearing. To inspect, remove the carpet in the trunk and look for spot welds along the back floor. These spot welds should be little flat circles. If they are sunk, or cracked, there will soon be a problem. Under the car, look at the C shaped mount to which the differential is bolted. Inspect for tears in the corners of C. Also look at the bottom of the trunk floor for signs of tearing or separation.

    Randy Forbes and Dinan both have kits that strengthen the diff mount and trunk floor. These can be used as a preventative measure.

    Leaking Around Windows:
    Look for discoloration and water stains on the carpet floor. Be sure to check behind the seats and under the floor mats. The cause of this is usually a leak near the top of the A pillar (front window) where the window meets the front of the soft top. Use a product like Gumi-pfledge to 'moisten' the rubber.

    Alignment Bushings and Brake Pads:
    While driving the car at least 40mph, lightly hold the steering wheel and press the brakes with force. If the car swerves, or does not stop in a smooth straight line, you'll need to inspect the following: front control arm bushings, tie rod bushings, brake pads and rotors. The control arm and tie rod bushings may be cracked or broken, causing extra 'play' in the steering alignment. The brake pads and rotors may be too worn or warped.

    2001-2002 ///M Roadsters and Coupes:
    The S54 engine in these cars had a very significant design flaw, that can be fatal to the engine. The rod bearings on the crank shaft can become misaligned, causing the crankshaft to move out of alignment. Replacing these bearings with an updated version is a permanent, but costly fix. All S54 owners should ensure that this problem has been corrected. BMW covered this problem under warranty on other models, and has been known to cover this issue on a case-by-case basis for the Z3.

    Manual Transmission Shifting:
    The manual transmission shift lever may lean to the right (5th gear) or may be difficult to put in 1st and 2nd gear. This indicates worn shift pins, sometimes due to excessively aggressive driving or due to mileage. Replacement parts about $100. The transmission needs to removed and special tools are need for the service. BMW does not publish service instructions for the Z3 transmission, so a seasoned transmission specialist will need to be consulted. These issues may be resolved with a simple fluid flush and change.

    Roadster Soft Top:
    The soft top may be frayed, torn or generally worn. Replacement tops can be purchased for ~$700. Installation is quite difficult, because of tension placed on the top by the frame. Installation can be performed by most indie shops.

    Motorized automatic tops may not perform as they should. As a temporary solution, you can disengage the hydraulic pressure system so that the top can be manually moved. The knob is behind the driver's side trunk carpet. Often a rusted motor or frayed wiring are responsible for non-working tops.

    Roadster Plastic Rear Window:
    The rear window may be foggy or have opaque creases. "Fogging" of the window is normal and is caused be normal use. Fogging can generally fixed with Meguire's Plastic Cleaner and Polish produces; cost about $20 from any auto care store.

    Creases in the window can cause the window to tear or wear holes. The window can be replaced using the "zipper" that's around the inside edge. The replacement window costs about $220. Installation is quite tedious, but can be done in a few hours.

    Slight Seat Rocking:
    With hard acceleration or braking, both the driver's and passenger's side seat may rock slightly. This is caused by two very soft rubber bushings that have deteriorated. You can order a fix it kit from Doug Whalen. Takes about 3 hours to fix both seats.

    Dash and Center Console Lights:
    The lights behind the gauge cluster and HVAC controls in the center console may be burnt out. The lights are very cheap, but replacement can take a few hours.

    Check that dash and center console lights are illuminated when the head light knob is pulled out. If they do no illuminate, try turning the head light knob in either direction. If the lights dim heavily when they're supposed to be lit, do not have a consistent slope of illumination or are completely dark, the head light knob circuit needs to be replaced. Parts are about $90 and installation takes an hour.

    A/C Control:
    Check that turning the "hot/cold" HVAC knob (center) has the desired effect. If the knob turns very easily, or not at all, there's a problem with the tension cable. If the knob moves too easily, the HVAC control may need to be replaced for about $150. If the knob doesn't move, especially from hot to cold, the tension cable needs to adjusted; 2 hours of work.

    Check that turning the fan speed knob (right) has the desired effect on all 5 settings. If the knob only works on the upper most settings, its likely that a resister in the fan control has broken. Parts cost about $30 and require 2 hours of labor.

    Blown Speakers:
    Check that the stereo speakers all sound normal. The subwoofer and kick-panel speakers will degrade over time. The subwoofer is very expensive to replace, but there are many aftermarket options such as The kick panel speakers can be replaced easily.

    Sagging, Squeaky Glovebox:
    The glovebox may sag, or not align correctly when closed. This is caused by poor design of the glove box door and latch. This can be fixed for about $20, and 2 hours of work.

    Rear Shock Mount Bushings:
    The rear shock mount bushings wear quickly in spirited driving. You will hear a solid "clunking" sound inside the cabin from either side of the rear. This indicates that these bushings have worn and need to be replaced. Parts cost ~$30. Roadster install time is around 2 hours. Coupes require disassembling almost the entire trunk carpet, and therefore takes around 3 hours. Many people will suggest installing Rouge Engineering Rear Shock Mounts, as they will allow much easier replacement of these bushings in the future.

    Parking Brake Cable Tension:
    The parking brake cable can stretch over time. This may cause the parking brake not to fully engage, and the cable may rattle against its retainer clips during normal driving. The rattling sound will appear to come from outside the car and over the driver's left shoulder. The cable can be re-tensioned using simple tools; takes about 30 minutes to learn. In some cases, a retaining clip and spring inside the rear wheel hubs may have failed, causing the rattle. These can be replaced for ~$20 and take about 30 minutes.

    Uneven Tire Wear:
    Moderately uneven tire wear on all four tires is normal. The factory recommended camber and toe setup will cause this uneven wear. Tires that are heavily worn on only on one side of an axle indicate a suspension geometry problem. This may be due to sagging springs, bent arms or nascar circuit driving. This kind of issues can be quite costly, and should be remedied before purchase.
    Last edited by wildag; 08-24-2009 at 09:41 PM. Web Services

  2. #2
    Join Date
    Apr 2013
    Dayton, TennUnited States
    My Cars
    1998 BMW Z3 2.8L

    Compression test

    While digging through the maintenance records after the purchase I found that my 1998 Z3 (125K miles) had been overheated. I suggest a compression test prior to purchase. My engine had 6,000 miles put on it since it was overheated, so although the compression test indicates a little damage from overheating I think the engine will continue to run OK for a long time. Knock on wood.

    10.2:1 compression ratio
    Average atmospheric pressure 14.7 psia
    So my 2.8L should read around: 10.2 X 14.7 psia = 150 psia - 14.7 psia = 135 psig. All cylinders should be within 7 psig of each other.

    I was reading 165 psig ?????????? and my lowest cylinder was 150 psig, 15 psig below the highest. Not extremely bad. Just a little. A cylinder will continue to fire until it is well below 100 psig.

    Be sure to disconnect the spark coils or you may die. You will need a tester that can reach around 6 inches down the spark plug hole. If valves are leaking from overheating expect the center cylinders to have a lower compression test result.

    You can find compression ratios here

    A quick check for ring blow by is to remove the oil cap and watch for a lot of exhaust gas to blow out. Expect the engine to idle rough with the oil cap off. My engine did not indicate blow by.

    While doing the compression test my starter appeared to be weak

    Check for a blown head gasket and or cracked head:
    On automate transmission cars: Remove the radiator cap, or disconnect the tube going from the radiator to the coolant reservoir and stick the end in a jar of water. Warm the engine. Lock the emergency brake hard and have someone with their foot on the brake, and in gear hold the rpm around 1500 - 2000. Watch for bubbles. Be careful. Sometimes coolant will shoot 20 ft in the air. On manual transmission cars you will need to drive it hard and see if it overheats.

    It's normal to see bubbles for a few minutes after the engine is warm but not continuously.

    Alternator check. Check voltage to be around 14 volts.

    Adjust radio speakers. The guy I bought from adjusted the balance so I couldn't hear the busted speakers.

    Automatic transmission check: On the earlier 4 speed models, put the transmission in manual, shift through the gears. If the transmission has over 100,000 miles on it expect the car to wind a long time in second, then a hard shift (wham/bam) from 2nd to 3rd. Knock $3500 off your offer or better yet don't buy it.

    If I had checked the car out better I would not have bought it.

    The guy advertised it with new tires, belts, and hoses. All that was a lie. He told me over the phone that it didn't have dents in the metal. There are three large ones. Also there was the trick of balancing out the radio's bass speakers. He made a point to turn on the radio for me. Also he wanted me to test drive it hard. The hard shift from second to third doesn't happen when accelerating hard. He is a weasel.
    Last edited by DuWop; 06-18-2013 at 09:45 AM.


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