Thrust arm bushing failure
The most common suspension problem on the E34. Common symptoms of a torn or cracked thrust arm bushings are shimmy under braking at freeway speed. Vague or rubbery feel in the steering, and excessive front tire wear. Extreme examples will also produce a clunking sound. EVERY 5 and 7 series car I have ever seen needs these replaced by 75K. Many need them by 40K.
Tie rod wear
5 and 7 series cars share the same basic front steering components, consisting of a tie rod end attached to each end of the center tie rod. All three components contain ball joints, and any of them may cause steering shimmy.
If any of the ball joint boots are cracked (you will see grease coming out), then the component will need to be replaced. All components should also be checked for excessive play and replaced if out of BMW spec.
Worn or blown shocks and struts
Factory BMW shocks on the 5 series cars are very robust, frequently working adequately for over 100K miles. They do wear out though, and most folks who have been driving their cars since new hardly notice the deterioration as it is gradual. Symptoms include:
- Diving under braking and acceleration
- Excessive lean and suspension compression during cornering
- Bouncy and uncomfortable ride
- Shocks and struts may also visibly leak shock oil.
Worn or failed sway bar end links
Worn sway bar end links can compromise handling. A worn sway bar can sound like a metallic clicking noise. There is no critical danger in a failed sway bar end link, but the handling of the car is compromised.
Torn subframe and subframe bushings
Torn or Worn subframe bushings may lead to subframe failure. Common symptoms of subframe failure are erratic handling and unidentified clunks, squeaks, and bangs from the rear of the car. Early detection of a torn or cracked subframe bushing can prevent costly subframe repair and welding.
Torn or cracked transmission mounts
On manual transmission cars, torn transmission mounts may lead to the dreaded 'money shift,' or mechanical over-rev and the possible (and likely) destruction of the car’s motor. Worn transmission mounts allow for an excess amount of transmission movement. Symptoms can be hard, notchy, and forced shifting during cornering, excessive shifter jerk during hard acceleration and braking, and muddy shifter feel.
Ripped or failed guibo
A torn guibo (Flex Disc) will result in a perceivable 'drivetrain elasticity'. Acceleration will be preceded with a loud clunk as the guibo bolts bind together.
Dirty automatic transmission fluid or clogged filter
Hesitation and/or hard shifting could be the result of dirty and old automatic transmission fluid or clogged transmission filter.
Water pump failure
Water pump failure is, without a doubt, the easiest way to cause extensive and expensive damage to your BMW. The main symptom will be a rapidly overheating motor. What occurs is that the bearing or impeller on the stock pump, breaks, completely disabling the cooling system.
If you ever see the temperature gauge on your BMW climb above the 3/4 mark – turn the car off immediately and call a tow truck!
I can't stress this enough. Failure to catch the overheating motor in time can result in a warped head or even more severe engine damage. I recommend changing out the water pump in six-cylinder cars every 60-80K.
Cracked radiator necks
BMW loves their plastic radiator tanks. Unfortunately, the plastic around the radiator necks become brittle and crack with age, often without warning (see warning above.) Radiators should be thought of as 80-100K mile wear items.
Thermostats and housings
6cyl and e34 V8's. The factory thermostat housing can eventually crack, causing a cooling system failure. Replacement with an aluminum housing, or replacing with the new composite units every 60k or so will prevent problems. I also recommend replacing the thermostat while the housing is off.
Fan clutch failure
Most fan clutches fail between 80 and 100k miles. They provide the primary cooling for your car and are easy for us to diagnose. If the car is hot (just drove it for a while) and you turn off the engine, you should feel a decent amount of resistance when trying to turn the fan clutch. If not, it's toast.
Accessory belt and tensioner failure
Worn tensioners and idler pullies will sound like a squealing noise from the engine bay. Belts should be inspected for cracks regularly. If a belt happens to snap, the cooling system will fail as the water pump will cease to operate. Power steering and the alternator will also fail to work. Again, pull over and shut the car off immediately should you suspect a belt failure or see the temperature gauge rise past the 3/4 mark.
Valve cover gasket
Prevalent on all BMWs, a burning oil smell could indicate a leaky valve cover gasket. If the condition continues unchecked, oil can seep into the spark plug holes and damage the ignition coils, resulting in costly replacement. Replacement of this inexpensive gasket is a good idea when changing spark plugs as the coil packs will already be out.
Oxygen (O2) sensor failure
Bad oxygen sensors could cause poor mileage, poor idle, and flat spots in the power curve. Even if your car isn’t throwing a check engine light, they may not be performing optimally. BMW recommends replacing the O2 sensors every 100k miles. Extended high-RPM running/racing and high-performance chips may shorten the replacement cycle.
Clogged and dirty pollen filter
If the flow of air out of the air conditioning and heater system is not as strong as it used to be, it strongly suggests the pollen micro-filter of your car has become dirty and clogged over time. A damp and musky smell can also indicate a dirty filter. This is a service II replacement item.