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Project e21 320i Pre Purchase Inspection
Body and Structure
 Walk around the outside of the vehicle and check for mismatched colors on the body panels; also check for body panels not in alignment with one another. These are signs of a collision. Minor dents and door dings may have been the reason for a repaint, however they are not always reasons to not purchase the car. Open the doors look for color changes in the door jams. Peel back a little of the door seals, this will reveal a possible color change. You can also peel back the trunk edge seal and look there. Look for any body rust. All BMW's are unibody construction. Rust in the body is rust in the structure. If what you find is only surface rust, or limited to a few common areas where moisture was trapped, then this rust can be removed or the panel can be replaced. The common rust zones for the E21 are bottom edge of the doors. This is due to broken or worn outer side window rubbers allowing rainwater to enter the door and collect in the bottom of the door. Another area is around the taillights. This is due to poor sealing around tail light assemblies and poor trunk seal protection. The water enters around the tail light seals and becomes trapped. Rear quarter window lower edge. This is due to poor drainage and water penetrating from the molding screws and water becoming trapped under the trim molding. Any vehicle that has evidence of a major collision should be avoided.
Under Hood and Engine
 The object here is that we know the condition of the engine prior to purchasing the vehicle. This would require first doing a valve adjustment to make sure you do not have a tight valve, and follow it up with a compression test. Since most of these vehicles at this age have from 180K to 300K it is quite possible they are on their 2nd or 3rd engine rebuild. Our vehicle is still on the original engine. A compression reading needs to be taken with a strong fully charged battery, coil wire removed, throttle wide open, and you must crank the engine over an equal amount for each cylinder test. (approx. 10 revolutions) Write down the results for future reference. Ideal is a variance of less than 5%. While under the valve cover look carefully for a worn cam, rocker shafts, or rocker arms. Worn parts in this area may be due to poor oiling or clogged oiling holes in the cam spray bar. Another weak point on the M10 engine is the timing chain. Due to timing chain stretch the timing chain tensioner can be extended to its limit. Causing the chain to operate loose on the sprockets. The symptoms are a loud rattle under the valve cover at idle that quiets when you increase R.P.M. This will also create a rough idle. Replacing the chain is the solution. Tensioner and spring can be replaced also, but are not the real cause of this problem. Check the spark plugs for variations in the burn pattern, or signs of oil deposits. Black plugs are too much fuel, a white crusty deposit is oil consumption, and could be a sign of valve seals, worn guides or piston rings. Any external oil leaks. Follow them to their source and document. Exhaust leaks, engine mounts, alternator alignment, belts, and cooling system leaks.
Cooling System
Check the hoses for bulges and cracks. Original BMW hose clamps are a sign of hoses that need to be replaced. Pressure test the cooling system, and document all leaks. Radiator, hoses, water pump, heater hoses, heater core, and valve, also check freeze plugs in the engine block as these could be rusted through. Check the temperature on the dash while you are road testing the vehicle. If the gauge indicates over 1/2 on a cool day you may need a radiator. However a gauge that flickers by 1/8 of an inch when you turn on the headlights is an indication of a faulty ground to the gauge cluster. Another area to pay attention to is inside the car. There could be a coolant leak at the heater valve or heater core. Things to watch for are, wet carpet especially on the drivers side, sweet smell of coolant inside vehicle, an oily film on the inside of the windshield, and a constant collection of moisture inside the vehicle.
Fuel System
Before attempting any in depth fuel system diagnosis or repairs the engine must be in good running order and proper state of tune. This means points gapped correctly, timing set to specs, I recommend new spark plugs, cap rotor and wires if there is any doubt to there condition. Compression must be within specifications as stated above. Replace fuel and air filter to avoid restriction related problems. Assuming all the above is correct. You must make certain there are no vacuum leaks. To avoid leaks replace all vacuum hoses and boots if there are any signs of cracks or that these items have become brittle due to under hood temperature. Small cracks in the hoses or boots creeping under the securing clamps are an indication of a leak. Additional areas of suspect are dipstick, oil cap seal, valve cover, fuel injector seals, and intake and plenum gaskets. Valve cover breather hose, auxiliary air valve hoses, auxiliary air valve, distributor vacuum diaphragm. In short there cannot be any vacuum leaks at all!! A simple check for vacuum leaks is to use a length of 8mm rubber hose. Hold one end up to your ear and the other end around each component of the intake systems, such as injectors, vacuum boots and hoses.
Front Upper Shock Mounts
 These will commonly rot, or have bearing failure. On our vehicle it was obvious that they had failed, and were pushing the struts through the body. This is more common on vehicles with a performance suspension kit, since the added load is being transferred through the body via these mounts. Any cracked, or rotted mounts will need replacing.
Shocks
This is a simple inspection, any damage, leaks, or shocks with mileage over 75k need to be replaced. Although shocks appear to be good, after a while they will soften in there normal ride zone. This is the 3 inches of travel that happens when dealing with all the little deviations in the road. Simply put, if you want a like new ride get new shocks!
Suspension Ball Joints and Bushings
 While you are inspecting shocks take a look at all rubber mounting bushings, and ball joints. On the e21 body check the following. The front control arms have inner and outer rubber bushings. Check ball joints first for play, or broken dust boots. Broken dusts boots indicate possibly dry and worn ball joints. If they are worn you will be required to replace the entire control arm. Since new control arms include new inner and outer bushings, on 79 or newer models it is almost better to go this route to avoid the added labor of pressing in new bushings. Another commonly over looked suspension bushing is the front sway bar mounts. In the case of the e21, the sway bar also plays the roll of the front stabilizer arm. Worn bushing in the sway bar mount will allow the wheel strut assembly to move from front to rear during driving and braking. Which will cause a stability problem, and severe pulling while braking.
Rear Suspension
This includes the rear trailing arm bushings, sway bar mount bushings, sway bar links, and the often over looked, and not so easy to replace rear sub frame mounts. The rear sub frame mounts are located at the outboard ends of the sub frame. The sub frame is the assembly that mounts the entire rear suspension to the body. If these mounts are broken or severely worn they must be replaced. If you don't know what they are and this is all news to you my guess is they are really worn out!
Rear Trailing Arm Bushings
 Here you have several choices if they are worn. You can press in new stock rubber bushings. These will restore your ride as when the car was new. You can upgrade to urethane bushings that offer a slightly firmer ride, which will improve handling. Or you can install our adjustable rear trailing arm bushings that will allow you to adjust rear wheel alignment for camber and toe correction. The e21 is notorious for having too much negative camber in the rear for everyday street driving. The problem was most apparent in the 77-78 models, and on all years if the vehicle was fitted with a lower suspension kit. Installing our adjustable bushing kit will allow you to properly correct alignment for better tire wear, and correct toe adjustment for better mileage.
Steering System
The e21 has a simple non-power steering rack and pinion. You have 5 basic wear points that would cause a sloppy feel in the steering. (1) The rubber mounts that attach the rack to the sub frame, if these are worn we offer a urethane set that will remove this movement. The urethane is an excellent choice for track driving and also a permanent fix for street application. (2) The dust boots, if these are broken, torn, rotted, or missing they must be replaced, but first you need to check the steering rack for play as soon as possible. Sand, dirt and road debris that enters this area will grind away at some very delicate seals and components. To check the rack for wear have the car lifted off the ground, and turn the steering wheel all the way in one direction this will extend the rack for cleaning and inspection. Use a common brake component or choke aerosol cleaner over a drip pan. Use a rag or brush to get it clean down to metal. With a person outside the vehicle slightly turning the steering wheel back and forth look at the space between the rack shaft and the rack housing. If you see a large gap or if the shaft is moving up and down inside the bore, then the rack is worn. Excessive movement will require a rebuilt or new steering rack. You should also inspect the inner Ball joint of the tire rod, which attaches to the rack shaft. Place your finger at the meeting joint between the ball and socket of the inner tie rod. Have someone slightly move the steering wheel back and forth; if you feel any amount of movement the tie rod must be replaced. At this time you can inspect the outer tie rod for ball joint play in the same fashion. Any play at either end will require the replacement of the entire assembly. If the steering rack is O.K. make sure the shaft is clean apply a liberal amount of grease replace tie rod if needed and install a new boot.
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