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BMW E30 325i - Bimmer Buyer's Guide Part 1

Paul Piola Advises What To Look For When Buying An E30 BMW 325i.

Jun 8, 2010

Have you ever seen an old, yet clean little BMW E30 325i on the road and thought to yourself it would be a great daily driver? These cars have a bulletproof reputation and plenty of old-school style to keep them looking fresh. With the cars dating back to 1986, there are some cheap examples out there, and you can easily run them for several more years with proper maintenance. However, just because it bears the Bavarian badge, doesn't mean you won't have parts to replace or things to look out for.

Eurp_1006_01_o+bmw_e30_325i+front_fender Photo 2/16   |   BMW E30 325i - Bimmer Buyer's Guide Part 1

We contacted our BMW tuning and maintenance friends at Bavarian Autosport, BimmerWorld, Turner Motorsport and UUC Motorwerks to exploit their intimate knowledge of what commonly goes wrong and the best way to fix them.

This month, we start with the 1986-1991 E30 325i, and hope to cover the E36, E46 and E90 in future issues. Obviously, there are other E30 models but we wanted to choose the most popular model, and many of the tips provided here apply equally to all models.

What we've highlighted here will help you know what to look for when purchasing an E30 325i, or help you to keep yours on the road for longer. However, the specialists listed here also sell aftermarket parts to make the 325i faster and handle better. They have everything from suspension systems to big brake kits, ECU chips, exhaust and cams. Call them or visit their websites (listed below) for more details.

Eurp_1006_02_o+bmw_e30_325i+engine Photo 3/16   |   BMW E30 325i - Bimmer Buyer's Guide Part 1

Engine
2.5-liter inline-six cylinder M20B25
• As an interference engine (meaning that if the timing belt breaks, the pistons will bend the valves), it's imperative the M20's timing belt and tensioner must be changed every 60k miles or every four years. It takes about three hours and $35 in parts. While you're at it, check the water pump for play, and fit a new ignition rotor and cap - these are easy replacements at this point.
• To reduce valvetrain wear, valves should ideally be adjusted every 15k miles. Rocker arms can crack over time at high RPM when valves are improperly adjusted.
• The airflow meter flap can cause driving issues if not portioned properly. It needs to be tuned back to spec.
• Gunk can often accumulate in the idle stabilization valve, causing a rough idle. Remove it and flush with brake cleaner. Other drivability issues can stem from a leaking intake boot, brake booster hose, idle valve hose or vacuum lines, so check them all.
• Quality fluids are a no-brainer. Use Lubro Moly, Redline or similar, preferably 15w-50.
• Check the cooling system by allowing the car to idle for 10min with the A/C on. Watch the temperature needle and listen for the auxiliary fan to come on to keep the engine cool. If the fan is seized, remove the wires from the radiator fan temperature switch and touch them together to see if the fan runs. If it doesn't, the fan's broken, if it does, replace the sensor. A low-temperature radiator control switch is recommended.
• The stock radiator's plastic end tanks can crack with age. A good upgrade is an all-aluminum unit with quality coolant. Bav Auto also carries Evan's waterless coolant we use in Project M3.
• An overheated M20 engine will never run right because the alloy cylinder head will warp and crack. A compression test is a good idea for any car you might be considering.

Eurp_1006_03_o+bmw_e30_325i+gear_shifts Photo 4/16   |   Sloppy gear shifts can be overhauled with stock replacement parts or upgrades such as this UUC short shifter kit

Drivetrain
• Even the slightest sign of wear on the rubber drivetrain isolation disc (aka "guibo") will cause vibration when the engine is under load. Replace the guibo and, while you're at it, check the tranny mounts, driveshaft center support, tranny output shaft seal and shifter selector seal when diagnosing the cause. All of these parts may need attention.
• The shifter can become sloppy with age, but its easily upgraded using parts from later BMWs. According to BimmerWorld (BW) you can use the shift knuckle and selector rod from an E36 328i to improve the feel. The shifter from a Z3 1.9L will shorten the throw by 20%. All of our featured companies sell aftermarket short-throw kits as well. In fact, we have UUC's unit in Project M3 and love it.
• For a worn clutch, Bav Auto sells a Sachs replacement, BW carries Clutch Masters parts and Turner Motorsport (TMS) sells high-performance Sachs kits. UUC has its own clutches with various discs for different power levels, including forced induction. On Project M3, we're using a BW unit with JBR flywheel.
• Good fluid is again important. Redline 75w90 synthetic is good for the differential. However, the transmission fluid will depend on the label color. If yours is green, use Redline MT-90; if red, use D4-ATF. Neither should use MTL. Using Redline drivetrain fluids and Lubro Moly engine oil on Project M3 released 8hp to the wheels...
• TMS sells a solid-rubber diff-cover mount to replace the webbed original. It will last longer and transfer more power to the wheels because of less wind-up.
• Bav Auto and UUC sell TyreGuardian tire puncture protection. The gel prevents punctures and seals porous leaks in older tires. What's more, it doesn't have a negative affect on wheel balance or performance. We run this on Project M3 as well...

Chassis & Suspension
• The "pig tail" ends on coil springs can break with age. You can replace with factory springs or upgrade with TMS, Bav Auto or BW parts.
• All rubber bushings deteriorate over time, causing suspension slop and a potentially dangerous situation. Bav Auto and TMS carry factory replacements, while aftermarket urethane and solid race units are available from Bav Auto, BW, TMS and UUC. TMS recommends KMAC units for the rear trailing arm since they allow camber and caster adjustment. TMS and BW also sell Powerflex bushings.
• Check the motor mounts by placing a jack under the oilpan, with a wide block of wood between to jack and pan to avoid the pan being punctured. Gently jack up the engine and watch the mounts. If they stretch or separate, they should be replaced.
• The front subrame tabs for the motor mounts can weaken and bend. BMW and TMS have a weld-in reinforcement kit.
• Sway bar reinforcement plates might be needed since the factory mounting points can crack over time. BW, TMS and UUC sell the reinforcement plates.
• The rear shock mounts have a short lifespan but Bav Auto, BW and TMS have inexpensive high-performance replacements.

Bodywork
• The main concern with the bodywork is rust. Common areas include front fenders, doors, windshield surround, trunk (including battery area), trunk lid, tail panel, rear-lower valance (on '89-newer models), rear wheel arches, steel wiring harness cover on battery cables and other harnesses, and rocker panel area of rear crossmember mounts
• If you smell fuel, your tank could be leaking. Fuel lines on top of the tank rust as dirt collects and retains moisture along the fuel transfer tubing. Check this and for rust at the seams where upper and lower tank halves are joined.
• On any sporty car of this age, check for signs of crash damage; look for deformed frame rails and a rippled trunk floor.

Brakes
• If your parking brake doesn't work, it's probably either broken cables or the brake shoes (inside the rear rotor hats) have come away from the backing plate. This may require new backing plates, which mean removing the drive flanges to install.
• Bav Auto, BW and TMS carry a plethora of brake replacement parts as well as big-brake kits. UUC also released its own four-piston brake kit for 15'' wheels.

Interior
• Odometers typically go before 200,000 miles as the gears wear. Nylon replacements can be bought cheaply and won't break.
• Gauges can become faulty. In the case of the fuel or water temp gauges, if the gauge moves when you smack the top of the dash, remove the cluster and tighten the gauge securing units to the circuit board.
• If the rev counter or other gauges are intermittent or inaccurate, and tapping the cluster or dash doesn't move them, the service interval board may need to be replaced because the memory batteries have failed. In this case, the service and oil change reminder lights will not reset either.
• If the radio is inoperative, shows "CODE" or "WAIT" messages, then the electrical power has been interrupted at some point. If you don't know the five-digit security code or it's not written in the vehicle paperwork, remove the radio to access the serial number and have a dealer acquire the code.
• Turn on the heater and check for dampness on the floor. If you find water, the heater core and valve may be leaking, which is a costly repair.
• The usual culprit for malfunctioning window is the switch. Fortunately, aftermarket replacements are cheap.

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