TOP DEAD CENTER: "Why can't I get any clearance on this valve? All the others seem to be OK!" The guy was putting together an aircooled VW engine. There didn't seem to be any reason; the valve height appeared OK, the push rod height was the same as the other valves in the head. What was happening was that the cam timing was 180 degrees off, which meant that it was really trying to be an exhaust stroke, with cam pressure on the valve. I've seen the same thing happen when, after an engine is assembled, it won't run--just spits and sputs. It's easy to forget that the crank goes around twice each cycle, while the cam goes around once, so it will look normal. One way to check for this is that on the top of the compression stroke, both intake and exhaust valves are closed (or "rocking", intake just closing and exhaust just starting to open) and the distributor rotor is pointing at the wire connected to the cylinder you're working with (usually #1).
BROKEN SPEEDO CABLES: Always check and make sure that the speedo head is free. On some cables, you can pull out a short length of cable; of course this is easier when the cable is broken. Poke the cable end gently into the back of the speedo and turn it with your fingers. If you feel resistance, the speedo needs to be gone through by a good speedo shop, because one of the thing that breaks cables (and cable angle drives) is the cable trying to turn different speeds at the two ends.
BMW DRIVESHAFT CLUNKS: Most BMW's have a two-piece driveshaft with a fairly conventional center support (what the American car folks sometimes call a "pillow block") that consists of a rubber bushing molded into a round bracket with a flat mount that sticks out on both sides, and a sealed ball bearing in the center. This is a one-piece gizmo. Where the driveshaft mounts to the transmission in the front of the shaft (rear of the trans) there is a rubber coupler or flex joint , which functions as a rubber u-joint. It is a flat pancake of rubber 4-6" around, with 6 to12 bushed bolt holes, half of which bolt to a flange on the trans and the other half to a flange on the driveshaft. At the rear of the driveshaft is usually a conventional steel spider-type u-joint, which is unconventional in that it is peened or tacked into the yokes without any circlips. It is not intented to be a replaceable part, however, the commonest one used is available, but replacing it is not a backyard operation, better left to a driveline specialist. The rear of the trans is commonly mounted with two small rubber mounts. If there is an oil leak in the engine or trans, the oil gets blown back along the driveline and can soften and damage all three of the rubber things--the trans mounts, the flex joint, and the center support. Even without this, we often find that if one of these things dies the common death of old rubber things, it will allow extra movement of the shaft and damage the other two. Always check all these items when chasing down funny driveshaft noises or movement.
JAGUAR "VALVE" NOISE: Jaguar 4.2 engines (6 cylinder engines 65-87) occasionally will begin to make little tapping noises that sound like a typical valve in need of adjustment. Do NOT neglect this noise, because it isn't a loose valve. Jag valves are shim-adjusted, and normally do not loosen with wear but as the valve faces and seats wear, they tighten up slowly. The tappets (lifters) float in the head in sleeves kind of like short fat valve guides, and these tappet sleeves sometimes come loose and wiggle upward and touch the camshaft. If this goes on, bad things (like a broken camshaft) can happen. The factory fix is a kit (which we stock) that is a set of steel retainers that bolt the tappet guides down. There was a suggestion at one time that putting in a set screw horizontally to hold them in was a suitable fix, but it turned out that the pressure from the set screw applied a side load to the tappet guides which pushed them slightly out of alignment. Any time you have the valve cover off of a 4.2 Jag, check the tappet guides, and check for set screws in any head you don't know the history of.
JAGUAR: We've noticed an unusual problem beginning to crop up in high-mileage Jaguar XJ6 Ser IV (XJ40) cars, 1988-94. The front crankshaft pulley is two sections with a rubber damper bonded between them, but we've seen a couple that come unbonded. One symptom is a strange squealing noise that goes away if you remove the alternator/water pump belt, but isn't associated with apparent bad bearings in water pump, fan clutch or alternator. It can also make the water pump and alternator run slowly, which can cause overheating and a low charging rate.
REPAIR MANUALS: When you can't find a manual for your car, don't forget the local public library. Most libraries have a reference section with a wide collection of automotive books. Even if they don't have one specifically on your car, check out the general professional manuals for the year and the system of the car you're working on, and you may find the specs or information you're looking for.
BRAKE CALIPERS: If you are rebuilding a Teves-type caliper ( two or more pistons in a clamshell type caliper), common to many European and a few early Japanese cars, DO NOT SEPARATE THE TWO HALVES OF THE CALIPER! It looks like you might have to take out those big tempting bolts to change brake pads, but you don't. The pads are held in by pins (look and see where the tabs at the top of the pads are) that you drive out. The bolts are very high-tensile strength bolts under very high torques, and if they are loosened and then retightened, they are not as strong as they were originally. Also, there are usually little seals sealing the fluid passages betwee the two halves, and those seals are not supplied with caliper kits (because you are not supposed to need them). It may be more awkward to be working inside the assembled caliper, but much safer. You may think that you've gotten away with it because it doesn't leak when you're done, but it may take several months for the bolts to stretch and allow it to seep. At this point, you need to replace the caliper. (see also BRAKE FLUID)
LOCKNUTS: Do not use spring-type lock washers on exhaust fasteners. The heat will eventually de-spring them and then the fasteners are loose. Our favorite thing for exhaust is the German copper-locking nuts which don't rust and hold really well. They come in two styles, one has a split collar that opens up and creates tension, the other is a flanged torque-lock, which are slightly oval. These are available in M8x1.25, M10x1.50, and M10x1.25 (which fits most Toyotas and many other Japanese cars as well.). British cars often use brass nuts, which are slightly softer and tighter than ordinary steel nuts. One really troublesome spots, like MGB catalytic converters, we use plated torqulock nuts. Don't use Nylock nuts; they can't take enough heat.
A/C TIP: Sometimes a car will have a "not very cold" air conditioning system, with the system full of refrigerant, no apparent malfunctions in the system. Check and see if the heater valve is stuck in ON position! Hot water in the heater core when it's not supposed to be there warms the cold air the a/c is working so hard to cool.
Don't stop looking when you find a probable cause for a problem. There is no rule that you can't have more than one problem at a time, just like you can have measles and chickenpox at the same time. Whenever someone tells me that "I've already done this, and this,and this, so it HAS to be this", my answer is that there is no such thing as "has to be this". It can always be something else. You'd think that a car is a straightforward mechanical/electrical object, but it is amazing how weird they can be. Almost as weird as people.
We plan to add to this page often; if you have a question about the operation of a car, or about an import marque in general, submit by e-mail to importautosbdo@juno.com. If it looks like it would be of interest to others, we'll discuss it here.
LEGAL STUFF:
All information here is offered as suggestions only; the final decision as to any car repair is that of the installer and/or the owner of the vehicle. This information is the result of our own best research and experience, but we make no guarantees or warranties of any kind as to its applicability to any specific situation.