Buying a Used BMW – part 2

Buying a Used BMW – part 2

by | May 18, 1988

 

This month we feature part two of Tom Nast’s ultimate article ob buying used BMW’s. Last month Nast covered some of the General Rules of buying. -Ed

Systems And Inspections

Chassis. The chassis has either been hit or it hasn’t (see “Crashes” last month), and you can tell the condition of the paint by looking at it. The main variable on a chassis is rust.

Rust is expensive and difficult to cure. “Curing,” in most cases, means only a lengthy delay in its reappear­ ance. I have seen some older coupes that would cost over $6000 to derust, and others that couldn’t be saved  at any practical price. Unfortunately , rust is easy to conseal for a while, so if you see new paint on an older car, your antennae should go up and the magnet should come out.

BMW got interested in rustproofing around  1974 when  it started  cavity coating, and got seriousjust before the ’82 model run, using a waxoil under­ coating and granting a limited seven year warranty (’82 and later models) . Although environment has everything to do with rust , the more recent BMW’s are generally rust free so long as the surface coatings have not been damaged. Bubbles under the paint are a sure sign of trouble, of course. On older cars, take  off  the  front  turn  signal lenses and look at the sheetmetal-this is where the first, most gruesome rust often forms. Check the front fenders toward the doors, another trouble area. Give the rocker panels close scrutiny, including where the inner fenders box them in. Put the car on jackstands and check the floorplan. Check the lower lip on the front of the car and seams (inside) where the front sheet metal is welded  to the fenders. Look on the bottom lip and flange of the d oors. Check the hood and trunk lid inside edges. Give everything else the once over.

Use a magnet to check for bondo (body filling plastic) if you are at all suspicious. Tapping with a finger you can also disclose repairs, as the plastic will ‘thump’ differently than metal. A sharp, thin rod can be used on suspected rust pockets (especially the rockers); if you can shove it though the metal, you’ve got rust. Just don’t let the owner see you doing it.

Make an intelligent guess at the cost of fixing any rust problems, or take the car to a body shop for an estimate. You will use this figure in arriving at your offer.

That *$&%& mettalic paint. Mercedes doesn’t seem to have much trouble with its metallic paint. Neither does GM. Why BMW does is one of life’s mysteries.

It is hard to say whether BMW has solved its problem with metallic paint. You can usually get five years out of it, and as i now observe the paint on the ’83’s going to hell, there is no reason to thing the problem is solved. I know, I know, “there is no problem” (like, “Ze output shafts never fail”). So when you’re not talking the car to the body shop to be repainted at a cost of $1500, you can say you weren’t warned.

All BMW metallic paints are subject. Personally, no thanks. If you want it or the car otherwise checks out, prorate the paint as appropriate.

Suspension. Suspensions have either been modified or they haven’t (see “modifications” last month). The only really expensive parts are springs, shocks and tires. If the car does not have bilstein shocks, budget for installing a set sometime in the future. They’re not cheap, but they’re worth it. Springs are a matter of taste. Plan on replacing the tires if they’re over four years old (I don’t care how much tread is left) or if for any reason you don’t like the looks of them. Assuming the brakes and engine work, there is no single component which affects driving pleasure and safety as much as tires.

Engines. BMW engines are tough little beasts. About the only way to kill the bottom end is to run them out of oil or not change it very often (this will kill t he valve train even faster, by the way). But the top end is a bit more prone to trouble.

Although the weak points in specific models are noted later, some general problem areas should be looked for. Where the rocker arms contact the rocker arm shaft is a classic wear area, exacerbated by the infrequent oil changes. An experienced mechanic can check for this. Loose steel pads on the rocker arms is another common defect. This makes for a noisy valve train.

Cracked cylinder heads are all too common on nearly all models . This has become less of a problem over the years, but any purchaser of a used BMW should be sensitive to the poten­ tial. Head gasket problems are not uncommon , but few sellers of a used cars would try to peddle their wares with a defect as obvious as this. The failure to use antifreeze results in severe corrosion of the alloy BMW uses, and it is a good idea to pull a water hose off the cylinder head and look inside for corrosion . I have seen corrosion on removed cylinder heads so bad that the head gasket  could no longer  seal the water jacket from the combustion chamber!

The cooling systems in BMW’s have traditionally been marginal and deli­ cate. Water pump failure is frequent, the  hoses  need  regular  inspection , rad iators lose efficiency (as noted above) and leak at the seams, radiator caps fail, thermostats fail, overflow tanks split seams, etc. The resulting lack of coolant is one reason why heads crack, and also is a motive for not using antifreeze-after all, the owner may have been adding water daily for weeks before getting the cooling sys­ tem sorted out. Great excuse, but bad result. Watch out for these cars.

A minimum engine inspection should include a {;Ompression test, inspection of the spark plugs, a look under the valve cover at rockers arms, shafts and cam, and for sludge build-up (a sign of overheating or infrequent oil changes), a look under the distributor  cap for shaft bushing wear and advance and return spring integrity, a check for water in the oil and vice versa, and a listening and driving test. Sniff for exhaust gases under the radiator cap, a sign of a cracked cylinder head . If available, a cylinder leakdown test is highly recommended, and exhaust gas analysis of fuel injected cars can be informative. I also look for general long term cleanliness of the engine and engine compartment.

Motronics. No, Motronics is not a new age band from Detroit. It is the Bosch fuel injection system used on all eta and 3.5 liter engines. Electronically it is a reliable system, but in applica­ tion it has been somewhat trouble­ some. I am told that this is due to the fuels available today , though one must wonder how rational it is to design a fuel system incompatible with availa­ ble fuels. Does Bosch intend to open a chain of gas stations? By using techro­ line (which BMW sells very reasona­ bly) , the fuels can be made to work with an engine which is already clean, minimizing future running problems, but   my   engineering   genes   remain troubled by the whole affair.

It seems that the fuel now sold (and it is chemically different from what was sold ten years ago) causes carbon deposits, principally on the back of the intake valves. Among other problems, these deposits cause the temperature and 02 readings fed to the injection computer to be erratic. The computer then injects an erratic amount of fuel causing an erratic running condition of the engine. One fix was the “yellow band” airflow meter, which has an adjustment screw to tailor the meter to the individual motor. That was not enough, and the present fix is to clean the carbon out. BMW just spent beau­ coup bucks on an engine campaign cleaning out carbon, using walnut shells, and they insist that techroline be used in the fuel thereafter.

What this tells you is that a poor running BMW with Motronics may just need cleaning and adjustment. If the seller doesn’t know this (and if he does, why doesn’t he get the work done?) you may be in a position to get a deep discount on the car.

Clutch. Clutch wear is really a func­ tion of owner abuse. BMW clutches are not particularly strong, given the output of the engines and weight of the cars. The throwout bearings are nota­ bly weak, and will not tolerate the owner resting a foot on the clutch pedal between shifts. Cheap part, expensive installation.

Clutch hydraulics are also a weak link, perhaps because the fluid is not flushed regularly . It almost always comes out filthy. This is true across the entire range of BMW cars.

Automatic transmissions. A great percentage of the six cylinder cars have been imported with automatics . Any six with a Borg Warner 65 will need a new  transmission  (one  made  by  ZF) -it’s just a question of when. Figure $1500-$3000 for the conversion. Parts for the BW 65 are hard to find and they’re not worth fixing anyway . Look on the passenger side of  the  tranny, just above the oil pan, for the BW 65 identif ying plate. Any six cylinder automatic built between 1972 and 1975 will have this gearbox.

The ZF and Getrag automatics are much better, and if I was buying a six cyl. automatic that’s what it would be.

It is difficult to recommend a four cyl. BMW with an automatic, as the margin of performance just doesn’t allow it. If you insist on diesel perfor­ mance from a BMW , the newer the car the better off you are. The fours have used ZF transmissions . For the 2002, the tranny is very maintenance-sensitive and the parts situation is getting touchy.

The 320i had a fairly respectable automatic, and the 3l 8i had a decent slushbox.

Exhaust . A BMW which is driven daily may get four plus years out of the exhaust system. A BMW which is driven two months a year will be lucky to get two years out of the same exhaust system. The rear muffler is almost always the first component to go, except for cracking in the plumb­ ing of catalytic converter systems. Most systems rust from the inside out, so the trick is to determine the condition of the inside. This is done with a set of channel lock pliers when the owner isn’t looking. If you can crush the pipe with the channel locks, it’s rusting out. You may want to be a bit more gentle on the muffler can itself, but if you can hear metal crunching in there, plan on replacement.

The six and seven series cars have painfully e,xpensive exhaust systems, so these are worth special inspection. The four cylinder cars have very rea­ sonably priced systems.

Stahl headers and stainless steel ex­ haust systems are worth an enhanced offer for a car, but almost nothing else is. Prima Flow systems are nice, but not worth  paying  extra for.  Deduct d ollars if a Mid as-type system is installed.

Driveline. All four cylinder cars can expect routine replacement of the guibo (rubber doughnut), which leads a diffi­ cult life just behind the transmission. Also rou tine bu t less frequent is replacement of the driveshaft carrier bearing. Watch for these weak points . They seem to fail less frequently on the larger cars.

All BMW’s have had driveshafts with sealed U-joints since the early seventies, which means they never need greasing but you get to replace the driveshaft (expensive) when the U­ joint fails. They will all fail, it’s just a question of when. Again, failure is less common on the large cars than on the smaller ones.

The boots covering the constant velocity joints on the half shafts used to split with undue frequency on the four cylinder cars, but this seems to have abated as materials technology creeps forward.

Brakes . Overall BMW has had excellent brake performance and reli­ ability. Problems are mostly mainten­ ance-related, such as failing to change the brake fluid annually. I am no fan of factory brake linings, which wear out quickly and dust badly . Try Repco linings’.

The drum brakes used in 2002 / 320i models are at best mediocre compared to rear discs. The 2002 drums need frequent adjustment, and the adjusters will freeze if they are not lubricated and moved regularly. Round off the adjuster and you get to install a new backing plate, which is a pain. The drums seem to wear almost as quickly as the linings, and the ·handbrakes are commonly misadjusted or out of spec. However, it’s hard to spend over $200 on rear (drum) brakes if you do your own work.

The vented rear discs used on 3.0CS, 630CS and 633CS sell very well, indi­ cating a problem . Likewise 320i vented front discs and 318i discs. Finally , 320i master cylinders, in both aluminum and iron versions, seem to be failing often.

It has been suggested that Repco lin­ ings cause brake disc warpage because the Repcos are harder pads requiring greater pedal pressure . Thissuggestion neither comports with my personal experience nor does the reasoning behind it convince me, but I duly note itfor  the record.

 Next month Sir Thomas will begin a review of specific models, highlighting some of the unique characteristics of each. Ed.


This article was originally published in the May 1988 edition of Zundfolge