Buyer’s Guide

Buying a 108 or 109 chassis Mercedes-Benz

Currently, most w108 and w109 vehicles are severely undervalued, creating a great market for those looking to buy. Don’t jump on the first vehicle you see – unless it’s one hell of a vehicle! There are a lot of great examples out there for not much money. Persistance and patience pays for both the buyers and sellers of these cars.

What to look for when buying a 108 or 109
108s and 109s typically range in price from $1000 for “Daily drivers” with issues to $10k or more for immaculate versions. 6.3’s can fetch $20k or more for concourse-quality rides. Don’t think that a 108 or 109 with 80k original miles is better than one with 180k – because the latter may have been better maintained, especially because it was driven, whereas the former probably has original rubber bits.

Here are some common faults. Note: Parts of this guide were taken from an Australian site, but have been modified.

  • A/C not working – an expensive if the compressor and hoses need to be replaced. Some have been converted to R134a, try to find one with stock R12. These haven’t been tampered with – most R134a conversions work for a year at most, due to the converter’s haste – aside from the fact that R12 is more efficient.
  • Heater levers broken – this can be a sign of frozen valves. They’re easy to get to in LHD vehicles, simply pull out the glovebox. Figure $200 in parts including 4 new levers.
  • Heater core leaking or blower motor not working. This means disassembly of the entire dash. If you think you’ll ever need defrost, pick another vehicle, or prepare to spend over 40 hours of DIY work, or $1000 minimum. New blower motors are about $500 alone.
  • Worn valve guides – the car will smoke on acceleration/deceleration. It could be just valve stem seals, but it’s usually more. Repair of the heads $500 – $1000 for a 6 cylinder motor and $1000 plus for a V8. More if you don’t pull them yourself. Heavy white smoke on deceleration is typically a bad diaphragm in the transmission modulator.
  • Rust – the spare tire wells in the trunk are prone to it, as are jack points, and the rocker panels (behind the front tires), as well as the tops of the front fenders immediately behind the headlights. These areas are often repaired with body filler. Make sure to check them before purchase!
  • Poor shifting (auto) – insist on driving the car from cold. If the changes are harsh, slow, or there is a slip between changes you might need to repair the tranny. Typically, a working used one is less. Be aware though, it could be as simple to fix as replacing a vacuum line to the modulator.
  • The steering box sometimes cracks the chassis rail where it bolts on. Check for this very carefully. This is common on rustier examples.
  • The engine mounts sag with age, and the exhaust manifold may eventually make contact with the steering box. This can result in a range of noises and vibrations especially when the engine is under load. Engine mounts are about $70/pair plus labor.
  • Front suspension repairs can be expensive, typically a front end rebuild starts at $1000.00. There should be only minimal movement in the kingpins. Parts themselves are cheap, it’s labor-intensive, however. Figure $100 per kingpin, $50 per outer LCA bushing, $50 per outer UCA bushing (eccentric bolt), $100 for sway bar mounts, etc.
  • Worn cams. More common on m116 and m117 V8s with neglected camshaft oiler tubes. Be aware that these cams should not be reground, but rather replaced.
  • Timing chains. A bad timing chain can cause catastrophic valve damage, especially common on m116 and m117 engines. The stretched chain causes the guide rails to break from stress, and the cam “skips time” causing valve/piston interference. $2000 per side to repair, minimum. A new chain and guide rails is under $150, and takes about 4-6 hours for a novice DIY to do.
  • Carbs (if applicable) – Many carbureted 250s and 280s models suffer from warped, leaky, or poorly-rebuilt carbs. Cold and warm starts should be easy and responsive, the vehicle should not stall at idle (cold or hot), and should not hesitate upon acceleration.
  • Trigger points (if applicable) – Many 3.5 and 4.5 engines have dirty trigger points, causing hesitation when cold and poor running (the feeling of running on only 2, 4, or 6 cylinders).
  • Fuel distributor (if applicable) – This can be cost-prohibitive to rebuild. 6.3 fuel distributors run about $2000.

Keep in mind that rubber bits on most cars need replacement. Some have been mentioned throughout this guide, but a more thorough listing includes:

  • Glass seals (doors, windshield, and rear glass). The doors use a special fabric that frays with age.
  • Subframe mounts – if these are original, the car will “Wander” on highways. Replacement is strongly recommended if they are >10 years old or are known to be bad.
  • Sway bar bushings
  • (Upper and lower) Control arm bushings
  • Rear trailing arm mounts and axle boot
  • Brake lines fuel lines, and flex disc*
  • Belts and hoses
  • Central locking system. The units actually use rubber diaphragms.

* – Before driving any w108 or w109, you should inspect the brake lines, fuel lines, and flex disc at the very least. Failure of these parts may be fatal. Keep in mind the 3.5 and 4.5 have high-pressure fuel-injection systems, do not drive them if under-hood fuel lines show any cracks!

Vehicles to avoid:

  • Rustbuckets. Minor rust is almost a certainty. If you can put your fist through an area of the vehicle, look for another. This is especially true if the driver’s floorpan is rotting out.
  • Bad seating. A headliner and carpet are easy to replace, but seats cost quite a bit to redo. And leather interior replacement is astronomically expensive. Used interiors can be cheap, but a bear to ship.
  • No service history – High mileage isn’t an issue but neglect is. A full history is worth a cool grand.

Good things:

  • A straight, rust free body,
  • A comprehensive, up-to-date service history,
  • A good interior,
  • Proper tires (it’s getting harder to find 14” tires that are load-rated for 108s and 109s),
  • Receipts showing repairs done and/or parts used.

109-specific Issues
The 300SEL has other common faults. In particular the air suspension components may need repair or replacement. Two valves on the front and one on the rear – they can run over $350 each! Each air bag is about $200+ each, and there are four of those.
The cost of owning and maintaining a W109 6.3 V8 in good order is usually estimated as being three times the cost of a W109 3.5 or 4.5. The parts catalogue for these magnificent cars is much more limited than that of the other V8s. For example, expect a rebuilt water pump to run you at least $450.

Checking for rust

  • Check jacking points for rust by inserting the factory jack and using this as a lever to check for any movement. Don’t jack from under these jack points!
  • The trunk wells.
  • The frame rails in the rear.
  • The fenders behind the headlights.
  • Under the doors at the frames.
  • Rocker panels
  • Behind the trim (both bottom trim and side trim). Note that 108s and 109s didn’t actually come with wheel well trim, any chrome trim there may be masking rust.
  • Under the cowl.
  • Under the master cylinder and under the battery.

A fridge magnet (the thin flat ones often used for advertising) is really good for detecting the depth of bog and holes. Some people use screwdrivers to check, but this may remove undercoating/paint that was covering sensitive areas.

A final word

Use your brain, not your heart when buying one of these beautiful classics. Many sellers think that they are selling a creampuff in great condition (there is a running joke on the Vintage Mercedes Forum I moderate about a 4.5 in Chicago that is a damaged rustbucket–worth far less than $3,000–that the seller initially wanted over $15,500 for, and some sucker spent nearly $8,000 on). The right vehicle won’t come to you, you need to search for it. Good luck!