From Citroen SM Wiki
The Citroen SM is a magnificent machine, but old age has created some very hazardous situations that need your immediate attention.
These items are things that you should check and confirm before starting the car for the very first time.
Oil Cooler Hoses
- The engine oil cooler hoses have separated on more than one car, spraying hot engine oil all over the engine, resulting in immediate fire loss or ruined bearings/destroyed engine.
- Replace the hoses if there is any suspicion that they are old. Conventional 5/8 oil cooler hose (e.g. Aeroquipt) is perfectly suitable.
- Note that the end fittings are Citroen-unique and must be retained from the old hoses, which is easily done with care.
Sodium-filled Exhaust Valves
- The sodium filled exhaust valves have aged poorly resulting in the exhaust valve heads detaching and often destroying the complete engine.
- Unless you know for sure that the valves have been replaced, pull the heads to check. Do not start or run any I.E. engine or 3.0L engine untill you are certain the sodium valves have been replaced. Solid modern alloy replacements are easily available.
- Not unique to the SM, but there are a lot of lines that harden and crack, spraying fuel all over. Replace IMMEDIATELY, ANY externally braid re-inforced tube, with internally reinforced modern pipe labelled 'fuel use'.
- Don't neglect those around the Fuel Pump and Fuel Filler.
- Be sure to have hose clamps on all fittings.
- On early injected cars, the injector part number is Bosch number is 0 280 150 003. The design of these is faulty and very prone to leakage from the body of the injector.
- Do NOT start, drive, or use any car with 003s. You WILL have a fire & loose your car.
- They were replaced (in later production) with Bosch number 0 280 150 043 which are still available and completely safe.
- Accelerator pump diaphragms fail with age & leak.
- Perhaps less likely, but the plugs sealing the machining passages can wiggle out.
- Consider rebuilding the carbs to renew gaskets and seals.
- The alternator feed wire is unfused, and this feed wire passes almost the complete 360 degree circle of the engine compartment, including through the ignition switch. Voltage regulators have an design defect and a tap on the can may lead to grounding of this wire. When grounded it carries so much current it can overheat and short in the steering column. Fit an inline fuse right by the attachment spade on the regulator or fit a Ford voltage regulator, which has an internal field coil transistor so does not require power from the ignition switch (this is a common modification for the Citroen DS).
- See Ignition Switch
- This can cause a burned wire in the steering column too if the wiring is damaged.