Decarbon Procedure & Noise Diagnosis

Pre-Emptive - Regular use of Techron or Redline SI1/SI2 in the petrol tank

Full TSB Solution, TSB 96113 Dated May 1996

1. Bring engine to normal operating temperature, then shut engine off.
2. Use a 61cm length of 1/8" I.D. vacuum hose as a feed tube for carb cleaner (Carburetor Tune-up Cleaner, ford # D9AZ-19579-BA), although it is strongly advised to use an aerosol cleaner to eliminate the risk of liquid loc. Do not use any of the vehicle's vacuum hoses for feeding cleaner into the engine otherwise they may deteriorate as a result.
3. Connect one end of the feed tube to the Purge Control vacuum port on the upper intake manifold and place the other end of the feed tube in the can of carb cleaner, or to the spray nozzle of an aerosol. If a liquid bottle is used the feed rate must be at least 30 secs to avoid hydraulic lock-up damage.
4. Pinch the feed-tube with locking forceps or locking pliars to prevent suction during start-up.
5. Restart engine.
6. Allow idle to stabilise, then feed the cleaner into the engine by releasing the locking pliars/forceps while lifting engine speed to 3000rpm until half the cleaner is used. If using liquid feed, ensure feed-rate is always erring on the safe side by kinking the tube (a thumb screw clamp is ideal). If using a spray feed (preferred) keep shaking the can vigorously. At the half point allow the engine to stall, or shut-it off.
7. The vehicle should be left to sit for 6-24hrs allowing the cleaner to saturate the carbon, the initial intake of cleaner loosens carbon by both dissolving and also by a cold-shock.
8. Flush remaining carbon by repeating the above steps using the remaining half of the carb cleaner. Do not let the engine stall during the procedure.
9. Remove the feed tube & reconnect the purge control vacuum line.
10. Change oil & oil filter to remove contaminants & carbon in the oil which will otherwise be pumped through all the HLAs.
11. Take the car on a 3-4 mile test drive, using the full-rpm range to remove any remaining cleaner or carbon from the engine.
12. Let the car sit for another 12hrs, restart - if the noise is gone then the cause of the noise was carbon build-up.

Noted the above procedure is a little complex and requires an oil & oil-filter change. The benefits can be felt on any engines after about 36-60k miles.

Full TSB re Noise from Carbon-Knock/HLA/Friction Gear see:

p1 p2 p3 p4 p5 p6 p7 p8 p 9 p10

Note how the HLA noise problem (different to carbon knock) may be also caused by aerated oil in the oil-pan via a faulty oil-strainer to block gasket (test fot this is listed) or faulty oil-pump.

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