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tected. This category can include everything from engine starters to rubber center clutch disks and mechanical actuation systems. Failure of mechanical linkages or cable systems have made up the majority of past non‑electrical or fuel system failures. After many years of service, starter systems can develop hot weather failure caused by a number of mechanical or electrical prob‑ lems. The two main parts of the starter assembly are the solenoid, which acts as a heavy‑duty mechanical actuator and electrical switch plus the starter motor and its drive system that engages the engine flywheel. 1. Starter systems solenoid is to bypass the ignition switch and most of the wiring. This is done by simultaneously touching terminals no. 30 on the starter (large red wire from battery) and no. 60 (yellow wire from ignition switch to solenoid) with a long screwdriver while lying on a rug next to the car. Important safety precautions need to be observed while doing this for the car to stay put and start: transmission in neutral, parking brake firmly set and ignition on. Bad or loose ignition switch modules, poor grounds and loose positive wire connectors at the battery can also cause similar problems and often are hard to trace. Make sure the engine troublemakers are under control. In the case of the pre‑1984 911s, this means getting the Carrera chain tensioner system installed. And if you have been putting off installing the air box pres‑ sure relief valve in a CIS 911, now is the time to do it before a major trip. For the 944, it means having the timing belt tension checked if it has been 10,000 miles since last done, or having a new timing belt installed if it has been 30,000 miles. A check of the 944 motor mount is also a prudent safeguard. 2. Critical engine components A thorough check of the cooling system is in order for summer travel. For air‑cooled engines, this includes inspection of fan belt condition, a check to determine that all cooling air passages are clear of debris, and that the engine sheet metal and seals are properly in place so that no hot air from below the engine can be re‑ingested into the fan intake area. For the 911, the owner should know the proper fan belt tension for his model. For example, on the 911s before 1980, the correct belt deflection was 10 to 15 mm, while the post 1980 models are down to 5 mm. The later 5 mm adjustment is achieved by first setting the tension to the standard 10 to 15 mm, and then removing one shim from under the pulley and putting it outside under the nut (don't leave it off entirely!). 3.Cooling systems The solenoid is often the most likely cause of a failure, although a lack of lubrication or binding in the actuation mechanism can also cause the starter to fail to operate. The solenoid consists of a large electromagnet that can simultaneously actuate the motor drive gear to engage the flywheel and apply full battery power to the starter motor. Figure 3. Starter System Basic Wiring Elements. Hot weather and summer vacation trips seem to bring out the worst in old starter solenoids and they may suddenly stall when overheated but be all right after they cool down. Sometimes even a sharp rap with a screwdriver handle or small hammer may get it going. If the starter won't operate because of a defective solenoid, and cooling or emergency measures don't help, it is sometimes possible to replace just the solenoid without replacing the motor and save money. Unfortunately, not all Porsche models are set up to supply separate parts for the starters and solenoids. For those that are not, it is still sometimes possible to get the proper solenoid directly from Bosch dealers if the equivalent Bosch part number can be identified. In many cases, starter failure may be the result of an electrical problem. The solenoid needs a good supply of voltage and current to do its job--this is obvious by the large diameter of the yellow no. 50 circuit wire that goes from the ignition switch to the solenoid. Any wiring defect or weakness between the battery, ignition switch, solenoid and ground can prevent the solenoid from getting adequate current flow and prevent the starter motor from running. The standard emergency fix to increase the amount of current to the For water‑cooled engines, the correct 50 percent level of anti‑freeze should be checked and the system bled. The air passages in the radiator should also be checked to make sure they are all open. A surprising amount of debris can be picked up in the lower radiator area and cause overheating. Belt condition and tension also need to be checked. Mechanical controls are sometimes overlooked in pre‑travel preparation because of their long‑term reliability. It is especially important for the older cars to have the main cable and linkage‑oper‑ ated controls, including the clutches, transmissions and throttles checked to make sure the primary cable or linkage is in good condi‑ tion and properly lubricated (if required). Any required intermediate supports or connections should be correctly installed and adjusted. Spare clutch or throttle cables can often prove to be invaluable. 4. Cable and mechanical linkage controls July 2011 37