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Technical Tips

A few technical tips from Derek & Jaguar Enthusiasts Club spares & technical help guru, Ken Jenkins. These are some of the most frequent faults we find on cars going through the workshop or questions we are asked on the J.E.C helpline.

OPUS IGNITION SYSTEMS

Amplifier units break down slowly over time. Our very latest uprated Reopus-H   amplifiers boost ignition efficiency. See New Products
V12 E-TYPES and series 1 XJ12s use a 5 volt ignition coil. This coil is a Lucas 13C12 and has this number stamped on the end of the casing. If this coil is fitted & working it will get the best results from an original system. Modern replacement coils do not work as well, but the Reopus H is unaffected by the change to a modern equivelant.
PETROL STARVATION
One of the most common problems with classic cars which are only used occasionally. All Jaguars up to the early 1990s have filters inside the petrol tanks as well as the external filter. These are often neglected & can completely block the fuel supply. In some circumstances fuel starvation can cause carburretor engines to "flame back" through the air intakes. We know of 3 MK2 cars that have had serious engine fires as a result.
UNLEADED PETROL
Almost all Jaguar engines if properly maintained will run happily on unleaded fuel. Some may need minor adjustments or the use of a proven good quality additive such as Millers VSP Plus. The fitting of an electronic 'U' box from AJ6 engineering is another good solution if your engine tends to 'pink' on unleaded fuel. Don't have an 'unleaded cylinder head conversion' unless you are overhauling the head anyway. If you want to give money away we can suggest a very good charity.
ENGINE OVERHEATING
Overheating can destroy an engine in minutes. We often find 'cooked' engines have had their thermostats removed some time before. Unless the thermostat is faulty or of the wrong type it should not be removed to cure an overheating problem. The problem is somewhere else! With XK (XK 120/140/150 :MK2 E-Type S-Type etc)engines removing the thermostat will actually make the problem worse. If in doubt please contact us
BRAKE SYSTEMS
Brake pads should always be changed in car sets, not axle sets, to retain correct braking balance, and never, never fit new pads to one caliper only. Flush through & renew your brake fluid every two years regardless of mileage. Use DOT 4 brake fluid or for rallying DOT 5.1 high boiling point. Some brake component manufacturers will not warranty parts if silicone fluid is used.
SUBFRAME RUSTING
XJS & XJ40 models suffer from rust in the front suspension crossmember, particularly above the coil springs where it can't be seen. An annual spray of 'Waxoil' or a similar product will help prevent this.
WHEEL BEARINGS
Front wheel bearings on all models should always be adjusted with a small amount of free play. Tight bearings will wear out very quickly and may destroy the stub axle. If the bearings will not adjust correctly the stub axle is probably already worn. Rear hub bearings on IRS cars (E-Type, S-Type, XJ Series 1,2&3 etc ) must have .006 - .008 inch end float (free play) which is adjusted by a spacer inside the hub. In extreme cases badly adjusted rear wheel bearings have been known to lock the wheel & lead to accidents !
DIFFERENTIALS
If your car has a power - lock (limited slip) differential always use limited slip diff oil.Spirex, 90DL, 90LS or similar. If you are not sure if your car has a power - lock diff, here's how to find out for sure. Raise the back of the car with both wheels clear of the ground & place it on axle stands. Put the car in neutral with the engine switched off and release the handbrake. Turn one wheel slowly clockwise and at the same time watch the other rear wheel. If the other wheel turns in the same direction you have a powerlock diff.
TYRES
Always check your tyre pressures carefully. Incorrect pressures are a contributory cause in around 50% of all fatal road accidents. Also check that your tyres are properly speed rated for your car. Insurance companies often refuse to pay out after an accident if low speed - rated tyres are fitted.

EARLY IGNITION SYSTEMS <