Technical Tips


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Extract from December's MGOC publication - Enjoying MG
by Richard Ladds

TECHNICAL TIPS

For technical tips this month I have reproduced some of the calls we have received on our technical help line.

LEAKING FUEL
My 1984 MG Metro suffers from petrol leaks around the fuel filler cap, especially when the tank is full, and this leaves unsightly stains on the lower wing. The petrol cap appears to be the correct type for the car and the tank itself seems to be in sound condition. Why does it leak?

This is a common problem with Metros. The fuel cap should be nonvented and sometimes a new cap will cure the problem. However, if a new cap brings no improvement, then check that the fuel tank breather tube is working properly and not restricted in any way.

BAD VIBES
I have a severe vibration in my MGB GT at around 60 mph, it seems to make the whole cockpit vibrate and even the rear view mirror starts to buzz. I have had the wheels balanced and checked the front bearings, but the vibration persists. What do you think is causing it?

Check the universal joints in the prop shaft. Insert a screwdriver between the joint and the prop shaft yokes, if there is any movement, then the bearings are worn and the universal joint must be replaced. You can replace the joints yourself but it is quite a skilled job. If you are not sure of your ability, then entrust the job to a specialist garage or buy a replacement prop shaft complete with new universal joints already fitted.

CONNECTING A TACHOSTROBE
I have just bought myself a Gunson's Tachostrobe DC timing lamp but it needs to be connected to the battery. The batteries in my MG are under the back seat and too faraway for the leads to reach. Can I use a power source from inside the engine compartment?

A DC timing lamp is ideal for setting the timing on most cars. However, the Tachostrobe needs its own power supply and the instructions say connect it up to your battery. This is no problem on a Midget, Metro or Montego, but not on the MGB or MGA where the batteries are so far away. The solution is to connect the red crocodile clip to the positive side of the coil and the black crocodile clip to a good earth on negative earth vehicles. This will provide separate power for the lamp. Then fit the spring plug connector between lead number 1 and plug number 1, which is the plug nearest to the radiator. If you have painted the timing marks and crankshaft pulley with Tipp-Ex, the strobe lamp will make the marks appear stationary when the engine runs. Remember to disconnect the vacuum advance on the distributor and set the idle to 1000 rpm.

CLATTERING FAN
There is a tinkling, clattering noise from somewhere near the front of the engine of my 1973 MGB whenever I rev it up. I have looked at the water pump, the bearing on the alternator and checked the fan belt several times. Any suggestions?

The engine driven fan on the MGB is mounted on little rubber cushioning grommets which can perish. When they have crumbled away the fan is able to rattle against the pulley. New grommets will put a stop to the clatter.

SEIZED CLUTCH
My car has been standing for many months and now the clutch has seized, can you advise me of a quick method to free the clutch?

First make sure that the problem is in fact a seized clutch and not a hydraulic failure. Check that there is enough fluid in the system and that the clutch operating arm is moving when the clutch is depressed. If you are satisfied the clutch hydraulics are working properly, then start the engine and run the car until it is warm and then switch off. Position the car on the road with the area ahead of it completely clear. Put your left foot hard down on the clutch, then select first gear and start the engine. As soon as the engine fires the car will start moving and leap forward because the clutch is already engaged. Be prepared for this and remember to keep your foot hard down on the clutch, then drive up the road in first gear for a few seconds, accelerating and decelerating, until the force of the engine acting against the locked transmission breaks the corrosion between flywheel and clutch, this usually happens quite quickly. This process will put a strain on the drive train and the half shafts but only briefly.

Some people recommend that the most effective way to prevent the clutch from seizing on to the flywheel when a car is stored over a long period, is to leave the clutch pedal permanently pressed down, by using a block of wood jammed between the seat and the pedal.

OVERHEATING MIDGET
My Midget has been overheating, can you tell me how to check if the cooling system is working properly?

Overheating can be caused by a number of different things or a combination of problems. Effective cooling depends on the coolant circulating correctly. If the thermostat sticks closed, it blocks the radiator out of the cooling system, and your engine will soon boil over. The best way to check for a closed thermostat is to carefully feel the radiator, if it is cold at the bottom but hot at the top then the coolant is not circulating then the thermostat is probably stuck closed. If the thermostat is stuck open then the engine will be overcooled and will not warm up. Check the radiator itself, the core can become corroded inside and will eventually block up, preventing the coolant from circulating. A sludge up radiator can sometimes be cured by removing the radiator, turning it upside down and flushing it through with a garden hose. If lots of sludge is washed out then you have found the problem. Sometimes the core will become corroded solid and then the only cure is a new radiator. A blown head gasket will also cause overheating, but this will be accompanied by loss of power, white smoke from the exhaust, an erratic temperature gauge and a cooling system that needs to be topped up constantly. Avoid blocking the air intake grille by fitting large spot lights, too many badges or anything else that can obstruct the flow of air to the radiator.

DISCLAIMER
WHILST EVERY EFFORT IS MADE TO ENSURE THAT THE INFORMATION AND ADVICE PUBLISHED IS RELIABLE AND MAKES PROPER REFERENCE TO CORRECT SAFETY PROCEDURES AT THE TIME OF PUBLICATION, THE MGOC CANNOT BE HELD RESPONSIBLE FOR ANY INJURY DAMAGE OR LOSS RESULTING DIRECTLY OR INDIRECTLY FROM THE READER IMPLEMENTING OR RELYING ON THE INFORMATION CONTAINED IN THIS PUBLICATION.

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