MG Trouble Shooting Guide

First published in "Abingdon Classics" November, 1981

Brakes | Engine | Steering | Fuel | Electrical | Clutch | Cooling

  John Twist at University Motors
youtube how-to videos
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Problem Solvers
Excessive brake pedal travel
  1. Brakes need adjusting or replacement.
  2. Air in system.
  3. Faulty master cylinde.
  4. Leaking or contaminated fluid.
  1. Adjust or renew brake shoes.
  2. Bleed hydraulic system.
  3. Fit new master cylinder.
  4. Bleed hydraulic system.
Brake fade
  1. Incorrect pad or lining material.
  2. Old or contaminated fluid.
  3. Excessive use of brakes or car overloaded.
  1. Fit new pads or shoes.
  2. Renew brake fluid.
  3. Check vehicle load.
Spongy brake pedal
  1. Air in hydraulic system.
  2. Shoes badly lined or distorted.
  3. Faulty hydraulic cylinder.
  1. Bleed system.
  2. Fit new pads or shoes.
  3. Check hydraulic circuit.
Brake pedal too hard
  1. Seized wheel cylinder or caliper piston
  2. Glazed fiction material
  1. Replace seized component.
  2. Fit new shoes/pads.
Brake pedal requires pumping or loss of pedal
  1. Brakes wrongly adjusted
  2. Air in hydraulic system
  3. Fluid leak from component or brake pipe
  4. Loss of fluid from master cylinder
  1. Adjust brakes.
  2. Bleed system.
  3. Check hydraulic circuit and replace parts as necessary.
  4. Check hydraulic circuit and replace parts as necessary.
Brakes grab when applied
  1. Contaminated friction material
  2. Wrong linings fitted
  3. Scored drums or discs
  1. Replace (don't clean) pads or shoes.
  2. Replace (don't clean) pads or shoes.
  3. Fit new drum or disc.
Brake squeal
  1. Worn retaining pins (disc)
  2. Faulty damping shims or shoe retaining clips
  3. Dust in drum
  4. Loose backplate or caliper
  1. Fit new pins.
  2. Fit new shims or clips.
  3. Remove dust from drums and shoe.
  4. Tighten caliper or backplate.
Brake shudder
  1. No clearance at master cylinder operating rod
  2. Shoe tension springs either broken or week
  3. Wheel cylinder or caliper piston seizing
  4. Faulty self-adjusting mechanism
  5. Seized handbrake mechanism
  1. Adjust rod if possible.
  2. Replace tension springs
  3. Fit new caliper or cylinder.
  4. Check mechanism.
  5. Check handbrake operation.
Brake pull to one side only
  1. Contaminated friction material on one side (grease, oil or brake fluid)
  2. Loose backplate
  3. Seized cylinder
  4. Faulty suspension or steering
  1. Replace shoes/pads all around.
  2. Tighten backplate.
  3. Replace seized cylinder.
  4. Check suspension and steering.
Handbrake ineffective
  1. Worn rear shoes or pads
  2. Brakes require adjusting
  3. Faulty handbrake linkage
  4. Cable or rod requires adjustment
  1. Fit new pads/shoes.
  2. Adjust brakes
  3. Check linkage and operating mechanism.
  4. Adjust cable or rod.
Servo (where fitted) late in operation
  1. blocked filter
  2. Bad vacuum sealing or restricted air inlet
  1. Clean or replace filter.
  2. Tighten vacuum hose connections and check hoses
Loss of servo action when braking heavily
  1. Air leak in servo-vacuum low
  1. Either overhaul servo or replace
Loss of fluid (servo only)
  1. Seal failure
  2. Scored servo bores
  3. Damaged or corroded fluid pipes
  1. Replace or overhaul servo.
  2. Replace or overhaul servo.
  3. Inspect and fit new pipes.

Index | Engine | Steering | Fuel | Electrical | Clutch | Cooling

Problem Solvers
Lack of compression
  1. Faulty valve seat, excessive wear in stem or guide.
  2. Faulty head gasket.
  3. Worn pistons, rings and bores.
  1. Recut seat and valve, fit new guide and valve.
  2. Fit new gasket or reface head.
  3. Either fit new rings, or if badly worn, fit new pistions and rings, and have block rebored.
Piston slap
  1. As #3 above.
  1. As #3 above.
Smoke from exhaust
Lack of power
  1. As above.
  2. Blocked crankcase breather.
  1. As above.
  2. Check breathing apparatus.
Noisy tappet (with correct clearance)
  1. Wear in rocker pad face and/or rocker sleeve and shaft (OHV).
  2. Worn cam follower (OHC).
  1. Reface pad surface, replace rockers or shaft (OHV).
  2. Fit new followers (OHC).
Big-end knock
  1. Wear between big-end shell and crankcase. Wrong torque on bolts.
  1. Depending on wear, fit new shells, regrind crankshaft and check torqu
Mains rumble
  1. Wear between main bearing shells and crankshaft.
  1. As Above
Cam follower tap
  1. Camshaft worn or follower dished.
  1. Examine and replace followers or camshaft. Or Both
Knocking when clutch depressed. Movement at crank pulley
  1. Excessive crankshaft end-float. Wear between crank and thrust washer.
  1. Fit new thrust washers and recheck clearance.
Clattering from front of engine
  1. Excessive or slack timing chain, worn chain tensioner.
  1. Fit new chain and tensioner. Adjust chain were necessary.
Small-end or gudgion pin knock
  1. Excessive wear between gudgeon pin and con-rod.
  1. Fit new bush or con-rod.
Lack of oil pressure
  1. Excessive wear in crankshaft journals.
  2. Faulty oil pump.
  3. Blocked oil pick-up strainer.
  4. Faulty pressure-relief valve.
  5. Blocked oil filter.
  6. Lack of oil
  1. Overhaul engine.
  2. Fit new pump.
  3. Clean pick-up.
  4. Fit new relief valve.
  5. Fit new filter.
  6. Install fresh oil.
Oil leaks

( normal)

  1. Sump gaskets or packings.
  2. Front and rear crankshaft oil seal.
  3. rocker or camshaft gasket.
  4. Oil filter.
  1. Fit new gaskets.
  2. Fit new seals.
  3. Fit new gasket.
  4. Check filter seal.
Lack of power /engine in good condition

( normal)

  1. Faulty ignition timing. Faulty sparking plugs, points or condenser. Wrong valve clearance.
  1. Tune engine.

Brakes | Index | Steering | Fuel | Electrical | Clutch | Cooling

Problem Solvers
Steering feels stiff
  1. Low tire pressures
  2. Incorrect wheel alignment
  3. Stiff track rod ends
  4. Steering box/rack needs adjustment
  5. To much Viagara!
  1. Correct tire pressures.
  2. Correct wheel alignment.
  3. Check and replace if necessary.
  4. Adjust if necessary.
  5. Wait a couple of hours and try again.
Steering wheel shakes

(haven't been drinking)

  1. Wheels and tires need balancing
  2. Tire pressures incorrect
  3. Incorrect wheel aligment
  4. Wheel hub nut loose
  5. Wheel bearings damaged
  6. Front suspension distorted
  7. Steering box/rack needs adjustment
  8. Shock absorbers faulty
  1. Balance as necessary.
  2. Correct.
  3. Correct alignment.
  4. Adjust wheel bearings.
  5. replace wheel bearings.
  6. Check, repair or replace.
  7. Adjust as necessary.
  8. Replace as nessary.
Steering pulls to one side
  1. Uneven tire pressure
  2. Wheel alignment incorrect
  3. Wheel bearings worn or damaged
  4. Brakes improperly adjusted
  5. Shock absorbers faulty
  6. Suspension distorted
  7. Steering box/rack worn
  1. Correct.
  2. Correct.
  3. Replace and adjust.
  4. Adjust brakes.
  5. Check and rectify.
  6. Check and rectifly.
  7. Adjust and replace.
Wheel tramp
  1. Over-inflated tires
  2. Unbalanced tire and wheel
  3. Defective shock absorber
  4. Defective tire
  1. Correct pressure.
  2. Check and balance if necessary.
  3. Check and rectify.
  4. Repair or replace.
Abnormal tire wear
  1. Incorrect tire pressure
  2. Incorrect wheel alignment
  3. Excessive wheel bearing play
  4. Improper driving
  1. Check pressures.
  2. Check wheel alignment.
  3. Adjust wheel bearings.
  4. Avoid sharp turning at high speeds, rapid starting and braking, etc.
Tire noises
  1. Improper tire inflation
  2. Incorrect wheel alignment
  1. Correct tire pressures.
  2. Correct wheel alignment.

Brakes | Engine | Index | Fuel | Electrical | Clutch | Cooling

Problem Solvers
  1. Improper seating or damaged float needle valve or seat
  2. Incorrect float level
  3. Fuel pump has excessive pressure
  1. Check and replace parts as necessary.
  2. Adjust float level.
  3. Check fuel pump.
Excessive fuel consumption
  1. Engine out of tune
  2. Float level too high
  3. Loose plug or jet
  4. Defective gasket
  5. Fuel leaks at pipes or connections
  6. Choke valve operates improperly
  7. Obstructed air bleed
  1. Tune engine.
  2. Adjust float lever.
  3. Tighten plug or jet.
  4. Replace gaskets.
  5. Trace leak and rectify.
  6. Check choke valve.
  7. Check and clear.
  1. Main jet obstructed
  2. Incorrect throttle opening
  3. Slow-running adjustment incorrect
  4. Slow-running fuel jet blocked
  5. Incorrect float level
  1. Clean main jet.
  2. Adjust throttle.
  3. Adjust slow-running.
  4. Clean jet.
  5. Adjust float leverl.
Poor acceleration (normal)
  1. Defective accelerator pump (if fitted)
  2. float level too low
  3. Incorrect throttle opening
  4. Defective accelerator linkage
  5. blocked pump jet
  1. Overhaul pump.
  2. Adjust float lever.
  3. Adjust throttle.
  4. Adjust accelerator linkage.
  5. Clean pump jet.
  1. Lean mixture
  2. Dirty Carburetor
  3. Clogged fuel pipes
  4. Manifold draws secondary air
  1. Clean and adjust carburetor.
  2. Clean carburetor.
  3. Clean and replace pipes.
  4. Tighten or replace gasket.
Insufficient fuel supply

(call Joel or Howie)

  1. No fuel in tank!carburetor
  2. Clogged fuel pipe
  3. Dirty fuel
  4. Air in fuel system
  5. Defective fuel pump
  6. Clogged fuel filter
  1. Get Gas!
  2. Dismantle and clean carb
  3. Clean fuel pipe.
  4. Clean fuel tank.
  5. Check connections, tighten.
  6. Repair or replace fuel pump.
  7. Clean or replace filter.
Loss of fuel delivery

(call Joel or Howie)

  1. No fuel in tank!
  2. Pump faulty (electric)
  3. Slotted body screws loose
  4. Diaphragm cracked
  5. Loose fuel pipe connections
  6. Defective valves
  7. Cracked fuel pipes
  1. Get Gas!
  2. Replace pump.
  3. Tighten body screws.
  4. Overhaul fuel pump.
  5. Tighten fuel pipe connections.
  6. Replace valves.
  7. Replace fuel pipes.
Noisy pump
  1. Loose pump mounting
  2. worn or defective rocker arm (if manual)
  3. Broken rocker arm spring (if manual)
  1. Tighten mounting bolts.
  2. Replace rocker arm.
  3. Replace spring.

Brakes | Engine | Steering | Index | Electrical | Clutch | Cooling

Problem Solvers
Starter doesn't turn
(lights dim)
  1. Battery flat or worn
  2. Bad connection in battery circuit
  1. Charge or fit new battery.
  2. Check all feed and earth connections.
starter doesn't turn
(lights stay bright)
  1. Faulty ignition switch
  2. Broken starter circuit
  1. Check switch.
  2. Check starter circuit.
Solenoid switch chatters
  1. Flat battery
  1. Charge or replace battery
Starter just spins
  1. Bendix gear sticking
  1. Remove starter and clean or replace Bendix gear.
Low or no charge rate
  1. Broken or slipping drive belt
  2. Poor connections on or faulty alternator.
  1. Fit new belt.
  2. Check and replace alternator.
No lights (or very dim)
  1. Flat or faulty battery, bad battery connections
  1. Check battery and connections.
side and rear lights inoperative although stoplights and flashers work
  1. Fuse blown
  1. Fit correct value fuse
One lamp fails
  1. Blown bulb
  2. Poor bulb contact
  3. Bad earth connection
  4. Broken feed
  1. Fit new bulb.
  2. Check connections.
  3. Check connection.
  4. Check feed.
Flasher warning bulb stays on or flashers twice as fast
  1. Faulty bulb or connection on front or rear of offending side
  1. Fit new bulb, make good connection.
Lights dim when idling or at low speed
  1. Loose drive belt
  2. Flat battery
  3. Faulty charging circuit
  1. Tighten belt.
  2. Check charge output and battery.
  3. Check charge output and battery.
One dim light
  1. Blackened bulb
  2. Bad earth
  3. Tarnished reflector
  1. fit new bulb or sealed-beam.
  2. Check earth connections.
  3. Fit new bulb or sealed-beam.
Wipers do not work


  1. Blown fuse
  2. Poor connection
  3. Faulty switch
  4. Faulty motor
  1. Fit fuse.
  2. Check connections
  3. Check switch.
  4. remove and examine motor.
Motor operates slowly
  1. Excessive resistance in circuit or wiper drive
  2. worn brushes
  1. Check wiper circuit.
  2. Remove motor and check brushes.
Brakes | Engine | Steering | Fuel | Index | Clutch | Cooling

Problem Solvers
Clutch slips
  1. Clutch facing worn
  2. Clutch facing contaminated
  3. Warped clutch cover or pressure plate
  4. Incorrect adjustment (if adjustable)
  1. replace clutch assembly.
  2. replace Clutch assembly.
  3. Replace clutch assembly.
Clutch drags
  1. faulty clutch hydraulics (if hydraulic)
  2. Faulty clutch adjustment (if adjustable)
  3. Clutch disc warped
  4. Clutch hub spines worn or rusty
  5. diaphragm worn or mal-adjusted
  1. Overhaul or replace clutch hydraulics.
  2. Adjust clutch.
  3. replace clutch disc.
  4. replace or lubricate clutch.
  5. Replace pressure plate
Clutch chatter
  1. Faulty pressure plate
  2. Faulty clutch disc loose or worn engine mounting
  1. Replace pressure plate.
  2. Replace clutch disc.
  3. Replace mounting.
Clutch noise
  1. Insufficient grease on bearing sleeve
  2. Clutch installed incorrectly
  1. Lubricate
  2. Check installation.
Clutch noise (pedal down)
  1. Faulty release bearing
  1. Replace bearing
Clutch noise (pedal on the way up)
  1. Damaged or worn pilot bearing
  1. Fit new bearing
Clutch grabs
  1. Contaminated clutch lining
  2. Clutch worn or loose rivets
  3. Clutch splines worn or rusted
  4. Warped flywheel or pressure plate
  5. Loose mountings on engine or power unit.
  1. replace clutch.
  2. replace clutch.
  3. Clean or replace.
  4. Repair or replace.
  5. Tighten or replace.

Brakes | Engine | Steering | Fuel | Electrical | Index | Cooling

Problem Solvers


  1. Inoperative thermostat
  2. Radiator fin choked with mud, leaves, etc.
  3. Incorrect ignition and valve timing
  4. Dirty oil and sludge in engine
  5. Inoperative water pump
  6. Loose fan belts
  7. Restricted radiator
  8. Inaccurate temperature gauge
  9. Impurity in water
  1. Replace thermostat
  2. Clean out air passage.
  3. Tune engine.
  4. Change engine oil and filter.
  5. Replace (or check electrical).
  6. Adjust tension.
  7. Flush Radiator.
  8. Replace temperature gauge.
  9. Use soft, clean water.
Loss of coolant

(call Howie)

  1. Leaking radiator hose(s)
  2. Damaged radiator
  3. Leak at heater connection or plug
  4. damaged cylinder head gasket
  5. Cracked cylinder block
  6. Cracked cylinder head
  7. Loose cylinder head bolts
  8. Bad heater control valve
  1. Replace.
  2. Repair or replace radiator.
  3. Repair or replace.
  4. Replace gasket. Check engine oil and
    refill as necessary.
  5. Replace cylinder block. Check engine oil
    in crankcase for mixing with water.
  6. Replace cylinder head.
  7. Tighten cylinder head bolts.
  8. Replace and dry out distributer.
(never a problem)
  1. Inoperative thermostat
  2. Inaccurate temperature gauge
  1. Replace thermostat.
  2. Replace temperature gauge.
Poor circulation
  1. Restriction in system
  2. Insufficient coolant
  3. Inoperative water pump
  4. Loose fan belt
  5. Inoperative thermostat
  1. Check hoses for crimping. Clear the
    system of rust and sludge.
  2. Replenish.
  3. Replace water pump.
  4. Adjust fan belt.
  5. Replace thermostat
  1. Excessive impurity in water
  2. Infrequent flushing and draining of system
  1. Use soft, clean water.
  2. Flush thoroughly at least twice a year.

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Oil is Killing our Cars


Editor’s note: Thanks to Keith Ansell of Foreign Parts Positively, Brush Prairie, Washington for this information. It appears that our Little British Cars are in jeopardy of being injured by the new oils that have been produced in the last couple years. The bottom line is follow Keith’s recommendations for oil or ZDDP additive when you go shopping for oil for your next oil change.



"If you're currently putting mileage on your classic vehicle and using the latest API grade SM oil, you are almost certainly doing irreversible damage to your engine."

William C. Anderson, ‘New Oils and Old Cars’, Old Cars Weekly 48


What’s this all about? In the middle 1970’s catalytic converters (cats) became mandatory on most cars. By the middle of the 1980’s it was noted that cats had a limited lifetime. With the addition of computer controlled fuel delivery, oxygen sensors were introduced into the exhaust system. Soon after this it was noted that one of the Extreme Pressure (EP) components of oil, ZDDP (Zink-Dialkyl-Dithio-Phosphate), caused deterioration of the oxygen sensors and cats. The auto manufacturers started to redesign engines so that they didn’t need this additive and by 2005 all major oil manufacturers started to reduce ZDDP in their oils with the goal of meeting “SM” classification. Most engines produced before 1980 were of the flat tappet design that were designed around and had to have ZDDP. As the “old” engines use only a small percentage of the total lubrication oil consumed today, the removal of ZDDP did not affect the majority of the oil market. Of the 500 million registered cars in the U.S. only 10 million are older than 1988.  Most well known companies therefore choose not to help people who own older cars, especially those with flat tappets. Those that are acknowledging our needs are limiting what is available and even what they offer may not be sufficient. The bottom line here is that if you are not using a lubricating oil with at least the necessary amount of ZDDP your car was designed to use (flat tappet design or high performance hot rod) you are damaging your engine.


 Here’s the number we need: Between 1,600 ppm. and with 2,800 ppm being about highest concentration of ZDDP (Zink-Dialkyl-Dithio-Phosphate), around 1,800 ppm seems desirable. Most of today’s oils have reduced this chemical to less than 400 ppm and in most cases their goal is Zero! Another point: Zinc and/or Phosphate do not equate to protecting our engines. ZDDP is the compound that protects our engines. Don’t accept oils or additives that claim to have what we need if they give just zinc and/or phosphate numbers.


There seem to be only two major North American oil companies producing products for us and they are Castrol (Syntec 20W-50 in the black bottle with “Recommended for Classic Cars” on the back) and Valvoline (VR-1 20W-50). Joe Gibbs Racing Oil is now producing street oils that seem the best available for our engines and distribution of this product is just starting in North America. Red Line Oil, a smaller manufacturer on the West Coast, is available at many racing shops, with 10W-40. Eastern States seem to be able to find Brad Penn Oil, Swepco and Hi-Z. Penrite Oil in Australia.


Now comes The News! Companies are now producing ZDDP additives that can be added to any oil! Rather than try to find oils that protect our cars, you can now add a prescribed amount of one of these additives to your oil of choice. The more concentrated the additive the better. Be aware that the larger the dose of additive required to reach 1,600 ppm, the “carrier” in the additive will probably dilute your oil and reduce the oil’s designed lubrication abilities.


First to come to market was a product called ZddPlus”. Kirban Performance, the manufacturer, has a web site that expands on what we have been learning over the last year and their approach to solving our problem. They are seemingly careful not to suggest any brand of oil and claim their product should be compatible with any company’s products. There is no new information on this web site but it answers many questions. They market directly on-line or through dealers.


The second product is “Cam-Shield”. This product has been developed by a person that has been in the lubrication business for many years and is a very experienced lubrication formulator for some of the largest racing programs from road racing to off-road. This product is very concentrated so it does not dilute your base oil. It comes in a bottle that has a built-in measuring device so that you can accurately dispense the product based on how much oil you put in. This company markets through local dealers, distributors and on-line This company also does not suggest any single brand of oil.


Other products that contain ZDDP are EOS, Torco, Crane, CompCam and STP. These are not specifically formulated for our cars and have limited use. Some are specifically to be used only during break-in. There may be others.


So we have a final answer! We can now know, by adding the ZDDP that was mandated out of most oil, that we are not internally wearing away our engines at an accelerated rate by restoring the ZDDP that our engines were designed around.


I want to acknowledge and thank the companies, large and small, and the individual people who have written and called me with input on this subject from all over the world. Many were aware of this problem even before my first article was published. All these inputs are used and are appreciated.




What oil to use with the additive I don’t think is a question that has a definitive answer. Most oils are similar enough that there aren’t great differences in the oils manufactured by quality companies. I’ll share what I have learned, especially over the last years. By going into any auto supply store you can see, by the fact that there are lots of different brands and types of oils, that there isn’t one answer.


Synthetic, blend, or dinosaur juice? It seems that the quality of all the lubricants may well exceed anything most enthusiasts would ever need. Synthetics are the best; many people, including some manufacturers, will admit that conventional oils are adequate in most applications. One manufacturer admitted to me that all their products were similar, just marketing and some modifications to additives got higher prices and sold more products.


If your car’s owner’s manual recommends a single weight oil and/or non-detergent, what should you do? Great improvements in oil since your car was manufactured make those old recommendations no longer valid. One exception: If you have been running a non-detergent oil it might be advisable to stay with what you have been using until a new engine is built.


Engine manufacturers realized in the early 1970’s that the new multi-grade oils were superior and completely dropped recommending single grade oils. I recommend using the grade of oil recommended during the last production dates of your engine if it includes a multi-grade. Lighter weight oils get more horsepower to the wheels and if properly used can increase engine life. The rule we use is that the oil pressure should be 10 Psi for each 1,000 Rpm of redline. i.e.: If the redline of your engine is 6,000 Rpm you should have 60 Psi, 50 Psi with a redline of 5,000, etc. If these numbers cannot be reached using a 20W-50 it probably is time for a new set of bearings.


If anything changes in the future I’ll put out new data. Now with the new additives and some new oils we have products that will keep our engines purring like they were designed to do! Just remember to have ZDDP at or above 1,800 ppm for flat tappet engines!


Keith M. Ansell

Foreign Parts Positively, Inc.

19900 NE 189th Street

Brush Prairie, Washington 98606