Technical Tips

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Extract from December's MGOC publication - Enjoying MG
by Roger Parker

Power Steering on the MG Maestro

Squeal from the power steering on an 89 MG Maestro was becoming a real problem for one member. The squeal began on full lock, but gradually worsened and the pump would actually stop all together. Eventually, just blipping the throttle with the car standing still would produce a squeal from the pump.

MG Maestro The instance on belt squeal on the power steered 2 litre Maestro and Montego models is such a common one. The circumstances described follow exactly the usual route of problems that many owners have experienced.

The problems usually start with instances of squeal once full lock is reached. Next, during cold starts on cooler and damp mornings the squeal starts to be heard even when no steering loads are applied, but which goes away once the initial dampness providing lubrication to the belt evaporates. From there the inactivity can accelerate the problems.

Correct tensioning of the two drive belts is very important, especially so since the water pump and its bearings are used as a pivot for drive transmission. Incorrect tension and/or different tension between belts often overloads the water pump bearings and leads to early failure of that item. This can be accelerated by owners trying to eliminate belt squeal by over tightening just the power steering pump belt. Approximately half an inch of free play movement of the belt is a rule of thumb to aim for when adjusting belt tension.

Essentially the power steering system is quite simple, containing only two basic components: the pump and the rack. In operation, the system pressures should be between 55 psi (maximum) with no loads, up to a maximum of 450 psi when the steering is held hard on full lock with the engine at idle. Increasing the engine speed to 1000 rom sees the pressure rise to between 850 and 900 psi.

Even with these normal pressures, the torque required by the pump to satisfy these needs is obviously quite considerable. This is self evident with a noticeable drop in the engine rpm at idle when any steering loads are imposed. If I now add that when the pump starts to go wrong, the pressures generated under these same conditions can increase significantly and peak at just under 1500 psi, we can see that belt squeal is going to be quite probable under almost all operating conditions. At these peak pressured the torque requirements from the pump is usually much greater than can be transmitted by the belt so the pump locks out.

These fault conditions with the pumps fitted to Maestro and Montego models are quite common and are usually the cause of the problems you have described. I would suggest that your problems will be found within the pump, which is a non serviceable item, and has to be replaced as a complete assembly. Sourcing one from any power assisted 2 litre engined Maestro and Montego models may be a problem, as you will find that this is one of the first items to be removed if it is any good. If you do find one ensure you have a cast iron guarantee that you can exchange it or get your money back if it doesn't work.

Over the years the various different pumps listed for all of the 2 litre petrol engined cars have been superseded, and now just one pump is listed for all applications. This does not mean that any 2 litre petrol Maestro or Montego can donate its pump and you can be sure it will fit, as long as the adjustment bracket comes with it. If you have to buy a new one then the part number applicable to your car is QVB 10015. Sit down when you are being told the price, as even my old price lists indicate a price of over £200.

Fitting of the replacement is straightforward and involves the removal of two hoses and four 10mm headed bolts, the two pivot and two adjustment bolts on the sides of the pump. Considerable fluid loss will occur so be prepared with containers and keep everything clean. Refitting is a simple reversal of the removal procedure, but before fitting the drive belt fill the pump reservoir with fresh automatic transmission fluid and rotate the pump manually a few turns to expel any air. The system is self priming but a little gentle manual priming is advantageous.

Start the engine and let it idle for a few seconds before operating the steering from lock to lock several times, then recheck the fluid level and top as required. Now recheck the belt tension. It is worth noting that under no circumstances should the steering be held at a hard lock for more than 30 seconds as this will cause the fluid to overheat which can damage the internal seals within the pump. When you think how easy it is to actually do this in normal town driving conditions, we can see how pumps can expire.

This also indicates how important it is to ensure the oil cooler is in the system. This is the simple loop of metal pipe found under the front of the car which catches all the debris, corrodes, and when holed is often bypassed! If yours is in a bad way you will not want to pay Rover prices for replacement. I have found that small bore central heating pipe is the same diameter, and being copper is easily formed and corrosion resistant. Painted black it provides an excellent and cheap alternative.

With my own Maestro Turbo I have exceeded 86,000 miles on the original pump with no problems, with just new belts fitted when I changed the cam belt at 48,000 miles. I do know of other cars with well over 100,000 miles on the original pump. The fact that these cars have been mostly in motorway conditions where little steering movement is needed may have some bearing on the subject.

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