The strength of the BMW M4 Coupé is evident in every detail.
There’s an old saying in the motor trade, “If it ain’t broke, don’t try to fix it”. I was reminded of this when I was asked to look at a car which, although it had no sign of power loss, the owner was determined to do a decoke.
I drove the car and it went well; I said that in my opinion very little would be gained by grinding-in the valves, cleaning the head and fitting new valve springs and renewing the head gasket, but he was determined to have a go at it.
A week or two later he appeared again, walking this time. He told me that while doing the job he found that the top dead centre (TDC) mark on the camshaft was two cam belt teeth out of alignment when checked against the manual.
And so he altered the camshaft timing to that shown in the manual and on testing found the engine had lost a good deal of power. Fortunately, he had put a dot of white paint to mark the original positions before carefully changing the timing.
Of course, in retrospect it was pretty obvious that altering the timing was the cause of the trouble, but he had begun to wonder if he had somehow damaged the control unit, or even the valves.
I told him to simply put the timing back to what it was before. All went well this time and the engine ran sweetly again.
When radiators made the change from copper to plastic, there was a great deal of adverse criticism. At first glance plastic seems to be the ideal material although the makeup of some plastics may show deterioration when subjected to constant temperature changes as is inevitable in a cooling system.
Added to this, generally speaking, once a plastic radiator is damaged it is finished. However, the most common cause of failure is damage inflicted by us when renewing hoses and impact damage.
Radiators can be expensive and I believe that before going for a new or reconditioned one, a good used one from a scrap yard makes sense. Mind you, vetting a plastic radiator is difficult because there may be no leakage stains which on a copper type would be obvious. All you can do is look for obvious damage such as that caused by cooling fan contact with the matrix and hairline cracks around the mounting lugs and filler cap neck.
Some radiators have a metal matrix with top and bottom tanks of plastic. Look for leakage at the joints as repair is practically impossible. If the matrix is damaged, reject the unit.
Copper radiators will normally show stains where leakage has occurred and leakage at the metal tanks may be repaired with a silver-soldering kit. Not a DIY job unless you happen to have the kit.
It’s unlikely that the scrap yard buy has been tested, so reach an agreement with the vendor to enable you to change it for another unit if it proves to be immediately defective.
Always check the matrix carefully because deformed, flattened fins may not allow leakage, but could certainly affect heat dissipation. -Mercury Motoring