PORSCHE TECHNICAL TOPICS
Technical problems solved
I recently spent a fascinating afternoon at MCE Porsche in Oxfordshire. Proprietor Mike Champion is an enthusiast of many years’ standing, and also a time-served and highly qualified engineer with a long career in the automotive industry behind him. And you have to admire a man who, while working on classic 911s, listens to classic vinyl albums of the same period. Ready to go on his bench-top turntable were, among many others, The Doors, The Beach Boys, Aretha Franklin, Jimi Hendrix and Led Zeppelin.
My visit, having first met Mike at a Porsche event just a few weeks previously, was primarily to have a longer discussion and a look around his compact but very wellequipped premises, but also to work out what stories we might collaborate on in future editions of the magazine. And, as luck would have it, there was an ideal candidate vehicle on the two-post lift even as I arrived.
A manual-transmission 987 Cayman ‘S’; 2005 model, around 70,000 miles on the clock. Obviously owned by a fastidious individual – another engineer – and equipped with at least two mods that mark him out as a knowledgeable and far-sighted enthusiast: a beautifully made stainlesssteel exhaust, and protective grilles for the front air intakes. Here’s someone who knows all about rotting radiators and the potentially disastrous consequences thereof.
His understandable worry on this occasion, however, was the engine’s seemingly high oil consumption. The car had been serviced – elsewhere – in the fairly recent past, but now, after just 1000 miles, the bar-type display in the instrument panel was suggesting that the level in the sump was down to the bare minimum. An engine of this type and mileage should consume no more than around half a litre of oil in that distance. Three times that amount was suggesting that something was clearly amiss.
Mike’s mission, then, was to establish whether this was due to either a faulty gauge or sender – by no means unknown – or perhaps to some other mechanical malady. (Famously, and for reasons best known to itself, Porsche abandoned the good, old-fashioned and in principle failsafe mechanical dipstick with the cessation of 986/996 production.)
Rather than wade in with diagnostic kit or an internal examination, however, Mike was sensibly starting with the most basic and easily measurable parameters. ‘I am always careful not to jump to conclusions about these engines,’ he says, ‘and prefer instead to take an objective, results-led view. Obtain the engineering facts, present them to the customer, and decide how to proceed from there.’ Armed, then, with Porsche’s published figures for the fill volume for the car (7.75 litres with a filter change; 7.5 litres if you leave the element undisturbed, and thus with around 250ml inside the housing), the first job was to drain and then accurately to measure what was in the engine to start with.
Result, after about 20 minutes, and when there were no more than a few drips oozing from the orifice: almost exactly 6.0 litres in the plastic container which, with his obviously customary precision, Mike had previously graduated with a ruler and permanent marker. Given the typically 1.0–1.5-litre difference you can expect between ‘max’ and ‘min’ on the average conventional dipstick, this suggested that the gauge was, indeed, giving a realistic view of the situation – and might even have been very slightly optimistic.
But even now Mike wasn’t convinced. ‘I have no reason to doubt whoever carried out the last service,’ he conceded, ‘but I have no way of knowing for sure that the sump was filled to the correct level 1000 miles ago. What I shall do, then, is first refill it with the same quantity of new oil as the amount I have just drained out, to see if that gives the same reading on the gauge. If so, I shall add more fresh oil – in known increments, checking the gauge as I go – until it’s up to the maximum. If the volume added matches what I would expect, then I can have confidence in the accuracy of the gauge. I will then let the customer drive the car normally for the next 1000 miles, knowing that we have both a controlled starting volume and a reliable means of measurement.
‘If, as I suspect it will, the gauge subsequently shows only the usual modest reduction in level that you might expect, then all will be well, and we can put it down to operator error. If within that distance, on the other hand, the level genuinely falls back to the same as it was today, then clearly there is a deeper problem that will have to be investigated.
‘In anticipation of further investigation being required, I shall also take the precaution of collecting a sample of the old oil, and sending that to Millers Oils in Huddersfield. As I’m sure you know, they offer a highly informative spectrographic analysis service, which for around £50 a time gives you a very detailed view of any contaminants and particulate matter. That should give me an accurate picture of not just the cylinder condition, but also of the piston rings and skirts, the crankshaft bearings, and even the valvetrain. And at this stage it’s far less costly than having me remove all six coil packs and spark plugs, and then start carrying out cylinder leakage tests, and so on – especially if the measurements reveal that it really was just a filling error during the previous service.’
Cayman owner was concerned that after only 1000 miles since last oil and filter change, lubricant level in sump had dropped to minimum mark. But was that because the engine was burning it, or because the gauge was faulty? Or even because the level wasn’t correct to start with? Only way to be sure is the application of some basic science, by precisely measuring the quantity of oil that comes out, and then refilling to the correct level and observing what happens over the next 1000 miles. Spectrographic analysis of the oil would be a good indicator of problems, too – or hopefully the absence of them – and after-market magnetic drain plug was encouragingly free from tell-tale swarf
With 911 & Porsche World’s consultant editor, Chris Horton