Last week we had a customer who came in with his Mini. He had quite a large oil leak and needed a new Head Gasket which is a relatively cheap and simple job. However when our mechanics got underway it became apparent that their was more problems with the little Mini.
Our mechanic removed the Cylinder Head to fit a new Gasket but when quickly examining the bore it became obvious they had become glazed.
When an engine is built, the cylinder bores are honed. The intention is to produce a crosshatch appearance with scratches from both directions. When this surface is magnified it is just a series of small peaks and troughs. Older engines would be used at this stage but would need ‘running in’ but these days the bore is machined to smooth off the peaks and get that ‘plateau’ finish and therefore avoiding having to run the engine in.
When our mechanic describes the bore as ‘glazed’ the troughs become filled with lacquer, displacing oil and preventing correct ring lubrication. This may seem like a relatively small problem but the consequences of a glazed bore means increased oil consumption and excess exhaust smoke along with a decrease in engine power and performance.
So our customer really had no other option but to have a new short engine fitted which is quite costly. Mini Sport provided the reconditioned engine and fitted it, making sure it ran well before our customer came to collecting his Mini.
Another job well done, but this is a good example of how repair costs can escalate.
Here you can see a bore being honed at Mini Sports engineering department, Hi-Tech.
If you look closely at the already honed bored you can see the minute scratches being made are not straight but cross over to create a cross-hatch effect. These scratches are what holds oil and helps lubricate the rings and give good compression.
To book your car into the Mini Sport garage please call 01282 778731.