Q – My 1990 Carrera recently developed a light rattling sound on light acceleration that disappeared on deceleration or at higher speeds.   My research on the web pointed out problems with the timing chain ramps, hydraulic tensioners, or a weak or broken valve spring.   My mechanic, by process of elimination, ruled out all those things and determined that the noise was coming from inside the engine. I had it removed and dismantled.   During the process, we found oily dirt packed into the right front cylinders cooling fins.   They were completely clogged.   As we took it apart, we found evidence of overheating on only that one cylinder, a loose wrist pin bushing and a rod bearing that had clearly overheated and in turn…damaged the crankshaft.   I have never tracked the car and have owned it since new. Even though it had 149,000 miles on it, could the damage to the rod bearing be caused by the clogged fins?   I never saw a warning light or got any indication of a problem by any of the gauges but now my entire engine needs to be overhauled.   Fred

A – Your conclusion makes sense to me.   The gauges take an average of all six cylinders.   It would not have spotted only one cylinder and there is no warning light to alert you for this problem.   On the earlier cars, the oil cooler was usually the part that got clogged up first and when it did, the oil temperature would rise. The oil cooler on your car is not mounted in that corner of the engine.   With your engine, you would never know there was a problem until you heard the sound. So this begs the question could anyone have known that your cooling fins could be clogged?   Frankly, until I heard your story, I would not have thought to check.   The cylinders and heads are completely obscured by the fan, fan shroud, and intake manifold.   One could argue that 149K is a good lifespan for any engine but you have to wonder “what if”.   I am sorry that your engine suffered this catastrophe but thanks for sharing it with other Carrera owners who have a similar car.   I will recommend a visual inspection with a borescope as cheap insurance against clogged cooling fins from now on.   MC