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Don’t know if this has been discussed, but here is another theory on the failures.
I ran into one of my lifelong friends today. He is a mechanic for Toyota, very smart and very good – he was the top apprentice in Australia for his year so he knows his stuff.
He has done quite a few valve spring recalls but his first one failed. He pulled the engine down and two of the main bearings had failed, they weren’t spun, just lost their protective coating and the engine was making a racket. He didn’t find any excess sealant anywhere – there was a very small amount on the oil pickup that was a different colour to the sealant he used and he reckoned that it was there when the engine was first built and the block was put together.
His theory is oil starvation on start-up. Oil is completely drained during the recall work and this includes the oil pump. On first start the oil pump is not primed so it takes extra time for the pump to start circulating oil. Oil has to go through the pump, up to the filter and back down to where it apparently then splits off three ways to start lubricating the engine. The two bearings that failed were in sequential firing order.
He now pumps five litres of oil around the engines he does the recalls on before starting them. He does this by using a pressurised gas bottle to blast oil into the engine by taking the oil pressure switch out and screwing the hose from the bottle into that. He also did this on the car where he had the first failure because this engine wasn’t rebuilt – they gave the customer a new short block engine. So concerned was he about ‘priming’ the engine with oil.
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