In Summary

I drive a 2002 Toyota RAV4 with D4 engine. I bought it three years ago and it has been running well. Lately it makes a rough metal on metal noise in the engine when I start it in the morning. My service bay mechanic cannot explain the cause. Another mechanic suggests that the engine has knocked. What is your opinion?

Hello Paul, I drive a 2002 Toyota RAV4 with D4 engine. I bought it three years ago and it has been running well. Lately it makes a rough metal on metal noise in the engine when I start it in the morning. My service bay mechanic cannot explain the cause. Another mechanic suggests that the engine has knocked. What is your opinion? Muwabe Hamisi.

Hello Hamisi, engine noise that sounds like metal on metal contact points towards engine lubrication failure and seizure or damage of moving metal components. The 2AZ Toyota engine in your RAV4 has a combination of alluminium and cast iron metallic components that are sensitive to quality of engine oil and prompt buildup of lubrication pressure when you start the engine. Good quality engine oil is blended with additives which prevent premature friction damage and metallic seizure, corrosion damage, buildup of harmful sludge which blocks oil passages and prevents prompt buildup of oil pressure when during cold engine starts.

The use of genuine or OEM oil filters ensures continuous unrestricted engine oil flow up-to drain date. If your engine oil service has not been carried out routinely with the use of good quality oil and genuine oil filters this may be the cause of the metal to metal contact noise you may be hearing. This noise will mean there is some level of damage happening. Initial inspection should involve checking the quality of oil in the oil sump to rule out presence of sludge and deposits.

If sludge exists consider cleaning the engine oil pan and strainer on the pickup tube. If there are no signs of metal debris from engine components then you could first clean sludge, replenish oil and filter. Renew the engine oil with a suitable multigrade oil like Shell Helix HX5 and a genuine Toyota filter. Should the noise continue then consider dismantling the engine to decide whether to replace the oil pump, timing chain and guides or any other fast moving metallic components the mechanics consider damaged. Escalate the inspection in stages as I’ve suggested.