Tick Noise Due to Collapsed Lash Adjusters - Possible Coolant in Oil - keywords contaminated contamination cool crankcase dex dexcool engine lifter noise rattle repeat valve valvetrain

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

On rare occasions, an upper end tick noise may occur inside of the engine when cold and/or hot. This noise may be due to a collapsed lash adjuster (s). In some cases, replacing the lash adjusters may temporarily correct the noise but it may have returned shortly after with collapsed lash adjusters again.

This may be due to Dexcool coolant in the engine oil, which is not as obvious as convention ethylene glycol coolant (green) in the engine oil. Since some of the evidence will break down and / or volatilize at operating temperature, an engine oil analysis may not indicate that there is Dexcool in the engine oil. Typically, the only visual evidence of Dexcool in the engine oil is significant black or brown sludge deposits that appear to be the result of not having the engine oil changed even though the oil has been changed according to the maintenance schedule / engine oil life monitor. If the sludge is a result of Dexcool in the engine oil, a low cooling system level will be found with no external leaks.

If a collapsed lash adjuster is found, inspect the cooling system level before replacing the collapsed lash adjusters. If the cooling system is obviously low and there are no external leaks, follow the "Coolant in Engine Oil" diagnosis in the Engine Mechanical section of SI and repair as necessary before replacing any collapsed lash adjusters.

If the cooling system is full and there is no evidence of Dexcool in the engine oil, replace the collapsed lash adjusters as necessary.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.