Car: 2006 V6 4.0L 4Runner, 164,000 miles.
Need help diagnosing engine bay tick. I first noticed after a slight overheat due to radiator failure. The tick is present when idling and increases with engine's RPM's and does not go away when car warms up. Based on the sound, it's likely an exhaust manifold problem, but how can I rule out if its engine wear without repairing the exhaust manifolds and seeing if the sound goes away? The OEM and cheap aftermarket manifolds are prone to the same failure, and good quality Doug Thourley manifolds are not available so it does not make sense to replace the manifolds in my mechanics opinion.
I wouldn't want to drive it and cause more engine damage if there are any engine issues besides cracked exhaust manifolds. Do I take it to the dealer/other mechanics for an inspection?
Background: I was driving up a mountain road when my A/T oil light went on. Engine temp gauge was normal, but spiked to "hot" once or twice for a few seconds. I immediately let the car cool off and noticed my radiator overflow was empty. I topped it off.
Sure enough, the radiator didn't hold any pressure and new coolant evaporated; so I got a new radiator installed. There was also a good amount of oil seeping from the timing cover down the the skid plates - however this is a common issue. I was about 0.5 quarts low on oil. I cleaned up engine bay, changed my oil and did one drain and fill on my transmission. My synthetic oil looked quite dark; transmission fluid looked pink-brown, not bad for never been changed since 2006. My mechanic suggested to keep an eye on the timing cover seep but it shouldn't be a problem.
As for the engine tick, mechanic says "it's normal" for my mileage. I posted a video of the noise on the 4Runner forums and the suggestion is that it's most likely a cracked exhaust manifold. It won't leave me stranded on the road. However the tick is so loud I can even hear it with the windows rolled up; the 4Runner is exceptional at blocking out outside noise. I don't smell any exhaust gases; a tick of this loudness should be leaking a lot of exhaust gases..
You might be able to pinpoint the noise with a mechanic's stethoscope. Listen around on various parts of the exhaust manifold and engine to see if you can isolate the sound to one side or the other, or one area, like near the lifters, etc. Obviously you'd want to do it on a cold engine and only in the first few minutes of it running so you don't burn yourself or damage the stethoscope, the exhaust manifold will get hot quickly.
