Toyota Repair: 2002 Toyota Rav4-4wd 2.0- 4 cylinder-99k, toyota rav4, valve adjustment

Question
Hello,

The rav has started to develop a valve tap noise on cold start and lasts until five minutes after warmed up.  Any suggestions?  The valves have never been adjusted and the car has 99k on it.  Does the rav4 require scheduled valve adjustment or is it self adjusting?  When should the timing belt be replaced?  Oil was changed 2k ago.

Can it be any of the following? Needs thicker or thinner oil?  clogged oil filter? sludge buildup preventing oil to get to the top end?

Thanks for the help!

Answer
The timing belt should be replaced at 90,000 miles, the valves are not self adjusting, they use a shim type of valve adjuster, they rarely go out of adjstment, the noise may be coming from somewhere else, to check for sludge the valve cover should be removed.