Developed slight valve tick

Could be the onset of coolant contamination from leaking intake manifold gaskets.

Has there been an unexplained loss of engine coolant? (radiator low, reserve bottle needs topping off?)

Havnt noticed but already had intake gasket replace at 80 or 90k miles.

I ran a 2.8 litre V6, which is of the same family, nearly 200,000 miles and then sold it. The leaking gasket issue is to be taken into account, but I think they are pretty good little engines in general.

Lifters, whether roller or hydraulic type, can get dirty or just have mechanical wear which can make them tick. Also, sometimes a bearing will wear and the oil pressure to a particular hydraulic lifter will be too low, causing a click. And last, a worn camshaft lobe can cause problems. The lifter bottom, in case of hydraulics, can be hammered out.

Since you have maintained yours so well, I would suggest that, before your next change, you add a really good detergented cleaner to the oil and run it a couple hundred miles.

(I have used Mystery Marvel Oil a few times and it seems to help clean the varnish pretty well, but there may be better answers. )

If the cleanup and oil change doesn't help, you may have to go deeper into the engine.

OK thanks fo the info

You have the same problem?

Yes I do constantly top off the coolant avery few months. But when I change the oil see no contamination in the oil.

I've replaced more of those gaskets than I care to remember. Never saw any contamination in the oil either.

The coolant is going somewhere, if you don't see any drips, it's probably going into the engine.

I ran a 3.1 about 200,000 miles also. Ran like new. I sold it to a 16 year-old, and later I saw it in the junkard and found he ran it off the road and screwed up the frame. So it never did die a natural death.

Does this happen on start up when its cold outside? Once the car is warmed up it goes away? If thats the case it could be one of the first four pistons making the noise.

If it is a stuck lifter, try SeaFoam -