Is it timing belt or rod adjustment or oil pump ?
I've a 2000 Outback 2.5L, just went over 160km. It starts good any weather all year around. But it has developed over last couple of years an annoying clikety clack off timing push-rod kind of noise after engine starting that goes from very noticeable to faint and completely gone for few minutes as the engine warms up. Colder the engine the louder it is and it also seems to lose power when it makes the most noise cold. So lately I started to let it warm up for few minutes before moving.. It used to be like crank it and drive immediately out but no more.
I'm wondering what it could be given that it passed emission test only 2 months ago in flying color ( of course it was done after engine got warmed up good).
Everything else runs good. Fuel consumption seems to be standard.
For example; month ago I go to Toronto 190Km back and forth no problem with no change in mileage. One thing that I noticed is that the car can stay parked for few hours even in the cold winter like we just had, say for 5-6 hours , and I can start the engine and have no trouble. I hardly hear the noise. So I assume the engine is by now cold enough but it give no effect. Last September I took it to a mechanic to show him but he couldn't hear a thing so we left it. But now I can feel it got a bit worse than last autumn . It is getting worse and worse with time albeit slowly. I have already done system cleaning on injector valve and pushrod several times over last 2 years with very little results.
On my last oil change in February it did get a bit better. What I did was this. I put a new oil filter along with a half can of STP engine treatment (that gooey thick oil that's supposed to help seal up piston better ) with about half-half mixture of 5w-20 and 10w-30, along with a additional engine cleaning fluid . It did perform better with about half the noise level. I am thinking it may be timing belt but than again oil pump or oil blockage or worn out push-rod . But they can't just change with engine temperature can they ? I've done push-rod adjustments before on many cars ( I am a home mechanic) and never seen it like that. Once a rod is out of spec it stays the course at all speed and temp more or less and not change it drastically in few minutes. A timing belt on the other hand could possibly change its sprocket gap a bit but it seems a bit too much even at that. Blocked oil pan ? It doesn't sound like oil pump . It should get bad as oil gets warm up as oil viscosity decreases when hot thereby producing less oil available as oil pressure also decreases.. I could use help figuring this out. Something else is off timing when cold ?.. Thanks to you all.