Hey Scotty,

Thank you for taking the time to read this and to answer this question.

I recently purchased a 2004 Toyota Celica 1.8l GT 1ZZ and it has 129k miles.  I don't know the history of maintenance.  I immediately drained the oil and put high mileage mobile1 5-20 synth in and it does burn a bit of oil, but not too much.  The engine is not loud by any means and is rather quiet, run rather smooth as well given its 20 years old.

I was wondering your thoughts on changing the timing chain and tensioner given that I have no idea when or if it was ever done.  Is there a rule I should follow? 

As for the water pump, I see no leaks and hear nothing but the vehicle has 129k on it and wondering if this too should be changed? 

I would rather be safe than sorry and be stuck. 

Also to note, as an indicator of possible prior maintenance, when i got it, it was a bit low on oil when I purchased it and the transmission fluid was dark.  It had hard shifts and sometimes it was stuck shifting from third to forth gear.  I did drain and change the strainer filter, cleaned the pan, and repeated this process about 4 times to try to get all the fluid swapped out.  Shifts are worlds better and the fluid is now showing red every time i check it.  Crisis averted on the transmission I hope....

Thanks for everything in advance!

Best regards,

Anthony