it also looses water and the resivoir bubbles

check 4 leaks and check your oil amount

Sounds like a head gasket to me. You should take it to the dealer to have it checked out. Its 15 years old, if you do not take care of it it will die soon.

believe me this problem is very common and is exremely rare and hard tto repair my suggestion is dont go with lexus anymore you should head with acura

Kenneth is kinda right.Check the head gaskets..

1. check you engine coolant.
2. check hoses for cracks or leaks
3. check engine gasket
4. check oil dip stick to see oil pressure
5. check your thermostat
6. check oil pan for oil leaks
you should be able to determine the issue checking these things.
gaskets are really cheap if that is the issue..

Sounds like a blow head gasket take to a good garage and
have them check with a chemical block tester to be sure.