I just had the local Volvo dealer replace my water pump and all the belts except the timing belt...it only has 30k on it. The washing maching noise is much better now with the new pump but I noticed significantly increased engine knocking when I accelerate. The tank was down to a quarter so I filled it up with 93 octane to see if that fixed it. It did always have a little knock but this is much louder and more frequent. I also put in about 3/4 quart of oil...it was a little low. Could the new belts have messed up the timing? The gas and oil helped a little but it is still nociably worse than before. Shall I call the dealer back or is this a stupid question???