Valves Tapping???

2001 Avalon with 78,000 miles. Have had oil changed every 3,500 miles since new. About 3 weeks ago my wife said she heard a tapping noise coming from the engine. I drove the car and heard no noise then. Well last week while driving under 25 MPH for several minutes I heard what sounded like valves clattering from lack of oil. If I let off the gas and then accelerated a bit the noise went away. Drove slowly again for a few minutes and the same thing happened.

I had just had the oil changed, Mobil 1, the weekend before. I checked the dip stick and the oil level was perfect and the oil was very clean. We drove a 1,500 mile round trip at Christmas and didn't hear any noise while on the road. Any ideas as to what could be going on? Could this be oil gelling?

Thanks,

MC

Try manually going thru the gears , sometimes a tranny will make noise in certain gears.

Good thought, I give that a look.

MC

often times the valves become misaligned. I'm a honda owner and honda's are notorious for this. Valva tap does not nessesarily affect the performance of your car, as long as the oil has been recently changed and the level is ok. You can have this fixed if you go to a good mechanic and have him realign the valves. I had this done and it cost under 80 bucks. For me it quieted the valves signifigantly.

Did you just switch to the M1? If so, it's possible that the M1--with it's greater cleaning properties--may have dissolved some varnish in the valvetrain resulting in your tapping noise. This may only be temporary. You should also simply check the oil level to be sure it's full.

Adjusting the valves is not a job for just any 'ol mechanic. Toyota uses valve shims/pucks to adjust the valves. You measure the valve clearance and if an adjustment is necessary, you replace the shim with one of a different thickness. There is no adjusting nut at the top of the valvetrain as there is on other cars. Toyota dealers have a selection of these shims that they can use to replace worn ones. A mechanic can order an assortment, but he would likely not use all of them (or run out of those he needed), and you would pick up the bill.

I don't think your valve noise is due to missaligned valves though... With this system, as the valves clearance goes out of adjustment (usually due to wear of the shim or cam lobe), the valves will actually become quieter. If the noise has gone away, I would not be too concerned. At most, I'd have it taken in to simply measure the clearance (though I wouldn't even do that if it's running okay now). In my own experience, the valves hold their spec for many miles more than you have.

Thanks for the feedback. I only heard the tap a couple of times and only for a quick second. Otherwise the engine is extremely quiet and smooth. I think I'll just keep a watch on it and see if anything changes like more or louder tapping.

MC