I have a 1996 Subaru Outback 2.2L with 87K miles. Just yesterday one of the valves started tapping; louder than the normal low oil or low temp tap and unceasing. My question is what happens if the car is driven with this condition. I can live with the raven at my door, but don’t want to do any major internal damage.
If this tapping has been going on for a while then damage may have already been done.
Your comment about the “normal” low oil or low temp tick is what got my attention.
Either the tapping has beaten the lash adjuster to death and if this is the case, then the cam lobe will not be far behind.
Other problems such as poor performance, bad fuel mileage, and clogged O2s and converters will follow.
A faint tick may not sound like much but over time it will beat through the hard surface of the adjusters, cam followers, cam lobes, etc. and once through that hardened surface things won’t last long.
I have re-built many Susaru motors and if you notlce at least 80% of them driving by have bad lifters or exaust leaks. Common problam with subaru lifters is air in the system. Rev the motor to 3000 R.P.M for 10 seconds if the chatter stopes for afew seconds then your oil pump is bad, If it only gets louder then the lifter is flat replace the lifters, note use grease to hold the rocker arms in place to put cam cover back on. But for your question It could some day burn a valve if you continue to drive it
Gunk makes a valve lifter quieting additive. CD2 detergent type might help too. I have had good results with these but they last only until your next oil change. Worth a try. Light clicking should not harm your camshaft, at least it did not bother mine in a VW. The only real fix is to replace the lifters.
I would like to hear a mechanical explanation of how a defective valve lifter can cause a valve to burn.
This car, for years, has had a faint tick, if oil drops to the low end of oil level (between the marks) or the weather is very cold. In both these cases the noise disappears within a few minutes.
The thing that stumped me is this new tapping occurred suddenly; it did not progress to becoming louder. I had driven the car and parked with no noise, came out a few hours later and upon starting the noise was present. The oil level was halfway between marks and adding oil made no difference and the noise is coming from only one cylinder head.
It could be that one of the lash adjusters just decided to give up the ghost.
If it’s tapping that bad then down the road you can expect some fairly serious problems; cam lobes, followers, or even mushrooming of the valve stem.
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I would like to hear a mechanical explanation of how a defective valve lifter can cause a valve to burn.
My guess is that the constant pounding of the valve on the valve seat causes excessive wear on the valve face (knocks out microscopic pieces of metal?) which leads to a bad seal of the exhaust valve, and the hot gases rushing past the badly seated exhaust valve causes exhaust valve burning.
Long term it can do damage.
But for a quick fix…try a quart of Rislone. Do a oil change and replace one quart of oil with a quart of Rislone.