I recently developed a new knock in my 91 Legacy 166xxx miles. It comes and goes, sometimes it will be really bad, to the point I will turn off the road and turn the engine off. after waiting a while i can start it up without hearing the knock. It will still knock when it is warm too, and will knock usually off the throttle or barely on it. The knock is sparatic and it is bugging the crap out of me. any ideas of what it might be?

Funny I ocasionally have it, too. So far, since about a year ago, I've heard it like five times, usually when I first start the engine (cold, I believe). Sometimes I rev the engine up a little and it will go away, other times, it won't. It would go away eventually. It seems to be coming from one of the sides, more like a valve is locked. You can hear "ta ta ta ta ta...." and no, it's not the regular ta that I hear everyday. It seems to be louder and more noticeable when it sounds. Not sure if I should try to figure out what's wrong or just keep driving until it goes to the grave.

Have you added freon lately? The A.C. on mine will knock if I get to much in it.

I recently developed a new knock in my 91 Legacy 166xxx miles. It comes and goes, sometimes it will be really bad, to the point I will turn off the road and turn the engine off. after waiting a while i can start it up without hearing the knock. It will still knock when it is warm too, and will knock usually off the throttle or barely on it. The knock is sparatic and it is bugging the crap out of me. any ideas of what it might be?

Your knock sounds like a main bearing, because mine does that and that is what a couple of mechanics have told me.

Funny I ocasionally have it, too. So far, since about a year ago, I've heard it like five times, usually when I first start the engine (cold, I believe). Sometimes I rev the engine up a little and it will go away, other times, it won't. It would go away eventually. It seems to be coming from one of the sides, more like a valve is locked. You can hear "ta ta ta ta ta...." and no, it's not the regular ta that I hear everyday. It seems to be louder and more noticeable when it sounds. Not sure if I should try to figure out what's wrong or just keep driving until it goes to the grave.

noise diagnosis 101

 

http://remanufactured-engines.com/page4.htm

 

 

Funny I ocasionally have it, too. So far, since about a year ago, I've heard it like five times, usually when I first start the engine (cold, I believe). Sometimes I rev the engine up a little and it will go away, other times, it won't. It would go away eventually. It seems to be coming from one of the sides, more like a valve is locked. You can hear "ta ta ta ta ta...." and no, it's not the regular ta that I hear everyday. It seems to be louder and more noticeable when it sounds. Not sure if I should try to figure out what's wrong or just keep driving until it goes to the grave.

Funny I ocasionally have it, too. So far, since about a year ago, I've heard it like five times, usually when I first start the engine (cold, I believe). Sometimes I rev the engine up a little and it will go away, other times, it won't. It would go away eventually. It seems to be coming from one of the sides, more like a valve is locked. You can hear "ta ta ta ta ta...." and no, it's not the regular ta that I hear everyday. It seems to be louder and more noticeable when it sounds. Not sure if I should try to figure out what's wrong or just keep driving until it goes to the grave.

 

Intermittant tapping noises can be caused by valves.

 

Engines are typically designed such that the valve is made to rotate very slightly with each actuation by the rocker arm. This is accomplilshed by having the center of contact slightly offcenter of the valve head, so that when the arem pushes the valve, it slides along one side of the center ofthe valve tip and causes a degree or so of rotation. This keep the valve head round and evenly seated in the seat. If the valve did not rotate, it would heat unevenly and wear unevely, leading to bent or burnt valves.

 

An intermittant ticking many mena that the valve is still rotating in the guide, but that at some point is is hanging up, seating too deeply, or otherwise causing a mechanical tapping.

 

As long as the noise is intermittant, you are probably not risking additional engine damage. The valve is still rotating. If the noise becomes constant , the valve is probably not rotating and eventually will burn in one spot.

 

I don't think a rod knock would be intermittant. It can disappear at idle, but woudl generally mirror engine load. Unless there is a serious malfunction in the lubrication system, I doubt oil pressure woudl be a factor. If it is, you have more serious problems than a valve.

Intermittant tapping noises can be caused by valves.

 

Engines are typically designed such that the valve is made to rotate very slightly with each actuation by the rocker arm. This is accomplilshed by having the center of contact slightly offcenter of the valve head, so that when the arem pushes the valve, it slides along one side of the center ofthe valve tip and causes a degree or so of rotation. This keep the valve head round and evenly seated in the seat. If the valve did not rotate, it would heat unevenly and wear unevely, leading to bent or burnt valves.

 

An intermittant ticking many mena that the valve is still rotating in the guide, but that at some point is is hanging up, seating too deeply, or otherwise causing a mechanical tapping.

 

As long as the noise is intermittant, you are probably not risking additional engine damage. The valve is still rotating. If the noise becomes constant , the valve is probably not rotating and eventually will burn in one spot.

 

I don't think a rod knock would be intermittant. It can disappear at idle, but woudl generally mirror engine load. Unless there is a serious malfunction in the lubrication system, I doubt oil pressure woudl be a factor. If it is, you have more serious problems than a valve.

 

The engine will make the noise at idle and it will basically knock in-sync with the rpm's Although my oil light doesn't come on I wonder if it could be the pump. I am going to send in a oil analysis on a couple of days and I will see what that has to offer. BUt for the main bearing, wouldn't that make more of a grinding noise then a knock? by the way this was after me and a bud ran the ************ out of it Friday, so who knows what it could be.

Check your oil. If its black or low. Thats what I noticed with my car when there was no oil