Knocking Noise.

[kNoykos]

My 81' Caprice makes a knocking noise when i start it. My dad says its the exhaust manifold & my boyfriend says its not that and that its rod knock. Im completely clueless and dont know who to believe.

[bhw33191]

My caprice has real low mileage and does the same but i'm pretty sure its normal. I heard it has to do with the emissions crap thats on these cars? Correct me if i'm wrong anybody.

[kNoykos]

yeah but mines really loud. its like tick tick tick tick... its not normal..

[bhw33191]

Originally Posted by kNoykos

yeah but mines really loud. its like tick tick tick tick... its not normal..

Are you sure? So it only does this when it first starts? Or does it tick until its warmed up? Let me get this straight is it a "tick" or a "knock." I know on mine right when you turn the key it knocks "but only once." But if its more of a tick noise then i may know what the problem is. How many miles do you have? What engine?

There is however this butterfly valve attached to the exhaust which directs hot exhaust into the air cleaner to warm the carb up. This valve may be the cause of this "tick" noise your talking about. I took mine off before it rusted off and now theres no more tick noise. So i'm not sure which way is the OPEN position on this flange valve, but you should see if you can find it because it may have rusted off, or the valve could be stuck in the closed position causing the ticking to occur all the time. Its located in the engine compartment right off the exhaust close to the engine "its a vacuum powered device so you might be able to follow the vacuum line to it."

[kNoykos]

the noise mine makes does it until i get up to 45-55 mph. and then when i slow down to 25/35 mph is ticks. im not sure what anything is on my car. my boyfriend and dad look at it.. i just know what it does.. :-/ but i'll have them read what you said about the butterfly valve.. but its a ticking. but i call it a knocking noise.. just because thats what i thought but it might be ticking.

[silicon212]

Originally Posted by kNoykos

the noise mine makes does it until i get up to 45-55 mph. and then when i slow down to 25/35 mph is ticks. im not sure what anything is on my car. my boyfriend and dad look at it.. i just know what it does.. :-/ but i'll have them read what you said about the butterfly valve.. but its a ticking. but i call it a knocking noise.. just because thats what i thought but it might be ticking.

It probably has a sticky valve lifter. You can free it up by running about 1/2 quart of automatic transmission fluid in the engine oil. This also has the benefit of cleaning out engine sludge, so make sure it's only in there for about 200-300 miles or so. Then, change or have changed, the oil and filter.

[kNoykos]

Originally Posted by silicon212

It probably has a sticky valve lifter. You can free it up by running about 1/2 quart of automatic transmission fluid in the engine oil. This also has the benefit of cleaning out engine sludge, so make sure it's only in there for about 200-300 miles or so. Then, change or have changed, the oil and filter.

k. ill try it this weekend. and then if it doesnt work.. whats it mean..??

[silicon212]

It means your car is nearly 28 years old and physical world items eventually wear out/fail/die. It can be fixed if it's mechanical, but it comes down to how much you're willing to spend on it to get it fixed. Some people view putting money in a car that old as a waste, while others don't mind and realize that a 28 year old car is considered, in most states, antique or classic.

[kNoykos]

hopefully its not dying. hopefully its something easy and cheap to fix.

[silicon212]

Originally Posted by kNoykos

hopefully its not dying. hopefully its something easy and cheap to fix.

The transmission fluid trick is a cheap way of unsticking sludged up lifters that I've been using for 22 years now. It works, and 9/10ths of all valve noise is caused by built-up sludge that causes the plunger within the lifter to 'stick'.

Other things to look at are simply valve train wear (you can adjust the valve lash on these to make up for this), and of course, something more sinister. However, my money is on sticky lifters.

[j cAT]

Originally Posted by kNoykos

yeah but mines really loud. its like tick tick tick tick... its not normal..

since your family members stated the manifold was the source of the noise i also have had this occur ..you must tie up the heat riser butter fly at the exit of the exhaust manifold on the passenger side...


to do this get some s/steel wire of about .030 dia and wire the buttery fly full open....you will see that this part is pretty much rusted ...

If this is not the problem changing the oil when hot and adding a engine oil additive to remove sludge is recommended prior to the oil changes...

changing the PCV is also recommended as this helps remove crankcase contaminates

[kNoykos]

k thanks. i'll have my dad or boyfriend check it out. im not sure what anything is.