Hey All,

My engine has been tapping for quite some time now. With the hot weather and windows down it is really noticable and frustrating. I have read only a couple threads on the tapping noise on the forum and need your input before I start tearing into the engine.

First let me give you the details:

92 SC400
118,000miles
Mobil 1 10w-30 (5.3qts, dipstick shows full)
Exxon 93octane gas used

Engine starts tapping from the moment I turn it on till the moment I turn it off, no matter what the weather condition. Tapping much louder and noticable at initial engine load, like when taking off at a light till you reach about 25mph. This is definitly tapping coming from the engine heads, and not the snap/crapple/pop sound from the heat shields (as one mechanic tried to tell me was making the noise )

From what I have gathered I am pretty much sure it is the valve adjustments/shims that need to be readjusted. Are these shims usually the main suspect when the engine taps like this, or is there something else I should look for, ie... valve lifter, springs, rocker arms, etc....

I have gone through the service manual over and over, and feel pretty confident about attacking the project of adjusting the valve shims (with the help of a friend, Lexus dealer mechanic )

Guess the point of this thread is:

- Is the valve tapping going to subside with the valve adjustment job, or is there other factors that could be creating this noise? Any other areas I should be focusing on?

- Is there any other remedy or quick fix to the problem aside from the valve adjustment job?

I know there is not going to be any easy way around this, need to gather up the facts and advises and jump into the engine.

Thanks in advance for any input/info.
LexusBiz

 

basically no easy way around it. It sounds like they need adjustment. on the bright side if you do it yourself it won`t cost too much. the shims are rather inexpensive, but if someone does it for you might be a little pricey.

 

I'm encountering the same problem. What kind of damage can happen if it goes without repair for a while?

 

It could just be fuel injector clatter. On that engine, as the injectors get old, they make a more pronounced "click" near idle and low speeds. All the Lexus V-8s do this to an extent, but louder on old cars.

 

Thanks for the input SC300T, I'll have to look into the fuel injector clatter as a possible suspect.

VegasSC400,
I'v been told the tapping really does not harm the normal operation of the engine in anyway. However, over time (years) the constant tapping of the camshaft lobe onto the shim may cause accelerated wear on the camshaft lobe with the incorrect valve clearance settings. As the camshaft lobe wears down a larger clearance is created between the lobe and the shim. This could result in minor engine performance loss since the intake and exhaust valves are not being opened to their full extent.

Don't take my word for it, I was given this information through the grape vine, so I can not validate its accuracy. But it makes common sense that the lobe would eventaully wear down over years.

Hope someone with mechanical knowledge can chime in.

Thanks
LexusBiz

 

just doesn`t sound like an injector tapping to me. but you never know! on the bright side it is basically free to check the valves if you do it yourself, will just cost you some time, and maybe some materials.

 

Sounds like valve clearances to me.

Oh, and if there are any lifters or rockers in your engine, I would get them removed!