HELP - Tapping sound (Valve???)

[svsgt1]

Hey guys I need your help. I was ta the dyno shop today getting the car tuned. It was running well for about 2.5 hours and then it started making a tapping sound from the left/drivers side bank. It was a metalic sound and was pretty fast. It didn't do it at all rpms and didn't do it until it ran for a couple of hours. When I went to trailer the car up after 30 min the sound definietly wasn't as loud. My engine is pretty much stock but with mild cams (about 8.5mm valve lift) and mild head porting. But I need to figure out what this could be so this is what I ask of you.

1) Possible causes that would be making this sound. (The guy at the shop said it may be a valve or rocker or something.)

2) Methods to figure out what is making the sound? Like what should I take apart and what I should look for?

A little history: My car actually had this tapping sound before and eventually that cylinder lost compression so it ran like crap. I sent the car to the factory and this is what the guy had to say. (Keep in mind that this place does really crappy work although he does sound like he knows what he is talking about.) So hopefuly this will help you answer my question. This is what the guy had to say:

The cams run on a hardened steel shim
which is contained within a bucket which also pushes down on the valve. The
bucket is made from aluminium and the shims come in different thicknesses so
you can adjust your clearance correctly.
What had happened was that the shim got a little bit of surface rust on it,
like the brakes did, which meant that what is normally a polished surface
that the cam runs on was now higher in friction. This meant that the cam
grabbed it each time it went by, slowly hammering the side out of the bucket
and eventually spat it out of the bucket. On the way out the shim damaged
the bucket which meant that although the cam pushed it partway down the bore
it runs in, the valve spring wasn't strong enough to push it back up. Hence
that cylinder had no compression as the valve was permanently open. The rest
of the shims showed no signs of any rust. I greased all these before the
engine left to try & prevent this occuring, but it did anyway! This problem
also accounts for the tapping sound the engine had. there are 32 of these
items.

Thanks,

Adam

 

[jibby]

A taping noise sounds like a bad lifter rod and that's worse case, but best case an exhaust manifold leak. If you think it may be a sticky valve try running one quart of transmittion fluid in with your motor oil for 500 miles or so, then change the oil completely, the noise should stop, transmittion fluid acts as a detergent and should help clean and free up any sticky valves.

It sounds like a rod noise to me but check for a header leak first for the cheap fix, as well, header leaks are usually louder at cold engine temp and then the noise lessons as the car engine heats up. You need to see where the noise is coming from use a long tube and put it to your ear at one end and roam the engine to locate exactly where the noise is coming from. I am not a mechanic but this is what I would do first. It always worked on my chevy's.

 

[Lextreme II]

I think the tapping sound is possible from not optimal tuning. Its possible with better tuning the tapping might be gone. Anything you can do is let the engine runs for few hours at different rpm like take it for a drive and the tapping sound should be better.

 

[svsgt1]

Jibby,

Thanks for the info. I don't think it is a sticky valve as it seems to be running just fine. The problem before was probably a sticky valve as it was not running on all 8 cylinders. But the tapping noise happened then before the valve stuck so it may happen again I guess.

The noise definitely happened when the engine was hot. I will see if it happens louder when it is cold but I don't think that will be the case.

Could it possibly be that the valve shim is too big or something? Or that the bucket has recessed to far and is being hit by the valve? (Don't even know if that last one makes sesne but it sounds good to me. lol)

Thanks,
Adam

About what you said, I understand how to look for an exhaust manifold leak but how would that make a tapping sound?

About it being a bad lifter rod, how do I check this out to see if it is bad or not.

 

[Matt Skinner]

Very unlikely its a cam follower/lifter as usually they tap when cold, not after several hours of running. It would get worse once the engine had cooled off again, rather than better. (you say it was better after the car sat for 30 mins)

I'm afraid to say I agree with Jibby. Sounds like its gonna be rod related.

 

[svsgt1]

Thanks Matt. But I am now a little confused. Jibby said it may be a "bad lifter rod" and you said that you agreed with him that it may be a bad rod but it is highly unlikely that it is a cam follower/lifter. I really don't know all the parts in an engine but I am pretty good with cars. So what do you mean. Do you think it is a bad lifter rod or some other type of rod? Sorry for the ignorance but I'm not that knowledge able about this.

I also started the car up this morning so it was obviously as cold as it coudl be and it didn't make the tapping sound. Even when the tapping sound was occuring yesterday while hot, it only made the sound at a certain rpm like around the 1500-2000 range. I have fresh oil in the car and I checked that it is full so its not that. Its not that it is very cold and it just takes a while for the oil to thin out as I live in South Florida. Would a bad rod (whatever type of rod you say) make the tapping sound all the time (hot or cold) at all rpms, or would it be intermittent? Could it possibly be that the valves need adjustment or would that make the tapping sound all the time if that were the case?

Thanks for your help. I really need to figure this one out asap.
Adam

 

[svsgt1]

I have been doing a lot of research on the valve adjustment and how that had fixed peoples problems with the tapping sound. (I guess I'm looking at this job as I wouldn't have to remove my timing belt or camshafts so I coudl keep the engine in the engine bay.) In order for me to get the timing belt off I need to get the engine out as I can't get to the tensioner any other way.

But would the valve adjustment and getting new shims solve my problem? I'm thinking that if the shim is the wrong size then it may be hitting something and causeing teh tapping sound. I'm also thinking that since the shims rotate that this may cause the tapping to be intermittent as maybe the shim is rusted or one side is bad so as it rotates to one side the valve taps but the other side it doesn't. I don't even kow if this makes any sense but it was something I thought of taht my be the cause. Any feedback on this thought woudl be appreciated.

Thanks,
Adam

 

[Matt Skinner]

I read rod as conrod. Dunno why a lifter rod (aka pushrod) would be in a 1uz....

 

[svsgt1]

ha ha ha, yeah I don't know why I would have a pushrod in my lexus V8 either. (I can't wait for someone to reply asking me how I got pushrods in my 1UZ because they didn't really read the post) But anyway, I'm not sure if Jibby meant a lifter rod (if that is something different then a pushrod which I would guess it is) or a connecting rod. Would a connecting rod make a ticking/tapping sound? Would it be all the time if it were?

 

[Matt Skinner]

If the big or little ends were on the way out yes. Ive never heard one going myself, though I know two people who have had a big end let go and punch several holes in the sides of their blocks.

I believe they tend to get noisier as the engine gets hot, as the oil thins out allowing parts to knock togeather where the clearances are getting too large.

 

[Lextreme II]

I hope this picture will help:

 

[Zuffen]

An engine bearing doesn't tick it rattles. Usually only at certain revs. Quite often as you accelarate or drop revs.

When a bearing is on the way out the oil light will usually come on at idle and if driven long enough you will get to see the faulty rod hanging out of the engine!

This sounds like the oil has thinned out due to the time on the Dyno and the valve clearance on that one valve was just a little too big.

Remember when running a car on the Dyno airflow through the engine bay is not optimal and the lack of flow will result in heat soak which in turn will overheat the oil or show up any deficiency in the oil.

I'd be inclined to change the oil and see how it goes.

If the ticking returns get the valves adjusted.

 

[svsgt1]

Rod,

I think you may have hit the nail on the head. I actually put a thinner oil in this time aound (0w-20) instead of the 10W-30 that I usually put in. I figured I would try something different. I use Mobil 1 Synthetic.

Here is an update. I took my friends stethoscope to try to figure this thing out. I started the car in the trailer so there was no air flow and I notriced my radiator fans never turned on (which is just an easy to change setting on the Link) I gues sthe tunner didn't put them to the right value. The noise was absent while the engine was cold and at normal opertaing tempurature. But once it ran for a while and the temp went up beyond normal (since the fans didn't kick on) the tapping sound cam back. I couldn't get it to happen all the time but when I started to rev it up to about 2000-2500rpm I noticed it but it didn't always happen. It would happen when I would hold it within that rpm range and sometimes when I would let off the throttle but would not happen at idle. Oil pressure is definietly there and is around 50-60psi while cold but it drops down about 18-20psi once warmed up. Using the stethoscope I wasn't able to pin point the noise 100% but from the little bit I got to use it, it sounded as if the noise was definietly coming from within the valve cover which would further confirm that is a valve problem. It also seems to come from cylinder #3. I believe that is the right number if the bank on the drivers side (Left) are all odd numbered. So it is the second one back on teh drivers side.

But now I have 3 questions:

1) If this is a valve problem that happens when the oil heats up and becomes to thin, why doesn't it happen all the time at all rpms when the engine is that hot?

2) If that valve needs to be adjusted, does that mean the shims just need to be replaced with ones that are properly sized or does that mean I have to do something else? If so, then what?

3) How much does a valve adjustment cost at a Lexus dealer?

Thanks guys,
Adam

 

[Zuffen]

When oil is cold it's thicker than when hot.

Remember there is always (or should always be) a thin film of oil between every mating or bearing surface in an engine. As the oil heats up itgets thinner and the minute variation may be just enough to allow the foller to tap. The variation could be as little as .5thou which is two thirds of bugger all!

If that valve was set a little wide to start with you could find it didn't take much to upset it.

You can check the shims on that one cylinder or do all 8. If I was doing 1 I would do the rest.

You need some specialist tools and a micrometer to do the settings. Basically to check the clearance on each valve then order the appropriate sized shims to give the correct setting.

Peter Scott has a great article on it on the ALSC Site.

One trick he used was to work out how much bigger (or smaller) each shim had to be and then by sorting through the shims he had he could re-use some on different valves thereby reducing the amount he needed to buy.

I have no idea what the Lexus Dealer would charge but I guess you could drive with only your left arm. The Dealer will have the right one!