Engine tapping noise when hot
 

I did a search and read threads.

Just had a valve adjustment done.

when engine is cold, it sounds nice and tight.

when engine is at operating temp, i have a tap on left side. cant really hear it in engine bay, but prominent at left rear wheel.

when i get the engine really hot, 220F (like coming off track) I believe its louder.

engine has 60Kmiles on rebuild, using Mobile 1 15/40. pulls strong.

Others think its fine, i find it annoying and wondering if i should have a concern.

88 911, andial 3.7L with c2 cams.

Acoustically speaking, i pulled into a BK drive up window, brick wall with roof. I had to turn motor off to hear attendant. I could hear tapping over exhaust noise.

B&B 1.75 headers and B&B 2 in 1 out muffler

the tapping noise could be a small number of things, but I believe you will find a loose valve tappet...it happens. Readjust the valves.

Mine taps when cold, then quiets down as it warms up. . .

Assuming there was no tapping before the adjustment,
is it possible you just found the answer to your problem?


Cheers,

Joe

+1> Maybe they have one that's not quite where it should be.


It WILL have to be checked again.


I've found that any tappet noises will increase with temp (not decrease).

Doyle

When the engine is cold, the oil is thick enough to mask the sound of a loose tappet until it thins out with heat.

exact same situation on my car when I bought it... turned out to be worn valve guides. DIY and $6k later was all fixed up. :-) I had a case of "while you are in there". I used the Wayne book.

Holy cow, let's start with checking the valve lash first!! One problem is you check it cold. Did you do the work? Use a stethoscope to pinpoint where the noise is coming from (hot). then go from there.

had it done by a Mech.....
should it be done cold, warm, hot?

Valves have to adjusted when the motor is stone cold. It is best if you let it sit overnight before adjusting the valves. Guys, correct me if I am wrong. I had an early car that was tapping and the tensioners/chains were loose.

Kirk

Sounds similar to mine. Left bank as well.
Very apparent when cold, goes when warmed up.
Valves are only to be set when engine is stone cold.

Is my understanding correct as below;
the specified gap is given inorder to allow for thermal growth once the engine gets to working temp.

So if the tapping noise gets lesser with a warmed engine, the gap has been closed up by the expansion.
If the Tapping noise doesn't reduce, the gap may have been set too large.

But if the tapping noise get louder with a warmed engine, this indicates a mechanical problem instead.

Lastly, if there isn't any tapping noise whatsoever (hydraulic tappets aside), there is a chance that too little or no gap has been set, and this could lead to the valves not fully seating & closing, and eventually excessive wear introduced to the rockers, tappets etc.

My 89 did the same when I purchased it a few years ago. Driving beside a brick wall or even the curb was quite disturbing.

It would be quiet when cold and get progressively louder when it warmed up.

It all quieted down after I adjusted the valves. I now hear tic-tic-tic instead of tap-tap-tap.

If you adjust the valves, do use wd40 to get the oil film out of the elephant foot. I believe this makes a big difference in being able to set the valve to the proper gap.

Have you checked for a possible exhaust leak?

Yes, Yes, Yes. thermal expansion will close up the gap a bit when it gets warm. Set the valves cold. Most 911's sound like a bag of parts in the back of a pick-up truck when idling around town. If you engine sounds good at idle and at 4-5k than I think your fine. I use to freak out when I drove downtown among the big buildings, sounds like I was running on 5 cylinders and the heat exchangers fell off. But back home everything was fine. Just another Porsche quirk.
However, non normal valve lash sound should be investigated prior further operation.
You can use a mechanics stethoscope or a long screwdriver placed in your ear.

after letting my car sit overnight, I turn the engine over (via crank pulley) 2 times. This seems to set the spring tension equally. If you still have problems, tighten down the adjustment screw to squeeze out any oil and keep the feeler gauge kleen.

I think that using a feeler gage is not the best way with "feel" too much a factor. If your mechanic can use a dial indicator instead you will get a better result.