Noisy after warmup

[azkiwi]

This is unusual...There is a loud tapping noise after the engine has fully warmed up. It reminds me of a deisel engine at idle. It does not appear to be coming from the valvetrain area but I cannot be sure. It sounds loudest in the engine compartment. I have done several valve adjustments over the last month thinking it was valve train related. I've even replaced the 911 adjusters with regular ones just to see if it makes a difference...it didn't.
The engine is a rebuilt longblock I purchased and it has less than 2,000 miles on it. The noise started up within the last several hundred miles. The weird thing is that it is louder than the exhaust note at idle but it does not get louder when I rev the engine. If I didn't have to let the engine revs drop I guess I wouldn't even notice it...Everything else feels fine on the engine...power torque etc...

Any thoughts..thanks in advance

[chrisreale]

Maybe an exhaust leak at the heads?

[azkiwi]

Originally posted by chrisreale
Maybe an exhaust leak at the heads?

Thanks Chris...I will check that out.

[chrisreale]

What I did, was remove the heat exchangers. Made sure the tops of the exchangers were even, using a large file. Put new copper gaskets with two or three beads of high temp RTV silicone. Put those into the exhaust holes on the heads. Then apply RTV to the tops of the heat exchangers. Tighten the echcangers to the heads in a cross pattern to 14 lbs. Easy to strip/break a stud so be careful. I new i had an exhaust leak because my car sounded like a VW bug/lawn mower.

[Andyrew]

Hey that makes me wonder, I thought I had a shot exhaust.. Might check into that!! thanks chris!

[chrisreale]

Azkiwi,
I am wondering why it makes noise only after it is warmed up. It doesn't do this when cold?
How is your timing?

[azkiwi]

Originally posted by chrisreale
Azkiwi,
I am wondering why it makes noise only after it is warmed up. It doesn't do this when cold?
How is your timing?

Not when cold...that was the weird part. I am used to things being noisier when cold until the heat expands parts and reduces the noise level accordingly. You mentioned to file the headers which I did but they may have loosened since break in and caused a leak which I can check. It is funny you mention the timing which I have not checked for a few weeks since I installed the MSD 6A and ignitor. The MSD definitely helped the low end torque which was easy to notice since the 1.7 has so little of it, that any slight improvement is noticeable. I will take a look at these things tomorrow. Thanks for the input Chris and wish me luck.

[ken180]

I assume the tap-tap gets faster as the engine is reved-up - may be changes loudness at different rpm's.
When driving, does the tap-tap go away or get softer when asking for power and then return at cruising speed? If so it may be a rod bearing even if it was just re-built.

Ken

[azkiwi]

Originally posted by ken180
I assume the tap-tap gets faster as the engine is reved-up - may be changes loudness at different rpm's.
When driving, does the tap-tap go away or get softer when asking for power and then return at cruising speed? If so it may be a rod bearing even if it was just re-built.

Ken

Thanks Ken,
As soon as I press the gas pedal the noise is drowned out by the exhaust. It is non existent (cannot be heard) at any other time except idle. Even at cruising speed (or even coasting in gear) I cannot hear it but I expect that if it is a bearing I will probably hear it more often as it should get worse with more use. This is one fear I have and am listening for more tell tale signs of it...so far I haven't heard any, but it then again it may be too early to tell.

[seventythree]

You may have a broken alternator bracket. Usually, it is the lower bracket, and if left unattended, it will ruin the cooling shroud.

[Dave at Pelican Parts]

Try disabling each cylinder in turn. Unplug the injector, or unplug the spark plug wire. (Use a rubber-insulated pair of pliers--gloves are NOT enough to prevent a ZAP when doing that!) See if killing any one cylinder stops the noise.

That can at least isolate the problem to a single cylinder.

--DD

[azkiwi]

Thanks for the suggestions, all...You've given me enough to keep me busy this weekend (and happy doing it).
Dave your advice is noted on the insulated pliers...I am nervous about even touching the plug wires with the MSD installed. I think I will also install a oil pressure gauge to see if there is any correlation between the oil pressure and when the noise starts.

I'll definitely do all the basics in the meantime and will report my findings. Thanks again.

Cheers.

Alex

[Dave Bell]

too much end play can give you a valve tapping sound...especially at idle... but what you describe sounds too loud for that?

[3D914]

Alex,

I am experiencing the same thing on recently rebuilt 2.0. Sounds like a diesel is the best description that fits for me also. And its not valve train noise. I've adjusted mine twice in the 2300 mi breakin period and there were a few valves that had tightedned up slightly. But its still there.

You'll probably find that the noise doesn't go away at higher rpm, you just can't here it for the exhaust or wind noise, etc. I have the opportunity to drive down a few roads that have brick walls along one sode of the road, so I can hear it then. You may also be able to notice it when passing large trucks or SUVs - as the sound bounces back at you.

I suspect either end play (as mentioned by D. Bell) or tolerances at the cam gear. I've actually got my car over at the engine builder today for a minor oil drip, but he's going to check into the noise as well. Keep you posted.

Music, what music. I don't hear any music!

[Bruce Allert]

Same, same... I had to replace a stud that fell from the exhaust manifold. That's is how I got so much experience adjusting my valves.
Replaced stud + tighten nut = no more tap-tap
bruce

[3D914]

Bruce,

I had similar problems with studs (and in one case the time-sert) loosening up or falling out on a couple different engines. I now check them every time I change oil or adjust valves. I've also found a quick check for the exhaust manifold leak, by shining my focused shop light where the manifold and head mate, and looking for the black carbon that will pass through if all is not snug. So far on this recent rebuild all is well with exhaust studs & nuts.

Enjoy!

[Bruce Allert]

Gerard, I hadn't thought of looking for the blackness. Good idea. I'll look at it before I leave fro Seattle on Friday.
Now, what is a time-sert? Is that anything like a scrotum casing?
No, seriously, I've not heard of the time-sert.
bruce

[azkiwi]

My checklist so far....

Timing set at 27 deg
Valve clearances at .006 in.
Exhaust studs and nuts...all tight and no signs of leaks (black soot was a good call..thanks Gerard)
Alternator brackets all okay...
Disconnected injector wires one at a time...other than the engine slowing a little while disconnected, the clicking sound remained regardless of which cylinder.

End play on the rocker assemblies is next...

Gerard, how soon did your noise start showing up? Mine was about 15-1700 miles into the break-in.

As I run my engine with the car stationary, and as the engine revs pass 2000 is when the noise becomes inaudible. It does not grow louder, I can hear it pick up speed with the engine revs, just not louder. I really think it is valve train related somehow.

I am going to search the archives on valve train geometry etc and see if I can pick something up there.

Thanks again for the input.

Alex

[Kenny Powell]

Maybe you have Hydraulic valves? or could be the Klingon yer anus Dumaflitch

[Dave at Pelican Parts]

A time-sert is a threaded insert, kind of like a nut that you thread into the part and then thread the stud or bolt into that. Kinda like a Helicoil but much more beefy.

--DD