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Tick in 2005 3.5 liter GM engine

A few months back, my 2005 Buick Terraza mini-van developed a tick. Some history; 3 years ago I installed a Jasper transmission and just over a year ago I completed a head job on the motor after a head gasket failed. I have a video of the engine with the ticking noise, but this site does not allow videos to be uploaded. If there is another way to share this video, please let me know.

In your search engine, enter GM 3.5 Liter Piston Slap.

You’ll get all kinds of hits.


Have you done the necessary experiments to determine if the tick is from the engine, transmission, axles, or wheels? For example if you hear the tick at 35 mph in gear, do you continue to hear it if you temporarily shift into neutral and coast? When idling in the driveway, does it increase in frequency if you increase the the idle rpm?

Some…but I have more left to do. When the engine is cold it does not have the noise. It only is there after it warms up. Its frequency does change with engine speed, but seems to go away when running above 2000 rpm. The engine seems to operate fine, just when we are idling, the ticking sounds rough. I was going to drop the starter and inspect or remove the 3 flex plate to torque converter bolts to ensure that they are not causing the problem or that the problem is not in the transmission…which incidentally I replaced with a Jasper remanufactured transmission in July of 2015.

Suggest you complete your experiments to determine what part is the source, from among engine, transmission, and driveline. Using a piece of old garden hose or vacuum hose as a stethoscope can help narrow down the location sometimes. Then it is time to call in the pros. Mechanics have years and years of experience in diagnosing sounds like this. There’s no way you can determine it accurately yourself. So let an experienced shop tech listen to it, of course providing the results of the experiments you’ve already done. They’ll tell you what’s causing it, and then you can choose to do the repair yourself if you like. They might recommend you just ignore it unless/until it gets worse.

I’ll add that ticking sounds which correlate with engine speed can be small exhaust leaks or minor faults with the drive belt accessories. My Corolla has had a little ticking sound only noticed at idle for 20 years coming from the alternator. It doesn’t go away when the engine is warm tho.

George, thanks for the advice. I did by the way upload a video of the engine to YouTube as well…see URL below.

The frequency seems too quick to be valve noise, sounds like harmonic balancer or cracked flex plate noise. Try to identify if the noise is from the front, center or rear of the engine.

That is a baffling noise! I’ve never heard anything like it. It seems to have an odd whistling sound immediately after the tick. It definitely is occuring in unison with camshaft speed rather than crankshaft speed. It isn’t typical of piston slap which is more noticable when the engine is cold and normally fades as the engine warms up.
Seems valve train related.

I’m wondering if the sound would change if you pulled off one spark plug wire at a time. Come to think of it, are your spark plugs in tight? That’s a long shot. Try Georges garden hose stethoscope suggestion, especially at the spark plugs.

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Did you personally swap the transmission out? If so, are you dead certain the torque converter was fully seated when mating the transmission to the engine?

If not fully seated, the flex plate can crack at some point as the bell housing bolts have a tendency to bow the flex plate a little.

It sure sounds nasty.

Since a cylinder head was off, what about the possibility of an exhaust manifold leak?

Thank you all for the replies. I did install the transmission myself, but did not notice any issues bolting the torque converter up to the flex plate. The torque converter slid right up to the flex plat and the bolts were torqued out at the specified torque; as I recall, something around 80 ft-lbs. I will try the garden hose stethoscope idea from George. Also, when I did the head job in November of '15, I obviously had to remove the exhaust manifolds, although it doesn’t seem to be coming from the exhaust manifolds, what’s the best way to check for an exhaust manifold leak?

The noise does not go away at higher RPMs, it is masked by normal engine noise IMO. When RPMs are high enough, the ticking becomes a continuous noise; you can’t distinguish it from the background at all.

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With the hood and driver’s window open, jazz the throttle. An exhaust manifold leak should get louder just as you push on the gas (bigger exhaust pulses into the manifold) and stop as the engine is slowing back down to idle.

you will also find a great video on youtube explaining how to make a smoke machine from a paint can for under $10 :slight_smile:

OK…I went ahead and pulled the flex plate/torque converter covers; there is one located at the bottom of the engine and one that goes around the starter. I was able to get a good look at the flex plate and torque converter without removing the starter and using the bolt on the harmonic balancer, rotated the flex plate and inspected it for the full rotation; checking to ensure the bolts were tight as well as verifying the plate was not cracked. While I had the passenger wheel off and a splash panel removed, I inspected the harmonic balancer as well and it looked good. Listened to the noise again today and it sure seems to be coming from the top end in the middle. Is it possible that this could be a bad/dirty lifter causing this noise? Even if it is not, would it hurt to run a can of one of those internal engine cleaners through it and if so, which ones are recommended?

Sure sounds like a cracked/broken flex plate to me. I can’t imagine that you would have been able to inspect near the crankshaft bolts in your inspection, and that’s where they typically break.

I think that the noise doesn’t go away with higher engine speeds, I think the frequency of the sound, it’s tone changes to a high enough pitch that you can’t hear it.

Quick question for the OP. Have you tried Georges garden hose suggestion yet to zero in on the noise? Also, let me explain my seemingly far-fetched suggestion about a spark plug being loose. If a plug has worked its way almost all the way out and just hanging on by a couple threads the combustion leak past it could make quite a bit of noise. If you’ve ever heard an engine running with a totally
missing spark plug you wouldn’t believe the noise it makes.

You know JayWB, I had somebody else tell me the same thing after I explained what I did. He went on to explain that the thrust movement of the crankshaft puts most of the stress on the flexplate near where it bolts up to the crankshaft; I failed to ask him how to check it. So…do you have any suggestions? Also, any thoughts as to why the noise is not there when the engine is cold and why it shows up after it warms up? So if I have a cracked flex plate, I guess I’ll be dropping the transmission again. Before I do that, what’s the likelihood of a flex plate failing completely?

My_2_Cents, I did try the garden hose suggestion and was not very successful, I was going to look into getting one of those automotive stethoscopes though and try that. Also, I haven’t checked the spark plugs yet but plan to. Thank you for the suggestion.

That’s where it breaks because that’s where it flexes. No idea why it’s silent when cold, but I can’t think of a reason why anything else would be silent when cold either.

Only way to check it to be sure is to pull the transmission. and look at the flexplate carefully. If it’s cracked and making all that racket it will certainly fail completely. Soon.

I must have a rare talent . . . I’m able to see cracked flexplates WITHOUT pulling transmissions

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