General Tech Loud Metallic Click Pop Every Time After Engine Off

[KVH]

Guys, I’ve gone through so many different issues with this rebuild over the last six months, but the car is now running great, the overdrive is working, and everything seems so fine.

However, I am continuing to hear a loud metallic click or pop about six or seven minutes after I turn the engine off. It happens every single time. Wild guesses would be the timing chain tensioner is stuck and then popping back. Another wild guess is that the starter Bendix is sticking and then popping back. Yet another would be one of the valve springs sticks on turn off. Yet another would be that the oil pan is expanding and contracting, or that the intake or exhaust manifolds are expanding and contracting. The point is – – I’ve never heard this with any other
British car.

I just can’t make any sense what I’m hearing.

Any ideas?

 

[poolboy]

Does your car have an anti-run on valve ?

 

[KVH]

no, nothing not standard

 

[KVH]

But I do shut the engine down using the clutch to avoid run-on. Related?

 

[Sarastro]

Might just be something moving in the exhaust system as it cools down. The exhaust system expands as it heats up and then contracts when it cools. Sometimes that creates stress that releases suddenly, making a snap. The same thing happens in the heating system in my house. When the furnace comes on in the morning, there is a whole symphony of clicks and pops from the ductwork.

 

[sp53]

I guess if you had a few minutes, I would pull into the garage and remove the valve cover quickly and watch. I have unstuck a valve with a mallet and it made a loud pop and metallic sound. If the valve is the case, I am not sure what to do. I guess it depends on if something like that wears into place. I would find it unsettling!

steve

 

[JHaydon]

Might just be something moving in the exhaust system as it cools down.

A carb heat shield could do the same, and since it's smaller than the exhaust system it could emit just a single "plink".

+1 to checking under the valve cover -- also, if it is consistent (and if you have a LOT of free time), put yourself near various areas of the car while it cools: stay in the seat, open the bonnet, sit near the rear axle.

Does it happen if you park after driving too briefly for things to warm up? For instance, if you were to just pull out of the garage and into the driveway? If yes, then it's not (likely) a heating-expansion / cooling-contraction issue.

 

[KVH]

Good point about short drives. I’ll check.

 

[CJD]

It's not a valve, as the engine would run like crap. I also don't buy the starter sticking while the engine is running and vibrating, only to unstick at shutdown. Ditto with the chain tensioner. Oil pans are full of oil, so it would have a very muffled sound...you can rule that out too.

My motto with weird sounds that I cannot isolate is to let them ride until the culprit becomes obvious. After all...go test drive any brand new car and then open the hood and listen when you shut them down. They tick, tock, and ping for 30 minutes after shutdown. Some things are not to be worried about.

 

[KVH]

Good advice. I'll take it. Until the next worry gets to me.

 

[mastaphixa]

And turn the radio up!

 

[Popeye]

You could post a movie recording the sound.