Jackhammer like noise under hood

I was driving today at maybe 55mph on the highway my car has 82,000 miles and I started to hear a loud jackhammer like noise come from under my hood I pulled over and popped my hood I didn’t really see anything mind you I’m no mechanic but I was able to make it home but when I accelarated it got louder any ideas what could be causing this problem?

First step is to check the engine oil. Knowing the type of car and engine might help in formulating some guesses from a distance.

Year, make, model?

And what engine?


You should not drive your car until it has been looked at. Have you checked your oil and other fluid levels? Did any warning lights come on? This can be something as bad as a rod bearing failing or as simple as a chunk out of a drive belt. Your best option is to have it towed to a shop and inspected, driving it may only make the problem worse.

IMOO sounds like spun a rod bearing.
I believe when this happens it stretches the connecting rod and it must be replaced.

A spun bearing was the first thing that came to my mind too.
'29 Hupmobiles will do that sometimes…

Bad rod bearing:

It is a 2006 Ford Mustang 4.0l v6 and I did an oil change around 80k and its currently at 82.4k miles and the oil change was about 2 months ago… My friend who works at a mechanic shop came by and said it sounded like it was coming from the back of my engine… From what he said its a bad knock in the motor and the motor is done

I’ve heard that dreaded noise a few times in my life. The last time was in my daughter’s '93 S-10 pickup with the 2.8 V-6. She had loaned it to a friend over a weekend who tried to get it out of a ditch. Make sure a good independent mechanic checks out your Mustang to make sure the engine is toast. A lot of things can make a bad knock in or on an engine.

I agree with @missileman, other things can cause knocks. Like a loose flywheel or torque convertor. Hopefully it is not terminal, 82K is way to short a life for this engine.

I’m bringing it to my friends dad shop today hopefully he finds out what’s wrong

I liked the video, insightful. Nice post.

The 4.0 engines are pretty good ones. If the engine is dying at only 80k miles this means some fluke problem or something in the maintenance history isn’t right. The odds of the latter are much, much higher than the former.

Those engines are pretty complex as far as timing chains, jackshafts, and so on go and if oil changes have not been regular the noise could be related to something in that area.

Ford engineering run amok yet again… :frowning:

A cracked flexplate . . . assuming this car has an automatic transmission . . . makes very ominous noises

I’'m not sure if this car has an inspection plate, but if it doesn’t, I’d be tempted to remove the starter and take a peek with a good light and a mirror

I only heard a sound like that once, it was a broken rod, it was a pontiac tempest wagon maybe 61 i think.

hmmm … well, the above posts are likely to be near or spot-on the problem, but here’s another idea. Exhaust leak. That can yield a sound that seems like somebody is shooting a gun, or firecrackers under the hood. It can be very loud and disconcerting, but isn’t indicative of a major engine problem usually. It would be more likely to be a broken exhaust pipe or cracked exhaust manifold.

Or a loose spark plug.

It’s a manual but the mechanic took a quick look and said it may be a plastic piece that guides the timing belt I don’t remember the exact name… He doesn’t think its a knock in the engine because it happened so suddenly. Right up until it started making the noise the car was running great and it still was on the ride home that day just with the addition of the loud noise under the hood

This engine uses timing chain cartridges and is the weak point of these 4.0L SOHC engines. The two heads are interchangeable, so one cartridge in the front serves one bank and the other in the rear serves the other bank.Typical failure is for a guide or tensioner to break, letting the chain bang around. The entire cartridge needs to be replaced as a unit and both should be done if one goes bad. The rear one is a particular PITA to do from what I understand. I have this engine in my Exploder, but luckily have not had to deal with this yet.

The flex joint in the exhaust pipe makes one type of noise but not the clanking noise. Only does it when the joint is blown out.

So it turns out it was the timing belt guide which is a $30 plastic piece it basically exploded and they replaced that cleaned out my oil pan since their were plastic pieces in that and did an oil change