Car mechanics: Why has my car developed this metallic rattling noise?

Have you checked the engine oil? if the oil level is low, the valves will rattle. this is a metallic noise. john

Hi there John, thank you very much for your suggestion. I hadn’t actually looked at the oil level, no – I will take a look when I get home tonight! Thank you so much for your help, once I’ve had a look I will post an update here with what I see.

Is oil level something that gradually gets lower when cars are functioning normally? Or, if it’s getting low, could it be indicative of a leak or some other problem?

@reverie Don’t drive it without checking the oil. The other possibility is the fan clutch will sometimes make a knocking or metallic sound.

@Tropical_Willie Thank you very much for your advice. I’m currently at my workplace and I drove here this morning, and it’s about a 16 mile drive back home. If I check the oil here and find it is low, is it safe for me to drive it home to refill with oil there, or should I head to a garage to refill the oil as soon as possible before doing the full journey?

There should be two marks on the dip stick. The lower of the two is usually one quart or liter down. If the drip stick is dry DO NOT drive it.

Thank you so much for your advice. I’ve just been out into the car park to have a look at oil levels, and the oil is about half to three-quarters of the way full (i.e., between the “min” and “max” marks on the dipstick, the oil is about 50–75% of the way towards the “max” mark, so it doesn’t look like it’s low on oil). I’m really not sure what to do with it now if the oil doesn’t appear to be low… I guess I should take it to get looked at asap!

Check heat shields and their fasteners. Sounds like some rusting heat shield could be causing it to droop on the exhaust system. The rattling would be it bouncing off the pipes.

Are you sure the sound is coming from where you think it is coming from?

The catalytic converter will do that.

@arpinum Thanks very much for your suggestion! I don’t really know very much about cars at all unfortunately, so what you mention is probably something I would need to get checked by a mechanic!

@ChazMaz Thank you for your suggestion. Whilst I couldn’t be confident of the exact area, I’m pretty sure that the sound is coming from the front of the car. With the car switched off, I opened the bonnet and had my boyfriend look inside, and then I got in and switched the car on (it usually makes the rattle as the engine starts too) whilst he watched and listened to the whole process, so he could get a really good view and listen to where the noise seemed to be coming from. We did this a couple of times and he seemed to think it was coming from this area on or near the engine, but obviously we can never be totally certain, although I’m pretty sure it’s not coming from the back. I’m worried, really hope it isn’t something expensive!

If you don’t already know. The catalytic converter is part of the exaust system. IE back of car.

Just for laughs, look underneath the front of the car to see if the chin fairing has come loose. This is a plastic lip designed to deflect wind. They’re easily damaged if you run into a parking block. They rattle in the wind, but it tends to stop at higher speeds.

I had the same noise only coming from the back end of my car awhile back, rattling at low speed and going over bumps or potholes..was the rear airshocks…maybe an alignment issue or struts. ?

Could be the heat sheild off the manifold! :-/

With the vehicles I have owned/driven over the years, I have heard a wide variety of weird noises. Rattling noises I have had over the years have been caused by:

- Loose body panels
– Loose dashboard panels
– Loose heat shields
– Loose air cleaner housing
– Misadjusted valves (unlikely in your case since most modern cars have hydraulically-adjusted lifters)
– Worn suspension components
– Random crap in my glove box, center console, or door pockets
– The ashtray

It’s hard to say without actually hearing the sound.

@jerv

And you know that NO BODY ever hears the sound when you need them to!

My mechanic alway’s says it’s the loose nut behind the wheel. lol

I’d check it for free if you’re North east! ;-)
;-)

One other source I forgot to mention is spark knock which is why I can not run 87 octane in my ‘85 Corolla. My ‘87 Corolla required 93 octane for similar reasons. The sound going up a hill, accelerating, or at low speeds where the engine was at an RPM below it’s powerband, the sound could be compared with a soda can with a few BBs being shaken.

It is highly unlikely that that would happen in a modern car (like yours) without tripping the Check Engine light unless the CEL bulb is out since the engine computer has sensors and programming to deal with that, but I had to mention it for the sake of completeness.

@Coloma I have yet to see that. I’ve seen a loose nut behind the wheel cause sudden acceleration or braking, weaving across four lanes of traffic, and just generally being an ass-hat though.

@jerv

I was kidding around..as in loose nuts behind the wheel when diagnostics fail to pinpoint the noise. Never mind..you seem the serious type…lol

@Coloma I just have a dry humor. I suppose that a driver distracted by a cellphone or some soccer mom filled with road rage don’t qualify as “a loose nut behind the wheel” then?

Wow! This is all incredibly helpful – thank you so much everyone for all of your suggestions, I really appreciate it. I’m so impressed with all of the knowledge here.

@jerv – you’re quite right, I wish there was some easy way of recording the sound, as I think that would help a lot! Actually, the sound seems to have reduced a little, but it’s still audible. It’s definitely only happening intermittently when it’s idling, at a low speed in a low gear (i.e., below 20mph in 1st, 2nd or 3rd gear), and at slightly higher speeds in inappropriately high gears (i.e., slowing down to 30mph in 5th gear, it makes the noise).

@ChazMaz – haha, with my poor knowledge of cars, I did at least know that :P

Well, I’m trying to get hold of my garage at the minute and hopefully someone will be able to look at it soon. I’ve had to drive it again today (not really avoidable) but will avoid using it again until I know what the problem is – I’ll let you know what the mechanic says, there have been so many great suggestions, I bet someone here is spot on!

@arpinum @Scooby @jerv You were all right with your suggestion! I’ve just had my car back from the garage, and it was a loose heat shield rattling. The mechanic welded it back in place for me and it cost next to nothing. Yay!

@reverie

Excellent!! ;-)
Rattle free driving, there’s nothing quite like it, glad to help out………….. :-)

Good news—Keep an eye on it. The next time it makes noise you’ll now know where to get it fixed.

Sorry to say think it is gearbox related.

I don’t know if this thread is still live but after stripping most of my fuel and starting systems for a rebuild after a complete engine failure, I have developed a similar rattling in the lower portion of the transmission. My vehicle is a Renault 1.9 DCI Grand Scenic II and an absolute nightmare for the home mechanic to maintain. The sound is a ‘tinny’ rattling that I sincerely hope is not the presence of a fallen centring dowel from the starter motor that has become lodged at the base of the bellhousing. Does the learned community believe that this could be a possibility without me having to remove the transmission facing to retrieve something that may or may not exist on a Renault starter motor? Haynes mentions the dowel and warns to not lose it but other starter motors seem to be absent this apparently vital piece of metal and I’m wondering if it’s something only on the petrol models?
Aside from this, I have been working under the vehicle and agree that it could be the razor sharp heatshield vibrating against part of the exhaust system. My other theory, as I have renewed the ABS modulator and all brakepipe is the possibility of loose clipped pipes vibrating against the vacuum-servo unit or against the transmission housing.
I’ll keep this thread posted as to my findings and may be inclined to post some helpful topics on how to remove the starter from these diesel models from above the vehicle without following the annoyingly concise Haynes manual that requires (in extremities) cutting the exhaust to remove the catalytic converter unit and removing unnecessary wiring and pipe, especially if your nuts and bolts are a seized and corroded as mine!

Old threads never die here :)