Knock, Knock. Who's There? CAR TROUBLE!
September 9, 2013 10:38 PM Subscribe
My car started making a weird noise on my drive home from work tonight. I got home, did some research, and discovered that the noise sounds a lot like "engine knock". I checked my oil level, and it's borderline low-ish. Is is OK to drive to a mechanic or should I walk/take the bus to AutoZone and top up the oil before starting it again? Am I already completely screwed?
I was under ten minutes from home when the noise started. I got it the rest of the way home very gently, and didn't experience any loss of power or seizing. Just the knock.
The oil level (an hour or so after shutting the engine off) is about halfway between the two dots on the dipstick.
I live a ten minute drive from my mechanic, and a five minute drive from ANY mechanic. Work already knows I'm having car trouble and will be in late, and an annoying half hour dealing with bus routes to AutoZone is worth saving my engine.
I don't think I have an oil leak -- at least not one severe enough to leave an oily spot under the car.
I was under ten minutes from home when the noise started. I got it the rest of the way home very gently, and didn't experience any loss of power or seizing. Just the knock.
The oil level (an hour or so after shutting the engine off) is about halfway between the two dots on the dipstick.
I live a ten minute drive from my mechanic, and a five minute drive from ANY mechanic. Work already knows I'm having car trouble and will be in late, and an annoying half hour dealing with bus routes to AutoZone is worth saving my engine.
I don't think I have an oil leak -- at least not one severe enough to leave an oily spot under the car.
YOU'RE FINE. The car will continue to drive. The engine won't fall out. Swing by your mechanic in the morning and explain the problem and see what they say.
Oil midway between the dots on your dipstick is totally fine. If you don't have a pool of oil under your car where you normally park, then chances are rather high you probably don't have an oil leak.
posted by incessant at 11:36 PM on September 9, 2013
Oil midway between the dots on your dipstick is totally fine. If you don't have a pool of oil under your car where you normally park, then chances are rather high you probably don't have an oil leak.
posted by incessant at 11:36 PM on September 9, 2013
I've driven cars with oil leaks when the oil didn't even register on the bottom of the dipstick. No engine knock came from that.
I did have engine knock from a motor I rebuilt myself where I didn't install the oil pump properly. But if you've got measurable oil in your crankcase, you should be fine to drive to a mechanic.
posted by u2604ab at 11:48 PM on September 9, 2013
I did have engine knock from a motor I rebuilt myself where I didn't install the oil pump properly. But if you've got measurable oil in your crankcase, you should be fine to drive to a mechanic.
posted by u2604ab at 11:48 PM on September 9, 2013
A knocking noise could be due to a variety of things. 'Engine knock' is usually an air/fuel mixture ratio problem. I agree w others it isn't due to oil in this case. Btw, reading the dipstick: you're ok to drive as long as the oil registers between the min & max lines.
But get to a mechanic to find out what the knock noise is about.
posted by artdrectr at 11:59 PM on September 9, 2013
But get to a mechanic to find out what the knock noise is about.
posted by artdrectr at 11:59 PM on September 9, 2013
Car noises can be so many things. Mine recently started making a weird dub-step type womp womp sound on start-up/turn-off. Freaked me the fuck out until I isolated it as being a lack of lube on the radio antenna to go up and down. Play around with possibilities if you feel comfortable, or else take it to the shop, but it doesn;t sound like any reason to be afraid of driving it.
posted by mannequito at 1:25 AM on September 10, 2013
posted by mannequito at 1:25 AM on September 10, 2013
Get your mechanic to tow it to his shop. It could be any one of literally hundreds of problems. Unfortunately a few of them could kill you, the car or some other poor soul on the 10 minute drive. I would not take that risk and I am not paarticularly risk averse. Be wary of online tech sources. They can be extremely misleading. Its pretty unlikely that the noise you describe is caused by "engine knock" traditionally associated with big end wear. I would put a speculative shilling on a suspension, wheel or brake problem.
posted by BenPens at 2:19 AM on September 10, 2013
posted by BenPens at 2:19 AM on September 10, 2013
Midway between the dipstick dots is not low at all; it's just fine. It's not even remotely low until it gets below the bottom dot, and even that isn't likely to cause problems unless it gets waaaay below that bottom dot.
I would drive it to the mechanic, and I'd do it sooner rather than later to avoid potentially worsening whatever it is. I would not bother with a tow based on what you've described. Unless your car has a zillion miles on it or has recently badly overheated, major engine damage seems unlikely. The oil certainly isn't a problem.
posted by jon1270 at 3:01 AM on September 10, 2013
I would drive it to the mechanic, and I'd do it sooner rather than later to avoid potentially worsening whatever it is. I would not bother with a tow based on what you've described. Unless your car has a zillion miles on it or has recently badly overheated, major engine damage seems unlikely. The oil certainly isn't a problem.
posted by jon1270 at 3:01 AM on September 10, 2013
As others said, right in the middle is the normal/optimal level for the oil to be at. That's where it is generally when you leave the shop or have just gotten an oil change. from right smack in the middle to a bit above.
All of the advice in the next paragraph is operating under the assumption that this is a continuous, not intermittent tapping/knocking sound. Now i don't mean that the sound happens 24/7, just that it's metronome like and taps symmetrically and not erratically.
If the problem occurs when the car is in neutral or park and idling, i'd be fairly concerned. If it only occurs when you give it a bit of gas in that scenario, i'd be somewhat less.(oh, on preview i'd also try shifting from neutral to drive/easing out the clutch in gear to just get a bit of resistance a few times to see if the "load" on the engine suddenly made the noise happen. That would be Bad™) In both of these cases i might consider towing it, and would by default if i had AAA or something. I'd assume the problem was engine related, and possibly the classic bottom end knock you were reading about. At this point i'd pop the hood and roll a paper cone from a sheet of printer paper and lean around trying to isolate the exact location of the noise. If it's a lighter, more high pitched "tapping" sound from the top of the engine i'd continue to the paragraph about it happening while in motion as far as seriousness goes, as it's likely just a stuck lifter/valvetrain noise thing.
My old car did that until the end of time because i couldn't give a fuck, and someones still driving it. My friends old miata is also still driving around doing that. If it's a top end noise thing like that i'd google "knocking sound modelofcar" "valve noise modelofcar" "tapping sound modelofcar" etc and see if there's a bunch of forum posts on some yourcarmodelmaniacs.com site where people are talking about that exact sound and some beastly master of knowledge about that specific model drops in to explain it. Certain cars upon reaching a certain amount of miles or age are well known to start making noises like this and messageboards will fill up with people talking about that noise on that car. Between me and my friends i think i've heard of two noises like this that turned out to be endemic to that model/year of car, and both times it was "here's a ridiculously complicated and possibly expensive solution" but you could also just ignore it. This might be your best case scenario, but look it up if it's a top of the engine sound.
If it only occurs while the car is actually in motion i'd rate this as "not likely to imminently explode". I'd still bring it to the mechanic the next time they're open, but i wouldn't be afraid of it being something imminently dangerous or destroy the engine serious. Doubly so if the sound is a bit random. I'd assume it was some kind of non-engine drivetrain thing, or possibly something loose in the suspension.
So yea, in all cases but a deep, bottom of the engine clunking consistent knock noise i'd just drive it to the mechanic under it's own power. This isn't something i'd sit on and "get to next week" though. Swearing would be involved if i was driving around and my car started doing this.
And to add to all that, as i was about to push post i thought of a bunch of other things that could make a knocking/clunking sound like this including odd things i'd encountered personally. But yea, pretty much determine if it's coming directly from the engine or not and then move forward from there.
I also hope brockles sees this thread and drops some knowledge, he's basically the resident expert.
And kinda like a lawyer post, although i do all my own work on my car... i am not your mechanic, i am not a licensed mechanic. I can't hear this sound in person or more importantly the exact quadrant it's coming from. I'm also not an expert or anything, i just know enough that i've never paid someone to do work on my car...
posted by emptythought at 3:20 AM on September 10, 2013
All of the advice in the next paragraph is operating under the assumption that this is a continuous, not intermittent tapping/knocking sound. Now i don't mean that the sound happens 24/7, just that it's metronome like and taps symmetrically and not erratically.
If the problem occurs when the car is in neutral or park and idling, i'd be fairly concerned. If it only occurs when you give it a bit of gas in that scenario, i'd be somewhat less.(oh, on preview i'd also try shifting from neutral to drive/easing out the clutch in gear to just get a bit of resistance a few times to see if the "load" on the engine suddenly made the noise happen. That would be Bad™) In both of these cases i might consider towing it, and would by default if i had AAA or something. I'd assume the problem was engine related, and possibly the classic bottom end knock you were reading about. At this point i'd pop the hood and roll a paper cone from a sheet of printer paper and lean around trying to isolate the exact location of the noise. If it's a lighter, more high pitched "tapping" sound from the top of the engine i'd continue to the paragraph about it happening while in motion as far as seriousness goes, as it's likely just a stuck lifter/valvetrain noise thing.
My old car did that until the end of time because i couldn't give a fuck, and someones still driving it. My friends old miata is also still driving around doing that. If it's a top end noise thing like that i'd google "knocking sound modelofcar" "valve noise modelofcar" "tapping sound modelofcar" etc and see if there's a bunch of forum posts on some yourcarmodelmaniacs.com site where people are talking about that exact sound and some beastly master of knowledge about that specific model drops in to explain it. Certain cars upon reaching a certain amount of miles or age are well known to start making noises like this and messageboards will fill up with people talking about that noise on that car. Between me and my friends i think i've heard of two noises like this that turned out to be endemic to that model/year of car, and both times it was "here's a ridiculously complicated and possibly expensive solution" but you could also just ignore it. This might be your best case scenario, but look it up if it's a top of the engine sound.
If it only occurs while the car is actually in motion i'd rate this as "not likely to imminently explode". I'd still bring it to the mechanic the next time they're open, but i wouldn't be afraid of it being something imminently dangerous or destroy the engine serious. Doubly so if the sound is a bit random. I'd assume it was some kind of non-engine drivetrain thing, or possibly something loose in the suspension.
So yea, in all cases but a deep, bottom of the engine clunking consistent knock noise i'd just drive it to the mechanic under it's own power. This isn't something i'd sit on and "get to next week" though. Swearing would be involved if i was driving around and my car started doing this.
And to add to all that, as i was about to push post i thought of a bunch of other things that could make a knocking/clunking sound like this including odd things i'd encountered personally. But yea, pretty much determine if it's coming directly from the engine or not and then move forward from there.
I also hope brockles sees this thread and drops some knowledge, he's basically the resident expert.
And kinda like a lawyer post, although i do all my own work on my car... i am not your mechanic, i am not a licensed mechanic. I can't hear this sound in person or more importantly the exact quadrant it's coming from. I'm also not an expert or anything, i just know enough that i've never paid someone to do work on my car...
posted by emptythought at 3:20 AM on September 10, 2013
Did you get gas very recently? I've had bad gas give me temporary knocking problems.
Drivability is prob fine for the 10 mins to the mechanic, but double check for differential diagnostic purposes:
Is your engine temperature in normal range when driving?
Are you fairly certain it's from the engine and not something hanging loose or caught under the car, in a wheel well etc? (Ie, was it random, intermittent or did the sound have a cyclic pattern)?
Do your brakes and steering feel normal?
Any strong smell or smoke/steam?
N'thing the Batsign for Brockles!
posted by spitbull at 5:09 AM on September 10, 2013
Drivability is prob fine for the 10 mins to the mechanic, but double check for differential diagnostic purposes:
Is your engine temperature in normal range when driving?
Are you fairly certain it's from the engine and not something hanging loose or caught under the car, in a wheel well etc? (Ie, was it random, intermittent or did the sound have a cyclic pattern)?
Do your brakes and steering feel normal?
Any strong smell or smoke/steam?
N'thing the Batsign for Brockles!
posted by spitbull at 5:09 AM on September 10, 2013
Also, consider whether what you heard was a "knock" vs. a "ping" or "clatter." Did the sound change at all when you changed speeds or engine RPM?
posted by spitbull at 5:12 AM on September 10, 2013
posted by spitbull at 5:12 AM on September 10, 2013
Best answer: As others said, right in the middle is the normal/optimal level for the oil to be at.
Full is the optimum level for oil, not midway. Max to min is basically your buffer to make sure that you have time to catch it before it is TOO low. You can even run it slightly (like 1/4 inch) higher than max in most cars but I'd only do that in an old clunker that burned/leaked too much and I wanted to go more than three days without topping it up....
If it only occurs while the car is actually in motion i'd rate this as "not likely to imminently explode".
Eh. Kind of agree but there is genuinely no way of knowing at all based on the lack of knowledge of engine noises generally of the OP (not a criticism) and the additional inability to describe it accurately in text. Trying to look up noises on the internet is a great way of persuading yourself it isn't serious, unfortunately.
HOWEVER. At this stage, the oil level is not the issue - if you have lubrication issues, then it is not a fault of the oil level so any damage resulting is well and truly done if that is the issue. So driving it 10 minutes will not be a difference between failure and FIRE AND FAILURE AND EXPLOSIONS. It's ok to drive. Just do so gently and give yourself lots of room for weird things to happen (Like the noise getting suddenly or progressively worse). Keep the speed down, give yourself space to pull to the side if that happens, maybe stick to the outside lane (Nearest the kerb) just in case.
So I have no clue what it is - not anywhere near enough info to diagnose over the internet and it isn't worth trying to do so, to be honest. Anyone that thinks they can or offers suggestion is largely making it up. It is either something completely minor (like something banging externally) or something major or anywhere in between. Being as you can't fix it yourself, just bite the bullet and take it to your mechanic. Be careful, make sure your cell phone is charged, etc., etc.
posted by Brockles at 5:31 AM on September 10, 2013 [1 favorite]
Full is the optimum level for oil, not midway. Max to min is basically your buffer to make sure that you have time to catch it before it is TOO low. You can even run it slightly (like 1/4 inch) higher than max in most cars but I'd only do that in an old clunker that burned/leaked too much and I wanted to go more than three days without topping it up....
If it only occurs while the car is actually in motion i'd rate this as "not likely to imminently explode".
Eh. Kind of agree but there is genuinely no way of knowing at all based on the lack of knowledge of engine noises generally of the OP (not a criticism) and the additional inability to describe it accurately in text. Trying to look up noises on the internet is a great way of persuading yourself it isn't serious, unfortunately.
HOWEVER. At this stage, the oil level is not the issue - if you have lubrication issues, then it is not a fault of the oil level so any damage resulting is well and truly done if that is the issue. So driving it 10 minutes will not be a difference between failure and FIRE AND FAILURE AND EXPLOSIONS. It's ok to drive. Just do so gently and give yourself lots of room for weird things to happen (Like the noise getting suddenly or progressively worse). Keep the speed down, give yourself space to pull to the side if that happens, maybe stick to the outside lane (Nearest the kerb) just in case.
So I have no clue what it is - not anywhere near enough info to diagnose over the internet and it isn't worth trying to do so, to be honest. Anyone that thinks they can or offers suggestion is largely making it up. It is either something completely minor (like something banging externally) or something major or anywhere in between. Being as you can't fix it yourself, just bite the bullet and take it to your mechanic. Be careful, make sure your cell phone is charged, etc., etc.
posted by Brockles at 5:31 AM on September 10, 2013 [1 favorite]
Oh, by the way, I was assuming you had established it was an engine noise - ie it happens when you start the engine and continues until you shut the engine off - whether the car is moving or not. It may (should) also change in pitch/frequency when you raise and lower the rpm while stationary. If so, it is engine. If it is road speed dependent (only happens when moving, happens more/louder when going faster) it is likely not engine and needs a touch more caution/further investigation before you drive it.
posted by Brockles at 5:33 AM on September 10, 2013
posted by Brockles at 5:33 AM on September 10, 2013
Response by poster: I was right -- it was an oil thing. The oil level was even lower than it seemed last night (and I may have been optimistic when I said "low-ish"). I drove to the nearest shop, they changed my oil (I was overdue for an oil change anyway*), and the noise went away. I'm considering myself very lucky that I didn't ruin my engine.
For the record, for future car panickers who may find this question:
- noise WAS happening as soon as I started the car, regardless of whether I was in drive or moving or what. Slowed way down on idle, though. It was continuous and sounded a little like a hand-crank or a train's chug-chug-chug noise. Very mechanical and clicky.
- I had about half a tank of gas. Last got gas on Friday, drove around all weekend sans noise. I last filled up at either a Chevron or a Shell, so bad gas? I dunno?
Get an oil change, guys!
*I recently went from driving a few days a week to commuting Monday-Friday, AND the job I'm doing right now requires a lot of driving around throughout the day, so I very suddenly put a lot of miles on my car. This may be how I came to be so overdue.
posted by Sara C. at 10:46 AM on September 10, 2013 [1 favorite]
For the record, for future car panickers who may find this question:
- noise WAS happening as soon as I started the car, regardless of whether I was in drive or moving or what. Slowed way down on idle, though. It was continuous and sounded a little like a hand-crank or a train's chug-chug-chug noise. Very mechanical and clicky.
- I had about half a tank of gas. Last got gas on Friday, drove around all weekend sans noise. I last filled up at either a Chevron or a Shell, so bad gas? I dunno?
Get an oil change, guys!
*I recently went from driving a few days a week to commuting Monday-Friday, AND the job I'm doing right now requires a lot of driving around throughout the day, so I very suddenly put a lot of miles on my car. This may be how I came to be so overdue.
posted by Sara C. at 10:46 AM on September 10, 2013 [1 favorite]
The oil level was even lower than it seemed last night (and I may have been optimistic when I said "low-ish")
I hope this is enough of a scare that you check your oil level more regularly in future. Possibly dodged a bullet, there (although maybe took a few thousand miles off the engine's life, admittedly).
/not your dad
posted by Brockles at 2:45 PM on September 10, 2013 [1 favorite]
I hope this is enough of a scare that you check your oil level more regularly in future. Possibly dodged a bullet, there (although maybe took a few thousand miles off the engine's life, admittedly).
/not your dad
posted by Brockles at 2:45 PM on September 10, 2013 [1 favorite]
This thread is closed to new comments.
Good luck. Hopefully it's something cheap and simple.
posted by Anoplura at 10:44 PM on September 9, 2013 [1 favorite]