Metallic "clink" or "knock" on hard acceleration

[aajami]

Hey guys,

First of all, I know the issue of the "clink" from the diff when slowly accelerating from a stop (especially during cold start) has been discussed to death -- this is not what this question is about.

I've been hearing what sounds like engine knocking when quickly accelerating from a coast. That is, when I'm coasting at about 40MPH in 3rd and then stomp the gas pedal to speed up quickly, I hear a metallic "clink" sound come from the engine that lasts a fraction of a second. It sounds a lot like an engine knocking or pinging, but it's not sustained. It's there and it's gone as soon as you give it gas.

Does anyone know if that's an actual engine knock? If so, any ideas how to remedy it? If not, any ideas what it might be?

[Beemdog]

Could be brief pinging, but I've also had a similar issue with the engine rotating on its mounts under a sudden load and hitting an exhaust shield off the car body. This was not an M3. Could even be the engine mounts themselves if they are failing.

If pinging, and given the knock sensing for this car relies on the spark plugs-- have they been changed at regular intervals (every 35-37k)?

[s85e90]

Originally Posted by aajami

Hey guys,

First of all, I know the issue of the "clink" from the diff when slowly accelerating from a stop (especially during cold start) has been discussed to death -- this is not what this question is about.

I've been hearing what sounds like engine knocking when quickly accelerating from a coast. That is, when I'm coasting at about 40MPH in 3rd and then stomp the gas pedal to speed up quickly, I hear a metallic "clink" sound come from the engine that lasts a fraction of a second. It sounds a lot like an engine knocking or pinging, but it's not sustained. It's there and it's gone as soon as you give it gas.

Does anyone know if that's an actual engine knock? If so, any ideas how to remedy it? If not, any ideas what it might be?

Yes this is knocking!! I have heard it in other cars (M3) and it's usually always when from cruising and pushing the gas down, the first tip in has a slight knock. You can try putting the car in a higher gear and slightly lug the motor and then step on it and I bet 100% you'll hear it all the time. This may unfortunately sounds like the beginning of a worsening rod knock and will only get worse (may take some time).

If you haven't already do an oil analysis or better yet you may want to consider swapping the bearings out.

[aajami]

Originally Posted by s85e90

Yes this is knocking!! I have heard it in other cars (M3) and it's usually always when from cruising and pushing the gas down, the first tip in has a slight knock. You can try putting the car in a higher gear and slightly lug the motor and then step on it and I bet 100% you'll hear it all the time. This may unfortunately sounds like the beginning of a worsening rod knock and will only get worse (may take some time).

If you haven't already do an oil analysis or better yet you may want to consider swapping the bearings out.

Thanks for the insight. For the uninformed (me), is there anything that can be done to mitigate a rod knock? If not, why is it assumed that it will get worse?

[s85e90]

Originally Posted by aajami

Thanks for the insight. For the uninformed (me), is there anything that can be done to mitigate a rod knock? If not, why is it assumed that it will get worse?

It may get worse, it may not change for some time. But I'm very sure that you are hearing the beginning of rod knock meaning that the lower end bearings are bad. Do a search on here and you'll find a wealth of info.

The way to mitigate the problem is in m first post: replace the bearings. GO visit a shop or BMW and have them listen to the noise. If (worst case, hypothetically speaking) it were to get worse, eventually you would "spin" the bearings which would no doubt kick a rod out of the block and force you to shell out BIG $$$ to put a new engine in the car.

[thekurgan]

Check engine mounts.

[spr]

It's the driveshaft. The u joints or more likely center support bearing is going.

[s85e90]

Originally Posted by thekurgan

Check engine mounts.

Originally Posted by spr

It's the driveshaft. The u joints or more likely center support bearing is going.

Do people just throw things out there? OP seems like he states it's isolated to the engine and these are the prelude a bearing/lower end issue. Slight knocking on tip in. I've experienced the same exact thing almost verbatim.

I hope for OP case it doesn't get worse, but if this is a driveshaft or mount issue I will be amazed.

[thekurgan]

Originally Posted by s85e90

Do people just throw things out there? OP seems like he states it's isolated to the engine and these are the prelude a bearing/lower end issue. Slight knocking on tip in. I've experienced the same exact thing almost verbatim.

I hope for OP case it doesn't get worse, but if this is a driveshaft or mount issue I will be amazed.

Everyone here is "throwing things out here", lol.

Verbatim doesn't mean dick here, there are countless noises from tip in, in any automobile.

I'm sure the OP will take as many suggestions as he can.

[s85e90]

Yeah but op says it sounds like engine knocking. Mounts and driveshaft wouldn't do that. He's 99% experiencing slight rod knock. I've heard it before on these cars.

[BPMSport]

Is your car stock or tuned?

[aajami]

Originally Posted by Mike Benvo

Is your car stock or tuned?

The only tune I have is what's in my sig: OEM 240J software.

[V1.47fan]

Originally Posted by thekurgan

Everyone here is "throwing things out here", lol.

Verbatim doesn't mean dick here, there are countless noises from tip in, in any automobile.

I'm sure the OP will take as many suggestions as he can.

Yeah but s85e90 our internet expert has already determined the problem. Why are you wasting our time?

[V1.47fan]

Originally Posted by aajami

Hey guys,

First of all, I know the issue of the "clink" from the diff when slowly accelerating from a stop (especially during cold start) has been discussed to death -- this is not what this question is about.

I've been hearing what sounds like engine knocking when quickly accelerating from a coast. That is, when I'm coasting at about 40MPH in 3rd and then stomp the gas pedal to speed up quickly, I hear a metallic "clink" sound come from the engine that lasts a fraction of a second. It sounds a lot like an engine knocking or pinging, but it's not sustained. It's there and it's gone as soon as you give it gas.

Does anyone know if that's an actual engine knock? If so, any ideas how to remedy it? If not, any ideas what it might be?

i used to have the same sound at low rpm, when getting on the gas on occasions, it went away on its own.

From BMW, it doesnt have to in 5th gear, i've heard of guys having the same type knock in third gear, low rpm, heavy load.

1.0 Engine
The new S65B40 V8 engine is a high performance engine designed and built to exacting BMW Motorsport tolerances which take into account the high performance nature of this engine.
The new S65B40 V8 engine has the following characteristic sounds which dealers need to be aware of.

1.1 Knocking type sound at idle
When the engine is at normal operating temperature and depending upon the accessory loads on the engine it is possible a low frequency knocking type noise may be heard in the car. This noise is a characteristic of the engine and is not an indication that there is a defect with the engine. In the event that you receive an inquiry about this noise it is important to reassure the customer that this
noise is a characteristic of this engine. The noise in no way affects the durability of the engine and will not lead to a failure of engine components.

1.2 Resonance at 2,000 rpm under load
The M3 has a characteristic resonance which occurs in a narrow rpm and load band. The resonance is directly related to the performance characteristics of the M3 engine and in keeping with the performance nature of the vehicle.
The driving conditions under which this resonance will be heard:
• Engine speed = 2,000 rpm
• Vehicle speed = approx 70-80 km
• Gear selected = 5th gear
• Road conditions = moderate incline

The resonance band is very narrow and can easily be avoided by reducing the load on the engine or bychanging down or up a gear depending upon the driving conditions.

[aajami]

Originally Posted by V1.47fan

i used to have the same sound at low rpm, when getting on the gas on occasions, it went away on its own.

From BMW, it doesnt have to in 5th gear, i've heard of guys having the same type knock in third gear, low rpm, heavy load.

Thanks for the link to the documentation. I'm not sure if this is the same issue. I hear it specifically on 3rd and 4th, at the moment that I tip-in from cruising at 3,000RPM. It doesn't sound like the same low RPM vs. heavy load issue.

I'll try to narrow done exactly what gear and rev ranges it happens.

[spr]

As an FYI, I got the knocking/ clunking noise on and off load in any gear and when moving the shifter from reverse to drive stopped. It was the driveshaft. Try that and see if it clunks.

[Sandye90m3]

A metallic high pitched clinking noises are what I hear since I bought the car under high gear , low rev acceleration. Once I get above 2700RPM it vanishes.

[s85e90]

Originally Posted by V1.47fan

Yeah but s85e90 our internet expert has already determined the problem. Why are you wasting our time?

OP seems smart enough to know the diff between a mechanical drivetrain clunk and engine knocking.

I have also posted that clip from the manual in the past. I have brought cars to the dealer for the same thing. I would be pretty cetain the OP is hearing a light rod knock. As advanced as the knock detection system is on this car, one should NEVER hear audible knock.

[BPMSport]

Originally Posted by aajami

The only tune I have is what's in my sig: OEM 240J software.

What is 240J software? Do you mean 240E?

If by J you mean "japan" spec software, it's 240EEKJV0, and this shouldn't be used in US spec vehicles and may be a contributing factor to the issue you are experiencing.

I was on mobile which doesn't show signatures.

[s85e90]

Originally Posted by Mike Benvo

What is 240J software? Do you mean 240E?

If by J you mean "japan" spec software, it's 240EEKJV0, and this shouldn't be used in US spec vehicles and may be a contributing factor to the issue you are experiencing.

I was on mobile which doesn't show signatures.

Doesn't Japan get the same equivalent of 93 octane. I see OP is in Cali, but he shouldn't be experiencing any audible knock at all. IMO hearing knocking is too late.

Unless this is something totally unrelated then I digress; however, I have noticed a few M3 that "pinged" bad under initial tip in of throttle while especially lugging the car. Bad bearings were the culprit as suspected.

[quicktwinturbo]

Damn it.. This kind of thread makes me nervous and my warranty is about to run out. Please keep us posted OP. Hope it's not the RB.

[s85e90]

FWIW I know of one car personally that had this noise exactly as described and everything was done to isolate it. The car did do probaly 65-80k without issue. So it may just stay as more of an annoyance. This one was there forever.