BMW 528i quiet tapping driving me bonkers

bmw
528

#1

Last summer I bought a used 2013 BMW 528i xDrive with 65k miles on it. The dealer had to put on new brakes and a new transfer case, but since then it’s been running really well. However, a few weeks ago I noticed a really strange occurrence: when the car is in park I hear and feel a quiet tap once every 2-3 seconds. I hear it through the floor board and it seems to be coming from the engine compartment. It’s does not seem to increase in frequency when I rev the engine, though it’s quiet enough that even just putting the car in drive makes it barely audible. Opening the hood and trying to find it there seems all but impossible as the noise is not really audible. It’s much more of a “feel” than “hear” thing.

I am wondering if this is the sound of impending doom. How can I prevent my and my car’s early demise?


#2

No idea. You might post this on a BMW forum.


#3

Newer gas engines that have direction injection do sometimes make a slightly audible “ticking” sound at idle.


#4

You mean after you’ve shut the engine off?
If so, this could be as simple as the exhaust system contracting as it cools.


#5

I can tell you that, at idle speed, BMW’s direct-injection engines sound more like a $12 electric corn-popper than a piece of fine German automotive engineering.

That being said, I don’t think that the OP’s noise problem is injection-related. Because the cheap, tinny sound of BMW’s direct injection engines is very apparent to a pedestrian walking next to the car, it would be even more obvious when the hood is lifted, and the OP stated that there is no noise when the hood is lifted.


#6

change any heater - a/c setting and see if the tapping changes.
every 2 - 3 seconds made me wonder if an electric blend door motor may be struggling to cycle.
buried in the dash, it could lead your ear forward toward the engine.


#7

I don’t think it has to do with the valves/etc. for two reasons. First, it does not speed up with engine speed at all. Second, the idle is very distinct. It’s quiet and subdued, but these taps don’t fall on the same timing at all. I hear a drt drt drt of the engine/exhaust and for every few of those there is one of these taps that I feel more with my feet on the floor than I hear.


#8

I’ll give this a try and report back.


#9

Bingo! I shut off the engine and just ran the fans and the tapping was there. So at least it’s not the sound of impending doom. Thank you!


#10

The two-three second frequency sounds like the water control valve for the heater. Find the valve near the firewall that has half inch heater hoses and a wire connected to it. Two hoses if you have single zone heating and three hoses if you have dual zone heating. Put your finger on it while it is clicking or use a stick or screwdriver as a stethoscope to listen to it.

I have had a couple of BMWs of different models that have made that slow click. It does not seem to hurt anything and on the first car, it went away when I did a cooling system rebuild so it may be related to a little air in the cooling system though I cannot figure out why.

Another theory just occurred to me while I ws typing - BMWs read the signal going through actuators to determine the position of the actuator that uses a simple two-wire connection. Perhaps the valve is sticky and the heater control cannot get readings that it likes so it cycles the valve trying to free it up. If this theory is correct, you can probably fix it by opening up the valve and cleaning it. Be careful not to damage the seals or the very fine wires inside. Those valves are expensive.


#11

Concur, it does sound like something with the hvac system. It might be totally normal, just the actuator homing, re-calibrating, to find its true position. If it isn’t the hvac system, the ABS system can make sounds like that too, often again that is just some test it is doing, normal.