[nicholas.hudson]

My car is making a loud tapping/knocking noise from underneath the car whenever the engine is running.
My car is a 2006 E92 with 157,000km in the clock, which I bought only 5ish months ago. It had the common case of lifter tick which I thought was fairly normal, but I later found that the previous owner had neglected to tell me that the car had been in a crash sometime in its life (I realized this when I found broken glass in the cowl, paint pen writing from the wreckers on the front subframe, and that the radiator wasn't sitting in its saddles and instead held by zip-ties). I have recently done some work on the car, replacing both oil filter housing gaskets after finding some oily other-worldly substance in the coolant res (shown below), and repairing the bent and cracked power steering brackets.

Below is the oily stuff I found in the cooling system.
https://photos.app.goo.gl/NRsTVkh1K9EgE5YE6

Since changing the oil and filter, the lifter tick has become less noticeable, and as such this other tapping sound has become more obvious. I used a scan tool to clear and recheck for codes and I currently have three codes on the DME:

29E1:Mixture Control 2
2E83:Electric Coolant pump, power-reduced operation (But I'm not getting any engine management warnings on the instrument cluster, and I know that the pump is working cos I bled the coolant system just the other day)
2D06:Air-Mass System

Not sure if these could contribute to or cause this knocking.
There was no forbidden glitter in the oil or filter when I changed it, so I don't think it's a bearing eating itself but I have no clue what this could be. The following video shows what the sound is like. It is more obvious from the side of the car and in the cab.

https://photos.app.goo.gl/ruuobrcncVjHVeqPA

I also have a leaking valve cover or eccentric shaft motor seal, and a leaking sump gasket. There is also a considerable amount of vacuum in the crank case.

I'm really hoping this isn't and expensive thing to fix.

[Suvorovo]

Before spending anymore money on the car, verify the alignment to see if there's a bigger issue after the crash and have the car inspected by a mechanic. I guess they'd see things that we'd miss.

You need a waterpump/thermostat ASAP before it completely fails.
Oily stuff in the coolant probably came from the oil filter housing gasket/cooler. These cars don't have problems with head gaskets.

Are you running a manual transmission? The knocking noise underneath the car could be a worn dual mass flywheel or there's a metal heat shield cover somewhere underneath that is known to become loose. I forget exactly, but have seen the issue in other posts. I think you confirmed it's not the engine, which is great.

Vacuum is a bad PCV, have that replaced ASAP. It's why you blew out the valve cover gasket, oil pan, and oil filter housing.

Oil pump/thermostat kit less than $400 USD in parts.
PCV $375 USD

For your 2D06, try cleaning the MAF first. It's kind of expensive to replace $200 USD, but do fail overtime. Could also be caused by a failed PCV causing unmetered air to enter. Cracked hose?

Only buy the pierburg water pump and borg warner thermostat.
I'd also recommend getting the Genuine BMW PCV system. No idea how reliable OE replacements are and have seen fitment issues for the hose connections. They're not that much cheaper anyway.
VDO MAF, if needed is fine.

To comfort you about the cost, I spent around $4000 in parts/tires between 120-125k miles to make sure my n52b30 is 100% reliable for the next 100k miles.

[nicholas.hudson]

Thanks for the reply.

Yeah, it's a manual trans. It was supposed to have a new clutch installed a few months before I bought it, but if was done by the same people who "fixed" it last time I wouldn't be surprised if there's something they missed or installed incorrectly.

The car also shudders a bit when revving down from around 2k rpm. Could this show a problem with the flywheel/clutch?

I just put the car on stands to see if I could find where this sound was coming from, and it sounds like it's inside the bell housing as it definitely sounds rotational.

I was logging some data just the other day and noticed that the coolant and oil temp was up to around 104 degrees Celcius while cruising at 100 km/h. And previously the oil temp never rose much above 80 Degrees Celsius.

I also saw that for some reason the RPM that the ECU is reading drops down to ~800 rpm while cruising down the highway. Could be linked with the mixture error codes?

[nicholas.hudson]

Also any recommendations for flushing out the oily gunk from the cooling system? I've tried coolant flush but that didn't seem to work very well.

[Suvorovo]

Could be an issue with the install or they cheaped out and replaced with a single mass setup. Those will cause a chatter. You'd really have to take a look.

104C is within operating spec. These cars run pretty hot.
Here's a post: https://www.e90post.com/forums/showt...'re%20fine.

Go to a mechanic for a coolant flush. They have the tools to pressurize the system. Not terribly expensive.

Can't comment on the ECU stuff, sorry.

[johnnyorange]

Originally Posted by Suvorovo

----

Only buy the pierburg water pump and borg warner thermostat.

----

why specifically the borg warner and not the mahle?

i am just curious really

i already have the pierburg pump in my cart at fcp

[k90]

Originally Posted by nicholas.hudson

My car is making a loud tapping/knocking noise from underneath the car whenever the engine is running.

At idle? Cold or after some bit of driving?
Does it change if clutch is operated?

[michaelalex17]

This was going to be my question. If you are are in neutral and you press in the clutch pedal does the knocking go away? If so I’m going with throw out bearing.

[nicholas.hudson]

hot or cold, clutch in or out, it doesn't make a difference to the nocking sound.


An update on my investigation into the high amount of vacuum in the crankcase. Ive pulled off my intake to find its a 3 stage intake (cool I guess but now I have to check the disas) and found a fair bit of oil in the intake. I thought this could be an issue with the oil separator, however, I have a plastic valve cover and can't find much information about replacing the separator or if I need to replace the whole VC. I'm going to do more research about this, but I thought I'd update this forum with where I'm at at the moment.

[Wolf 335]

Wouldn't hurt to properly flush the whole cooling system, including the heater core.

Do you have any information on the accident?
What part was damaged?

Also, get a cover for the washer fluid reservoir fill port, before something makes its way down there.

[nicholas.hudson]

The only information I got from car vertical about the accident was damage to the front bumper, wings, and a sill on one side. The guy who sold it to me gave me no information about it.

I plan to get the cooling system a proper flush once it's running again. I have a suspicion that all the oily shite has caused damage to the water pump and that is why I was getting that error code.

[nicholas.hudson]

Another Update:

I removed both my DISA valves to check them and there was a BUNCH more oil in the intake manifold. Both the large and small valves were wide open when I removed them (I thought they were supposed to be closed when the car is idling) and I can't move them with my hands (not sure if I'm supposed to be able to). From what I've seen elsewhere, a faulty PCV system can cause the oil in the intake manifold and cause issues with the DISAs.

I have stuttering symptoms that are supposed to come from bad DISAs, so maybe this is the problem.

[nicholas.hudson]

Unsure if anyone is still looking at this thread but I'll post an update.

I decided to replace all the lifters on both the intake and exhaust cams (you'll probably need some help with the intake side due to the Valvetronic springs). During this job, I saw that the exhaust camshaft and ledge was pretty badly beaten and scoured:





I knew that this was not a good sign, but I went ahead and reassembled the engine anyway. The car started first try but the tapping and rattling was still there no matter if the engine was hot or cold. After a little more research, I found that worn cam journals could lead to a low oil pressure in the lifters which can cause them to not 'inflate' properly which would cause the rattling.

I then searched around for a while looking for new exhaust cams and ledges but could only find new or refurbed ones for over $1500AU. So I jumped onto Facebook marketplace and found someone who was wrecking a 323i with the
same motor and picked up the cam and ledge from that engine for $500 AU.

The second-hand cam was in far better condition than the one I pulled from my car and once swapped in solved the horrendous rattling.

I am now noticing however that the car will sometimes make a deep hollow thumping noise when it's warmed up that I can't identify.

I've also noticed that if the car is started and stopped in a short period of time (like when shuffling cars around) the lifter tick is almost guaranteed to come back the next time you start it, but does disappear after some driving