Hammer like knocking sound-What is it?

[Autobacs]

So I pulled up to my cousin's driveway, after a 65 mile or so trip. His driveway was not steep, but not flat either. I am guessing it is about a 15 degrees or so incline. I put the transmission in park, engaged the parking brake, then shut off the engine. As I alighted to go inside, I heard this knocking sound coming from my X5M. At first I thought it was coming from somewhere else as the engine was off and It could not be coming from the SUV. I decided to pop open the hood and sure enough, the knocking sound was coming somewhere from the engine. The engine was definitely off and the sound was like a hammer hitting a metal part. I touched the plastic cover on the front air intake and the sound was definitely coming from underneath. I started to engine and it fired right up and everything sounded normal and I shut off the engine again. Anybody have a clue what the sound was I heard? Car run normally, no CEL's.

[Sophisticated Redneck]

Most likely your auxiliary turbo water pump, it's amazing the horrific noises that little piece of crap can make when it goes. It's the only thing that will be running when your engine is off. Next time you hear it squeeze your main radiator hose and you should hear the pitch and noise change and you will feel the vibrations very strong to the hose. if it does turn out to be it, there is a recall on it but I'm not sure if the recall is applied to M models even though it's the same part number as the N63 engine.

[Autobacs]

Wow! Funny and at the same time good to know. So, on a hunch I checked the coolant level on engine coolant expansion tank and found the level low. I ended up adding 2 pints of distilled water to bring it up to max level. So if it is the auxiliary turbo water pump, the knocking noise must be because it did was not fully submerged in coolant as the vehicle was parked in an incline. Does that theory sound right? Again no CEL's and vehicle drives just fine.

[Sophisticated Redneck]

Originally Posted by Autobacs

Wow! Funny and at the same time good to know. So, on a hunch I checked the coolant level on engine coolant expansion tank and found the level low. I ended up adding 2 pints of distilled water to bring it up to max level. So if it is the auxiliary turbo water pump, the knocking noise must be because it did was not fully submerged in coolant as the vehicle was parked in an incline. Does that theory sound right? Again no CEL's and vehicle drives just fine.

Yep sounds exactly like what mine did, even when new if the coolant gets low and the pump looses it's prime, it makes that horrific sound, I couldn't believe it either as the pump itself is pretty small.

A good way to re-prime it is to pop off the a couple of the turbo coolant hoses from where they join the metal tubes that run to the turbos on top and use a small funnel to poor coolant down, lay some paper towels on top of your alternator to soak up the excess that will run out when you reconnect.

And ya no CELs ever with mine either. It's not to bad of a job if you have to replace but sounds like it was just low on coolant if its quiet now after putting in coolant.

[Autobacs]

Thanks, really appreciate the knowledge. I got back last night from the trip and never heard the noises back so it seems it was primed then with level parking, although I had to add 2 pints this morning. What's clear is there is a coolant leak so I'm gonna have that sorted out.

[Sophisticated Redneck]

Originally Posted by Autobacs

Thanks, really appreciate the knowledge. I got back last night from the trip and never heard the noises back so it seems it was primed then with level parking, although I had to add 2 pints this morning. What's clear is there is a coolant leak so I'm gonna have that sorted out.

No problem happy to help, for the coolant leak as you know there is a ton of coolant lines in there but two of the most common leak points are the temperature sensor on the lower passenger side of the radiator (remove aluminum top brace to see it) and the expansion tank loves to leak at the seams or level sensor on the bottom.

[Autobacs]

Originally Posted by Sophisticated Redneck

No problem happy to help, for the coolant leak as you know there is a ton of coolant lines in there but two of the most common leak points are the temperature sensor on the lower passenger side of the radiator (remove aluminum top brace to see it) and the expansion tank loves to leak at the seams or level sensor on the bottom.

So took a short trip and checked the expansion tank right after. Sure enough I see a little bit of presumably coolant at the bottom of the expansion tank towards the engine side. Looks like time to replace it as just checked my aftermarket warranty and i do not see it covered in the cooling system section.

[Sophisticated Redneck]

Originally Posted by Autobacs

So took a short trip and checked the expansion tank right after. Sure enough I see a little bit of presumably coolant at the bottom of the expansion tank towards the engine side. Looks like time to replace it as just checked my aftermarket warranty and i do not see it covered in the cooling system section.

Its not a bad job if you do it yourself, just a bit of a pain. Grab a adjustable mechanics mirror (or borsecope) and a mini automotive pick set (one with a curved 90 degree in it) The main connection has a clip you have to undo on the bottom and you cant see it without a mirror. The sensor on the bottom can just be rotated 90 degrees and will just fall right out so you dont have to fight its electrical connection, sometimes its easier to take it out that way.

[Autobacs]

Originally Posted by Sophisticated Redneck

Its not a bad job if you do it yourself, just a bit of a pain. Grab a adjustable mechanics mirror (or borsecope) and a mini automotive pick set (one with a curved 90 degree in it) The main connection has a clip you have to undo on the bottom and you cant see it without a mirror. The sensor on the bottom can just be rotated 90 degrees and will just fall right out so you dont have to fight its electrical connection, sometimes its easier to take it out that way.

So I did a couple of test runs to replace the expansion tank and it looked like a pain getting the C clip off the bottom coolant hose connection. I called a shop on how much for them to do it and got quoted $156 plus tax. I went back and forth between having the shop do it and me doing it and I finally went for it and got it done!

The additional tip I want to add is you can swivel around the the bottom coolant connector, using a 90 degree needle nose pliers, to where you can see the top end of the C clip. Then using 90 degree pick, you can pull it just enough, as you can clearly see it. I was worried that without clearly seeing the top of the C clip, I might pull too much and lose the clip.

[Sophisticated Redneck]

Originally Posted by Autobacs

So I did a couple of test runs to replace the expansion tank and it looked like a pain getting the C clip off the bottom coolant hose connection. I called a shop on how much for them to do it and got quoted $156 plus tax. I went back and forth between having the shop do it and me doing it and I finally went for it and got it done!

The additional tip I want to add is you can swivel around the the bottom coolant connector, using a 90 degree needle nose pliers, to where you can see the top end of the C clip. Then using 90 degree pick, you can pull it just enough, as you can clearly see it. I was worried that without clearly seeing the top of the C clip, I might pull too much and lose the clip.

Nice and great tip! There is always a certain satisfaction that completing the work yourself can only bring.

[pjfox23]

Originally Posted by Sophisticated Redneck

...It's the only thing that will be running when your engine is off...

Doesn't the electric fan run on these vehicles with engine off, too?

Genuinely curious as my fan is acting funny recently.

[Sophisticated Redneck]

Originally Posted by pjfox23

Doesn't the electric fan run on these vehicles with engine off, too?

Genuinely curious as my fan is acting funny recently.

Yep they can and possibly the noise he was talking about but he said it sounded like it was from when engine cover area and that is where the turbo water pump is and it can make this exact noise when it starts to fail