Hello all,

Driving back home Christmas day, I began hearing what sounded like knocking grinding from my engine. It sounded much like a mix between a loose timing chain and a bad pump or bearing. It is also intermittent in that it will start and stop every mile or so, when it does so it sounds like something spinning out that then "catches up". When I got out to inspect motor while idling, it appears to be coming from the supercharger, but we all know how sound can propagate in an engine bay.

This happened 30-40 miles out of town, with no cell service, on Christmas day, so I had to drive it home like this. I would think with a spun bearing or other rotating assembly failure, it would not manage that. While driving the engine ran 100% normal except for the noise. No power loss or stuttering.

Here are two videos of sound at idle:

In person it sounds much like timing chain slap, but to test that, I pulled off the valve cover and inspected the timing chain while idle/slight rev, and it is not moving around/slapping anything. That being said, if I can prove it is not the rotating assembly (spun bearing or similar) I will replace the timing assembly.

So far my top guesses are either spun bearing, or supercharger/PTO failure (though I also have normal boost, and coolant temps are normal), with a hedge bet at a horridly failed alternator shaft bearing.

If I can exclude a failure in the rotating assembly, I can afford to fix the car. If not, I can not afford to, and will have to part out/sell/something.

My thought is for a quick and easy test, I can remove the serpentine belt and start it. In theory the BPV should stay open and the car should idle fine, without the accessories rotating. If the sound is gone, it would exclude the possibility of a spun bearing. My question is, will it run sans belt long enough to listen to it idle?

If the sound doesn't go away, my next plan is to check the oil filter and engine oil for metal debris, and then finally pull the oil pan.

Another point of note, when turning the motor over with coil disconnected so it wont start, there is no noise...I would think I would hear a rod knocking around in that case? The noise only becomes evident at idle and above.

Any ideas or insights would be highly appreciated. Thank you so much for your time!

 

I've experienced both problems unfortunately, although I have yet to read of a spun bearing in a mini yet.

In the few spun bearing cars I've seen and worked on, none of the cars really ran. Very hard to start and they certainly didn't run well, they barely idled. Highly doubt it's your problem.

My sc gears got chewed up early last year, hard to hear if it's the same sound with that recording though. Kind of sounds like it but really hard to tell. My car didn't show any signs of overheating and it won't affect the boost since it's just the water pump gears dying. I wouldn't trust the mostly worthless temp gauge though. Mine seems to have 3 settings, low, middle, and oh crap.

Good luck, hopefully just one of your pulleys.

 

If you want to rule out the belt drive components de-tension the belt and see if the noise goes away. That will be your quickest easiest part of this diagnostic process, if it doesn't go away then you will need to delve further into the diagnostics.

 

Spun engine bearings are very rhythmic and accelerate with engine rpm. Also with 40 miles of driving on a spun engine bearing the knocking would be very loud and the engine would rev noticeably slower. The oil would also be very black and burnt.

 

I bought mine with a spun bearing. Probably related to oil starvation due to a cage-less oil filter collapsed inside a new style oil filter housing. It was otherwise nicely optioned and clean. The bad part was the PO drove it long enough the crank couldn't be salvaged/ground, but had to be replaced and they weren't available at the time. Don't know if MINI ever restocked them. Found a used one in good shape after a while.

You can inspect the bearings by dropping the oil pan. It's about a 2 hour job each way (you have to put it into service mode to unbolt the AC compressor (don't vent it) and disconnect the lower engine mount from what I recall. Plan ahead and have a new gasket ready. If it is a bearing, you will see debris in the pan and will be able to wiggle the connecting rod.

 

Thank you everyone for your input! I massively appreciate the additional insights and points of view I can get from forums any time I have a car issue!

Last night I pulled the belt and started it, and no noise! Upon inspection, I found that the alternator was completely munched! It would actually seize up to where I could not turn it when I threaded the belt around just the alt pully and spun it (easier to reach).


So I am fairly sure it is just the Alt bearings and shaft grinding/connecting with the inside of the alt.

Since I definitely need a new alt I am going to start there, it works out, because I wanted to upgrade to a high output alternator anyways. I figure while I am there I will also change the oil in the supercharger, and any other little things I should get to while in front end service mode. Possibly replace the positive lead to the battery as well.

Thanks again, everyone for your time and input!
Matt

 

Glad it was the alternator, it's a quick fix.

I wouldn't replace the battery lead, as it runs to the back of the car and is part of the passenger restraint system, it has a small charge in it to detonate battery contact in the event of an accident.

Give us a call if you need any help or parts, as we have everything you need on the shelf and the knowledge to assist.

Detroit Tuned
586-792-6464

 

It's part of the passenger restraint system? That is extremely odd. Interesting. I'll definitely have to research that more. Maybe just to a run in parrelel then. I'd really like to upgrade that line to make way for some audio upgrades I have down the line (it is going to be a rather...involved... SPL/SQL setup).

 

There is a pyrotechnic charge on the cable in the battery box, which once it is set off will illuminate an airbag light and cut all power.

 

What is stopping me from replacing that with a suitable fuse, out of curiosity? Ideally a slow-blow fuse to handle power spikes from the starter.

 

It is designed to disconnect all power in the event of a crash. Shut down fuel pump, cut power to airbags, protect emergency workers... Not at all the same role as a slow blow fuse.

 

^This.

 

But it does so by disconnecting the main power line via the odd black piece near the terminal that would attach to the positive lead of the car, doesn't it?