Noise Off the Engine, Ideas Before I Dive In?

[Tanner Frisby]

Hello all,
I’m a novice car guy learning fast. After pulling and reinstalling an engine (and everything else in the bay) I’m getting an unpleasant noise most if not all the time the engine is running. A quick listening-to-a-stick test didn’t get me anywhere but I ran out of time. The big catch is that once the engine is turned off the noise immediately stops even though the belts continue to turn until friction eats up the belt’s momentum. This happens every time. So my question:

What devices are engaged only when the engine is actively running and are disengaged as soon as fuel stops being delivered to the engine even though the engine and accessory belt continue to turn for another second or two?

I think that the answer to the above question is the best place for me to start looking.
Added information, whether relevant or pertaining to a different problem altogether: The red battery light on the dash stays on while the car is on. I believe this is a warning light that the battery isn’t getting charged? If these two are indeed related, the alternator seems to be a likely suspect.

Now I’m not asking for a definitive “this is what’s wrong with your car” off such little information, but I would like a point in the right direction.

Thanks all,
Tanner Frisby

Topic

[none]

With most help questions posted in online forums, year, make, and model helps us help you. In this case, automatic or manual transmission might be good to know too.

There is no belt on an engine that should keep turning once the engine stops. Once the crankshaft stops turning, so do the belts. Take the accessory drive belts off entirely. Does the noise go away with all the belts off?

Since this engine swap is a first for you, go back and check the basics. Did you put oil in the engine (and did you put in enough?) before you started it up? Check those electrical connections to your alternator. You should have a main cable screwed down to a post on the back and then a smaller wire or wires plugged in near by. Check all your nuts and bolts. If you have an automatic transmission, did you remember to bolt the torque converter down to the flex plate?

[Tanner Frisby]

Ah yes, how careless of me: 02 Jetta Mk4 2.0L 8v with automatic transmission.

Similar to say a drill press, when you turn the power off the head doesn’t immediately stop spinning. If its spinning at 2000 rpm before power is cut, it will take a few seconds before the drill bit is stationary and you can retrieve your part. That is what is happening hear. When the engine is steady state on, the noise exists. As soon as the engine hits running-transient-non-running the noise disappears. After the gas/spark is cut, the crankshaft has momentum left which it imparts on the accessory belt. The accessory belt continues to spin for another second or two as the crankshaft goes from 600 rpm (idle) to 0. I hope this is a little clearer. I’m really kicking myself for not taking a video when I was last at my shop.

The engine has oil, and enough oil. I’ve checked (when the light came on), topped off and checked again a few starts later. The connections on the alternator need checking and are on my list (as per the red battery warning light) but I wouldn’t think electronics would account for a noise. It is an automatic, but the transmission was pulled with the engine and they have remained one piece for the duration of the build. I guess you can’t be 100% sure all the bolts are tightened down, but I really don’t think this is the problem.

While I have never heard the sound a dying bearing makes, an older car tinkerer mentioned that it sounded like a bearing going out. I have no basis to assert this other than the opinion of a man who used to work on cars “before dang-flabben computers and sensors and sh!t”. I didn’t want to mention this earlier as this may sway opinions. I’m looking for an answer based off of the unique circumstances in which the noise exists.

Thanks for a quick response. I’m sure I’m going to have to take the accessory belt off, but I’m not sure how I can take it off of one accessory at a time. The belt is a finite length. Belt on and belt off make since to me, but how do you go about removing only one item (say all accessories minus alternator) and still have the belt taut? I feel that since the fact that the noise goes away right when the engine looses power would be indicative of a very specific problem, which would save me diagnostic time. Or at least that is what I’m hoping for.

Thanks all,
Tanner Frisby

[Lorrin Barth]

Knocking noise or constant? If constant, squeal, roar or hiss?

[Tanner Frisby]

It is a constant and rhythmic closest to a squeal. No roaring and nothing hisses except the power steering fill up reservoir the moment the engine is turned off (It sounds like it is venting to atmosphere, is this normal or is a hose loose or something?).

I feel like this is turning into a bad AAMCO commercial.

I was looking through my phone and the only sound bytes I have are from when the engine first fired back up a week ago and the noise isn’t present. That may open up the possibility of the A/C as the on/off button gets bumped all the time while I’m working on the car (and the hazards and horn and the turn signals…)

Here is a diagram of my vehicle’s belt:

I’ll be back in the shop by Tuesday and should be able to get a video of the problem up by Tuesday night (if I can’t figure it out myself) but again, any pointing in the right direction is appreciated.

So if I take the belt off, is the proper diagnostic to spin each spindle and listen for noises / resistance?

Thanks,
Tanner Frisby

[Lorrin Barth]

I’d run it with the belt off. This won’t hurt anything if only for a few seconds. Then spin each belt pulley by hand to see and feel if it moves freely without roughness or noise.

If this is a diesel it has a weighted and spring loaded flywheel know for making racket and vibration.

[Tanner Frisby]

Hello all,
I eventually figured it out.
Before
After

I’m very thankful for the plot of land that I have to work on my car, but it is far from a garage. With that said, most all of the project is constantly exposed to the elements. The ignition cylinder apparently got grimy and the spring that returns the key from crank to drive was getting stuck. The noise in the “before” video is the starter constantly running with the engine. This also explains why the noise disappears while the engine is dying down when the key is turned off.

Thanks to all who took the time to read , post and lend some knowledge. I’ve learned a lot in the last two months building this car and I’ve got about one more month to go. For those interested in the full story: Build Thread + 100s of pics

Thanks all,
Tanner Frisby

[Bryan Castor]

That’s great man! Glad you were able to figure it out. It really had me thinking about the possibilities of the reason why your engine was making those noise. And the only thing i though about was that maybe the engine might have been neglected – like haven’t had the oil and filter changed regularly that its’ making those bearing noise or that the bearings are loose. But good thing you found out that it was the ignition cylinder.

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Steel Tube Philippines

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