Why so loud, motor?

[MattL]

My motor is REALLY loud, even at idle. It sounds like a throttling wood chipper. Or a prop plane. Looking for some ideas/things to check, and as always with me: don't worry about hurting my pride with suggestions that seem basic to you. I have a long way to go before I reach even novice stage with this stuff. 

 

I hope this video link works:

https://photos.app.goo.gl/Mp4hVzyffSKTRmbs9

 

That's at idle, just started up. When it warms up and the choke switches off, it gets a little quieter, but not much. I don't remember things being this loud when I bought the car last summer, but that's no guarantee that it didn't. I've had it off the road for the winter and some replacements/upgrades in the brakes and suspension, but it was loud when I put it away in the fall. I haven't done anything to the engine at all since purchased besides add a couple quarts of 20W50.

 

Any ideas? I'm not big on the idea of driving a Stuka around. 

[2002Scoob]

Check that the donut gasket between the downpipe and midpipe is there, and that the connection is tight? 

[2002Scoob]

Also, your idle seems pretty high... that sounds like 12-1300.

[MattL]

Thanks, Scoob. The choke is on in the video, but you're right: the idle is pretty high regardless. That's a jetting issue, right? 

[ingramlee]

Honestly it doesn't sound that loud to me. I would like to hear it after the choke is off. If you're comparing it to your new car you will be disappointed.

[halboyles]

16 minutes ago, 2002Scoob said:

Also, your idle seems pretty high

 

I agree with this.  It also sounds like something is loose and rattling.  Downpipe and muffler are good places to start tightening things up.  I'd also check fan/belt/alternator for noise.

[Mike Self]

34 minutes ago, halboyles said:

Downpipe and muffler are good places to start tightening things up. 

Clearance between the exhaust system and various other parts is extraordinarily close at a number of points.  Check the two hangers that support the muffler; they're supposed to have a plastic spacer that's pressed into the hanger on the muffler, with a figure 8-shaped rubber grommet fastening muffler to body.  If even one is missing, the exhaust system will start banging somewhere.  There's also an exhaust system bracket fastened to the rear of the transmission that's often missing, or at least missing its rubber mounts.  Another noise source if not properly configured. 

 

And then there are engine-related noises--loosely adjusted valves, partially blown-out exhaust manifold gasket, vacuum leaks around the intake manifold etc.

 

mike

 

 

[MattL]

I'll take a video of the motor running warmed up/choke off. In the meantime, I can say that I'm definitely not comparing it to my more modern cars. It's difficult to tell from the video, but the motor really is super loud. Tough to hear anything less than a shout over it. 

 

A big part of the noise sounded like a grinding or wearing, as opposed to untamed exhaust. Now that you mention it, though, Hal, that could be something loose too. 

 

My checklist so far:

1. Gasket between down/midpipes

2. Idle (Jets? Dizzy?)

3. Loose exhaust components and hangers

4. Fan/Belt

5. Alternator

6. Engine-related noises--loosely adjusted valves, partially blown-out exhaust manifold gasket, vacuum leaks around the intake manifold etc.

 

With the motor running, it's probably impossible to hear any of those individually, obviously. There's just too much noise. But I'll go through that list with it off. I'll also get a video of it running warmed up. Thanks, all. 

Edited March 25, 2019 by MattL

[Simeon]

Not sure if this advice has already been delivered or not but you can try running the engine (for a few seconds) with the fan belt removed to isolate the alternator and water pump from consideration. 

[Mark92131]

Actually, it sounds pretty good for that high an idle.  Valves are a little clicky, but a noisy valve is a happy valve.  The exhaust note sounds a little like it is drones, are you running stock resonator and muffler?  Here's a video of my old Pastel Blue 1975 for comparison at approximately 900 RPM idle.

 

Mark92131

 

 

[thinksound_mike]

3 hours ago, MattL said:

Thanks, Scoob. The choke is on in the video, but you're right: the idle is pretty high regardless. That's a jetting issue, right? 

It's not the jets, it's the idle speed screw that will raise or lower the rpm. Once it's warm, what's the idle at? 1k? 900? or is it higher?

 

If you do touch the idle speed screw, do it after the car is warm and the choke is off.

 

Do you have a solex or weber carb?

[2002Scoob]

It does seem to have a metallic-y sound going on on top of everything... maybe your timing chain/oil pump chain has some slack to it? Or as mentioned, maybe water pump or alternator. When did you last do a valve adjustment?

 

I notice some rust-bubbles on your nose, given thought to maybe your exhaust might have rusted out, and the extra drone is an exhaust leak?

 

 

Sent from my iPhone using Tapatalk

 

[MattL]

I'll keep that disconnect-and-isolate tactic in mind, Simeon. Thank you.

 

Thanks for the comparison vid, Mark. I still think mines pretty cacophonous, but that does make me feel a little better. (I love the sound of that sidedraft, by the way.)

 

Mike, thanks for the idle info. When I read "idle speed screw" I practically kicked myself for having forgotten that. Obviously I haven't done anything with the carb, yet. It's a Weber 32/36, though. I took off the filter housing and noticed that there's a pretty substantial gap between the housing and the carb itself. A few mms all the way around. The hole for the carb looks to have been cut out by hand...with a butter knife. No gasket or anything. 

 

I'll check again, maybe tonight, but I think the idle comes down to around 1k when it's warm. 

 

Scoob: Yeah, there's definitely a metallic-y sound. That's really the sound that's most unnerving. I'll add the timing chain/oil pump chain to the checklist. 

 

I've never done a valve adjustment myself, having only had the car for less than a year. I have the previous owner's receipts, but they only go back to 2015 and don't show an adjustment. 

 

...they did replace most of the exhaust (including resonator and muffler) with an all-new stock setup. The exhaust header looks original to the car. I've inspected it pretty closely from above and below, and haven't found any holes. Those actually aren't rust bubbles on the nose but rather plastic hole plugs, painted pastellblau. (I removed the reflectors.) The body is very solid, especially for a 40-year-old East Coast car. My departed 1974 taught me that lesson. 

 

Thanks for all the input. It's much appreciated. 

[2002Scoob]

11 hours ago, MattL said:

Scoob: Yeah, there's definitely a metallic-y sound. That's really the sound that's most unnerving. I'll add the timing chain/oil pump chain to the checklist. 

 

You could do yourself well by ordering a Mechanic's Stethoscope.

 

They're like 10-15 bucks on Amazon, or available from your local parts store. They're basically what your doctor would use to give ya a checkup, but with a long pointy metal bit on the end. 

 

They're great for pinpointing engine noises, just start poking around touching areas of the engine till you can pinpoint the loudest source, and that will tell allot. 

 

While the timing chain is pretty easy to check for slack (just pull your valve-cover after you do some googling for 'valve adjustment procedure bmw 2002 faq), checking your oil-pump chain is a PITA, and requires dropping the oil pan, which is best done out of the car on an engine stand, and at which point you've embraced scope creep and are planning on replacing a handful of things 'while you're in there'.  

 

But with a mechanic's stethoscope, you can at least prod around the the motor to see where the noises that make you uncomfortable are coming from. (hint, oil-pump is located on the lower front of the motor, so you'd wanna be prodding from under the car, below the crank pulley/front of the oil pan.)

 

Best of luck!

Edited March 26, 2019 by 2002Scoob

[Stevenc22]

Matt, check with your local car club. A seasoned 2002 guy will take 5 minutes to figure out where the problem is and to adjust the idle down a little.