Popping/Crackling Sound after build
 

http://www.youtube.com/watch?v=1sKaY...ature=youtu.be
(Might have to turn the volume up)

The noise is like a crackling, popping, tapping, creak.

I've looked above the engine for anything obvious and will be crawling underneath tomorrow. The car has been making this noise ever since I got it started after the build. I'm 99% it's not engine related, because it does it at idle and off throttle and at any rpm. I cannot hear it on throttle but that does not mean it's not there. It is really easy to hear under idle and braking because their are no other noises (like in the video) but it will make the noise in and out of gear. I heard it once while sitting idle at a light.

It's not consistent either. Does it warm and cold (ambient and operating), but not always. The previous 30 seconds of that video are me driving to 25 mph, hitting the brakes and nothing, but on the 4th try I got the sound. Again, it's easiest to hear doing the brake deal, but it does it off throttle with no brakes as well.

Anyone have any clue what that is?

Facts:
These are new parts in this build that could cause this noise.
Brand new built bottom end
949 Race Clutch
949 braided clutch line
Deleted the charcoal canister, EGR, and OEM Oil Separator system.
Both side of valve cover are VTA.

I'd say it's exhaust rattle. Happens at braking when the engine is leaning one way. Accelerate, and it torques away from whatever it's hitting. What exhaust are you running? Hopefully it's not stock so you don't have to look into shielding, but look for anything it's close to. PPF, subframe, diff, etc.

Factory MSM mani, turbo, DP, exhaust. All heat shields removed. Recently punched the cat due to it being clogged. It was very clear of debris when I was finished with it. No left over wires or anything on the inside. New Mazda Comp motor mounts. I'll check into the exhaust more tomorrow.

Edit: I will add it sounds the rattle is coming from around the back of the engine.

I took a look at all of the exhaust components and didn't see anything that could be hitting to make that noise. On the brakes it's basically a guarantee. Off throttle is 75/25. It's not the brakes though. Wierdest F'in noise. I'm going to zip time the go pro in the engine bay to see if that helps me figure it out.

Any other ideas?

I know!

It's possible, but it just doesn't sound like it could be clutch related.

Tha shi is noisy as fu

When you hear the noise, try puttin the clutch pedal in. If it goes away it is clutch.

So the list of the updated yes/no conditions
1. Does - Off Throttle Coast (any rpm)
2. Does - During Braking with engine running in gear, in neutral, and with the clutch in.
3. Does Not -during braking with the engine turned off in neutral or with the clutch in.
4. Does Not - Free reving or free fall
5. Does Not - Acceleration

Today it made a ticking noise based on road speed for just a brief moment (5-10 secs) and then the original ticking noise based on the above conditions came back. The road speed noise started at about 20mph and stayed around until 40 or so until I lifted.. The road speed noise never came back all the way to work.

I have been under the car and through the engine bay and isolated anything that I thought might rattle.

Forgot to mention that this is a transmission from FM that is "new to me" as well. My original transmission was the OEM 2004 MSM 6-speed. It was replaced with a 2000 6-speed.

Based on the above conditions, I am stumped where it could be coming from. They all seem to point to a different answer and be canceled by a different set of conditions.

Car has no loss in power or other noticable quirks.

Update. Inspected the exhaust, pulled the transmission to check out the new clutch. I thought maybe that bolt that holds the transmission sandwich plate to the block might have backed out. Double checked the motor mounts, the manifolds, checked for things rubbing the steering shaft. Have nearly everything isolated from vibration. Still haven't found the noise and I'm running out ideas. I guess I'll have to pull the pan next and take a look. Really hate to do that though unless it's 100% the cause.

New video from inside the car: http://youtu.be/Elhit8GBMc4
This video starts at 50 mph (briefly), clutch in, out of gear, clutch out. Let revs fall to idle (~1000rpm). Begin Braking to 0. The engine was at idle during the entire noise.

So it only made the noise when you let the clutch out?


If I may ask, why did you swap the orig. 6spd for a 2000yr 6spd?

Hmm. that does not sound like the various twindisc clutch noises actually.

Pic of engine bay please

Also I would do a compression test for "justincase"

It has no relation to clutch position. Primarily under in gear coasting and during braking (in or out of gear)

I removed the original 6speed because I fried a perfectly good transmission. Apparently they need lube.

I haven't run compression numbers yet because the motor feels incredibly healthy. Pulls hard. I guess I'll do it for "just in case".

So it's not RPM dependent. It's not load dependent. It's not clutch position dependent. Strange. Watch your RPMs next time you hear it and see if they are low/drooping. I know when I get idle droop, I get increased clutch chatter/noise.

From what I could hear, it almost sounded like a cooling fan contacting something...but I don't know how likely that is. Have you checked the tightness of the engine mount bolts/assembly?


BTW- looking at your list of mods, I hope by "charcoal canister delete" you don't mean the canister by the intake manifold. On NBs, that is a fuel catch can kinda deal, the coal canister is a shoe box sized item o nthe pass side, behind the rear wheel.

https://www.miataturbo.net/attachmen...ine=1329973689
https://www.miataturbo.net/attachmen...ine=1329973689
https://www.miataturbo.net/attachmen...ine=1329973689
https://www.miataturbo.net/attachmen...ine=1329973689
https://www.miataturbo.net/attachmen...ine=1329973689

Engine pics as requested. 2 hoses that are off of the Valve cover are not hooked up to anything in that picture. I have them pointed to the ground right now. I am getting a decent amount of water vapor from hot side. I think it was the air condensing in my catch bottles. The valve is still in place on the cold side. No flow through it at all. The excessive number of zip ties, is my trying to make sure nothing is rubbing anywhere.

Ran compression numbers all mid-upper 150's dry and low 160's when wet. Cylinder 3 was 170 wet.

The charcoal canister I got rid of was the same as this guys:
https://www.miataturbo.net/attachmen...6&d=1318721224

I'll log the RPMs next time and see what happens but I can repeatedly make this happen idling and braking from a roll. I am starting to think this has to do with an engine pulley or something. If I turn the car off and brake like normal, there is no noise. If the car is idling and then I apply the brakes I get the noise. I did around pulleys and fans and didn't see anything that would be contacting them. I checked all of the suspension joints again. I check the mount mounts again.

WTF is going on?!

If you can reproduce the sound while idling with the brakes on, have someone sit in the car and hold the brakes while you poke around under the hood. Also, turn the lights on and the fan on full blast (without the brakes applied) to see if maybe is some strange load-based alternator problem(?). Also check the bolts that hold the water pump pulley and the 4 bolts on the front of the crank pulley. Maybe even check the tension of the belts? (belt slap sounds kinda like that).

It only makes the noise with the brakes on in motion and with the engine running (Braking and the car off makes no noise). I checked the water pump pulley last night. I tightened them, but did not check the torque spec. I need to go back and double check the torque spec so I don't get the dread water pump bolt shear. I'll check the 4 bolts on the crank pulley as well.

I think your belt slap idea is a good one. I know the belts are a little loose (squeals everyone once in awhile). I'll recheck/tighten everything up tonight and see what happens.

Also verified RPMS are not changing when the clicking begins.

At what brake pressure does it make the noise? Meaning does it do it when you are barely dragging them, or do you have to have a good amount of pressure on the pedal? It doesn't sound like the belt to me, it definitely sounds metal to metal.

Maybe its something tinging around in the oil pan...or a thrust bearing since its under braking with the engine running, and off throttle coast with it still in gear...could it be the throw out bearing?

Sorry, I understood it that with the car stopped, at idle and with the brake applied that you would get the noise as well. The wole "under braking" thing really makes it hard for me to think of a lot of other things that could make sense. You know when you will find it, the problem with be something small and ovbious lol

At lunch, I tried braking and reving the engine at the same time. The noise did not change frequency. The noise does not change it's frequency with road speed or engine speed. It isn't a constant rate. It's variable. It's not always the same rate. So that elimates anything pulley related.

Dragging the brakes doesn't make the noise come on as strong, but it does still make the noise. Moderate pressure defintely works.
I think the throwout bearing is eliminated since it makes the noise with the clutch in and out.