12 replies to this topic

[HLF]

Okay, I drove the Miata from Houston to College Station (~100 miles) for a track day at TWS a couple weekends ago. 

 

This noise started/was noticed after the second 20 minute session of driving 7/10ths. My last effort lap I noticed my temps were getting high so I backed off and left it in 5th and the temp dropped to normal in about a minute and then took a cool down lap and came off. I immediately checked oil levels and they were normal and no metal flakes on the stick. 

 

The noise is not coming from the top of the head and sounds like it is coming from behind the water pump. also, it does get louder with an increase in RPMs. I stopped tracking it after I heard the noise and trailered it back home with a rental truck and trailer. I was stuck lapping the M5 the rest of the day - yes poor me

 

I am changing the oil for the first time since that weekend on Friday or Saturday night to check for metal - fearing a spun bearing. 

 

I know diagnosing via a iPhone video sucks, but here it is: 

 

After the oil change I will report back. I plan on taking it to a shop (most likely Gas Head) for a professional diagnosis but that might be 2-3 weeks away since I'm back in school which is 8-5 M-F plus work after school and my wife now works. 

 

-Kyle

 

 

 

 

[Keith Novak]

If you don't have a stethoscope, there is an easy way to get a better idea where the noise is coming from:

[Qik Nip]

If I were guessing (and I am) I'd look at the crankshaft pulley. It's  held on by four 10 mm bolts and they have a bad habit of shearing off. If two of them are broken it will make a very scarry noise in the vicinity of the water pump.

Rick

[HLF]

Keith - my dad taught me that trick almost 15 years ago. Super helpful!

 

Qik - That one of the things I checked at the track (thanks to an experiences miata driver). They are all fine still and torqued properly. 

[steveracer]

Loosen the alternator belt and check the water pump for play.

[SaulSpeedwell]

If you don't have a stethoscope, there is an easy way to get a better idea where the noise is coming from:

 

I'm confused how holding a can of contact cement while touching the frame through a bandaged and bloodied thumb is going to be effective ...

 

So much bad information on here!!!

 

[SaulSpeedwell]

Sounds weird over iPhone, check for header leak, take spark plugs out and check for broken off tips or signs of unwanted metal "popcorn" in there.

 

Poor you, indeed, on the M5 ... people might begin to think you are "a BMW guy", just trying to look cool, with no respect for reliability and serviceability 

[HLF]

Finally got a chance to work on the car today. 

 

Loosened the belt and checked the pulleys and found that the crank main bolt was loose, not the 4 smaller ones (can't believe I didn't see this at the track when I check the 4 other bolts.

 

Tightened the crank bolt and the belt and no it runs solid and no noise. 

 

What do y'all torque that main crank bolt down to? OEM? Also, does anyone use Loctite on that bolt?

[HLF]

Also, cut the half cage out today because I got a hardtop. Finally. 

[Keith Novak]

 

What do y'all torque that main crank bolt down to? OEM? Also, does anyone use Loctite on that bolt?

The factory spec is 116-122.  I have always used a torque wrench.  I've never used a thread locker.  It's never come loose.

[HoneyBadger - BrianW]

The factory spec is 116-122.  I have always used a torque wrench.  I've never used a thread locker.  It's never come loose.

+1 I use a 1/2" air impact and have never had any issues.

[Qik Nip]

Finally got a chance to work on the car today. 

 

Loosened the belt and checked the pulleys and found that the crank main bolt was loose, not the 4 smaller ones (can't believe I didn't see this at the track when I check the 4 other bolts.

 

Tightened the crank bolt and the belt and no it runs solid and no noise. 

 

What do y'all torque that main crank bolt down to? OEM? Also, does anyone use Loctite on that bolt?

I'd take a close look at the keyway in the pulley and in the crank's nose (and the key itself). If the crank nut was loose there's a good chance that one, both or all three are now wonky.

Rick

[davew]

I'd take a close look at the keyway in the pulley and in the crank's nose (and the key itself). If the crank nut was loose there's a good chance that one, both or all three are now wonky.

Rick

 

My bet would be the key was installed wrong and that is what allowed the bolt to come loose. By now, you have probably ruined the crank and pulleys.

 

Dave