pushrod36 New Reader
6/27/12 7:45 a.m.

Alright, gumshoes. My 1990 miata started making this whirring noise (http://youtu.be/LF1uGrQtCtQ) after I did the timing belt and water pump. I have determined that it is not any of the accessories as I removed both of those belts and it still makes the noise. The noise turns into a supercharger-esc whine starting at 2500rpm and getting louder as rev's climb. I drove it into work today, and I did not notice anything wrong from the driving perspective, but it’s very unnerving.

I found a grm thread that said it’s likely from the timing belt tensioner being too tight. Last night I adjusted that again, and the noise didn’t change. I am going to post a link to the video over there, too, to see if anyone has an idea.

I've heard it suggested that perhaps the belt/tensioner/water pump need to wear in a bit. Sounds sketchy to me.

Thanks in advance for any suggestions!

Dashpot Reader
6/27/12 8:15 a.m.

Sounds like belt misalignment? You should see wear signs on the belt edge, and/or witness marks on the cover if that's the case. The belt may show slightly off center on the cam sprockets too.

Make sure your crank sprocket is fully seated because that sets the belt position. Be careful and follow the shop manual instructions closely - the '90 seems to be the one that people screw up the crank nose on...

Good Luck!

pushrod36 New Reader
6/27/12 8:22 a.m.

I found this: http://www.youtube.com/watch?v=IMT-CbtLqeU&lr=1. Skip ahead to 7 minutes, and it's the exact sound that mine is making.

I did give the crank sprocket some thought, too. I didn't remove it when I did the belt for fear of angering the key.

I'll check both items tonight.

psteav GRM+ Memberand HalfDork
6/27/12 8:25 a.m.

After I changed the T-belt on mine, it whirred for about 5,000 miles, and gradually subsided. It's now been running for 35,000 miles, no harm and the whir is no longer audible. YMMV.

dansxr2 HalfDork
6/27/12 10:03 a.m.

Possibly the Timing Gear rubbing the inside of the plastic cover lightly? Thats my guess ;-)

Jay_W Dork
6/27/12 11:21 a.m.

^ This, more than likely. Pull the cover and see if there's belt fuzz in view.

pushrod36 New Reader
6/27/12 12:00 p.m.

Will do. Thanks everyone!

I suppose that if there is belt fuzz I'd best put another one in there to ensure more miles of happy motoring.

pushrod36 New Reader
6/28/12 7:38 a.m.

I took it apart last night, and there is a bunch of dust in there, so the belt certainly seems to be rubbing. I found that one of the timing belt guides behind the crank pulley was rubbing on something, and then recalled that I guessed at the order they go back in (they all fell off when I took it apart). I assembled per this image http://www.miata.net/garage/hsue/crank/crankshaft01.jpg but it made a worse noise after that.

Does anyone know if this image is the correct order? Also, I am not sure if the black rubbery side of the large diameter guide faces the radiator or the engine.

pushrod36 New Reader
7/2/12 7:50 a.m.

After I assembled per the image in my previous post a new much worse noise started. It also flattened out the larger diameter timing belt guide plate. A new one is on the way.

I still am not sure which way the black rubber side faces. Does anyone recall?

motomoron Dork
7/2/12 10:45 a.m.

My NA did it after replacing the T-belt, cam+crank seals, water pump, belt cover seal strips.

I took the easy covers off, disconnected all accessories, checked and rechecked belt tension. I'm guessing on my 130k engine there was enough wear on the timing sprockets for a new belt to need to wear in a bit, not unlike a new bike chain on old sprockets.

Seeing this post reminds me that at some point in the ensuing couple thousand miles, it stopped doing it. Aside from a little lifter noise on cold start up, it's quiet now.

dansxr2 HalfDork
7/2/12 10:02 p.m.

Looks correct to me ;-)

pushrod36 New Reader
7/9/12 1:24 p.m.

I got everything put back together, and I'm crossing my fingers that the belt will break-in and the noise will go away. Drives OK, and with no other symptoms.

Regarding the timing belt guide plates, the larger one goes on first with the black rubber part facing the radiator. Then the small thin place, crank pulley, and finally the gold colored thicker plate.

Thanks for the help, everyone!

miatana1_6 New Reader
3/30/24 5:40 a.m.

In reply to pushrod36 :

I know I'm a bit late to the game but did you ever manage to fix this problem? Also recently changed the timing belt and have the exact same noise at minute 7:


Did the noise ever settle after a few miles?



calteg SuperDork
3/30/24 9:49 a.m.

Could also be a tension issue. You should be able to flex the t-belt very slightly by pressing down on it. 

miatana1_6 New Reader
3/30/24 10:21 a.m.

In reply to calteg :

That's what I'm thinking but it seems like any tension adjustment I used led to the same problem. Doesn't matter if I do it exactly as the manual says or by cheating a bit by moving the tensioner slightly both ways.

It might as well be the new belt, it's a dayco brand so not OEM. It's the only thing that was in stock at the time and I've been running it for a 1000 miles approx. and nothing bad happened yet, the noise is still here though.

Seems like I gotta get me a OEM belt and start the whole procedure again...

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