Pepovr

Hello everyone! I'm a 22 year old sociology student from Bulgaria and I just bought a 00 miata 1.8 with a 6 speed and a torsen diff. It runs ok and is a blast to drive but it's gonna need a lot of work as the previous owners didn't really look after it too good. It has a few problems but whats worrying me most is a very nasty metallic whine that is heard in every gear at revs under 2500 under acceleration. It disappears if i let off the throttle or go above 2500ish rpm. I hope it's not the the diff or the gerbox but something tells me its gonna be one of the two . I'm gonna check for any metal shavings in the diff oil first thing tomorrow. If anyone had similar problems or can point me in the right direction to figure it out i'll be very grateful!

sixshooter

iTrader: (12)

Usually if it is the diff it will change sounds with the ground speed. If it is the middle of the transmission it can sound differently in different gears. If it is the output side of the transmission it will change sounds with ground speed just like the differential. If it is the input side of the transmission then it will change sounds with engine RPMs.

Are you certain it is not just a vibration of the exhaust against the frame under acceleration? The rubber engine mounts are at least 16 years old.

And welcome to the forum. We have commonly contributing members in Greece, Turkey, and Slovakia but I cannot recall any in Bulgaria. The closest I've been to there is Budapest this summer.

What are your plans for the car?

ridethecliche

iTrader: (2)

I'd check for metal shavings in the diff and trans and change fluids.

Can you hear the direction the sounds coming from?

Pepovr

Thank for the quick response ! Glad to be the first bulgarian in the forum haha . My current plans for the car on the short run are to get it running just like it should and getting rid of all the nasty noises like the one i mentioned above (there's wheel bearing noises too so i'm gonna replace 1or 2 ) and to get rid of all the rust i keep on finding the more i look around. On the long run i'm hoping to boost it some day and get it close so the 200whp mark with a diy turbo kit. But right now i'm just trying to mend anything that is broken.

Pepovr

It seems to me that its coming from the gearbox. When i went under the car i noticed that the gearbox had red gasket silicone on it close to the output end so it was opened at a sertain point. Could it be from there?

Pepovr

The noise changes with the engine speed and is there in every gear. It starts when i press the gas at low revs and raises its pitch with the revs until 2,5k after whitch I don't think i can hear it. So sounds like the input side then?

ryansmoneypit

iTrader: (6)

My stock box had red silicone . I bet it's a wheel bearing, or something banging on tha chassis.

Pepovr

Ok a little progress today. Turned out there was water in the coolant system so i drained it all and got some antifreeze. Good thing i checked it because its gonna get below freezing point during the night around here pretty soon. Also found out that there is no termostat which explains why the motor runs cold during highway cruising. Checked the oil level in the tranny. As i undo the nut the oil started coming out so i guess its ok. Gonna drain it though to see for any shavings in it. Also couldn't help but notice al the rust especially on the chassis legs. Something tells me this is gonna be a long thread.

yossi126

iTrader: (6)

What you describe is a common 6 speed sound and every miata I've ever known have this including mine. Though it happens when you are in wrong gear trying to accelerate.

Pepovr

A little update. The egr pipe was loose on the intake so I decided to do a egr delete. I made a copper plug and screwed it on the exhaust manifold with the nut from the egr pipe. Right now I'm working on a block off plate for the intake side. I'll make some pictures so i can show off my fabrication skills

Pepovr

Diy metal plate

Pepovr

Good news! The noise turned out to be a blowing exhaust. It broke of after the cat yesterday and I'm planing to fabricate my own exhaust after the manifold to the back. Any suggestions on what size pipes i should use? I found 60mm stainless (2.36in) is that a good size?

sixshooter

iTrader: (12)

If turbo, we recommend 3in exhaust. If not turbo, it doesn't matter.

az-ben

That EGR blockoff plate counts as a mod. Congrats on the car.

Pepovr

Hahah, thanks. I guess I'm a tuner now

Pepovr

Could someone tell me why my tig welds look like ****? Argon not pure? I'm still learning so cut me some slack

ryansmoneypit

iTrader: (6)

Bead color looks fine, that's how it looks when it's been cooked multiple times. It's your welding. you need to practice. You clearly missed the target area on startup and probably aren't using enough amperage. I'm guessing this based on the size of the little weld beads all piled up.

put up a picture of your torch, set up and ready to weld. side and angle view.

How much amperage were you using? you are going to need 160 ish for that. that's where I would start anyway.

EDIT, on second look, amperage was probably ok. Although I don't know how long you sat to build up heat.

Pepovr

I'm using 45 amps because I don't want to melt the muffler but its not enough to melt the thicker rod. Thats why i stacked it up so much. The filler rod just won't join the surface an sits like a bubble. I'll turn up the amps tomorrow and see what's gonna happen.

az-ben

My welds would have that brown around it if I dipped the tungsten and continued welding. As for the rest of the weld, more heat. Ideally, you are melting thru the base metals and replacing them with filler material. Your weld looks like you merely heated up the material until you got a little puddle and added filler as you marginally melted the top most layer of your base metals. Keep practicing and it will click!

ryansmoneypit

iTrader: (6)

45 amps is not going to do a damn thing. like I said I would start at 160, 120 minimum . they give you a pedal so that you can back off the power as you wish, it will also add power, but it has to be available . in this instance I would start near the intersection concentrate on the hanger, get a bead started and then draw it down to the thinner material . once the first puddle is started it should be focused 90% at the hanger and just adding enough filer to get down to the thinner material .

you need to practice. 3/8" to .040 is a pretty advanced weld. certainly not an easy one to learn at first.