Strange engine/tranny noise, need diagnosis help

[NStone79]

So my '07 3s problem child has developed yet another problem... after on 'n off driving around town for about an hour a strange noise developed. Here's the symptoms...

- Rather loud clank/rattle at startup (sounds like exhaust vibrating against body, but ive checked the exhaust). Goes away real quick, probably 1sec in duration.

- Strange whine/subtle grind noise when clutch is pressed in during gear shifts. Performing the shift quickly (ie, pushing the clutch as little as possible) reduces the noise

- Loudest whine when transmission is under reverse load with clutch in, eg. engine braking, but noise goes away with clutch all the way depressed or tranny put in neutrel

- Noise is speed dependent not RPM dependent

- Noise appears to be transmitted through the body and seems louder inside the car than out


Anyone have any ideas? I had the clutch done at Mazda 8mo/10k miles ago, and the damn original clutch only lasted 50k, so I hope it isn't a tranny issue. Could this be a motor mount? I really want to get a good grasp on this before taking it in to the stealership and getting screwed again.

 

[sick_role]

def check the motor mount. I used to have a 3s. clutch was fine...motor mount not so much. I can't say for sure with the "driving" symptoms you are hearing because I stopped driving mine as soon as i knew something was wrong. Mazda ended up replacing two mounts. stop driving it and check the mounts. That "exhaust vibrating against body" might just be your motor...

 

[NStone79]

Ive determined that the noise has always been there it was just really quite before & now its a whole lot louder. U know that gear whine you get when u downshifting, well its the same noise, just before it sounded really muted like there was some sound insulation on the backside of the firewall. Now its much louder and seems to be coming thru the body, almost like a whole bunch of sound insulation was removed. The heat shield is intact, and there isn't much else between the engine & passenger compartment.

What are the symptoms of an engine mount failure? Is it obvious when the mount fails? Should I be able to see a physical deformity in the rubber insert?

 

[Darth Vader]

The thing is, if the trans mount fails, the engine drops on your halfshaft, destroying that too.

You need to pull the battery box/ECM combo to inspect the thing. It's not as hard as it sounds and you'll be able to see the mount then. It'll be obvious if it's busted.

As for rattles on startup, check the camchain tension by sticking your finger down the oil fill and pushing on the chain. Any deflection here indicates a possible VVT actuator failure and needs immediate attention.

Grinding sounds on clutch actuation could indicate a throwout bearing problem.

You changed out the trans fluid and inspected it? Your problems may be internal to the transmission.

 

[NStone79]

I've come to the conclusion that it is the clutch throwout bearing that is the issue. Overall the car drives just as well as it ever did and the symptoms are all noise related. My next question is this: I had a new clutch put in 8mo/10k mi ago by the dealer. Shouldn't the throwout bearing have been replaced at that time? and therefore be covered under the 1 year warranty on the dealers clutch work?

 

[ras]

Not sure about the throw bearing, but call another dealer in the area and ask them or a local transmission shop. That way if you find out they should have replaced it you now have some info. to go on. How much did the dealer charge you to put in the new clutch, if you don't mind me asking.