Hi all, I have a strange rattle I cannot diagnose.

 

I drive a Ke74 Corolla, 5kj engine and T40 box, there is a rattle when decelerating. I can't tell if it is coming from the drivetrain or the engine... it only seems to happen in 3rd or 4th gear, when decelerating and completely off throttle between 4000 - 3000rpm. Adding a little throttle or clutch in ever so slightly and the noise goes away. Could it be a lean condition when off throttle? A bearing in the gearbox?

 

Cheers for any input, Ol.

Have you checked your gearbox and engine mounts condition and tightness?

 

Have you checked it isn't an exhaust or heat shield rattle?

Unlikely to be a g'box bearing unless you could already hear it with the driver's door open at idle. If it rattles then just push the clutch in and see if it vanishes. Usually g'box bearings whine & growl, and often vanish in 4th gear.

 

When you lift off the car is pushing the motor, so it does rotate it a little the opposite way. Hence the mounts comment above. Another one is the driveshaft being pushes back against its UJs, so check the UJs carefully.

 

What sort of rattle?? Fast or slow?? Engine rpm? Rattley like a tappet or tinny, like a heat shield??

 

The "clutch in" is interesting. Is that disengaging the clutch, or just pushing on the pressure plate?? Just pushing on the pressure plate would load the thrust bearing, maybe that rattles at those rpm.

 

Altezzas have one as you slow down through 3000 to 2800rpm, its very distinct. Caused by some resonance in the flywheel it seems. Most of my rolla ones have been heat shields or similar.

Unlikely to be a g'box bearing unless you could already hear it with the driver's door open at idle. If it rattles then just push the clutch in and see if it vanishes. Usually g'box bearings whine & growl, and often vanish in 4th gear.

 

It can't be heard at idle, the bearings do rumble a little, but never rattle at idle.

 

What sort of rattle?? Fast or slow?? Engine rpm? Rattley like a tappet or tinny, like a heat shield??

 

It's definitely not heat shield, because that also rattles and I haven't got round to fixing it. It's a distinctly different sound. Nor is it hammering like a tappet. It honestly sounds similar to pinging, high pitched and fast.

 

The "clutch in" is interesting. Is that disengaging the clutch, or just pushing on the pressure plate?? Just pushing on the pressure plate would load the thrust bearing, maybe that rattles at those rpm.

 

Just pushing on the pressure plate, so yes, could be that. I may be swapping out for a 5speed soon, so I'll find out then

 

Cheers for the input.

I have had a similar sound in the past making the noise backing off in gear above 2500 rpm and took ages to track it down, ended up being clutch plate springs loose,