1989 Series 5 RX7 GTU model.

Just passed LEGIT CALI SMOG (its okay if you dont believe me )

So during cold start, car turns on without hesistation, NO SMOKE AT ALL

Now during warm up is where things get funky

- Theres a grinding/rumbling noise coming from the bottom of the car where the rear rotor meets the transmission

- Engine quirks and makes pulsing movement

- 1100-1500 RPM bouncing


now car is fully warmed up gets even weirder:

- Car no longer has RPM bouncing. Stays at a constant 1000 RPM with no hesistation

- The grinding/rumbling noise is only present SOMETIMES at a stop (red light, etc)

- Car does not burn coolant or oil EVEN AT REDLINE



Heres a few things ive tried and noticed:

- Rumbling noise also does happen going over a soft bump or a dip.
- checked heat shields to make sure everything was torqued properly.
- rumbling/grinding/pulsing noise does not happen on driving
- Just did an oil change, noticed no metallic flakes whatsoever
- I can feel the movement/grinding noise by my foot near the gas pedal
- There is NO CHANGE of the noise whether i have the clutch pressed in or not. This eliminated the thought of the throwout bearing.



Here is what i can guess:

Perhaps the tranny needs gear oil?
Perhaps the pressure plate or flywheel need servicing?
Maybe the rear rotor is going bye bye?
perhaps its combustion noise and needs tps/air idle screw adjusted properly?

Any help would be appreciated!!!

 

Check your motor mounts, if you had a dead rotor i highly doubt you would've passed emissions unless it went kapoof right after you had it done

Also, clutch parts SHOULD make noise at any rpm driving or not, but that doesn't mean anything.

If you've never changed the motor/tranny mounts thats where i would start. For piece of mind do a compression check, cheaoer and easier

 

Could be a throw out bearing. (shrug). The forum wouldn't let me use the smiley

 

compression check following this method:

Rotary Resurrection home of the budget rebuild.



nearly about 110 compression

 

i thought it was a throwout bearing too but the noise is present whether i have the clutch pedal down or not

 

Input shaft bearing? I'm not a transmission expert so...

 

update, now im thinking it may be the engine. drove for about 15 minutes and arrived home. Before turning the car off i let it sit and idle a bit

Shortly the grinding/pulsing noise came back

I turned the steering wheel (I have powersteering) and the noise went away. Left the steering wheel in one place and the noise came back?

 

sure its not the power steering pump?

 

^ yes, or air in the system. Check fluid level?

 

Is that overall? Overall pulses? One rotor? Both rotors?

 

The power steering pump on my Honda makes wicked noises at really cold temps. I think you may have found your problem.

 

Checked power steering and it looks good .

Update: now the noise has seem to have gotten worse even though I only drive the car weekends. Lots of grinding/vibration by the gas pedal. Went underneath and it looks like it's where the engine meets the transmission housing. Going to change the mounts and hope that fixes it :/

 

isolate. remove belts one at a time, until the noise ceases. if it's a belt/pulley/pump issue, the noise will cease with its affective belt removed. if it still makes noise, you're looking at a engine/drivetrain issue.
of course, before anything, look for any signs of something rubbing on anything which uses engine rotation

 

if you think its the mounts, get under there with a pry bar while the engine is running. pry up/away to see if the noise changes/lessens

 

Ok that's a good idea. I went underneath and narrowed down where the shaking was coming from. I'll remove some belts and see what results I get

 

okay so pulled off ALT belt and Powersteering belt and no change. So heres another list of what i notice:

1. its more of a pulsing
2. Grumble/grinding/whiring noise ( Cant really describe it accurately)
3. NOISE ONLY HAPPENS ON IDLE. CAR DRIVES PERFECTLY FINE
4. Going over a speed bump triggers the noise


Now im going to change out the engine mounts this weekend but hopefully this is the issue. I went under the car and i cannot move the engine too much with a bar but i can move it slightly. I did not try moving the transmission because its possible it could be a mount there too

 

Exhaust heat shield rattling?

 

thats what i assumed too but i tugged and jerked at that thing and no budge!

 

do you feel the same noise/pulsation in the shifter also?

 

could it be the drive shaft possibly???

 

Doubtful, cause he said he feel/hears the noise when it sitting and running also

 

I feel the vibration all the way through to the shifter however I know for a fact the vibration is horrid by my feet (gas pedal)

 

You could be looking at a input shaft bearing failure

 

Honestly that's what I'm hoping for. I hope it isn't the engine :/

 

Has this thing been apart before? I wonder if someone missed installing a dowel pin between the engine and transmission. That can cause huge problems down the road.