Lessons learnt so far....



WARNING: Replacing the fuel filter
This is a potential big gottcha. There are several sites on the web that tell you about replacing the fuel filter. But none suggest that the in-tank fuel pickup filter that is attached to the bottom of the pump should be replaced or cleaned too!

I found that I had problems with a low fuel level in the tank and the engine cutting out. The fuel filter was collapsing under the suction of the fuel pump and starving the engine. I also had a lean condition on full boost. Once I removed the pickup filter I discovered that it was hard to blow through. I managed to clean it with detergent and water pressure, but eventually decided to replace it (only $NZ30 from Mazda).

This is a serious problem, and I suspect is the cause of many high milage RX-7's failing with detonation. My car had done 140,000K's, I know of at least one other car with similar K's that had the same problem. Have you checked yours?

Frozen Air Pump
The previous owner had disconnected the wire to the air pump. I reconnected it and immediately stalled the belt, which caused a plume of smoke as the engine was still turning over! So I stripped the pump down to find it badly corroded inside. I believe the corrosion was caused by moisture rising back up the pipe from the cat'. I have now removed the old clogged cat', so there is no need for the air pump. The pump was 5Kg of dead weight, so it's been removed.

Remember to block off the pipe it plugged into. I also blocked the pipe that is used by the emissions control because it caused a lumpy idle, this is the top hose that takes air from the air filter to a valve behind the intake manifold.

Removing the Down Pipe
Hmmm, reading FAQ's off the net make this look easy, just watch out for rusted nuts on the heat shields! (plan ahead with some CRC) But those FAQ's are written for left hand drive! So for right hand drive... mark the splines on the steering shaft with twink, and remove the shaft before you lose some knuckle skin!!

Removing Gear Box
The real gotcha with removing the gear box was to watch out for the engine sag. There are excellent FAQ's on this job, but they fail to mention that the engine is held in position by two engine mounts and the gear box. With the gear box removed the engine will tilt forward and stress all the hoses etc. around the engine. You can get away with putting a jack under the sump, but preferably you should lift the engine with a block and tackle or similar to suspend it while you have the gear box out.

Remember the best way is to unbolt the clutch pressure plate from the fly wheel before removing the gear box. I managed to get the whole job done on my own with the car on axle stands. With a bit of luck, I managed to put the gear box back in one hit using a jack to balance it on.

Replacing Rear Brake Pads
This had me going for a while, but I finally found an FAQ on the web. I thought it would be worth while mentioning it here. Basically when you remove the old pads, you need to retract the pistons. Push as hard as you like, it's not going to happen! The pistons are on a thread that is pushed by the hand brake. You simply take some long nose pliers and screw the piston in :-) Don't forget to open the bleed nipple to stop old fluid going back through the system. Also make sure that the grooves in the piston end up horizontal, as the pads have a lug that sits in the groove.

New front disc brake rotors
I guess the previous owner of my car had a few panic stops :-)

The rotors were down to the minimum width, and had hot spots. Normal braking was OK, but as soon as the rotors heated up they warped. Not a nice feeling. I chose to get standard Mazda rotors. No grooves and no drilling. I don't want to weaken them and the new pads are not going to eat them. I'll let you know how they survive the race track.

Update: They survived OK, but I did get them smoking. With two people in the car, I think I pushed them to the limit and even though I had DOT 5.1 fluid, I still got brake fade. I think the brakes are going to be a project all on their own. Ideally now that I have the 17” RS wheels, I should get my hands on a set of RS big brakes! :-)

Suspension bushes
Clunk, thud, clak, clunk. Hmmm that doesn't sound too good.

A common fault with the FD suspension is that it gets a bit noisy over time.

While putting in the new shocks and springs I took the opportunity to replace the rear upper outer bushes, and the front upper inner bushes.

The rear hubs are held by three steel swivel bushes, the upper one is load bearing because the upper arm has the shock and spring off it. Once replaced, the ride quality was significantly improved. With a bit of patience, and a gear puller (really need a proper press) I managed the job with only a few cuts an blisters.

A problem with the pre '93 models was the front A arm bushes. Mazda did do a recall, but I guess my car was missed out (from what I hear, there were a lot missed out). The old bushes were a simple nylon bush held in place by some pressed inserts. Over time the inserts moved and gave a fore/aft movement with a clunk. The new bushes are of a swivel design and are much more solid. I managed to press the old ones out and put in news ones with the gear puller, while keeping the A arm attached to the hub.

A satisfying job, with a noticeable result.

New O2 sensor
What's the deal here? Well, my car has done 110,000 km's and the O2 sensor is a little tired. I have wired up an LED bar graph using an LM3914. I have calibrated it to show 0.82v right on the cusp of a green and yellow LED, and to swing from 0.65v to 1.1v. This voltage range is all I am interested in. At WOT, the green LED at approx. 0.95v is typically what I see. This is good :-)

With the new O2 sensor, the reaction time of the LEDs has noticeable increased. Also when cruising around town, the car used to hunt, but with the faster reacting sensor the car runs much smoother.
 

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