Sunday, 11 November 2001

The following is a discussion of issues and solutions to 1st gen Power Steering problems. I hope you find it interesting-- even if you don't have PS on your car.

Those who bought 1st gens new found them to be exceptionally reliable--much like today's Miata. However, compared to the Miata, the 1st gen RX-7 has more "GT" in its DNA, making it more suitable for long commutes and long distance traveling. Thus, low mileage examples are rare, and those who buy the cars used must deal with age and "use" related problems.

(Sounds like something my doctor would say, as he explains why the most recent proof that I am no longer a teenager is going to hurt for awhile, and then--maybe after a year--will go away.)

One of the less known, but still irritating problems with 1st gens is the power steering. Not many of the cars came equipped that way. I know it was an option on GSL-SEs-- possibly bundled with leather seats. There are two major parts involved, the steering box, and the pump. Seals in both wear out, and the connecting hoses also eventually leak at their ends. The result is slowly dripping ATF--usually first noticed by a few drops of red stuff on the ground under the car, or hanging off the bottom.

Donnie Peters, at Sun Auto (a mostly RX-7 "used parts emporium" and service facility near York, PA), put a new seal kit in my PS box. It has held nicely. The situation with the pump is different. I have had two seal kits put into it over the past two years, and neither has lasted very long. I am told by my local mechanic that the end play in the pump's rotating shaft is controlled by a simple circlip ("snap ring" in the shop manual). He says he has seen those things fail in this kind of pump--releasing the shaft (with the pulley on the end) to go floating forward. Donnie says the particular pumps in 1st gens don't have a record of failing that way, but both agree that it is a bad design.

I don't even want to think about it.

Once worn, it is logical to guess that a little extra play in the shaft, combined with wear, will create a situation where the red stuff can again seep past the oil seal.

Pump replacement is the logical choice, but last time I checked into it, the cost was more than a set of aftermarket wheels. I don't know if what Mazda is selling is new, or factory rebuilt (like the last starter I bought from a dealer), but I didn't want to spend that kind of money and still end up with the same problem down the road.

The other obvious solution is to swap out the power steering for manual steering. Donnie has done this operation--a labor intensive process involving a different steering column. It is at least twice as costly as replacing the pump, and you lose your power steering.

The PS system on 1st generation cars is a good one-- sensitive to vehicle speed, and with a quicker steering ratio than the manual system. I wanted to keep it.

Mazda went to a more robust pump on the 2nd gen cars--a better engineered pump with no reliability issues. Donnie proposed adapting one of those pumps for the GSL-SE. Some of the 2-gen PS systems were "engine" speed sensitive as opposed to "vehicle" speed sensitive. Most, if not all of the later cars ('89-'91) were back to "vehicle" speed sensitive, so that is the pump to use.

Transplanting the pump was not exactly plug and play. The hole through which the pump protrudes in the mounting frame needed to be larger. The pump itself is best modified to remove no-longer-used mounting brackets--to bend the filler neck so the dip stick will be accessible (if the receiving car has A/C) and to redirect the hose barb to work with the parts of the GSL-SE power steering system. A proper connecting hose must also be made to work with existing fittings.

The worst part of the project was finding a way to get the GSL-SE two-wire pressure switch to mate to the 2-gen pump. This switch is the only electrical link between the pump and the rest of the system. The sealing technology is different, and later 2-gen pumps used a one wire switch that (by experiment) did not work with the GSL-SE electronics. However, early 2-gens did use a 2-wire switch, which (of course) was not physically compatible with the later 2-gen pump. In the end, Donnie had to mate parts from two second gen pumps (one early, and one late) to get it to work. Also, they had to put the proper GSL-SE connecting plug on the end of the 2-gen pressure switch wire.

It is amazing to do this kind of thing at Donnie's place. He has been dismantling wrecked RX-7s for many years, and has a barn full of used parts. I can't imagine a Mazda dealer saying, "Let's go in the back and grab another pump from the earlier cars and see if we can't make something up." By the time the job was done to Donnie's satisfaction, we had gone through four PS pumps.

Results are good. The system feels just like it did when new, and for the first time in what seems like years, I am not trying to figure out where the red stuff is coming from. The only difference in practice is that the later pump uses Dextron II fluid, while the earlier one used "ATF Type F."

I told Donnie others might be interested in this upgrade. He says he can produce a kit using appropriate parts from two used pumps. There will also be a connecting hose, modified mounting frame, and pressure switch.

Price for the kit would be $450, and Donnie guarantees all of his used parts. I figure a good mechanic can install the kit in under two hours. Shade tree types like me would probably take half a day of head scratching, goofing off, cursing, and cleaning up spilled red stuff.

For what it's worth, Donnie has worked up fixes for other RX- 7 problems, like leaking front mounted oil coolers, bad 2-gen logicons, and switch sets. Contact info is at:

http://www.sunautorx7.com/

Addendum: 12 November 2001
I just got a note from Donnie, who read my post about upgrading the PS pump. He said:

"For the record, I agree with your local mechanic that the original pump clip often DOES become too small to hold the shaft in, and the shaft moves forward with catastrophic results."

Best wishes,
David Lane
dlane@peabody.jhu.edu
'85 GSL-SE (Cartech Turbo)http://www.wankel.net/DavidLane/