Max Cooper's RX-7 Web Site www.maxcooper.com
GalleryParts InformationVendorsMy CarHow-ToLinksSearchContents

 

This document has the following structure:

Tools

I recommend the following tools for this job:

  • Sears Craftsman Handi-Cut cutters for cutting the hose cleanly. If you do not cut the hose cleanly, it can split.
  • Small diagonal pliers (dikes) are useful for cutting stubborn hoses that refuse to come off and for cutting the tails off the cable ties.
  • Small long-nose pliers can be used to twist the small hoses to break them free before disconnecting them. You can also cover them with cloth or pull on taped hoses to help install new hoses in tight quarters, being careful not to damage the hose. Use these to pull the tails of cable ties and to hold onto them when cutting so you don't lose the tail in the engine compartment.
  • A standard screwdriver is useful for holding the cable tie in place as you pull the tail to tighten it. You can also use a screwdriver to pry hoses and electrical connectors loose.
  • Masking tape can used to cover up the turbo and intake manifold holes so you don't drop anything in. It is also useful for wrapping hoses before you install them in tight quarters to keep the walls of the hose rigid. You can also pull on the tape if you make a tab to grip with some pliers.

Materials

Cable Ties 

Update July 7, 2001:

I used to have some info here about what cable ties would stand up to the underhood temps on the RX-7. However, I no longer think that any kind of clamp, glue, or cable tie is necessary or desirable for holding the hoses on. I have been replacing some hoses on my car as I do various repairs and upgrades and the cable ties don't seem to help much. I have been running many of the hoses without cable ties for quite a while and I haven't had any pop off. The only exception to this recommendation is for the connections to the black plastic pressure chamber near the flattened pipe between the y-pipe and intercooler (with the stock plumbing in place). I recommend using a cable tie for each of those connections, and that a "normal" cable tie from the hardware store or auto parts store is sufficient because the connection is easy to fix if the cable tie fails. It might be hard to accept this recommendation, but it works on my car, and you can avoid a lot of hassle by not using cable ties.

Hose

Executive Summary

Buy 30 feet of 4 mm hose and 8 feet (15 if you are installing a manual boost control) of 6 mm hose from Peter Farrell Supercars (PFS) [(703) 368-7959], Baker Precision [(800) 959-7757], or MazdaTrix [(562) 426-7960]. Or consider some Viton tubing; see the updates below.

Update March 13, 2000:

Mike Putnam posted some information to the RX-7 list about Fluorine Rubber tubing that makes it seem like a good choice. Its main advantage over silicone is the abrasion and kink resistance. Here is some additional information:

  • (Sold under various trade names such as Viton, Fluran, etc.
    I think that Pettit sells Good Year's version of this tubing)
  • Operating temp -25 F to 400 F
  • Resistant to oil grease and solvents
  • Durometer Shore A hardness 60
  • kink resistance - good
  • abrasion and cut resistance - good
  • Spring clamps can be used for securing. ($0.20/clamp at Home Depot)
  • Comes only in black
  • Not available at most auto supply stores/catalogs
  • Cost (from tubing/hose supply catalog) $1.44/ft

Update July 7, 2001:

Mike Putnam has put together some excellent information on tubing materials that I suggest you read before deciding on silicone. The URL for the page with links to the documents is http://www.geocities.com/MotorCity/Garage/8255/technical.html.

I tried some thin-walled Viton tubing to see if it would work in the interest of saving money. However, I quickly concluded that it was too thin and would kink too easily or get sucked shut under vacuum as it heated up. I tried small stainless steel springs to keep the tubing open, but it was not possible to select a spring with right diameter to fit easily into the tubing but not enter the nipples I was connecting the tubing to. The bottom line is that I concur with Mike's sizing recommendations -- thinner, cheaper tubing just does not work.

Quantity

I recommend 25-30 feet of the 3.5 mm or 4 mm hose if you want to do them all and make a few mistakes. You need about 8 feet of the 6 mm hose, unless you plan to replace the pills in the wastegate and turbo pre-control lines with bleed valves. If you are adding the valves, get 15 feet. Get a bunch extra if you plan to do more work on the car in the future. Perhaps 50 ft of the small stuff and 20 feet of the bigger stuff would be good.

Gaskets

You may need to replace the throttle body gasket (N3A1-13-665 $12.95), the extension manifold gasket (N3A1-13-112 $12.10), and the inlet gasket on the first turbo (N3A1-13-712 $6.85).

Replacing Broken Parts

Solenoids

You many need to replace solenoids if you break them, or find that they are broken or non-functional. These can be purchased from your local Mazda dealer or from owners that have removed the valves from their cars. I broke the double throttle control system solenoid (1480-13-240A) while I was removing my manifold (be careful!) and it cost me $51.55 for a new one from the dealer.

Depending on the function of the valve, you may consider eliminating it from your system. If you remove the valve entirely, you will need to install a resistor so that the ECU does not report an error condition.

Check Valves

I found several check valves to be either broken or questionable during my hose replacement job. The metal one connected to the purge control solenoid flowed air both ways, and I got a replacement (NF01-13-890) from the Mazda dealer for $16.20. Two of the plastic ones behaved strangely, while still providing the check function. One made noise when I blew through it in the passing direction and the other just seemed very hard to blow through. I heard one report that someone witnessed the same restricted flow behavior, but that the new replacement they got from the dealer was also hard to blow through. Nonetheless, I am replacing them with some generic check valves that I got at my local auto parts store (HELP! part #47149). I haven't run the car with them yet, so I will have to report back on how they work out.

Update March 13, 2000:

One of my cheap check valves failed! The one that is under the pressure chamber at the top center of the engine flows freely in both directions now. It lasted about 10,000 miles, but it probably is not worth the cost savings for these parts since they are hard to diagnose when failures occur. I recommend using the OEM parts instead. It appeared to be some combination of heat and oil that killed it.

 

 

The information on this page is Copyright 1999-2002 Max Cooper
If you have any questions or comments about this page, send email to: rx7@maxcooper.com