C2/C4 Technical Stuff

Below are some of the things that I have done to my car

I backed my 911 out of the garage one morning and noticed a sizeable puddle on the garage floor where the front of the car sits. My first thought was a leaky front differential and I immediately got that terrible feeling in my gut. When I inspected the fluid it was brake fluid. I was able to determine that the leak was coming from the green anodized pressure warning switch that screws into the hydraulic servo pump up by the front bumper (see picture).

Others had told me that this part had some problems and was superseded by a newer switch. Located on the switch is an O-ring and I thought I would try one of those before spending $179 for a new pressure switch. I bought the O-ring, part # 999-707-094-40 at my local dealer for $2.25. It still leaked so I bought a new pressure warning switch part # 964-606-904-00. To do the swap you first need to relieve the pressure in the system by pumping the brake, with the key off, until the brake pedal gets very firm; approx. 30 times. You can then proceed by removing the lower black line that connects to the bottom right of the pump. First, remove a small set pin located under the black line. Pull the black line off and get it up over the brake fluid fill reservoir quickly and it will not drain much. I first clamped the line to minimize spillage. Next remove the high-pressure steel line with an appropriate 11mm brake line wrench. Next, undo the two electrical plugs. You will then be able to loosen the single mounting bolt (12mm) and remove the pump from the car. Put the pump in a vise and break out Porsche special tool 9524. It's basically a 35mm or 32mm (can't remember which) deep socket. Put the socket over the green switch to undo. Lube the new O-ring with brake fluid only and install the new switch, tightening to 19 ft./lbs. Re-install pump and hook up the lines. Connect the top electrical plug ONLY at this time. DO NOT connect bottom electrical plug yet. It is now time to bleed the pump. Locate the black metal hydraulic reservoir located in the lower part of the trunk just to the left (as your looking at it) of the ABS module. You will notice a bleed nipple with a rubber cap on it. Remove the cap and attach a tube to it running it out of the car and into an appropriate container. Open the bleed nipple with a 9mm wrench. Now turn your key to the on position. Go back to the pump and while firmly holding the bleed tube with one hand, temporarily plug the bottom electrical plug in to get the pump running. Fluid will quickly exit the bleed tube so be careful. Only run the pump for a couple seconds at a time by pulling the plug in and out. Once you get all of the air out and the tube is free of air bubbles close the bleed nipple. CAUTION!! This pump system has an operating pressure of 180 bar, or 2,600psi!! Be very, very careful. Wear protective eyewear, gloves, etc. Ever see what a pressure washer can do to wood or concrete? Do not open that bleed nipple if it is under full pressure. You're just about ready to go now. Make sure you get any spilled fluid up because it will eat away the paint. Top off the brake fluid if necessary and make sure everything is back together. Good luck!

From 1987 on, 911's have had a feature that lets you control the windows and sunroof in your car after you turn your key off. This feature is disabled as soon as you open a door and an interior light comes on. I was having a problem with dead batteries in colder weather when I let my car sit for more than 24 hours. What happened is that my door switches were getting tired and in the cold weather they became less reluctant to move like they were designed to. It would sometimes take 15 seconds or so for the spring in the switch to trip the lights after I had opened a door. Because my lights didn't switch on while exiting the car, it assumed I was still sitting in it thus keeping the window and sunroof circuits on. This would drain my battery by morning. The fix was to replace both door switches. My interior lights now come on within a second or two, even in very cold temps. The part numbers are as follows; you will need two of each:

964-613-147-00 switch $4.14

901-615-615-20 washer $1.62

900-031-001-60 washer $0.12

901-615-616-20 rubber cover $1.89

I was using a battery that had some dead cells in it for about a year. After the door switch fiasco it was time for a new one. The 964's use a group 48 battery. The dealership wanted an arm and a leg for a Porsche brand and the Optima batteries were also expensive. I went to my local AutoZone and purchased their group 48 Duralast battery for $59.99. It has a two-year replacement warranty and a 7-year prorated warranty. It sits in the 911 mounting bracket perfectly. The 911 now cranks over much more quickly. The AutoZone battery is also a great deal lighter then the factory Porsche battery.

Not that this is very technical but I did swap my black Carrera 4 script for a silver Carrera 4 script from the 993 series. The swap came after I broke the original black emblem at the "C" while drying the car with a towel. The 993 script is a little less wide than the 964 series. I wanted to try the silver script because the black is so hard to see. Also my car is blue with polished wheels. The silver script is a nice compliment. In my opinion it looks 1000% better. The part number for the silver "Carrera" is 993-559-237-02-4PU. The "4" part number is 993-559-241-01-4PU. To remove the old emblem, take a piece of dental floss and pull it through the emblem. This works best on a hot day but you can use a hair dryer if need be. After removing the old emblem carefully remove any dirt and abrasives with some soapy water and a sponge before trying to remove the excess double back sticky tape. After all the tape was gone I hit the rear deck with a buffer and some polishing compound. I could still see the outline of the old script and was able to use it for reference when installing the new shorter script. The old outline is still barely visible under certain light conditions and only if I'm looking for it. The outline is left from the paint, which has not seen the effects of UV light on it. I assume that over the course of a year the unexposed paint will blend into the surrounding areas.

I was having a problem with my engine loosing rpms and stalling when I would push in the clutch and let the revs drop. If I had the single mass flywheel set up this can be expected, but I do not. With help from fellow 964 owners I tried replacing my DME relay. The relay is located in the fuse box panel under the hood on the passenger's side. The original relay had a part number that began with a 944 number. The new relay has a part number of 993-615-227-00 so it is an updated part. The swap takes less than one minute and all is better now. It is a good idea to keep an extra spare relay in your 911 at all times as this under $17.91 part has left many 911 owners stranded.

Paint Job:

In November of 2000 I was at a local restaurant and as hard as I try to find the perfect spot where I can take up a good space with lots of room, someone backed into my 911. The guy who hit it actually came back into the restaurant and found me, God bless him. I got his insurance info and a day or two later a quote from Stoddard for the repair which was just under $1,000. I then took the 911 to a local paint shop that I have used several times in the past. He would be the only one, other than Stoddard, whom I would trust with the car. This guy has won our local Auto-Rama show the last two years for his paint work on 50's and 60's cars. When I first purchased my C4 there was some paint work to both rear quarter panels from the previous owner backing into a narrow space, which he didn't fit. Believe me those turbo fenders really stick out. The previous owner had the work done by Fred Baker Porsche here in Cleveland. The paint job was terrible to say the least. I swear they used color 38B Maritimblau instead of the 37U Cobaltblau. There was also some specks and fisheye in the paint. So I wanted to get the paint on the rear quarter panels corrected while it was in for the back end. Also, with 50K miles on the odometer my hood had some pretty good battle scars in the form of rock chips; I wanted the hood re-sprayed as well. About a day later the paint shop calls and basically says that every panel except the roof was going to get sprayed. He was doing the entire rear end (trunk and bumper), the rear quarters, which would be blended into the doors, and spraying the hood which would be blended into the front quarters. There was a lot of blending involved so he offered a suggestion. He asked if I would consider an entire paint job for a professional look. I do have an excellent eye for paint and he said that a keen eye would certainly be able to pick up the blending under certain light conditions. We talked back and forth on price and arrived at an excellent deal. I referred at least a dozen customers to this guy's shop over the year so that was my trump card. I was about to pay about 1/5^th of what Stoddard would have charged for a full re-paint. He knows what Stoddard charges as his father-in-law was the head body man at Stoddard one time. So I said yes. I visited the car just about every other day for the next 29 days that it took. The bumpers were removed, lower body cladding, glass, mirrors, door handles, wipers, rear wing and all body moldings and gaskets. The entire car was sanded down and spots filled in where needed. The car looked like hell. Then the paint went on, same factory cobalt blue metallic, using the PPG paint system. 5 coats of clear were put on. After wet sanding it with 1500 and rubbing it out using the new 3M System III it looked like it was ready for the showroom. I used new gaskets between the front fenders and cowl, as the old one looked terrible. The 4 pieces of StoneGuard for the turbo-look were close to $200. I went with the silver 993 Carrera 4 script again. Overall I feel the car is in much better condition, the old mismatched paint was really embarrassing at times, especially on a sunny day. I think the color is a shade darker if anything but even I can barely tell. Then again perhaps that was the original color without the 7 years of sunlight to fade the paint. It even has that slight purple hue to it at times that the original paint had, and which the Fred Baker previous owner fix it job lacked.

Anyone have a clue as to these numbers I found when the rear bumper was removed? My only guess is production of the 26^th week of 1992. My door jam has a build date of 2-93.