Permission to publish this article is provided generously by Robin Sun at www.p-car.com. Be sure to visit his site for loads of 993 info!
This DIY provides a relatively easy way to clean the secondary air injection (SAI) ports and replace the SAI check valve. The car is a 96 993 with 40,000 miles. The car is stock except for a K&N cone air filter. The parts cost about $200. The job took about 6 hours, but this was done with the car on a lift. (Photo 1) I suspect doing this with the car on jack stands would take longer.
The basic procedure is to put solvent and compressed air into the SAI system on the top of the engine and clean the ports from the bottom until air runs freely through the passages.
Before you get started, you will need some parts, supplies, and two custom made tools. The parts needed are: 1 SAI check valve, 6 gaskets that go between the heat exchanger and the head, 12 lock nuts to fasten the heat exchanger to the head, and two gaskets that go between the heat exchanger and the center portion of the exhaust. (Photo 2) A note when ordering these two gaskets: according to the dealer, the exhaust will have stamped on it either ?Gillet? or ?Bischoff?. It matters because each type takes a different gasket. You will also need a plastic or PVC 1/2 inch barbed fitting, available at any hardware store. (Photo 3)
The supplies you will need two bottle of carburetor cleaner.
(Carburetor cleaner method suggested by
Besides the normal wrenches, sockets, and screwdrivers, you will need to make two special tools, which will be discussed later.
The first step is to remove the air cleaner assembly. In my case, it was very easy because of the cone-style K&N filter. (Photo 4)
Photo 5 is what you should be looking at with the air cleaner assembly removed.
The check valve is located between the forward-most intake runner and the chrome-looking pipe with two 90 degree bends in it. (Photo 6)
Next loosen the hose clamp and remove the rubber hose on top of the check valve. It?s ok to pry up on the hose with a screwdriver against the intake manifold, but DO NOT pry against the chrome-looking pipe, as it is relatively fragile. Prop the rubber hose out of the way.
The next step is to remove the check valve. This is easier said, than done. You will need to modify an opened end wrench to fit the check valve. I started with an old 15/16 ? wrench and, with a bench grinder, ground the opening until it fit the check valve. The two ?fingers? that fit around the hexagon-shaped part of the check valve must also be ground down until they will fit between the upper portion of the check valve and the housing the check valve fits into. Finally, the wrench must be heated up and bent in two places. (Photos 7 & 8)
Reach the wrench in under the chrome-looking pipe and loosen the check valve. (Photo (9) Relax, the hard part is over.
Now it is time to make the second tool. Take the old check valve and separate the two halves. If you look closely, you?ll see that there is a seam in the middle where the edge of the top folds around the edge of the bottom. Separate the two halves by grinding off the folded over part. (Photo 10)
Now hammer the PVC barbed fitting into the bottom half of the check valve. (Photo 8)
Next screw the check valve/PVC fitting back into the hole it came out of. This is where you will pour in the Techron and blow in the compressed air. (Photo 11)
Remove the heater supply tubes. (Photos 12, 13 & 14)
Remove the heat exchangers. (Photos 15 & 16)
Now that the heat exchangers are off, you can look into the exhaust port of each head and actually see the SAI ports. These are holes about a quarter inch in diameter near the exhaust guide. Clean them out and clean the carbon from around the port. I stuck baling wire up into the port, sprayed carb cleaner into the port, scraped carbon from around the port with a flat screwdriver, and used a small wire brush. My ports were not plugged up so there wasn?t that much work to do. Your ports may require more work.
Pour some Techron into the PVC fitting. Don?t put too much in. It may splash back out. Blow air into the PVC fitting to help force the Techron through the passages. The PVC fitting is important because it allows the rubber end of the air nozzle a place to seal up against so that you can force the compressed air through the passages. (Photos 17 & 18)
Repeat this process until the compressed air blows out of all 6 of the SAI ports. If necessary, you can plug up five of the ports with used chewing gum, which will direct all of the compressed air to one port. I know this sound kind of hokey, but it worked. I?ve heard this described as kind of like plugging one nostril and blowing out the other. Work your way around until all of the nostrils, I mean ports, are clear. Blow compressed air through the system until the ports are dry.
Once everything is clean and dry, replace the heat exchangers using new gaskets and lock nuts. Replace the heat supply tubes.
Install the new check valve. Replace the rubber hose onto the top of the check valve and tighten the hose clamp. Feel up along the forward side of the rubber hose. There is something else in the hose just above the check valve that a much smaller rubber hose plugs into. (Look at Photo 12 just above the gray PVC fitting.) Make sure that the small rubber hose is hooked up. Mine came undone when I pushed the larger rubber hose out of the way.
Replace the air filter assembly, and you?re all done.
Additional information contributed by Bill Nobel on 6/5/06
993 SAI repair article is well written and helpful, here are a few more
helpful points that you could drop in if you care to:
Tools needed -
a 7 mm swivel socket, 1/4 inch drive is very helpful in loosening the hose clamps that are in out of the way places - it's so much easier than a screw driver
making the SAI check valve removal tool using a 1" crowfoot is by far the better choice. Grind to 27 mm, and thin it down until it fits - I used a crafstman crowfoot - the metal was too hard for my milling machine so I had to grind it by hand, nonetheless, with a caliper it was not hard to get it within 0.1 mm of 27, and thin enough (about 10 mm). Room is quite constrained in there so the crowfoot gives you more choices on how to attack things than a bent open end wrench.
a long (11 inch or so) 1/4 inch extension is very handy with the 7 mm swivel socket to loosen the clamp that holds the mass air flow sensor in place - you need to loosen that to rotate the sensor to unlock it from the air
be sure to have several 3/8 extensions available - a long one for the nuts that hold the heat exchanger to the head, and several shorter ones (and a swivel) to get the upper bolt on each side of the connection to the catalytic converter off.
on my car, I had to remove the sway bar to be able to get the driver's side heat exchanger off - but this may not apply to other cars. if you find the sway bar is in the way, just remove the 4 bolts that hold it to the frame (don't disconnect from the suspension) and slide off the rubber bushing and you should have enough clearance.
I found that carburetter cleaner sprayed into each of the SAI orofices was pretty good at loosening carbon deposits. I used 160 psi air blown through the SAI port to make sure all was clear - I plugged each port but one with newspaper and then made sure that the unplugged port blew air. I'm not at all sure that using the fuel injector cleaner does anything except let you see that the passage way is open - in my one attempt, the carburettor cleaner did all the work. NOTE - FOR SAFETY, wear eye protection when you are blowing the carb cleaner into the ports - you really really don't want that stuff to drip into your eyes.
on reassembly, use a small amount of sticky grease (two dots, 180 degrees apart) in each slot in the head to hold the head to heat exchanger sealing rings in place while you lift the heat exchanger into place. The grease will burn off when you start the engine, so don't use very much.
When you reassemble one side, put just two nuts in place to hold the heat exchanger as loosely as possible to the head, and then get the seal to the catalytic converter in place - if you try to do this after everything is tight, it's much harder. Also, be sure that the rubber hose that goes into the top of the heat exchanger is in place so you don't have to fight it later.
Additional information from webmaster added on 6/5/06
Regarding removal of a stuck SAI valve, one of the most difficult part of this DIY is to remove a stuck on SAI valve. As the location of the SAI do not give you too much access, some have even damaged the manifold and surrounding pipes while trying to remove a stuck on SAI valve.
I suffered the same fate when I tried to remove my stuck on SAI valve, spend 2-3 night of trying different tools and method, finally the valve started to become weak around the body and I was able to break the valve off above the nut area. Afterwards I was able to stuck on a 27mm socket and able to turn loose the stuck on valve.