bruce7

DIY - Changing the SAI Check Valve

Without going into the whole SAI issue, which has been covered elsewhere many times,
I just want to cover the procedure I used to remove and install the the SAI check valve.
Hopefully this may be of some interest to those that might want to do this themselves.
Part 2 will show how to clean out the SAI air passages.

Pictures that help illustrate the procedure can be found here:
https://picasaweb.google.com/bruce.c...CJuMvK_UnKK3GQ


The Secondary Air Injection System

The secondary air system pumps ambient air into the exhaust stream after a cold engine
start to reduce the warm up time of the catalytic converters and to reduce the hydrocarbon
and carbon monoxide emissions. The engine control module controls and monitors the secondary
air injection system.

The injection pump draws in ambient air and supplies it to the shut-off valve.
An electric solenoid (change-over valve), activated by the control module, switches vacuum to open
the shut-off valve. Once opened, the shut-off valve allows air to be pumped into the exhaust
steam via the cylinder heads. The check valve stops exhaust gases getting back into the air
injection pump when it switches off.

Secondary Air Injection Components

1. Secondary air injection pump
2. Shut-off valve
3. Change-over valve
4. Check valve
5. Air tube to cylinder heads


Materials Needed

SAI Check Valve 993-113-250-03 $71.55 at Sunset Porsche
Copper Anti-Seize Paste (Lubro-Moly) (optional)
protective blanket
knee pads


Tools Needed

10mm socket 1/4 inch drive
1/4 inch drive ratchet
12 inch long P2 phillips screwdriver
7mm flexible nut driver
special tool (modified 27mm crowfoot)
4 inch long 3/8 drive extension
3/8 to 1/2 inch drive adapter
10 inch long 1/2 inch drive extension
1/2 inch drive ratchet
1/2 inch drive breaker bar
2x3 inch inspection mirror


Notes on the Special Tool

I followed the lead of other Rennlisters who have been down this path before.
You will need a 27mm crowfoot that measures 7mm thickness at the open end.
Since no one makes a crowfoot that thin, you will have to make it by modifying something close.
A 27mm crowfoot is harder to find and more expensive than a 1 inch crowfoot.
Stahlwille makes one but it is $76 and you would still have to machine it down to 7mm.
I found a GearWrench 1 inch crowfoot for about $12 which was 9mm thick. A local machine shop
machined it to 27mm open end and 7mm thickness for $70.


Steps to remove and install the SAI check valve:

Setup

Note mileage

Open the engine lid and press the latch down to turn off the compartment light

Place a blanket or other protection on the rear of the car and place some knee padding
down on the ground

Removal

Remove the air cleaner and MAF sensorRemove the hose connection on the top of the valvePull hose off valve and move out of the way

Position crowfoot on valve using the 3/8 extension initially in the rear most position.
The wiring going to the injectors will need to be moved aside.

Remove the 3/8 inch extension and snap-on the 1/2 inch extension with 3/8 inch adapter to the crowfoot

Attach the 1/2 inch breaker bar and break the valve loose

Remove the breaker bar and attach the 1/2 inch ratchet and rotate the valve as far as possible, about 1/8 turn

Reposition the wiring going to the injectors out of the way and rotate the valve again as far as possible , about 1/8 turn

Now that the wrench has been rotated as far forward as possible, it will have to be repositioned back to the
rearmost position

Repeat the 1/8 turns until the valve can be removed by hand.

Installation

Apply some copper anti-seize paste to the threads (optional)

Install the check valve by hand as tight as possible

Using the crowfoot special tool tighten the valve until tight, about 1/8 turn

Install the hose on top of the valve and position the hose clamp for easy access

Check the vacuum line connection between the shut-off valve and the change-over valve

Install the air cleaner and MAF sensor.

Finish Up

Open the engine lid latch before closing the lid

Update the log

IXLR8

There is no sealing ring listed, so I assume the threads are a tapered pipe thread on the check valve?

bruce7

Yes, as you can see in the photos there is no sealing ring.

-bruce

gonzilla

Thanks for the writeup Bruce. Another thing to put in the "to do" pile!

JB 911

Very well written and explained thank you. Saving the thread. Thank you.

Only comment might be if you put the pics on Rennlist instead of picasaweb, they will always be there and there'll never be a dead link. Although that is written well enough it works even w/o pics.

My PO Gifted me with a new check valve in one of my boxes of goodies so this one is in my near future. Thanks.

bruce7

Thanks for that. I tried at one point to use Rennlist but ran into difficulty with
captions for the pictures so gave up. Not sure if there is a way around that or
it can't be done.

-bruce

bruce7

Was just reviewing the procedure and realized that the fooling around with the
injector wiring could probably be avoided by just disconnecting the cable at the
injector and moving it out of the way to the back. If that would work then you
could get a full 1/4 turn on the valve instead of 1/8 turn and speed things up.
Anybody tried that?

Also an idea occurred to me for another custom tool to speed up the removal
of the valve. If you could jam a 1-3/4 inch socket down onto the valve, then
you could remove it very quickly. It would need to be machined down at the lip
to provide a gradual bite into the valve body. I'll look into it and report back.
I can test it with the old valve.

I will also cut the old valve in half to see what it looks like inside.

-bruce

osugasman

I tried the hammer a socket down from the top trick as well as hammering a hex socket into the valve air hole trick with no luck. Was even able to use an impact wrench for maximal effect. Still no luck. Awaiting my 27mm crowfoot arrival. BTW: at least mine was functional so the drill out from below with the brake cable was easy with all 6 ports open and unclogged!!! One blow for freedom. I'm just going to go a step further and remove the Varioram so that I can R&R the known failed oil pressure sender (since I purchased the car over a year ago) and do a R&R on the oil temp sender as a while you were there item.

--Brian

bruce7

I don't think it is possible to drive an unmodified socket down onto the valve,
I tried. The socket is too blunt and the valve too hard to permit it and also
there is limited room to swing a hammer in there.

I just dropped off my socket at the machine shop and will pick it up tomorrow.
Going to add a chamfer to provide a gradual bite to the valve body. Whether it
will bite into the valve body enough is the question.

-bruce

nine9six

Bruce, great documented write up...Can someone (Administrator) on RL look into the ability to add text when uploading photos?
(Pelican has the ability)
Hmmm, (Subscribed) Sounds like good preventitive maintenence for 993's. Maybe a 50k mileage maintenence tip?

eddie_993

Thanks for the post, I plan on doing this and the port cleaning in about a month.

kjr914

If you put the photos in the post, you can just put text below each.... (a hack attempt below, but you'll get the idea from this stub code....spaces in places there shouldn't be so you can read it as text.)

[ IMG ] http / wheremypicsare/pic1.jpg [ /IMG ]
This is the caption for my pic above.
[ IMG ] http / wheremypicsare/pic2.jpg [ /IMG ]
This is the caption for the 2nd pic.

bruce7

Got the socket back today and bench-tested it using the old check valve.
A 15 degree chamfer was machined into the socket. I used Delga Prototype,
an engineering and precision machine shop in Canoga Park. They are the
ones I used to make the crowfoot special tool and they are fabulous. If you
have have any need for precision machining speak to Andrew Del Gatto and
he will take care of you. He is also a Porsche owner. 818-887-0512

The socket cost $23 at Sears and the machining cost $50.

To bench-test the socket, I took a 2 lb. hammer and tapped the socket onto
the valve to jam it down. I only raised the hammer a couple of inches to simulate
the swing room than you would have in the engine compartment.
It went down and jammed pretty hard. I'm pretty sure that it would grab hard
enough to be able to loosen the valve in the car, but to be 100% sure, it would
need to be tested in a real situation.

Next, I removed the valve from the socket using a hammer and punch.

I put the valve in a vise and cut it in half to see what the insides look like.

See the photos below for visual details.

This valve was removed at 74,000 miles. I got the car at 43,000 miles.
So for sure the valve has 30k miles on it. Possibly it has 74k miles.
The part number was a -02 and the new one is -03.

My current plan is to treat the SAI check valve as a maintenance item
and replace it at least at every 30k major maintenance period.

-bruce

bruce7

Hi Keith, thanks for the tip. What I ended up doing this time was using
Preview on the Mac to annotate the photos which I uploaded inline. Only
drawback I see is there doesn't seem to be the capability of adding a drop
shadow to the text.

-bruce

peter y.s pang

Just question of what is the function of SAI valve.