SAI port unclog + flush
09-01-2011, 04:20 PM
#1
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SAI port unclog + flush
After putting this off for over 3 years, and with the gracious help 
of Pedro Rennlister PNogC2s and Pete Pressle's crow's foot wrench, I finally got my sai ports unclogged! 
In fact, the more difficult part was actually taking off the heat exchangers.
A few things to mention, which I hope will help others with this procedure. Before starting, blow compressed air from the top to check which ports are clogged. The only ones that were clear were the 2 on the rear (1 left and 1 right). Pedro recommended using motorcycle brake cable, we ended up using scooter cable which is the same gauge, however, what really makes the difference is the stiffness of the cable. I wasn't able to get guitar strings which may have worked better. After struggling with the flexible brake cable, I had some old bike brake cable laying around which was helpful. We used both cables and snaked out each port while blowing compressed air back down to get the built up carbon out. It also helps to plug some of the other ports to know how clear they've gotten. Pedro said it would have taken a lot less time if we the cable we had was stiffer. Total unclogging time approx. 3 hours.
Take a look at my sai check valve after only 6,000 miles since I last changed it. I wonder if now that the ports are unclogged, will there be as much rust as next time I change it out.
I'll be crossing my fingers that error code won't come on anymore, but we'll have to wait and see. Thanks again to Pedro for driving out from Novato to San Francisco to help me out! I'll see you at the FD BBQ with wine bottles in hand! Pete, I'll give you a call next week to give you back your crow's foot wrench. Thanks to the Rennlist community, you all are awesome!
-nelson
of Pedro Rennlister PNogC2s and Pete Pressle's crow's foot wrench, I finally got my sai ports unclogged! In fact, the more difficult part was actually taking off the heat exchangers. A few things to mention, which I hope will help others with this procedure. Before starting, blow compressed air from the top to check which ports are clogged. The only ones that were clear were the 2 on the rear (1 left and 1 right). Pedro recommended using motorcycle brake cable, we ended up using scooter cable which is the same gauge, however, what really makes the difference is the stiffness of the cable. I wasn't able to get guitar strings which may have worked better. After struggling with the flexible brake cable, I had some old bike brake cable laying around which was helpful. We used both cables and snaked out each port while blowing compressed air back down to get the built up carbon out. It also helps to plug some of the other ports to know how clear they've gotten. Pedro said it would have taken a lot less time if we the cable we had was stiffer. Total unclogging time approx. 3 hours.
Take a look at my sai check valve after only 6,000 miles since I last changed it. I wonder if now that the ports are unclogged, will there be as much rust as next time I change it out.
I'll be crossing my fingers that error code won't come on anymore, but we'll have to wait and see. Thanks again to Pedro for driving out from Novato to San Francisco to help me out! I'll see you at the FD BBQ with wine bottles in hand! Pete, I'll give you a call next week to give you back your crow's foot wrench. Thanks to the Rennlist community, you all are awesome!
-nelson
09-01-2011, 04:54 PM
#2
Rennlist Member
sweet, congratulations!
The guitar strings would not have helped... you guys went about it the right way.
Just FYI, be careful about plugging exhaust ports in the heads and blowing compressed air. If the exhaust valve is open, you can blow crud into the cylinder.
The guitar strings would not have helped... you guys went about it the right way.
Just FYI, be careful about plugging exhaust ports in the heads and blowing compressed air. If the exhaust valve is open, you can blow crud into the cylinder.
09-01-2011, 05:35 PM
#3
Rennlist Member
Is there a way to prevent the issue of blowing crude into the cylinder? How else would you clog the ports to blow air thru the other ones? TIA
09-01-2011, 05:52 PM
#4
Rennlist Member
Not really a way to avoid it if you try to plug the exh ports at the head.
The only other option would be to try to plug the SAI ports themselves, which is pretty tough.
You really don't need to plug the ports at the heads. You can gauge air flow pretty well with all of them open. The restricted SAI ports will flow less air. If clogged, it is even more obvious.
If you run the cable up each passage, the ports will be cleared. The clog tends to happen at the turn, where the head meets the cam tower.
09-01-2011, 05:54 PM
#5
Racer
Nelson,
I'm glad I was able to help out!
Mark,
We didn't plug any of the exhaust ports until after we'd blown air through at free-flow. So all the loose crud should have blown out first. The main reason for plugging the other ports was to get a sense of flow volume from each port to make sure we had them properly cleared out. We also didn't plug them super tightly so some air was still able to flow out of them even when plugged. Again, more for the purpose of checking flow on specific ports rather than building pressure.
See you guys at the FD BBQ!
I'm glad I was able to help out!
Mark,
We didn't plug any of the exhaust ports until after we'd blown air through at free-flow. So all the loose crud should have blown out first. The main reason for plugging the other ports was to get a sense of flow volume from each port to make sure we had them properly cleared out. We also didn't plug them super tightly so some air was still able to flow out of them even when plugged. Again, more for the purpose of checking flow on specific ports rather than building pressure.
See you guys at the FD BBQ!
09-01-2011, 06:21 PM
#6
Rennlist Member
Hey Kent
Not really a way to avoid it if you try to plug the exh ports at the head.
The only other option would be to try to plug the SAI ports themselves, which is pretty tough.
You really don't need to plug the ports at the heads. You can gauge air flow pretty well with all of them open. The restricted SAI ports will flow less air. If clogged, it is even more obvious.
If you run the cable up each passage, the ports will be cleared. The clog tends to happen at the turn, where the head meets the cam tower.
Not really a way to avoid it if you try to plug the exh ports at the head.
The only other option would be to try to plug the SAI ports themselves, which is pretty tough.
You really don't need to plug the ports at the heads. You can gauge air flow pretty well with all of them open. The restricted SAI ports will flow less air. If clogged, it is even more obvious.
If you run the cable up each passage, the ports will be cleared. The clog tends to happen at the turn, where the head meets the cam tower.
09-01-2011, 06:39 PM
#7
Rennlist Member
Nelson,
I'm glad I was able to help out!
Mark,
We didn't plug any of the exhaust ports until after we'd blown air through at free-flow. So all the loose crud should have blown out first. The main reason for plugging the other ports was to get a sense of flow volume from each port to make sure we had them properly cleared out. We also didn't plug them super tightly so some air was still able to flow out of them even when plugged. Again, more for the purpose of checking flow on specific ports rather than building pressure.
See you guys at the FD BBQ!
I'm glad I was able to help out!
Mark,
We didn't plug any of the exhaust ports until after we'd blown air through at free-flow. So all the loose crud should have blown out first. The main reason for plugging the other ports was to get a sense of flow volume from each port to make sure we had them properly cleared out. We also didn't plug them super tightly so some air was still able to flow out of them even when plugged. Again, more for the purpose of checking flow on specific ports rather than building pressure.
See you guys at the FD BBQ!
No worries then
Great, have fun!
As Nelson said, removing the exhaust is the hardest part, depending on how crusty the HW is.
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09-01-2011, 09:13 PM
#9
Seared
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Ever since gleefully removing my entire SAI system a few years ago, I've wondered why the tops of SAI valves usually show rust.
Could it be that since the SAI system pulls its air from the rear of the air box, rainwater or moisture works its way into the hose? I know it's a stretch, but...
Andreas
Could it be that since the SAI system pulls its air from the rear of the air box, rainwater or moisture works its way into the hose? I know it's a stretch, but...
Andreas
09-01-2011, 09:42 PM
#10
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I had mentioned this procedure to my mechanic a few weeks ago. He pooh-poohed it saying that there were cross channels that would not get cleared out with this procedure and the code would just come back. Is that right? Are there cars out there that have been cleaned this way and avoided the code far a long period?
I hope he is wrong and it works for you!!
I hope he is wrong and it works for you!!
09-01-2011, 10:03 PM
#11
Racer
Did mine 2 years ago... a little less than 10K on the clock since then and no problems.
With all due respect, your mechanic is pooh-poohing it because he either doesn't understand it, or is hoping to hit you up for a top-end rebuild when your CE light comes on.
The passages make a sharp turn fairly close to the "end" before letting out behind the exhaust valves. Maybe they narrow in that spot as a result (can't say for sure), but that seems to be where they clog up. On both my car and Nelson"s, the cable went in the same short distance, then once it broke through the clog it went way up w/o any other resistsance.
The way the system detects SAI failure, it doesn't matter if there are any cross channels or if they are clogged... if enough air gets to the sensors it doesn't trip the CE. That's why a couple of RL'rs have been able to bypass the SAI system and feed air directly into the exhuast before the sensors. With sufficient clean air flow, there's no SAI fault code - period.
With all due respect, your mechanic is pooh-poohing it because he either doesn't understand it, or is hoping to hit you up for a top-end rebuild when your CE light comes on.
The passages make a sharp turn fairly close to the "end" before letting out behind the exhaust valves. Maybe they narrow in that spot as a result (can't say for sure), but that seems to be where they clog up. On both my car and Nelson"s, the cable went in the same short distance, then once it broke through the clog it went way up w/o any other resistsance.
The way the system detects SAI failure, it doesn't matter if there are any cross channels or if they are clogged... if enough air gets to the sensors it doesn't trip the CE. That's why a couple of RL'rs have been able to bypass the SAI system and feed air directly into the exhuast before the sensors. With sufficient clean air flow, there's no SAI fault code - period.
09-02-2011, 07:04 PM
#12
Did my SAI procedure back in June 2008 and posted it " currently in 993 DIY". The car has been perfect. I have also heard back from other Rennlisters that have performed this technique, and all have been successful. 
09-02-2011, 07:17 PM
#13
Rennlist Member
The passages make a sharp turn fairly close to the "end" before letting out behind the exhaust valves. Maybe they narrow in that spot as a result (can't say for sure), but that seems to be where they clog up. On both my car and Nelson"s, the cable went in the same short distance, then once it broke through the clog it went way up w/o any other resistsance.
The way the system detects SAI failure, it doesn't matter if there are any cross channels or if they are clogged... if enough air gets to the sensors it doesn't trip the CE. That's why a couple of RL'rs have been able to bypass the SAI system and feed air directly into the exhuast before the sensors. With sufficient clean air flow, there's no SAI fault code - period.
The way the system detects SAI failure, it doesn't matter if there are any cross channels or if they are clogged... if enough air gets to the sensors it doesn't trip the CE. That's why a couple of RL'rs have been able to bypass the SAI system and feed air directly into the exhuast before the sensors. With sufficient clean air flow, there's no SAI fault code - period.
That sharp turn creates turbulence and the exh gasses pushed up the SAI port collect there. This is happening the entire time the engine is running (after the air pump shuts off).
It lasts a very long time... how long depends on valve guide wear which is largely indicated by oil consumption
09-03-2011, 01:30 AM
#14
So is it worth doing a cleaning of the ports before the CEL comes on, perhaps before they plug completely? I would think that this would be easier without complete blockage, getting the wire through.
09-03-2011, 04:03 PM
#15
Racer
I don't think the advantage to getting them done before they are fully clogged offsets the work to get to them. However, if you take your exhaust manifolds off for some other reason, then cleaning the SAI ports might be worth a "while you're in there" --- But you will also need to examine/replace the SAI check valve (since you need to remove it to blow air through).
Otherwise, I'd just wait for the fault code and then go to it.
Otherwise, I'd just wait for the fault code and then go to it.