First Post - SAI Issue with my 993
Instructor
Joined: Apr 2011
Posts: 122
Likes: 1
From: Alexandria, VA
Thanks Jeff. Great information.
More questions
Re this Q in their FAQ section
"Q: My check engine light is not on, what preventative maintenance can I do?
A: The system has no maintenance intervals, cleaning the lower ports is not advisable or recommended unless or until the problem occurs"
Seems like this is not entirely correct and that replacement of the check valve could be taken as preventative maint.
I was sad to hear a lot of his 100 cars were from Texas and Fl as I am in Texas. Since I don't have a problem yet I really want to avoid one if I can.
He suspects frequent start stops are to blame and perhaps the heavy ac usage that one would expect in Texas.
I am going to use ac but not a frequent starter stopper.
My understanding it is only on during cold starts is that correct? Or am I confused. Like if you drive 20 mins. Park. Then decide immediately you want to change parking spots. It doesn;t come on again right?
More questions
Re this Q in their FAQ section
"Q: My check engine light is not on, what preventative maintenance can I do?
A: The system has no maintenance intervals, cleaning the lower ports is not advisable or recommended unless or until the problem occurs"
Seems like this is not entirely correct and that replacement of the check valve could be taken as preventative maint.
I was sad to hear a lot of his 100 cars were from Texas and Fl as I am in Texas. Since I don't have a problem yet I really want to avoid one if I can.
He suspects frequent start stops are to blame and perhaps the heavy ac usage that one would expect in Texas.
I am going to use ac but not a frequent starter stopper.
My understanding it is only on during cold starts is that correct? Or am I confused. Like if you drive 20 mins. Park. Then decide immediately you want to change parking spots. It doesn;t come on again right?
Remember, the most common "cause" is worn valve guides which allow more oil into the combustion chamber, more carbon, more build up, etc… The fix for worn valve guides is a top end rebuild and there is not much preventative you can do. Frequent, regular oil changes are about it.
I would not worry that much about it. Drive and enjoy the car.
There is mixed thinking on whether high RPM runs to really heat up the motor do much good. (track cars don't seem to have the issue) My mechanic thinks it could help. But since it's kind of fun, I do it anyway. So periodically "drive it like you stole it", push the redline and work the motor hard.
If the issue arises, the flush with mechanical means and solvents did work on my car. It took a couple attempts but we got there.
Work with your mechanic. Replace the check valve and do so every couple years regardless of miles. I also do mine on the "as long as we are in there" schedule.
If you have the exhaust fully removed for any other issue consider doing a flush of the SAI system at that time. You don't want the solvents getting into the exhaust and cats.
Last edited by Jeff U; Mar 23, 2013 at 01:33 PM. Reason: typo fix
Banned
Joined: Oct 2011
Posts: 5,464
Likes: 31
From: Oregon
The SAI check-valve is not an expensive fix and is almost always (unless recently replaced and in excellent condition) the first step in trying to address the SAI issue. I think the valve itself costs around $175 (maybe a little less, I can't recall). It's not a huge job to replace it either... managable DIY.
If your car has north of 100K miles and no record of replacement, the check-valve will be dust (literallly) inside.
If your car has north of 100K miles and no record of replacement, the check-valve will be dust (literallly) inside.
Actually, when ordering the new valve, the correct nomenclature is, Check Valve for Crankcase Ventilation, 993 Carrera/Carrera 4 P/N: 993-113-250-03 (aka SAI Check Valve)
Pricing ranges from $72 - $90 depending on who you do business with. The $72 price was as quoted from Susset within the last week
Here is a link to the DIY...
https://rennlist.com/forums/993-foru...eck-valve.html
By doing the maintenence work in lieu of actually addressing the SAI problem, only postponed the inevitable and spent money on items that may not have needed replacing.
HTH...
Rennlist Member
Joined: Feb 2011
Posts: 2,212
Likes: 135
From: Plano, Texas
Ok It seems there are a lot of potentially contributing factors to this issue.
Here is a question I am really curious about. Does the potential for carbon deposits within the passages occur ONLY when the SAI pump is running OR the entire time the car is running.
Here is a question I am really curious about. Does the potential for carbon deposits within the passages occur ONLY when the SAI pump is running OR the entire time the car is running.
Instructor
Joined: Apr 2011
Posts: 122
Likes: 1
From: Alexandria, VA
Entire time
Race Car
Joined: May 2003
Posts: 4,268
Likes: 105
From: SoCal
"do you have a personal rec for frequency on replacement of the check valve and/or feel it is helpful or at least can't hurt?"
Really can hurt, if the engine is over 50-60K.
"One question about the link.
"4. We'd minimize that constant revving above 5K, i.e. high revving will NOT reduce the SAI problem but likely increase it.
Note: High speed driving, e.g. freeway driving, versus "stop & go" driving does NOT reduce the likelihood of SAI problems."
Re the "note" portion. I am correct to assume the stop and go portion is ok ONLY as long as it DOESNT result in higher op temps i.e engine tray off, limited ac if for prolonged times etc?"
It's my view that it's the high temps that's one of the key factors.
"If the entire time then what is the purpose of the one way check valve?"
The valve is upstream from the passages. The valve prevents exhaust gases
from reaching the SAI pump.
Really can hurt, if the engine is over 50-60K.
"One question about the link.
"4. We'd minimize that constant revving above 5K, i.e. high revving will NOT reduce the SAI problem but likely increase it.
Note: High speed driving, e.g. freeway driving, versus "stop & go" driving does NOT reduce the likelihood of SAI problems."
Re the "note" portion. I am correct to assume the stop and go portion is ok ONLY as long as it DOESNT result in higher op temps i.e engine tray off, limited ac if for prolonged times etc?"
It's my view that it's the high temps that's one of the key factors.
"If the entire time then what is the purpose of the one way check valve?"
The valve is upstream from the passages. The valve prevents exhaust gases
from reaching the SAI pump.
Instructor
Joined: Apr 2011
Posts: 122
Likes: 1
From: Alexandria, VA
However, the ports are supposed to have flow only going one way, intake to exhaust.
This is not the system on a 993 but it's a useful picture.
The check valve will not prevent all carbon build up but it's failure will allow significantly more carbon to get back up into the inaccessible narrow ports in the block.
Make sense ?
Newer cars have the same internal ports but they made them much larger diameter to eliminate a clogging issue.
Last edited by Jeff U; Mar 23, 2013 at 09:20 PM.
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Thread Starter
8th Gear
Joined: Jan 2013
Posts: 8
Likes: 0
In response to JB 911 question a couple of days ago - did I replace the check valve? Yes, that was part of the procedure. I have enjoyed all the responses, and know a whole lot more about the problem than when I made the post.
Intermediate
Joined: Sep 2013
Posts: 37
Likes: 0
Sorry, if this has been answered, I can't find it, but is the check valve first and then the ports or are the ports first and then the check valve?
In other words, is there any merit to just replacing the check valve only without cleaning the carbon out of the ports?
In other words, is there any merit to just replacing the check valve only without cleaning the carbon out of the ports?
Racer
Joined: Mar 2020
Posts: 259
Likes: 145
From: Kansas City
As Lorenfb says, the check valve's primary function is to protect the air pump.
However, the ports are supposed to have flow only going one way, intake to exhaust.
This is not the system on a 993 but it's a useful picture.
The check valve will not prevent all carbon build up but it's failure will allow significantly more carbon to get back up into the inaccessible narrow ports in the block.
Make sense ?
Newer cars have the same internal ports but they made them much larger diameter to eliminate a clogging issue.
However, the ports are supposed to have flow only going one way, intake to exhaust.
This is not the system on a 993 but it's a useful picture.
The check valve will not prevent all carbon build up but it's failure will allow significantly more carbon to get back up into the inaccessible narrow ports in the block.
Make sense ?
Newer cars have the same internal ports but they made them much larger diameter to eliminate a clogging issue.
Hi, I love to read and learn all about my 993 at this forum.
Recently bought a 97 993, after 6K, SAI light came on after the required state inspection.
Being a home mechanic trying to do least work and spend even less money and still enjoy my 97 993, I post following.
1. What would be the damages to the engine if the SAI ports or the check valve are NOT addressed for a long time?
2. What if I added a 3 way fitting (properly capped) to the tubing above the check valve to be able to add some injector cleaning solution at a regular operating hours after a good cleaning of ports?
Thank you.
Rennlist Member
Joined: Feb 2006
Posts: 3,847
Likes: 558
From: Chicago Bears
Maybe all you have to do is simply replace the check-valve.
Mine was rusted through and was the root cause for my SAI issue. In other words, flushing the system was not necessary.
Banned
Joined: Sep 2011
Posts: 1,201
Likes: 31
From: Toronto, Ontario
My SAI drove me insane till I drilled out the exhaust ports.
Do the research first > drilling would b last solution.
More tedious than difficult
Check codes first then work through them
TJ993
Do the research first > drilling would b last solution.
More tedious than difficult
Check codes first then work through them
TJ993