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Discussion Starter · #1 ·
Hey everybody! New to the SaabCentral forums, and I have a probably stupid question, but I can't find anything around that explains to me what I'm seeing. I was cleaning the engine bay on my 1994 9000 Aero recently, and I noticed a small diameter hose leading into the intake manifold that isn't connected to anything. It has a small amount of vacuum pressure, so it's sucking air in, and when I block it with my finger while the engine is running, it idles rough and about 100 rpm lower than normal. I just wanted to know what this hose and nipple might be for? Why isn't it connected to anything? Should I be worried? Just looking for some sort of explanation. It's obviously not urgent since I've owned this car for about a year and a half and it's run fine the whole time including long 1000 mile roadtrips at a time, but I don't like having any loose ends so to speak. What is this???
Thanks in advance for the help, you guys rock. ;ol;
 

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You are missing a one way PCV valve and another section of hose which connects to a plastic Y fitting pressed into a rubber grommet on the cam cover, the other and larger hose not shown also connects to this fitting and runs down to the turbo compressor intake. Your PCV system is open to atmosphere which is not emissions legal and not good.

Only the Trionic system is allowing your engine to run well by adding fuel to compensate to what is probably a significant air leak.

A photo taken from further back will allow us to see the fitting in the cam cover to confirm what else may be missing.
 

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Discussion Starter · #3 ·
@Superaero THANK YOU! I do still have the Y joiner, and the larger hose is indeed plugged into it, heading into the cam cover. I feel very very dumb now because it's obvious that this hose just popped off the smaller nipple on the Y. Wow I'm stupid haha thank you.
 

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That is the correct routing but it appears that the check valve (one way valve) that should be in the hose you just reconnected is missing. The valve is to ensure the turbo doesn't pressurize the crankcase and cause oil leaks...
 

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Discussion Starter · #5 ·
Thanks, that's good info. Sorry if all of this is really obvious I have no formal training at all, and I'm basically starting from scratch in terms of car (Saab) maintainence. Will I be able to fit a new valve on the existing hose or will I need an entirely new hose with the fittings attached?
 

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Just insert a new check valve in the hose - it doesn't really matter where it is located. This is $5 on the Dorman rack at most Advance Auto stores:

 

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Thanks, that's good info. Sorry if all of this is really obvious I have no formal training at all, and I'm basically starting from scratch in terms of car (Saab) maintainence. Will I be able to fit a new valve on the existing hose or will I need an entirely new hose with the fittings attached?
What Chengny said (and good tip on the dorman part locally available!)

Just snip the hose where it's convenient and insert the part pictured into the hose opening.

Be sure the valves facing the correct way! You want flow to go into the intake manifold.
 

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Disconnect the hose until you can fit the valve, over pressuring the crankcase is a more serious problem than the air leak.
 

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Here is some basic info on the positive crankcase ventilation system:




The engine has a fully enclosed crankcase ventilation system with blow-by gases exiting via an opening in the camshaft cover.

The crankcase gases are then led away from the cam shaft cover and into a flow dividing nipple.

Depending on operating conditions, the gas flows through either one of two hoses:

1. A small diameter hose to the throttle body (or the intake manifold - depending on the year and the model).

2. A large diameter hose to the intake hose upstream of the turbocharger where the gases are mixed with the intake air and burned in the engine.

The crankcase gases are always evacuated through the smaller diameter hose. The only exception is when an overpressure condition exists in the intake manifold.

At that point, the check valve in the smaller hose shuts off the flow. The gases are then evacuated through the larger hose which leads to the turbo charger inlet piping.

The hoses and their connections are sized to give satisfactory evacuation of the crankcase gases from the engine under all operating conditions.

To avoid icing, the system is water heated.
 

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Discussion Starter · #10 ·
Thank you! What informative posts..I've disconnected the hose again to avoid overpressure, (haven't boosted hard since it was connected thankfully) and I am going to go get a check valve tomorrow - either way I can't imagine having this system functioning incorrectly is very good for the engine, and is an apparently easy fix so thank you guys again! :)
 

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Thank you! What informative posts..I've disconnected the hose again to avoid overpressure, (haven't boosted hard since it was connected thankfully) and I am going to go get a check valve tomorrow - either way I can't imagine having this system functioning incorrectly is very good for the engine, and is an apparently easy fix so thank you guys again! :)
The engine doesn't mind do much but the environment does. The very first emission control mandated in California was PCV to ensure engine blowby gases were burned in the engine.

Mind you, it is SAABs clever engine management system that allows your engine to run in this fashion so good idea to repair this ASAP.
 

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Best to stuff a bolt or? plug into the airline to the throttle body as a Temp patch.
Dunno about your engine running well with it disconnected/air leaking tho.
When my/that vac line split at the valve nipple, the driveability change was immediate and unmistakable. Certainly got my attention.
Emissions issues aside..
The Saab method of redirecting Blowby gasses (oil mainly) to the Turbo compressor results in the Intercooler accumulating a surprising amount of oil in its' bottom can.
Many delete this circuit, retrofitting a Catch can setup.. deleting the pesky Rube Goldberg water cooled pipe thing as Bonus.
Merely pointing out possible options.
 

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Trionic uses an absolute barometric pressure sensor for air mass calculation. Basically it doesn't care where the air comes from as it measures the absolute air pressure in the intake manifold and calculates air mass equivalent from that and the temperature sensor in the intake pipe upstream of the throttle plate. So, unless a lot of extra air gets dumped in Trionic can handle the calculation. Very clever.

Having said that I agree that the small vacuum tube would better plugged with a bolt pending replacing the missing check valve although the opening in the cam cover will leak in about the same amount of air....

Bypassing the PCV system will be illegal everywhere I should think and is antisocial even if not actually illegal.
 

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Baby steps Davide, baby steps. If we ignore all the small things because the big things are too big we never address the big things either. NYPD discovered this when they started arresting people for jumping the subway turnstiles and found out the majority of those jokers also broke much more serious laws. Bypassing your vehicle emission controls is as irresponsible as spitting on the sidewalk. Just don't.
 
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