9-5 2.3lpt PCV/breather hose burst

The hose from that check valve is what melted, not the valve itself. Must proofread posts so I don't any words out.

One frequent cause of the small hose splitting or collapsing is that the plastic tit on the part that comes out of the cam cover becomes blocked and therefore the hose collapses due to vacuum, check the hole and if needed clean out using a 2mm drill bit. Also make sure that the check valve is working correctly, ie that you can suck in the direction of the arrow on the side and that the arrow points towards the throttle body when installed. It is also wise at the same time to clean around the throttle plate with carb cleaner. The larger hose goes between number 1 and 2 inlet tracts and down to the breather box on the back of the engine. Both these hoses need to be checked at service as they are perished by the oil vapour passing through them and quite often are blocked inside. In severe cases they can cause exhaust smoke due to the increase of crankcase pressure preventing the oil from the turbo drain returning to the sump, [oil pan] and letting the oil into the exhaust. HTH Tom.

I have a new hose on order (it's in stock at the dealer, will pick up this afternoon), and it has the plastic fitting on the end of it. So that should be OK then.

Good to know. My first priority is getting the hoses back on so I can drive it home, I'll clean it up there.

That is consistant with what I'm seeing. The inside of the big hose was actually _gummy_. So that's normal-ish of a failure mode then? I'm thinking the reason it won't run is that that turns into un-measured air and throws off the mixture, does that make sense? It tries to run, no ugly noises, no spilled fluids or anything, so I think it's just a case of "hose broke down and burst under pressure" than anything particularly otherwise bad.

Anything else I should check because of this failure, Tom? I'm very comfortable on the c900 and older models, but this is my first GM-ish Saab and I just don't have much experience in the new ones (because nothing has broken).

Thanks very much, Dave Hinz

These hoses has a hard time in certain cars and will get all mushy/sticky and/or fall into pieces. Some engines doesn't seem to be as har on the hoses. I have never replaced any of these hoses on my 1999 9-5. Perhaps different engine oils have different additives that the hoses can tolerate more or less.

Yes. Any failure that lets extra air in after it has meen through the air mass meter will create more or less problems for the engine management. If you let enough air in the engine will simply not run.

I have had a page about the crankcase ventilation system of the 9-5 on my web site for a year now. I finally made the translation into English and put it online at this address:

The page contains information about how the crankcase ventilation system works, what problems it has, what changes should be done and what should be inspected to reduce the risk of engine damages by a broken crankcase ventilation system.

Perfect, thank you very much. Printing now to take with me.

Dave

Surely 9-5s do not have an AMM!! They stopped using them during the 9000 run, and I assume all this work is now done by the sensing plugs and the Trionic system?

Are you suggesting that I don't know what I write about?

Yes, the Trionic 5 engine management system used in the last model years of the Saab 9000 and ng900, and the first model years of the og9-3 did not have an AMM. Trionic 5 used a MAP sensor and temperature sensor to find out the air mass.

However, that doesn't say anything about the Trionic 7 system used in the Saab 9-5 and later model years of the og9-3. Trionic 7 has both AMM and MAP sensors to determine air mass.

The spark plugs can't be used to sense air mass.

You're confusing timing with mixture. The engine management still needs to know the mass of the air in the chemical reaction so it can put the right amount of fuel into the chambers; the sensing plugs are for determining when to fire the spark.

Dave Hinz

No, that's why my statement was not definitive. So if the MAP sensor replaced the AMM in the 9000, why did they have to use both in the 9-5, "backward evolution?" The AMM has always seemed to me to be a rather delicate bit of technology.

No they are not, AFAIU they are to check the result of combustion.

Nope. That's what the O2 sensor is for. Here's an article (in English even) that goes into way more detail than you asked for, but, er, you asked for it...

Dave Hinz

The word "Surely" surely indicated some level of certainty. You could have written "I didn't know the 9-5 had an AMM".

Why is it a "backward evolution?" The MAP sensor is certainly cheaper than the AMM sensor, but Saab probably felt that using only the MAP sensor wasn't good enough. I don't know exactly why Saab decided to go for both a MAP sensor and an AMM sensor, but the fact is that Trionic 7 do use both of these sensors.

Yes, I have read that before, but that only SEEMS to deal with the timing aspect of the plugs as sensors. Please don't tell me off again, I am very sensitive. I quote from The Saab publication (270603) 1997 Form and Function about Trionic. "By applying a relatively weak voltage (approx. 80V) to the spark plugs, we can measure the density of ions in each cylinder and thus determine whether combustion was complete or if a setting needs to be changed. .....it can adjust the quantity of fuel being injected during the brief moment the inlet valves are open...... which rations each and every drop of fuel and minimises exhaust emissions." Hilsen

Apparently.? I don't think I'm "telling you off", I'm disagreeing with your interpretation of how things work is all.

OK, fair enough. I'm sure that's buried somewhere in the 8 page article as well, but I didn't read it through this time.

Dave

I'm not going to tell you off but I am going to tell you that you are wrong. The D.I unit or the sparkplugs can not detect combustion mixtures. The system of applying a weak voltage to the sparkplugs is to detect which cylinder is on compression stroke. It does this by measuring the voltage at the plugs that is not enough to jump the gap, but as the compression goes up the voltage will go up as the amount of air in between the gap will increase. There are also sensors in the D.I unit to detect knocking. The mixture is determined in a Trionic 7 system by the air mass meter and the two map sensors, and then is fine tune by the readings of the o2 sensor (which there is two in later models).

Ok, I will tell SAAB that there own publication is wrong, and they ought to read this newsgroup to find out how their engines work;-( Oh, I see he is an Aussie!! War is declared!

Could be that it also does some post-spark analysis of the mix, I was not aware of it if it does.

Wait, .au and .nz are different countries now? When did that happen? /me puts hands in pockets, walks away whistling, looking innocent...

Dave Hinz