Date: Sun, 03 Nov 2002 15:20:40 +0100 From: Robert Brown <rjbnopsamripnetvvv.se> Subject: Re: crankcase ventilation [long reply]
g c wrote: > This might be an interesting problem.....! Hope someone else has solved it > cheaply! > Car is a '92 900 Turbo, manual, about 165,000 km (100,000 miles) > When running, the oil filler pipe emits a light hazy pulsing vapour, and the > crankcase > ventilation pipe (large diameter) is under pressure, not excessively high, > but pulsating and felt on the palm of my hand. There >is< a check valve in > the small diameter line to the manifold, it is in the right way round and > sucks >out< of the valve cover. I've had higher than I'd expect oil > consumption for a while, and some drips from the valve cover gasket. > My first thought is a leaking valve stem pressurising the valve cover and > crankcase... > Anyone got any less expensive thoughts? > Thanks in advance.... Hi, I doubt that this will solve your problem directly but you may get an idea from a similar situation I had many years ago. Take with a grain of salt in other words. The problem was on my 1983 900 GL non-turbo 8v single carburettor engine at roughly the same mileage. Symptoms were the same but in this case they were caused by a blockage between the valve cover and the air filter canister. That may sound weird so I better explain that on the non-turbo 8v carburettor Saabs, blow-by gases are pushed up to the area under the valve cover. I think they go via the timing chain housing. They are evacuated via a small pipe roughly 2 cm in diameter and fed back into the air filter canister for recombustion (though "downstream" of the air filter so as to not dirty it up). In my case there was a screen in the top of the valve cover that was blocked up. You can't see the screen because it's built into the cover. In my case the excess pressure was causing the gases, including oil vapour, to condense and run down the tube into the air filter. I'll paste in a reply that I posted two years ago (see below) but I want to warn that I don't know how blowby gas evacuation is done on your engine, which I'll assume is a 16v. Anyhow - use this if it fits your case ;-) /Robert --------8<--------start---- Subject: Re: Oil in air filter,Saab 900 GLS Date: Sat, 09 Sep 2000 23:04:38 +0200 From: Robert Brown <rjbnopsamnetnospam.se> Reply-To: robert.brownnopsamnetnospam.se Newsgroups: alt.autos.saab References: 1 I've had the same problem on two cars (1983 900GL and 1983 99GL both single carb). If you're new to the Saab crankcase ventilation system, you might find some background info useful: The crankcase fills with blowby gases (the stuff that forces its way past the piston rings during combustion) and these have to be evacuated somehow. You'll find that this is done via the valve cover that sits atop the cylinder head. Note the rubber hose running from it to the top of the air filter canister. Before the gases leave the cover and down the hose to be recycled, they go through a small screen in the same cover. When the screen starts to get clogged, excess pressure inside the valve cover is generated and this causes more oil vapour to go through the screen, which means that oil starts running down the rubber hose and clogs the air filter. Yuck. The easiest way to fix this is to remove the valve cover (8 long allen key bolts - make sure that you turn the flywheel to 0 degrees i.e. top dead centre). It's best if the distributor - without cables - is still bolted on, otherwise you may have to redo your ignition timing. Invert the cover, put a metal pan under it, and put some petrol through the opening in one end. Avoid getting the petrol on the distributor end. Once screen - which you can't actually see - is cleaned and completely dry, clean out the valve cover and refit. Note that the sprigs on the distributor shaft are off-axis and have to be aligned with the camshaft. You may have to rotate the distributor rotor 180 degrees to get the right orientation. This is why you needed to get the flywheel to TDC earlier. Whatever you do, don't force. Might be a good idea to clean out the rubber tube from the valve cover to the air filter canister as well. If the above description is too confusing, email me with a question or 2 and I'll explain a bit more that way. Remove the "nospam" in the address. Good luck, tell how it goes. Regards, Robert Gothenburg marinpetrovnopsameja.com wrote: > I was changing the air filter on the Saab 900 GLS > (double carburator, produced '83) that I acquired > recently and was quite unhappy to see that it was > almost soaking with engine oil. Being quite new > with saabs, I'd appreciate some advice on how to > interpret this and what should I do. Thank you! > > Sent via Deja.com http://www.deja.com/ > Before you buy. ------8<----end-----
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