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Discussion Starter · #1 ·
is the ng like some cars that a bad oil cap will cause a vacuum leak?
 

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Any gasket or seal can and will EVENTUALLY leak, you could always SPARINGLY spray some starting fluid (ether) around the lines and intake (not the intake itself, just the piping/manifold) to see if it runs better all of a sudden.
 

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Discussion Starter · #4 ·
i'm not wondering because i'm really suspecting a vacuum leak i'm asking because my oil cap is broken and someone told me that it would always cause a vacuum leak. but it doesn't seem to have any connection to the top end like a car that has the filler cap in the valve cover for instance. i'm more just curious
 

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Well, you have the notorious rubber gromet in the valve cover, many times a new gromet makes the engine idle better. I guess that would be the same type of vacum leak, as a leak at the dipstick?
 

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Well, you have the notorious rubber gromet in the valve cover, many times a new gromet makes the engine idle better. I guess that would be the same type of vacum leak, as a leak at the dipstick?
Anything that penetrates the block and leads to the crankcase can eventually leak and let air in or oil out, if oil is coming out air can definitely get in. The crankcase on modern cars is under negative (vacuum) pressure to prevent the gases from 1. building up to a high pressure and forcing oil out the seals 2. burn the gases from combustion and any vapors in the crankcase so they dont escape to the environment and all this is accomplished through a PCV (CDR on a diesel) valve that only opens when there is correct vacuum applied to the valve from the manifold, the amount of air that can normally be scavenged from a crankcase is usually small so on some cars when you remove the cap the engine will idle noticeably higher due to the extra air in the system now, some may even trip the MIL light due to a lean condition due to the extra unmetered air flowing into the engine if it is fuel injected. All that being said if someone knows otherwise that is what I know about that system but if something is wrong I hope someone will say so :p Anyways if you have a leak at your oil cap you will get unfiltered dirty air into your crankcase that WILL slowly contaminate your oil and lead to premature engine wear.
 

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Trionic 5 does not have a mass air flow sensor, thus you aren't letting in any "unmetered air". As long as the PCV valve on the vacuum line between the PCV nipple and the throttle body is good, you'll be fine.

The worst that's going to happen is oil vapor and water vapor may condense on things near the cap and make a mess.
 

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Trionic 5 does not have a mass air flow sensor, thus you aren't letting in any "unmetered air". As long as the PCV valve on the vacuum line between the PCV nipple and the throttle body is good, you'll be fine.

The worst that's going to happen is oil vapor and water vapor may condense on things near the cap and make a mess.
Sorry, have no experience with the turboed cars, mine is unfortunately a gutless turd :(
 

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You have a lot of different types of crankcase ventilation systems. They are in princip all doing the same thing. Quote:[crankcase on modern cars is under negative (vacuum) pressure to prevent the gases from 1. building up to a high pressure and forcing oil out the seals 2. burn the gases from combustion and any vapors in the crankcase so they dont escape to the environment and all this is accomplished through a PCV (CDR on a diesel) valve that only opens when there is correct vacuum applied to the valve from the manifold]Quote. The type you talk about here is the most common I think. SAAB and Volvo used a very simple type on some of their none turbo engines. A small hose goes from the crankcase/valvecover to a small fitting under the throttle, this fitting has a metered hole in it, to control the amount of vacum. This ventilates the crankcase during idle. Then there is another bigger hose that goes from the crankcase/valvecover to just above the throttle (SAAB mostly), or to the top of the airfilter cover(Volvo mostly). This takes care of the gases from maybe 1500rpm and up. On turbo engines you get a lot of problems because you switch from vacum to pressure in the intake. See for instance this SAAB kit: Crankcase Ventilation fix kit for Saab 9-5 2.0 2.3 M98-03 [12.1200] There was a site that explained all the different SAAB types. from 1999 and up. Can't find it now, but if you search on the internet you will find a lot of info about it. There is probably some info here on TSL to?
 
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