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Old 04-29-2002, 05:18 PM   #1
jeffg
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Default excessive crankcase pressure

I was in the process of changing the oil in my car this weekend, when I noticed something odd. I added some oil, then rolled it off the ramps and started the car. I checked the oil level and decided to add some oil. I pulled the oil fill cap off and was greated by a large amount of air pressure out the oil fill tube. This was with the car running, if that helps.

There was enought air that if I put my hand over the fill tube it would push it back off. I tried to pour some oil down there, but it just spit right back out the tube.

What would cuase this much crankcase pressure? I pulled the PCV valve to check for stuck/broken, but it looks fine.

Also the oil is jet black when it comes out of the car. This is mobile 1 synthetic, which I thought would last longer, and was about 3800 miles on the change. There was about 3000 of which was freeway ~75mph cruising.

Any help at all would be appriciated.

I am going to do a compression test sometime soon. what numbers should I be getting for a "new stock" type reading.

Also how to I keep the coil pack from throwing big sparks onto the block when I crank it with the wires pulled?

Thanks in Advance.
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Old 04-29-2002, 06:17 PM   #2
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Sounds like it could have a blowby which is cause by compression leaking thru the rings into the crankcase.How many miles?
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Old 04-29-2002, 06:22 PM   #3
Jademonkey
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I noticed the exact same thing when I last changed my oil. I would just assume it was normal? I also use mobil1 synth...and it gets dirty that fast for me as well.

hey, how long did you have your engine running? If i let it get nice and hot, I notice the same things...but if i start it immediately after filling, on a cold motor, i don't have all the air pressure.
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Old 04-29-2002, 06:24 PM   #4
jetfan8178
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Oil doesn't really get dirty.It discolors due to heat breaking it down.If your engine had dirt inside it you may as well scrap it.
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Old 04-29-2002, 06:35 PM   #5
Jademonkey
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Quote:
Originally posted by jetfan8178
Oil doesn't really get dirty.It discolors due to heat breaking it down.If your engine had dirt inside it you may as well scrap it.
Well, I didn't mean "dirt" as in the **** in the ground. It was just a way to say the oil had broken down, and become discolored, as you had pointed out.

if it was blowby, wouldn't you see signs? Like lower gas mileage, or loss of power according to butt dyno?
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Old 04-29-2002, 06:36 PM   #6
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I would hope that this is normal, but that was a LOT of air. It had to be coming from somewhere. The car as about 22k on it.

would a leak down or compression test point to bad rings or valve seals?
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Old 04-29-2002, 06:43 PM   #7
jetfan8178
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Not always a big difference.A very minor drop in compression and perhaps a little smoke.I doubt that you will feel the difference.It isn't really a terribly destructive thing.Just keep an eye on your oil level and try not to overev the engine.The worst that can happen is that the pressure in the oil valleys in the heads gets too high and blows the head gaskets.(I talk from exsperience with other cars,Subeys may be different)
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Old 04-29-2002, 06:46 PM   #8
jetfan8178
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Quote:
Originally posted by jeffg
I would hope that this is normal, but that was a LOT of air. It had to be coming from somewhere. The car as about 22k on it.

would a leak down or compression test point to bad rings or valve seals?
Maybe.Cant hurt to try.This often happens if a car overheats or if you run it with low oil and they dont properly lubricate.A very minor fluctuation in the rings integrity will quickly become a blowby.

Keep in mind you could get 100k easily with a blowby.It could never hurt your engine or it could kill it.All luck.
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Old 04-29-2002, 06:59 PM   #9
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I am curious if something like this would be covered under the warenty. I have reciepts for all my oil changes, and it has never been low, at least according to the dealer printout.

I would sure like a new engine if that were a posibility.

jeff
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Old 04-29-2002, 07:13 PM   #10
ColinL
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re: PCV, even if it seems unblocked it would be smart to swap it if you've never done so and have more than 15,000 miles.

re: coil pack sparking, just unplug it. there's a connector that goes in to the left side of it, unplug and it doesn't fire.

Last edited by ColinL; 04-30-2002 at 08:38 AM.
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