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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: devanray on March 10, 2011, 11:13:09 am
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77 C-10, 350 with a 400, unsure of gearing, 1980 Rochester Quadrojet.
Driving the other day for about 10 minutes at 35 to 45 mph when I noticed smoke from under the hood. Popped it open and found that the PCV had come out and leaking oil from the valve cover opening and that oil was leaking from the top of the dipstick. The PCV had been rattling as I drove and thought perhaps it was not functioning 100%, so I drove to the auto-parts store and got a new one, it it tighter and has not popped out but the rattling is still their and the oil still leaks from the top of the dipstick.
I have heard of something like overblow, could this be an effect of that? Is that the right word?
I have no oil pressure gauge, is this were I should start?
Thanks
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I've only heard it called blow-by--gases making it past your rings into the crankcase. Your pcv valve opens as needed to let your carburetor suck those gases back up and reburn them. That system only tolerates a small amount. Do you have the pcv hose from the valve routed into your carburetor (as it should be)? Remove the pcv valve and remove the hose from the other valve cover that routes into the breather. Start the truck and see if smoke comes out of the now open holes in your valve covers. You need a working oil pressure gage--always. I thought I could get by for one day without one once. I don't like talking about what that cost me. If this happened suddenly you may have a cracked or deteriorating ring, maybe worse. If you're not running adequate oil pressure rings don't last long. I don't know of anything simple that would cause your symptoms.
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Blow-by, thats it. Yes when I remove the PCV smoke does come out of the opening. The hose on the PCV goes to the riser on the carb, as it should.
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I will get an oil pressure gauge on it ASAP and update. Someone else said that the rings could be the issue. Anybody know about how much something like that would be to have fixed? I don't really have the knowledge or work area to pull an engine and the head to replace rings. Would checking the compression in each cylinder tell me anything?
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is the oil level at the right leval?
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It was a quart low when last I checked, about 2 weeks after initial check that turned out good. Topped it off but haven't checked yet after 50 miles of driving. Its pouring rain outside, I'll check it again when the weather takes a break.
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Start the engine, remove the pcv valve from the valve cover. See if there is suction at the PCV valve.
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Plenty of suction, it makes that "shwoop" sound when I pull it out. Oh, at the valve, I'll have to check that. Should it be sucking in or out (that's what she said)
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Plenty of suction, it makes that "shwoop" sound when I pull it out. Oh, at the valve, I'll have to check that. Should it be sucking in or out (that's what she said)
??? When you pull the PCV valve out of the valve cover you hear a shwoop sound?
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I do find it difficult at times to type sounds but its a suction like sound. If I can get myself off of the TV watching this earthquake/Tsunami I'll check the vacuum from the pcv itself.
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Plenty of suction from the PCV, I have replaced the oil filler cap with a breather and now the PCV doesn't buzz or rattle as I drive. I know it's no fix, but I figure realeasing some pressure may assist with preventing further damage.
Got a pressure line to reattach my oil pressure gauge and will get it in tomorrow and let you know what the pressure reading is.
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So you didn't have a breather?
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No breather.
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No breather. The valve covers only had a PCV and oil filler cap, I replaced the cap with a breather in hopes of releasing some of the pressure.
I hooked up the OE oil pressure gauge with new tubing and started it up to see the pressure level cruze to about 40, within 5 minutes @idle it was sitting at 60. Hmm... I am going to pretend for now that the reason the previous owner cut the tubing was because the gauge doesn't work. I'm going to get an after market gauge and see what happens.
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Your problem isn't oil pressure it's improper crankcase ventilation. Ever pour a gas can without the vent open? How can you have a pcv valve in the crankcase with no fresh air breather? You need to have a breather and a pcv valve.
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I put in a breather and the PCV is still in, but the oil pressure readings are still wonky, ever hear of a OE gauge going bad?
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My oil pressure gauge is still showing 30 at idle and gets up to about 50 while driving. The pcv rattles like its about to blow, this with the breather in. The pcv is new and the tubing is good. I'm assuming that the blow-by is causing the pcv rattle. Any ideas?
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The pcv valve is supposed to rattle. It opens and closes rapidly and makes a ticking sound. If it doesn't rattle then it's either plugged up or otherwise not functioning, or there is no vacuum supplied to it. As far as your oil pressure those numbers are not anything that would give me concern. If you want to verify that your gauge is giving you an accurate reading, hook up a mechanical diagnostic pressure gauge to the inlet at either the oil pressure switch (above the filter) or at the oil pressure sending unit inlet (behind the distributor).
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Okay, thanks Grim. So, they designed that pcv to make such a racket? I mean, its loud. Loudest thing under the hood for me.
I'll feel okay about things until I can get a pressure gauge and really see whats going on.