Oil Catch Can Help.
- Thread starter LZSN95
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jozsefsz
15 Year Member
I don't have the on3, but did have to deal with the turbo pressurizing the crankcase. I run the cap breather like you have, and also a small breather (attached to a hollowed-out PCV valve) at the back of the intake manifold where the PCV valve used to live.
It's really important that the rest of the PCV system be disconnected - or a reliable check-valve added. Otherwise, whenever you hit boost, the crankcase is going to see all of the pressure and can even blow seals. It's also important because - when using an oil-cap breather - the PCV then becomes a large vacuum leak (in the stock configuration the crankcase is closed and there's a little hose from the intake to the oil filler neck where the crankcase gets fresh air -- that hose connects to the air intake after the MAF so it's 'metered air.')
If you've done this, and you're still getting a lot of blowby through the breather, your engine might be getting worn. A compression test could help you determine if that's the case.
It's really important that the rest of the PCV system be disconnected - or a reliable check-valve added. Otherwise, whenever you hit boost, the crankcase is going to see all of the pressure and can even blow seals. It's also important because - when using an oil-cap breather - the PCV then becomes a large vacuum leak (in the stock configuration the crankcase is closed and there's a little hose from the intake to the oil filler neck where the crankcase gets fresh air -- that hose connects to the air intake after the MAF so it's 'metered air.')
If you've done this, and you're still getting a lot of blowby through the breather, your engine might be getting worn. A compression test could help you determine if that's the case.
I finally got a minute to look at it tonight. I took the valve cover off and this is what I found. All I have to relive crank case pressure is the breather on the passenger side fill. All the pcv stuff is deleted. I think I frothed the oil and pushed it all up in the valve covers. I need to get this crank case pressure under control. I was going to cut another hole in the passenger side valve cover and then i found this.
jozsefsz
15 Year Member
I've never seen oil froth like that, in the absence of a lot of water (i.e. blown head gasket or if you're super-lucky a lower intake manifold gasket). You can get some aeration from overfilling but it doesn't look like that (modern detergent oils won't foam to that degree). That unfortunately looks like the typical milkshake from when that happens. Do you happen to also be missing quite a bit of coolant? And the oil level is higher than it should be? You'll definitely want to investigate before running again - bearing damage may already have happened. I hope I'm wrong.
Yeah it's pretty bad. I have been having issues with the cooling systme. I blew one set of head gaskets already when I first got it running, I hope not another one, hopefully it's just the intake. The only reason I think it's the intake is because I'm not getting anything out of the exhaust like i did when I blew the head gaskets.
Also if this thing needs to be rebuilt I'm considering doing a 351/408
As far as I know, ford added the pressure release hose on the oil filler neck in order to equalize the crankcase pressure in parallel with the PCV valve. They didn't simply use a bigger PCV to vent the crankcase. This might've been due to cost saving, but it might've also been by design.
If I were you, I'd try to see where exactly the gasket blew. If it's in the back of the engine, then I'd bet that unequalized pressure is the culprit, since you DO have a breather vent, which might even have adequate flow, but the flow from the back of the crankcase to the front might not be sufficient for the pressure you're building, thus it escapes through the gasket. If the gasket blew in the back, try adding another breather at the back of the crankcase, at the PCV or even the valve cover, it might be a fix.
Either way, finding the location of the leak will clue you in to what the problem is.
jozsefsz
15 Year Member
The hose on the oil filler neck is there to equalize the crankcase pressure - that is, the PCV is drawing a vacuum on the crankcase, and unless it has a way to pull in air from somewhere, it can suck in gaskets and cause other issues. It doesn't release pressure, but rather sucks in air from that hose. It's connected to the intake (after the MAF) so that the air it's sucking in is 'metered' (accounted-for when adding fuel) otherwise you'd get a lean condition from a large vacuum leak as the PCV draws in air. It's a fairly common design, and wasn't a cost-cutting measure at all.
A blown lower intake manifold gasket allowing coolant to leak into the oil is unlikely to be related to boost pressure at all (the cooling system applies a positive pressure of ~16psi). If it is properly installed and tightened, that gasket would see very little boost from the lifter valley. And if it were boost blowing that gasket, you'd have oil in the coolant and not coolant in the oil. I could see this explanation being reasonable if it were a valve-cover gasket. But you're right it doesn't hurt to vent the location of the PCV valve to supplement the oil filler breather. I've had the oil cap and PCV-location vent for 9 or 10 years now running ~11psi and haven't had any gasket issues.
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