Exceasive crankcase pressure

Driver460sz · Mar 30, 2023

I am running a 351w (427) speed density car with no EGR, 90mm TB, trickflow intake, deleted smog, deleted A/C. Anyways, I just set put in a new wideband O2 sensor, new PCV, new vacuum lines. Now there is a whinning sound (From crankcase pressure). The line is clear (I can blow through it easily), filter is new, even tried a second one.

Anyways, after about10 seconds the preasure builds, whines louder. When I pull the oil cap the pressure leaves and the whine stops. The idle stays the same when that happens.

What is the cause? I have heard bend rod or valve. Clogged system (But I don't think so). Revs fine, no engine ticks (Outside of the Ford tick). Plugs, wires, oil are all new as well.

I heard don't do a breather as well as you can run a breather. Maybe I should run a hose from the oil cap (Trick flow already have a spot for one) to the intake??? I feel a breather would work but will it really. Is there a bigger problem at hand.

The motor has like 1000 miles on it. Let me know what you all say/think.

Thanks

90sickfox · Mar 30, 2023

If you run a MAF there should be a hose from the oil fill tube to the throttle body nipple. In the past I drilled an oil fill cap for an aftermarket valve cover and added a nipple inside it. Ran a hose from there to the throttle body.

Driver460sz · Mar 30, 2023

SD. I should have mentioned that.

Sorry

TOOLOW91 · Mar 31, 2023

Aftermarket speed density ecu ?

Did it do this before ? If not what changed when you did the repairs / upgrades ?

Did the car have an issue before this ? Is the screen clogged under the pcv or put back in correctly ?

manicmechanic007 · Mar 31, 2023

You hook up the PCV vacuum supply hose wherever you want as long as it is real strong vacuum
The kind that will kill the motor if unplugged abruptly
Then, when you have it hooked up, it should suck through the pcv valve strong enough to see vacuum at the other valve cover
Not exactly vacuum that you can measure, rather it should suck a piece of paper to the cover with the vent removed
You mention 427
If you have a stroked fire breather, you may need a crank evac system with one way valves

LILCBRA · Mar 31, 2023

I hate to mention this since it's such a new engine, but it's also possible that it has a broken piston ring. It's happened to me unfortunately, I hope that's not the case for you. (Insert fingers crossed emoji here...)

Driver460sz · Mar 31, 2023

LILCBRA said:
I hate to mention this since it's such a new engine, but it's also possible that it has a broken piston ring. It's happened to me unfortunately, I hope that's not the case for you. (Insert fingers crossed emoji here...)

That is where my concern lies. Going to comp check all the pistons and hope they all come out the same.

Driver460sz · Mar 31, 2023

TOOLOW91 said:
Aftermarket speed density ecu ?

Did it do this before ? If not what changed when you did the repairs / upgrades ?

Did the car have an issue before this ? Is the screen clogged under the pcv or put back in correctly ?

Microsquirt, did not do this before I replaced my O2, PCV, a few vacuum lines, header gasket.

Now the AFR wideband reads high tens where as it was climbing and off the charts lean (dash dash dash). It has NEVER done this. But I also had a mess of a problem before all if this where my tune went wild (My bad), the motor flooded with fuel, wouldn't start. MAY have messed something up qith crankcase pressure that locked it up (Vapor/fuel lock).

manicmechanic007 said:
You hook up the PCV vacuum supply hose wherever you want as long as it is real strong vacuum
The kind that will kill the motor if unplugged abruptly
Then, when you have it hooked up, it should suck through the pcv valve strong enough to see vacuum at the other valve cover
Not exactly vacuum that you can measure, rather it should suck a piece of paper to the cover with the vent removed
You mention 427
If you have a stroked fire breather, you may need a crank evac system with one way valves

It whines fairly loud all hooked up which tells me vacuum is strong. It builds then whines. I then pull the oil filler cap off, the pressure releases and if I did put a paper over the cap it woild hold it in place, not suck it in strong.

-Firebreather.... 10.1 come, 500 torque kinda power. Nothing crazy but all N/A and I guess I wouldn't call that "stock". Stage 2 TFS cam.

TOOLOW91 · Mar 31, 2023

Not that it fixes your issue but you can 1000 percent run lines from covers to catch can open breather style and plug the pcv hole . Hell I did it on a stock ecu car .

You sure the line are all routed right ? Sometning seems off in the tune given what you’re saying it’s like yhe car may have been tuned around the mechanical issue you have.

If you flooded engine that bad it could have washed the walls and ring seal may not be as good now

manicmechanic007 · Mar 31, 2023

What I mean by sufficient vacuum, is in the PCV system and the huff
When all hooked up on a normal car, the pcv valve will put enough suction in the valve cover that the other cover has enough negative pressure to pull a piece of paper to the valve cover with the vent (intake) out. If you have tons of pressure in there, with big pistons and such, you might have too much positive pressure for one PCV valve to handle, try putting one in each cover. That is a makeshift crank evac

manicmechanic007 · Mar 31, 2023

With that setup, you definitely might have too much blowby for a stock pvc valve
They made several, find one with a bigger hole. (or find 2). That is what Ford used to do for altitude compensation.
A bigger valve at altitude over 5000

WhiteCobra95 · Mar 31, 2023

I'm a bit confused about your setup, so please forgive me if I'm not understanding something here. However, it sounds like you have the PCV valve / line hooked up to your intake manifold, but no fresh air feed to the crankcase. If this is the case, you will be pulling manifold vacuum in the crankcase which is completely wrong and really bad. These flow circuits are much easier to draw out on paper, but I'll try to write it out instead.

For an emissions legal naturally aspirated engine, the PCV system typically has two lines which make up the circuits. The system functions differently at low / part load than it does at high load. The intention in both cases is to pickup HC gasses in the crankcase and burn them in the combustion chamber instead of venting them to atmosphere. It's better for emissions, it prolongs the life of the oil, it improves fuel economy, and reduces corrosion of internal components like bearings. Unless you have a crazy radical race engine, there is no reason not to run a PCV system - it does not hurt power at all when it's functioning properly.

On SN95 5.0s and probably Foxbody 5.0s (it's been some time since I've messed with a Foxbody but it should be nearly the same), there is a hose downstream of the MAF sensor which connects to the filler neck on the valve cover (with a baffle at the bottom of the filler neck). This is the fresh air feed at low loads and dirty air line at high loads. There is another line which connects to the PCV valve at the back of the intake manifold, with one end of the PCV valve exposed to the crankcase, and the other end of the valve connected to a hose which attaches to the bottom of the intake manifold. This is the low load dirty air circuit.

At low loads: Vacuum from the intake manifold draws "dirty air" from the crank case through the PCV vavle into the intake manifold where it gets pulled into the chamber and burned. The PCV valve has a check valve which opens up under vacuum and the flow rate of the dirty air circuit is limited by the orifice size of the PCV valve. At the same time, fresh air flows into the crankcase from the high load circuit / fresh air feed through the valve cover to replenish the air drawn into the intake manifold. This prevents the crankcase pressure from dropping to the vacuum level of the intake manifold. There will be some pressure drop compared to ambient pressure, but it's only very slight - like a couple of mBar at idle or cruising.

At high loads / WOT: The manifold pressure is nearly at ambient pressure level. The check valve in the PCV valve closes which shuts off the low load / dirty air circuit. The high air flow through the air induction system pulls a small vacuum across the high load circuit, so that any blow-by or positive crankcase pressure from running at high loads is drawn into the air intake system. This "dirty air" flows through the throttle, and subsequently flows through the intake manifold to the combustion chamber where it's burned. A baffle is used in the filler neck to prevent oil from being sucked or pushed into the high load line which can and does happen (much worse on boosted engines due to higher blow by). At high loads, the flow of the PCV system essentially reverses and the fresh air feed to the valve cover becomes a dirty air feed upstream of the throttle.

A couple of notes: The fresh air feed / high load circuit is located after the MAF sensor so that any air drawn through the crankcase into the intake manifold at light loads is metered air by the ECU. At high loads, this isn't an issue because the PCV flow rate is insignificantly small compared to the total fresh air flow into the engine and usually the blow by gasses at high load are mostly inert (like EGR).

Okay, so back to your issue: Do you have a fresh air feed / high load circuit hose connected to your valve cover or filler neck? If you don't, but you have a PCV valve and PCV line connected to your intake manifold, then you have a dead-headed system and your crankcase is getting pulled down to somtehting close to manifold vacuum. The crankcase is not designed for this low vacuum level and the whistling noise you're hearing is air getting sucked into the crankcase through the weakest sealing gasket location on your engine (most likely a valve cover gasket or between the china rail and intake manifold seals/RTV). This is REALLY bad! You will need to add a factory style fresh air feed to resolve this.

One option is to just stuff an open breather cap / filter on the valve cover, but if you do this with a MAF system, you'll need to remove the PCV valve and low load circuit. I've run those "open" systems on my drag cars in the past, mainly because they had huge cams and didn't pull much manifold vacuum, but I don't recommend this for a street or street/strip car because oil vapors tend to come out through the breather which will dirty up your engine and anything located in that area.

I hope this helps!

Driver460sz · Mar 31, 2023

Hummmmm. Never heard of this option. It seems that the hose is handling the movement of air out of the motor but something from the intake (draw) is too much. Of course it's cyclical so it all goes together. If I pull the oil filler the pressure levels out and no drop in idle. If I pull the PCV hose and check motor to intake there is nothing coming out. If I check draw from the line into the intake the pull is very apparent. If I block the line into the I take the car almost stalls and then comes back to life.

With the whole system connected it idles nicely at 900 rpm and afr around 12.5 (still low) and with the oil cap off around 11. Both ways the idle is still smooth.

I will check comp tomorrow. Hoping the tune can help but that doesn't seem logical to correct blow by or this high crank case pressure. I am soooo hoping its not rings, rods or valves.

I also tried running a line from the valve cover to intake but that didn't do anything either (Still whistled).

Maybe......just maybe, there is a slight gasket problem and that's causing the whistle which I CANT locate. When I shut the car off the whistle continues for about 4 seconds and then goes away. I wonder if the crankcase pressure is just fine but there is JUST enough of a vacuum leak somewhere to cause the noise.

Driver460sz · Mar 31, 2023

WhiteCobra95 said:
I'm a bit confused about your setup, so please forgive me if I'm not understanding something here. However, it sounds like you have the PCV valve / line hooked up to your intake manifold, but no fresh air feed to the crankcase. If this is the case, you will be pulling manifold vacuum in the crankcase which is completely wrong and really bad. These flow circuits are much easier to draw out on paper, but I'll try to write it out instead.

For an emissions legal naturally aspirated engine, the PCV system typically has two lines which make up the circuits. The system functions differently at low / part load than it does at high load. The intention in both cases is to pickup HC gasses in the crankcase and burn them in the combustion chamber instead of venting them to atmosphere. It's better for emissions, it prolongs the life of the oil, it improves fuel economy, and reduces corrosion of internal components like bearings. Unless you have a crazy radical race engine, there is no reason not to run a PCV system - it does not hurt power at all when it's functioning properly.

On SN95 5.0s and probably Foxbody 5.0s (it's been some time since I've messed with a Foxbody but it should be nearly the same), there is a hose downstream of the MAF sensor which connects to the filler neck on the valve cover (with a baffle at the bottom of the filler neck). This is the fresh air feed at low loads and dirty air line at high loads. There is another line which connects to the PCV valve at the back of the intake manifold, with one end of the PCV valve exposed to the crankcase, and the other end of the valve connected to a hose which attaches to the bottom of the intake manifold. This is the low load dirty air circuit.

At low loads: Vacuum from the intake manifold draws "dirty air" from the crank case through the PCV vavle into the intake manifold where it gets pulled into the chamber and burned. The PCV valve has a check valve which opens up under vacuum and the flow rate of the dirty air circuit is limited by the orifice size of the PCV valve. At the same time, fresh air flows into the crankcase from the high load circuit / fresh air feed through the valve cover to replenish the air drawn into the intake manifold. This prevents the crankcase pressure from dropping to the vacuum level of the intake manifold. There will be some pressure drop compared to ambient pressure, but it's only very slight - like a couple of mBar at idle or cruising.

At high loads / WOT: The manifold pressure is nearly at ambient pressure level. The check valve in the PCV valve closes which shuts off the low load / dirty air circuit. The high air flow through the air induction system pulls a small vacuum across the high load circuit, so that any blow-by or positive crankcase pressure from running at high loads is drawn into the air intake system. This "dirty air" flows through the throttle, and subsequently flows through the intake manifold to the combustion chamber where it's burned. A baffle is used in the filler neck to prevent oil from being sucked or pushed into the high load line which can and does happen (much worse on boosted engines due to higher blow by). At high loads, the flow of the PCV system essentially reverses and the fresh air feed to the valve cover becomes a dirty air feed upstream of the throttle.

A couple of notes: The fresh air feed / high load circuit is located after the MAF sensor so that any air drawn through the crankcase into the intake manifold at light loads is metered air by the ECU. At high loads, this isn't an issue because the PCV flow rate is insignificantly small compared to the total fresh air flow into the engine and usually the blow by gasses at high load are mostly inert (like EGR).

Okay, so back to your issue: Do you have a fresh air feed / high load circuit hose connected to your valve cover or filler neck? If you don't, but you have a PCV valve and PCV line connected to your intake manifold, then you have a dead-headed system and your crankcase is getting pulled down to somtehting close to manifold vacuum. The crankcase is not designed for this low vacuum level and the whistling noise you're hearing is air getting sucked into the crankcase through the weakest sealing gasket location on your engine (most likely a valve cover gasket or between the china rail and intake manifold seals/RTV). This is REALLY bad! You will need to add a factory style fresh air feed to resolve this.

One option is to just stuff an open breather cap / filter on the valve cover, but if you do this with a MAF system, you'll need to remove the PCV valve and low load circuit. I've run those "open" systems on my drag cars in the past, mainly because they had huge cams and didn't pull much manifold vacuum, but I don't recommend this for a street or street/strip car because oil vapors tend to come out through the breather which will dirty up your engine and anything located in that area.

I hope this helps!

My car is SD and not MAF so unmetered air shouldn't be a thing for me. So, what I take from this, and it all makes sense is this.

As I currently do not have a breather on the valve cover. Which on the stock setup was a tube from the filler to the TB, I am creating too much pressure and I am in need of a breather there to offset crankcase pressure and to let in fresh air. Perhaps the reason this was not a problem previously was because I had a vacuum leak which was in fact helping the system reduce crankcase pressure and allowed in air.

So, as I have an SD system, what I am hearing is. Keep the PCV as is and add a breather and I should be good to go.

Sound about right?

Thanks

Monkeybutt2000 · Apr 1, 2023

What brand is the TB?

CAMTWO1070 · Apr 1, 2023

Driver460sz said:
I am running a 351w (427) speed density car with no EGR, 90mm TB, trickflow intake, deleted smog, deleted A/C. Anyways, I just set put in a new wideband O2 sensor, new PCV, new vacuum lines. Now there is a whinning sound (From crankcase pressure). The line is clear (I can blow through it easily), filter is new, even tried a second one.

Anyways, after about10 seconds the preasure builds, whines louder. When I pull the oil cap the pressure leaves and the whine stops. The idle stays the same when that happens.

What is the cause? I have heard bend rod or valve. Clogged system (But I don't think so). Revs fine, no engine ticks (Outside of the Ford tick). Plugs, wires, oil are all new as well.

I heard don't do a breather as well as you can run a breather. Maybe I should run a hose from the oil cap (Trick flow already have a spot for one) to the intake??? I feel a breather would work but will it really. Is there a bigger problem at hand.

The motor has like 1000 miles on it. Let me know what you all say/think.

Thanks

Experience tops all in lots of engine problems and once you know about how engine internals operate you'll get the ideas to solving issues.....

When my 351w started its blowby it was due to the rings....Doing a leakdown test [not a compression test]revealed the bad cylinders quicker and easier.

I took some transmission fluid and put some in the gastank and shook the car to mix it well in the tank then grabbed a box of Bon-Ami revved the piss out of the engine and chucked in a few handfulls of granulated soap into the intake which scuffed the bores enough to get the rings rotating again and the blowby stopped then I drove it around to let the trans fluid clean the ring grooves...

What most people dont know is that there are lots of internal engine parts made to spin like the rings the valves the pushrods and the lifters on non-roller cam engines...

One time I built a SBC350 at 14yrs old and listened to the wrong advice on how to install and space the rings and when running the splits on 3 pistons aligned the blowby spit 2 quarts out of the engine on 1 hefty burn out....

When I took the engine apart my dad looked over my work and noticed the rings were too tight in the ring grooves so we rehoned the cylinders with a ball hone and got some new rings also my dad opened up every ring land and oil groove on all 8 pistons a small bit and when I reassembled the engine it ran awesome..

Good Luck

CAMTWO1070 · Apr 1, 2023

Another point you brought up is the crankcase breather........I NEVER leave my crankcase to vent out on its own and heres why......

Look at this picture below of my see thru breather tube that goes to my very tiny but very effective catch can that I modified with a draincock from a radiator and have to drain every 2-3 days plus the water is always clean and clear but smells like paint thinner...

Another thing to point out is Im running tall aluminum valvecovers and Im also running the internal baffle plates inside both covers to keep oil from going inside and I also run a different type of catch can on the PCV valve side too thats made for filtering oil out from the higher suction and whats evacuated resembles pancake batter............LOL

The pictures below were taken after going on a 1hr run.....

Do you notice the humidity inside the see-thru tube.....?

The suction of the intake removed that moisture...Just letting the crankcase vent out on its own so pressure will do its job but working against gravity will do very little to expel that water before turning to steam and steam is no good for bearings/ piston rings...

All of that moisture gets caught up inside your oil filter causing your oil filter to bypass doing its job and thats bad and is what causes the Ford Tick when the engine is at operating temps because trapped steam is escaping the filter!!

On my 410w Im planning on going with a remote dual filter setup .....The angle of the filter compromises proper filtering also so my remote setup the filters will be mounted vertically to take advantage of the whole of both filters without trapped air and water/steam..

Another thing I run is a water seperater filter on the return line back to my gastank and I go through a filter every oilchange...Thats mainly how the water gets into the crankcase as ethanol produces the water by pulling it from the air and it ends up getting mixed with the oil.......

The other way water gets in the crankcase and under the valvecovers is by good old naturally formed condensation when metal cools way down also during humid/rainny days...

When people comment about how much water is exitting my tailpipes I reply back Its better going out the pipes than staying in the pan.....LOL

Good Luck

Driver460sz · Apr 1, 2023

Monkeybutt2000 said:
What brand is the TB?

90mm Accufab. No hole in it.

shifty_50h · Apr 1, 2023

I had a very similar problem it caused the whistle and a hiss and when I took the oil cap off it would make a whoosh sound and then clear up it happened to be that the intake manifold was sitting too high on the heads because the heads had been milled the walls at the end of each end of the block we're pushing the intake manifold up too high with the little cork or rubber gaskets in place so I removed those and put a nice bead of silicone reinstalled intake manifold and the problem was gone I also had a problem with it running a lot weaker than it should have for the build and afrs were all over the place sounds like this could possibly be a problem I only had about 100 miles on the build when that happened and I was chasing my tail it's worth a look

Driver460sz · Apr 1, 2023

shifty_50h said:
I had a very similar problem it caused the whistle and a hiss and when I took the oil cap off it would make a whoosh sound and then clear up it happened to be that the intake manifold was sitting too high on the heads because the heads had been milled the walls at the end of each end of the block we're pushing the intake manifold up too high with the little cork or rubber gaskets in place so I removed those and put a nice bead of silicone reinstalled intake manifold and the problem was gone I also had a problem with it running a lot weaker than it should have for the build and afrs were all over the place sounds like this could possibly be a problem I only had about 100 miles on the build when that happened and I was chasing my tail it's worth a look

Today I popped a breather on to the valve cover. Moved the new O2 sensor to a different spot on the exhaust and changed the angle. I was previously using the stock O2 placement which had it pointing down, not up 10 degree or more.

Upon start up, which it did just fine, it idled high until it warmed the sat at 900. Eventually it started to bounce 775-950 for a bit. Took a 1/2 turn on the TB and that made it so it bounce less (850-950).

However.......it blew some, what felt to me, serious white smoke until it "warmed up". Which was about 2 or 3 mins of idle.

Tomorrow I have someone remoting in to look at the tune. Maybe there is something in there that is way off. I can't imagine the tune is doing all of this nonsense.

Anyways, based on all that is going I have to think it's a head gasket, although my coolant hasn't moved at all, oil hasn't leaked, no backfire, no fuel un the oil.

If it's all a mess tomorrow I will do the leak down test, Como test. Go from there. Maybe add some reduce smoke oil in there to see what happens before tear down. I will totally look at what you are saying. See if it aligns properly.

My car did drive fine up until a tune problem which caused a massive flooding condition. Could have washed the cylinders as well. Again, leak down/comp.

Wondering what the next process is if those two checks come back clean. At least it's not whine with the breather on but still worry about it messing vacuum with the PCV in place still. Some say fine some say no way with that one.

Thanks for the help.

Exceasive crankcase pressure

Driver460sz

90sickfox

Wasn't a pretty sight...and I've got big hands

Driver460sz

TOOLOW91

If you're the village idiot what's that make me?

manicmechanic007

LILCBRA

I wish I didn't have all of these balls in the air

Driver460sz

Driver460sz

TOOLOW91

If you're the village idiot what's that make me?

manicmechanic007

manicmechanic007

WhiteCobra95

Driver460sz

Driver460sz

Monkeybutt2000

Mustang Master

CAMTWO1070

Active Member

CAMTWO1070

Active Member

Driver460sz

shifty_50h

New Member

Driver460sz

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