North American Turbocoupe Organization



Last question on this damn valve cover blowing out, I promise.
Kev Offline
Posting Freak
#1
I'm sure you guys are tired of hearing about my valve cover blowing out, but the mechanics that I'm dealing with, this board, and myself can't seem to figure it out. So, I have a few final questions.
1. If the lower pcv hose is plugged around the baffling to the crank case, would this cause the VC gasket to blow?

2. Why in the world does the valve cover gasket blow instead of the breather element pop out of the rubber grommet when the pressure builds up?

3. What are all the parts of the pcv system, what is the route air pressure takes, and why?

4. Could the holes inside the head and block that are for the oil to flow back down get plugged and cause the gasket to blow? If so, wouldn't the valve cover fill up with oil too?

Just for anyone who hasn't followed this problem of mine or doesn't remember...I've blown 3 valve cover gaskets since the change of the head 2-3 months ago. After the second gasket blew out, I changed the pcv valve (ford part), took off and cleaned out the breather element and the connection hose. Used the new expensive blue rubber gasket to replace it and it didn't leak, it completely blew out the back of the valve cover. After the 3rd gasket blew out, I had the compression checked and it read 150 across the cylinders. And that pretty much catches you up. Thanks for any thoughts on this, I'm completely stumped and looking for answers.

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Kev
88 TC 5spd Black body, red leather, K&N in front of the radiator, bypassed BCS at around 17 psi, polished throttle body, 2 1/2" dynomax ultraflow mandrel bent duals. 255 lph fuel pump, totally rebuilt head with Melling cam kit
Kev
1988 TC 5spd
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Pete D Offline
Administrator
#2
1. yes, if plugged then pressure in the crankcase from normal blowby (there is always some blowby even in a very healthy engine) can't be vented up through the oil seperator, up through the pcv and into the upper intake.
Therefore pressure would build up in the crankcase and the valve cover (if the breather is also plugged)

2 Depends on how easy your breather pops. I have seen some that come right out and I have seen some that you couldn't blow out with a stick of dynamite.

3. Pressure travels from the crankcase, up through the oil seperator, up the lower pCV hose and through the PCV, through the upper hose and is sucked into the upper intake where it is drawn into the cylinders.

4 They could, anything is possible, BUT they don't. Think about it. If they got plugged all the oil would quickly get pumped to the top of the head and stay there, not drain back and real quickly the rod and main bearings would starve and the engine would sieze.

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NATO Member. it's not a vice, it's an obsession
Good judgement comes from bad experience, and a lot of that comes from bad judgment.
88 TC X 2, 86 SVO, mods list at
http://www.turbotbird.com/showroom/pd_88tc.htm
Pete Dunham


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Kev Offline
Posting Freak
#3
Thanks Pete, everything you said makes perfect sense but...why would you want the dirty air from the crankcase to be sucked back into the cylinders? Is there a better alternative, or is this just the environmentally friendly subject again? Seems like unwanted crankcase pressure would just be vented into the atmosphere. I'm not thinking of doing this, I'm just trying to understand the system. And there is absolutely no way for pressure to travel back through that hose that connects to the breather, right? Even if something is wrong with say...the turbo? Not that anything is wrong with my turbo, I'm just looking for answers. By the way, the car runs absolutely awesome except for the busted valve cover gasket.
Kev
1988 TC 5spd
Reply

Jeff K Offline
Administrator
#4
Did you try to blow thru the PCV to crankcase hose to see if it is plugged?

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Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 20 psi, forced air intercooler, water injection, bypass valve, Ranger roller cam, subframes, etc., etc.. // 86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP nitrous, ignition, gears, suspension, etc., etc.... // 91 Escort: Bone stock winter car // 02 Taurus Vulcan(wifes car)
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
05 Taurus SEL Duratec daily driver
04 Taurus Duratec (wifes car)
02 Pontiac Grand Prix GT
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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Kev Offline
Posting Freak
#5
Not yet Jeff, how do you get your head down there??? just kidding
I plan on taking the entire system apart today to check and clean everything.
Kev
1988 TC 5spd
Reply

Pete D Offline
Administrator
#6
Kev,
You won't be able to remove the oil seperator from the block without removing the lower intake which is a PITA. Just find a way to "extend" the hose to the seperator and blow through it as a check. If you can easily blow through it, there is no reason to take those parts out.

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NATO Member. it's not a vice, it's an obsession
Good judgement comes from bad experience, and a lot of that comes from bad judgment.
88 TC X 2, 86 SVO, mods list at
http://www.turbotbird.com/showroom/pd_88tc.htm
Pete Dunham


Reply

Kev Offline
Posting Freak
#7
OK, Pete, but I had another thought...Why doesn't the breather vent off the pressure in the valve cover no matter how much pressure it is? Is there some sort of limit, or does air pass the other way through the breather element sometimes?
Kev
1988 TC 5spd
Reply

Pete D Offline
Administrator
#8
Kev,
Personally, I think air can move in both directions thru the breather, assuming it isn't plugged. I can't prove it. I have heard of breathers becomming clogged, but it hasn't happened to me --- yet.

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NATO Member. it's not a vice, it's an obsession
Good judgement comes from bad experience, and a lot of that comes from bad judgment.
88 TC X 2, 86 SVO, mods list at
http://www.turbotbird.com/showroom/pd_88tc.htm
Pete Dunham


Reply

Jeff K Offline
Administrator
#9
Under boost, the PCV valve is closed, and any crankcase pressure (either from blowby, leaking intake valve guides, or PCV valve not closing 100%) will vent out the breather on the VC and down to the turbo inlet. When the PCV valve is open (most of the time), air flows from the turbo inlet, to the VC breather, and into the VC, down thru the crankcase, and out to the intake thru the PCV valve / hose.

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Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 20 psi, forced air intercooler, water injection, bypass valve, Ranger roller cam, subframes, etc., etc.. // 86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP nitrous, ignition, gears, suspension, etc., etc.... // 91 Escort: Bone stock winter car // 02 Taurus Vulcan(wifes car)
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
05 Taurus SEL Duratec daily driver
04 Taurus Duratec (wifes car)
02 Pontiac Grand Prix GT
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
Reply

Kev Offline
Posting Freak
#10
Update. All hoses and hardware are completely cleaned out and free flowing. I did as Pete suggested and extended the lower pcv hose. I could blow air into it easily and hold my hand above the hole where the breather attaches and feel air coming out. I blew both directions through the breather with ease too. I also blew into the tube that goes to the turbo just for the hell of it, and it's easy to blow into also. The problem is, I didn't have to clean anything out, it was all clean to begin with so I didn't solve any problems. So this brings me to a new question. Jeff said that while the pcv valve was open (which is most of the time) air travels from the turbo inlet to the breather through the VC into the crankcase up through the pcv valve to the intake and finally to the cylinders. Ok, why? Why would you want air to move all that way? Does this whole system need to breathe? If the turbo inlet wasn't connected to the valve cover, would the VC gasket get sucked in? I guess I'm asking what is the purpose of this design? And is there any way that boost from the turbo could move through the turbo inlet hose and into the valve cover this way? With everything checking out ok including the compression check, I'm stuck with thinking it can only be a bad (new) pcv valve. Is that where you guys would go next? If I can't fix it this time, I'm gonna have to take it to the dealer and let them dissect it and tell me I need a new engine. I'm stuck. But thanks for the patience and the guidance guys.

Kev
Kev
1988 TC 5spd
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