First 5.0 and leaking oil..Need help with valve covers

99ls1z · September 22nd, 2011, 02:06 PM

Just got a 90 Carb 5.0 and it leaks oil out of the breather on the valve cover under WOT. I'm thinking this is because it doesn't have a PVC connection from the valve cover to the carb.

Will I need new valve covers and PVC? I'm not sure what all I need to do to fix this. What parts do I need to get?

fogged306 · September 22nd, 2011, 03:54 PM

Is there a baffle under the breather? What else is done to the car?

99ls1z · September 22nd, 2011, 04:21 PM

I'm not sure what has been done beside being converted to a carb motor. I just got it and was told about the oil leak. Just idleing or crusing around no oil leaks just under wot.

94bossgt · September 23rd, 2011, 09:07 AM

its blow by caused by tons of crank pressure being built up not much you ca do about it except rebuild the bottom end you can try and run breathers in the valve covers but chances are that its too late

fogged306 · September 23rd, 2011, 02:19 PM

Pull the valve cover and check and see if there's a baffle under the hole. Could be as simple as rockers throwing oil out the breather hole. If it happens at WOT, chances are it's what bossgt mentioned, you just have too much crankcase pressure. You can run a catch can if that's the case, but it won't solve the fact that you're getting too much blowby.

99ls1z · September 23rd, 2011, 03:45 PM

I was mistaken it doesn't have a breather out of the valve covers just a crome oil cap. That is where the oil is leaking out of. I did hookup a pcv valve and same issue. Would you try replace the cap with a breather there?

fogged306 · September 23rd, 2011, 04:08 PM

Well if you had no crankcase ventilation at all then it will leak from somewhere. Depending on what's done to the engine, the PCV may or may not work. When you start to make decent power then the PCV can't keep up and you need a set of breathers. If you're still stock (cubes, heads) and the PCV isn't working, then it's too much blowby which means you're rings are worn.

99ls1z · September 25th, 2011, 07:02 PM

If looking at the motor should the oil fill be on the right or left or does it matter? Mine is on the right (driver's side) with the PCV on left towards the rear of the valve cover. From other motors I have looked at this seems reversed with oil fill on the left. Was just wondering if this could be causing my problem?

fogged306 · September 25th, 2011, 08:14 PM

Doesn't matter what side the oil fill is located on. You sure the PCV is still good? Take it off and shake it up and down and see if it rattles, if it doesn't, it's shot.

September 22nd, 2011, 02:06 PM	#1
99ls1z Newbie Join Date: Sep 2011 Posts: 4 iTrader: 0 reviews	First 5.0 and leaking oil..Need help with valve covers Just got a 90 Carb 5.0 and it leaks oil out of the breather on the valve cover under WOT. I'm thinking this is because it doesn't have a PVC connection from the valve cover to the carb. Will I need new valve covers and PVC? I'm not sure what all I need to do to fix this. What parts do I need to get?

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September 22nd, 2011, 03:54 PM	#2
fogged306 MM Fanatic 89 GT Join Date: Apr 2007 Location: NY Posts: 4,875 iTrader: 2 reviews	Is there a baffle under the breather? What else is done to the car?

September 22nd, 2011, 04:21 PM	#3
99ls1z Newbie Join Date: Sep 2011 Posts: 4 iTrader: 0 reviews	I'm not sure what has been done beside being converted to a carb motor. I just got it and was told about the oil leak. Just idleing or crusing around no oil leaks just under wot.

September 23rd, 2011, 09:07 AM	#4
94bossgt Regular 94 mustang gt too slow to tell Join Date: Jun 2010 Location: northampton pa Posts: 233 iTrader: 0 reviews	its blow by caused by tons of crank pressure being built up not much you ca do about it except rebuild the bottom end you can try and run breathers in the valve covers but chances are that its too late

September 23rd, 2011, 02:19 PM	#5
fogged306 MM Fanatic 89 GT Join Date: Apr 2007 Location: NY Posts: 4,875 iTrader: 2 reviews	Pull the valve cover and check and see if there's a baffle under the hole. Could be as simple as rockers throwing oil out the breather hole. If it happens at WOT, chances are it's what bossgt mentioned, you just have too much crankcase pressure. You can run a catch can if that's the case, but it won't solve the fact that you're getting too much blowby.

September 23rd, 2011, 03:45 PM	#6
99ls1z Newbie Join Date: Sep 2011 Posts: 4 iTrader: 0 reviews	I was mistaken it doesn't have a breather out of the valve covers just a crome oil cap. That is where the oil is leaking out of. I did hookup a pcv valve and same issue. Would you try replace the cap with a breather there?

September 23rd, 2011, 04:08 PM	#7
fogged306 MM Fanatic 89 GT Join Date: Apr 2007 Location: NY Posts: 4,875 iTrader: 2 reviews	Well if you had no crankcase ventilation at all then it will leak from somewhere. Depending on what's done to the engine, the PCV may or may not work. When you start to make decent power then the PCV can't keep up and you need a set of breathers. If you're still stock (cubes, heads) and the PCV isn't working, then it's too much blowby which means you're rings are worn.

September 25th, 2011, 07:02 PM	#8
99ls1z Newbie Join Date: Sep 2011 Posts: 4 iTrader: 0 reviews	If looking at the motor should the oil fill be on the right or left or does it matter? Mine is on the right (driver's side) with the PCV on left towards the rear of the valve cover. From other motors I have looked at this seems reversed with oil fill on the left. Was just wondering if this could be causing my problem?

September 25th, 2011, 08:14 PM	#9
fogged306 MM Fanatic 89 GT Join Date: Apr 2007 Location: NY Posts: 4,875 iTrader: 2 reviews	Doesn't matter what side the oil fill is located on. You sure the PCV is still good? Take it off and shake it up and down and see if it rattles, if it doesn't, it's shot.

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