Oil cap flew out while WOT

[elcobrita]

Has anyone had this happen to them?

I was running the ol girl against an e85 Paxton Coyote. First two runs went great. Car felt powerful. 3rd run car also felt great but I noticed some stuff on my windshield after the run. We get off on the next exit and I notice its oil on my windshield. I open my hood and see that my oil cap is missing and there's oil all over the driver side.


It was late so I just put a rag on the hole and limped it home. Car still idled fine. Car ran fine, granted I didn't go into boost at all. Oil pressure was good. Oil was still over 3/4 to the top on the dipstick.

I had done a compression test on it a week before and all cylinders were 150.


So what caused this. I really doubt i left the oil cap loose. I'm thinking a bigger catchcan will fix the crankcase pressure?

 

[dblj32774]

Check out CFM website. They have a baffled soul cap, with filter breather to release crank pressure while under boost. Might be an option. I have one but just got my car done with new TVS so really have ran it real hard.

 

[elcobrita]

Check out CFM website. They have a baffled soul cap, with filter breather to release crank pressure while under boost. Might be an option. I have one but just got my car done with new TVS so really have ran it real hard.

I looked through the website but i only found JLT catch cans. I forgot to say that I already have a JLT catch can and prefilter on the passenger side.

 

[dblj32774]

http://www.c-f-m.com/performanceparts/pc/home.asp

It I see not a catch can. It is a replacement oil cap that has a baffle that opens up.

 

[dblj32774]

 

[elcobrita]

View attachment 75932

Ok I see. Wouldn't that throw off my a/f?

 

[dblj32774]

I don't think. Some guys here can correct me if I am wrong. The way I understand it is it works like a normal cap while driving without producing boost. Once you got to WOT the ball valve opens to release Positive crank pressure to try to get crank pressure back to like if you were driving while not producing boost, but now you are. I have never heard anyone says it changed their A/F's but I could be wrong.

 

[elcobrita]

I don't think. Some guys here can correct me if I am wrong. The way I understand it is it works like a normal cap while driving without producing boost. Once you got to WOT the ball valve opens to release Positive crank pressure to try to get crank pressure back to like if you were driving while not producing boost, but now you are. I have never heard anyone says it changed their A/F's but I could be wrong.

Ok nvm. I just saw that it has a check valve to prevent unmetered air from coming in. I thought it was just a small filter at first. I'm gonna give that a try. Thanks a lot

 

[Bdubbs]

I'm running one works great.

 

[MG0h3]

Does our PCV system have a checkvalve of any sort before the PCV valve from the factory? I sourced a Supra PCV valve for my old turbo fox and never had problems. Been thinking about this since I saw the catch can thread come up again and now this issue.

My Cobra has what I would assume is a checkvalve installed about 3" before the PCV valve. Whatever it is isnt factory but I just havent bothered to take it apart.

 

[01cobravortech]

I'm running one works great.

How are you measuring it works great?

 

[elcobrita]

Does our PCV system have a checkvalve of any sort before the PCV valve from the factory? I sourced a Supra PCV valve for my old turbo fox and never had problems. Been thinking about this since I saw the catch can thread come up again and now this issue.

My Cobra has what I would assume is a checkvalve installed about 3" before the PCV valve. Whatever it is isnt factory but I just havent bothered to take it apart.

It's probably an aftermarket check valve Jason. I imagine it's there so that the gases don't come back around.

I just ordered this breather from CFM. I'll let you know if my issue is fixed. I think it will tho. When I first went with this pulley setup I would see some oil coming out of my cap after some strong WOT runs. Now with the cooler weather and an extra 2lbs I believe the pressure was enough to pop that sucker off.


Sent from my iPhone using Tapatalk

 

[cj428mach]

How are you measuring it works great?

I have a cfm breather and the breather just pushes on to the aluminum base. I noticefd that when I popped my hood the breather would be raised up on the base like it was being pushed off.

After some testing I learned that if I stayed out of boost the cfm breather stayed down, if I'd beat on the car it would be raised up like it was being pushed off. I put a tiny hose clamp on it and now its down permanently but to me this means its venting pressure under boost.

 

[Shadow Grey 03]

Does our PCV system have a checkvalve of any sort before the PCV valve from the factory? I sourced a Supra PCV valve for my old turbo fox and never had problems. Been thinking about this since I saw the catch can thread come up again and now this issue.

My Cobra has what I would assume is a checkvalve installed about 3" before the PCV valve. Whatever it is isnt factory but I just havent bothered to take it apart.

What he said. Is the valve a light grey color?

OP, you must not have tightened the cap all of the way. I've yet to hear of one un-screw itself under pressure.

 

[MalcolmV8]

I don't think. Some guys here can correct me if I am wrong. The way I understand it is it works like a normal cap while driving without producing boost. Once you got to WOT the ball valve opens to release Positive crank pressure to try to get crank pressure back to like if you were driving while not producing boost, but now you are. I have never heard anyone says it changed their A/F's but I could be wrong.

If you have the factory PCV system in place it would in theory affect your A/F under boost. All air through the crank case is metered air so blowing any out in theory throws off the A/F. Since you're getting blow by under boost it's hard to say how much. A data log prior to and another after the cap install will tell you.

 

[c6zhombre]

elcobrita...how much boost are you running? I have never heard of a threaded oil cap flying off, unless it wasn't tight to the click. But that's on a factory motor and factory cap.

I know on my car I do tighten the cap to the click...but to line it up I will "back it off" so the writing is square. I suppose it could be backed off too much and create an issue.

I would tighten it good and try getting into boost again to see if it repeats

 

[cj428mach]

Does it affect his afr? I realize its lost metered air but what difference does it make if the lost metered air goes out the breather or is being forced past the rings into the crank case under boost.

My car didn't require a retune after the cfm breather with check valve.

 

[MalcolmV8]

elcobrita...how much boost are you running? I have never heard of a threaded oil cap flying off, unless it wasn't tight to the click.

That's a good point too. I was running 30 PSI on a built motor with larger than stock ring gaps which means I was having more than factory blow by and never seen this or even heard of it honestly. Normally excess crank case pressure will pop up the dipstick first and or blow out your front or rear main seal before anything else.

 

[elcobrita]

I have a cfm breather and the breather just pushes on to the aluminum base. I noticefd that when I popped my hood the breather would be raised up on the base like it was being pushed off.

After some testing I learned that if I stayed out of boost the cfm breather stayed down, if I'd beat on the car it would be raised up like it was being pushed off. I put a tiny hose clamp on it and now its down permanently but to me this means its venting pressure under boost.

Your breather being pushed up confirms that the oil cap is one of the places that takes the biggest hit.

Is your dipstick pushed out as well when you find the breather pushed out?

 

[elcobrita]

elcobrita...how much boost are you running? I have never heard of a threaded oil cap flying off, unless it wasn't tight to the click. But that's on a factory motor and factory cap.

I know on my car I do tighten the cap to the click...but to line it up I will "back it off" so the writing is square. I suppose it could be backed off too much and create an issue.

I would tighten it good and try getting into boost again to see if it repeats

It could have been my oil cap wasn't tightened all the way. I'm very sure that it was tho, but then again there's always that possibility. I did 3 back to back runs. 40-140.. maybe it loosened up with every run. I'm at 21-22 lbs

And my oil cap is long gone. It must have fallen on the highway in Mexico somewhere.