Head gasket question

mchustle · 08-12-2012, 06:49 AM

Ok so here is the deal. I'm almost certain I'm lifting my head under boost. When I'm boosting oil is spraying out somewhere in the back around cylinder 4. I did a compression test and all cylinders were 170 except number 4 was around 120, the engine wasn't fully warm but decent number in my oppinion other than #4. Since comp is low and oil is spraying somewhere around there would you all think it was the head lifting? It's on factory bolt at around 21psi on a 16g. If so I'm thinking about just getting a felpro composite, head decked with new valve seals and arps and it should be fixed. What are your oppinions I don't have access to a leak down tester.

iugrad92turbo · 08-12-2012, 07:32 AM

I would try to find a leak down tester and get some results, lifting at 21 psi, i ran 25 ,and never had a issue like your saying or a head lifting.

Kreez · 08-12-2012, 07:39 AM

A compression test shows how much compression an engine is making. You want to do a leak down test too. That will show you how much pressure the engine is holding. And if it's not holding pressure, you can use a mechs stethoscope to listen for the leak.

You're probably going to have to get in there and get your hands dirty from the backside (that's what she said). Do your best to clean the area that appears to be the source of the oil leak and you might be able to eyeball the problem area.

Edit: too slow

mchustle · 08-12-2012, 07:59 AM

I've cleaned it to search for the oil leak to no avail. It will only leak under boost. I'm going to try to turn on antilag and have someone hold the gas while I look and see if I can find the leak. I'll try to get ahold of a leak down tester, I might be able to rent one at advance or something.

iugrad92turbo · 08-12-2012, 08:04 AM

Try autozone compression tester, Cylinder Leak-Down Tester

Kreez · 08-12-2012, 08:11 AM

Do the leak down test before you attempt that anti-lag scheme you mentioned above.

mchustle · 08-12-2012, 08:19 AM

Will do lol. Like I said it runs great just leaks oil from somewhere when I'm on it hard and smokes from the engine bay from the oil burning.

Could lifting the head on the corner by the Cas spray oil out or is that not really possible. I'm not having any fluids mixing or anything.

3kgt2nv · 08-12-2012, 01:33 PM

i would inspect the valve cover. also. could be the vc gasket is shot and from pressure in the crank case its forcing it out of the vc area and running down the head.

usually if your lifting the head you will push coolant, mix oil into coolant or vise versa. and doing the anti lag while looking might be unpleasant if you get hot oil inn your face so be super careful.

also do you have an aftermarket oil pressure gauge? are the balance shats removed? could also be if the block and heads have been decked the oil drain from the head to block is slightly closed off causing high oil pressure in the head.

mchustle · 08-12-2012, 04:43 PM

Well I sprayed it down with brake cleaner and went for a drive. It appears it might be the VC gasket, but it actually looks more like its coming from the 1g CAS. Would the cas oring or the actual cas being bad maybe spray oil under boost? Im guessing anything is possibly. I think tomorrow ill go get a new o ring and switch the cas out for a spare i have, worst case scenario it doesnt work lol.

Kreez · 08-12-2012, 06:58 PM

The area under the VC isn't under a huge amount of pressure, but if the gasket has never been redone then it's possible that it's leaky.

I'd just pop off the cover and check the seal. Might be an easy fix.

bryzenga · 08-12-2012, 07:10 PM

Yes, the O-ring for the CAS can cause a good size leak under load. A bad valve cover gasket can and will make a mess out of things fast. I've replaced the VC gasket once and under-torqued the bolts because I was paranoid of stripping the bolt holes out. Took it for a drive and the intake manifold side of the engine bay was covered in oil. Made a mess of things rather quickly. I'd start with replacing both and torquing the VC to spec. Bigger question is why one cylinder is low on compression. 120 compared to the others sounds yucky

My1GLaser · 08-12-2012, 07:20 PM

A bad PCV valve can let boost into the VC and cause excessive crankcase pressure. I have one of these in line since the stock PCV can barely hold back 10 psi.

mchustle · 08-12-2012, 07:34 PM

OK im pretty sure the VC gasket is good but ill take it off to be sure worst comes to worst ill use some rtv on the gasket to reseal it. Ill also pick up a new o ring for the cas. Anyone know if the cas can leak other than from the oring? I dont have to worry about stripping the VC threads anymore I did a couple and just helicolled everyone, so as long as i dont crack the VC im good lol.

I know its not the pcv, I originally thought it was so I tee'd both VC ports together into a catch can then the other side of the catch can to the turbo intake, and plugged the Intake mani nipple.

As for the bad comp in one cylinder I assume its probly the rings but ill know more when i can get a leak down tester. When I did the comp test I messed up a little and the motor wasnt fully warmed up and I forgot to hold it WOT. I know this wouldnt cause that low comp but ill try to do another one tommorow and get accurate numbers.

Thanks for all the input though, Oil leaks are the worst to hunt down. Hopefully it will be a easy gasket but we will see lol.