How to fix your oil cap from leaking [Merged 3-8] leak leaky

[underdogTSI]

OK, my oil cap seems to leak, and when I take it off with the motor running, it shoots alot of air out, I also had that dip stick problem where it always pops out. I have bent the dip stick tube enough to keep it in there and put in a new pvc but nothing has stopped this...Anybody have this problem or solution?? Thanks.

 

[hiimnotcool]

i got the EVO oil cap because my car was having this problem..put it on..checked it after awhile to see if the problem still occured and there's still oil on the valve cover. Its been 2 weeks since I put it on though, and there isn't a WHOLE lot of oil..but it's definitely pooling in the bottom corners of the cover. Does anyone have any idea as to what it could be? Or if it is even a huge problem? The car runs great and everything, just don't want there to be something majorly wrong.

 

[IceMinion]

Hey guys, i know my post count is pretty low here, but hear me out, I am a long term DSMer with some insight to share.

I have read the whole thread, and I hate to inform you(the group as a whole), but you are approaching this problem incorrectly.

Just step back for a second and think about the design that went into the DSM oil cap, it was never designed to hold back a torrent of air and waves of oil, it was designed to prevent stuff from getting into the oil, and to maintain a vacuum seal (inside the crankcase) so that the harmful gasses can get sucked through the PCV valve and burned in the engine, rather then allowing them to break down the oil in the crankcase.

While our cars are idling, the (normal, healthy) blowby blows past the cylinder rings, down past the crank, and up through the oil drain galleys and (hopefully) the gasses get sucked into the intake manifold and are burned.

Now, the two-face part of this problem is that when we are under BOOST, there is a huge amount of blowby and it needs to go somewhere.

the PCV valve closes under boost.

Q: So where does it go?
A: next to the cas there is a small tube that (stock) is attached to the intake snorkel. While the car is under boost, the only source of vacuum in the car is right before the spinning blades of the turbo.

Unfortunately, many DSMs just get a breather added, as the stock intake snorkel is removed and replaced with aftermarket parts.

Now that the stock system has been modified, the only source of vacuum is no longer attached, and the blowby has to force its way out of the breather by the cas.

Now, if you imagine for a minute, that large quantities of blowby gasses are trying to force themselves through something with the diameter of a standard drinking straw, you will see quite quickly that the gasses will bottle-neck and pressure in the crank case is going to build.

As the rate of blowby increases, the rate of gas that needs to escape the crankcase increases and soon it starts to build pressure.

Where does the pressure go? it goes out through the ONLY OTHER HOLES IN THE CRANKCASE!!!! the dipstick and the oil cap.

Since those seals were NOT DESIGNED to hold back BOOST, the dipstick pops up and the oil cap farts out gasses and oil comes out with it.

>>>>>>>>MODIFYING THE DIPSTICK AND OIL CAP TO HOLD BACK BOOST IS LIKE TRYING TO FIX A HEAD GASKET LEAK WITH DUCT TAPE!!!<<<<<<<<

What needs to be done is to find and ALTERNATIVE path for the blowby to go.

First, we need to come together as a group and remind ourselves of the DSM superstar John Shepherd.

Lets look at john shepherd's masterpiece of a car:
::Shepracing.com - Race Car::
(click the engine bay picture)

What do you see?

Large AN lines welded to the PCV and the breather holes in the intake valve cover.

John Shepherd has solved this problem by giving the gasses a much larger hole(s) to escape from.

I am not saying that everything John does needs to be emulated, but this is how he solved the problem of blowby building up in his crankcase.

The important thing to realize is a one-lane freeway gets jammed up pretty quickly, expand it to a four-lane one, and the problem is solved!

I really hope this helps people, I hope you UNDERSTAND what I am saying, not to blindly follow some random idiot's ideas.

On that note, if you think I am FULL OF SHIT, please, let me know. I have been wrong before, and if people have the guts to correct me, I have the decency to admit my mistakes and learn from them.

Thank you and good night

-IceMinion

 

[steve]

While our cars are idling, the (normal, healthy) blowby blows past the cylinder rings, down past the crank, and up through the oil drain galleys and (hopefully) the gasses get sucked into the intake manifold and are burned.

Now, the two-face part of this problem is that when we are under BOOST, there is a huge amount of blowby and it needs to go somewhere.

I think you need to actually measure the blowby.

What I've found in my personal experience the fricking PCV valves don't seal under boost and they pressurize the crankcase not blowby. Try hooking one up to an air compressor and see how much flows at real boost levels.

The leaking boost is blown through the rocker cover baffles and caries all the oil into the intake.

While I haven't put flow gauges on the breather and PCV. I've seen the direct impact on popping the dipstick and pushing oil resolved by just changing the PCV.

 

[IceMinion]

Even if the PCV valve fails completely, the amount of air that passes through it (~20PSI @ 1/4 inch hole) is only a drop in the bucket compared to ONE cylinder (~hundreds of PSI @ ~circumference of piston)

My point being is, if you do it correctly, your crankcase breather system should be able to compensate for a failed (or partially failed) PCV system.

DO NOTt treat the SYMPTOMS, treat the CAUSE. Build a functional crankcase ventilation system.

 

[steve]

Even if the PCV valve fails completely, the amount of air that passes through it (~20PSI @ 1/4 inch hole) is only a drop in the bucket compared to ONE cylinder (~hundreds of PSI @ ~circumference of piston)

I think your logic is faulty.

If you have 100% blowby on a cylinder you have bigger problems than the breather.
Try running some back of the envelope numbers for reasonable blowby and them calculate the flow restriction of 2" of 1/4" tubing.

My point is that when the system is working like it should, it is a functional crankcase ventilation system. Having the turbo purge the crankcase is outside of reasonable design.

 

[spyder97gs]

i got the EVO oil cap because my car was having this problem..put it on..checked it after awhile to see if the problem still occured and there's still oil on the valve cover. Its been 2 weeks since I put it on though, and there isn't a WHOLE lot of oil..but it's definitely pooling in the bottom corners of the cover. Does anyone have any idea as to what it could be? Or if it is even a huge problem? The car runs great and everything, just don't want there to be something majorly wrong.

Have you made sure you got it COMPLETELY dry after changing the cap? I thought the same thing too and it was just old oil. It's kinda tough to get all the oil wiped clean along the corners.

 

[IceMinion]

I think your logic is faulty.

If you have 100% blowby on a cylinder you have bigger problems than the breather.
Try running some back of the envelope numbers for reasonable blowby and them calculate the flow restriction of 2" of 1/4" tubing.

My point is that when the system is working like it should, it is a functional crankcase ventilation system. Having the turbo purge the crankcase is outside of reasonable design.

First, thank you for just saying you think im wrong, if this were on DSMstyle, we would be calling each other names by now.

Second, I did the calculations, BUT THAT IS NOT THE POINT, the point is, the CRANKCASE is experiencing BOOST, and lots of it. The reason I say this with such conviction is i installed a new dipstick and dipstick tube, and i took her out for a 15PSI spin, it shot the dipstick up and was stopped by the hood....this was on my >>>completely stock<<< 90 TSi (with 98,000miles on the odo)

Third, the crankcase ventilation system was designed for cars running stock boost on healthy motors. NOBODY HAS BOTH OF THOSE THINGS ON THIS BOARD. ALL CARS HERE ARE MODIFIED OR HIGH MILEAGE OR BOTH.

Fourth, you said "Having the turbo purge the crankcase is outside of reasonable design" uh, no, you are wrong.

maybe you are unfamiliar with how a stock car is wired up, stock, the turbo sucks the crankcase clean while under boost. I dont LIKE the way it is stock, but it is STOCK.

And finally, weather or not you like what I am saying, if you can't conceptualize the crankcase being pressurized then there is no reason to continue debating.

Do as you wish, I just copy John Shepherd, you dont have to.

 

[bmoha2]

My oil cap has worked awesome ever since I modded it with a stronger spring made of a ss fork!~

 

[rEclipserGST]

I have a leaking oil cap too. Bought a new one from autozone... LEAKS MORE oil. So i jacked the "o" ring out the new one, and placed it around the old oil cap. Now i have less leakage. A little clean up now and then. But what does it matter if your popping the hood every weekend to do a daily check? Go

 

[IceMinion]

an update: I have had good luck with venting the crankcase to atmosphere NOT allowing gas pressure to build up.

Old 4G63 engines have alot of blowby, turbo engines in general do have quite a bit of blowby.

Old 4g63's with crappy compression (so long as it is even) still can make 4-500hp just fine, and the lower cylinder pressure can actually help prevent knock.

Although a catchcan is still a good idea, I am now drilling a hole at the end of the (turbo side) balance shaft housing. You might need to find another location if your turbo is water-cooled, pics to follow.

remember guys, replacing seals does not always resolve the issue.

 

[GSXchick]

Glad to know i am not the only one with this problem. I am new to DSM and was wondering what the hell was going on. I have replaced the cap twice and its still leakin like a champ.... I heard a catch can would solve the problem??? Anyone else heard of that??
Since there is all that built up pressure and im obviously pushing too much oil, could that make my car smoke bad as well?? I have an AWFUL smoking problem. NOT the head gasket, just replaced it.

 

[kainam00]

I've had oil leaking out of the valve cover bolts (hairline cracks) and oil cap. Fixed by bending the tabs on the cap up a bit to make it seal tighter and "gooping" a bunch of JB-Kwik (20 minute JB weld)... kind of a half-ass solution, but it has held through a stage rally, a rallyX and is still dry a year later.

 

[KKneipper]

like most of the people who've replied, i crimped my dipstick tube about 1/2 inch from the top and it worked. i too had the oil cap problem, and to fix it i bought some red gasket maker paste (rtv). i took the existing gasket out of my oil cap, then filled the area where the gasket sat with that paste. then i put the gasket back and wiped off the excess paste that leaked out the side of the gasket. let it dry for a few days and you should be good to go.

replacing the cap did not work for me, and hasn't worked for anybody i know with a dsm. the paste is cheaper than the new caps that won't fix the problem.

 

[kneipperk]

a catch can will keep oil out of your intake pipe

oh yeah my old talon was leaking from the cap, sold it to the homie and he put his oil cap from his evo8 on and it never leaked since. i seen that some1 said the evo cap didnt hold too well for him so i dont know... but yeah i seen my brothers and his isnt leaking. he is the 1 that sugested the red rtv. he got the black powercoated valve cover and it still look nice n clean maybe give it a try. maybe even use the black rtv since its made for oil (oil pan gasket maker)

 

[4g63eagle]

so thats how the small amount of oil would get on my valve cover the oil cap is leaking guess ill order one of those 2

 

[KKneipper]

i'm telling you guys, oil caps cost like 15 bucks and they probably won't fix the leak. i've tried 3 different caps and none of them worked. my brother bent the tabs on my cap a bit, but that made the leak worse.

the solution is easy, and only costs about 5 bucks.

GASKET MAKER PASTE.
i used the red, but black is made for oil gaskets.

 

[steve]

i'm telling you guys, oil caps cost like 15 bucks and they probably won't fix the leak. i've tried 3 different caps and none of them worked. my brother bent the tabs on my cap a bit, but that made the leak worse.

Sealing the oil cap with RTV is a bandaid not a fix. I can tell you that a good gasket on a good cap works perfectly well. I've replaced the gaskets two or three times since new. I'm pretty sure it's still the original cap.

Making sure you don't have a leaking PCV valve or excessive blowby and a functioning breather system helps.

 

[Hal]

i'm telling you guys, oil caps cost like 15 bucks and they probably won't fix the leak. i've tried 3 different caps and none of them worked. my brother bent the tabs on my cap a bit, but that made the leak worse.

the solution is easy, and only costs about 5 bucks.

GASKET MAKER PASTE.
i used the red, but black is made for oil gaskets.

No, the fix is to reduce the crankcase pressure that's forcing the oil out between the gasket and cap/valve cover surfaces.

If putting a new gasket in the cap does not cure the leak, then the leak is only a symptom of another problem.

Fix the problem, not the symptom.

Oh and in case no one has noticed, the oem oil cap gasket is "directional".

The ribbed face goes against the valve cover.

 

[GooeyGus]

Wow reading this thread makes me feel a bit better about my car.

I've had every "DSM problem" you can think of, but somehow I managed to skate by this one. I haven't seen a drop leak out from under my cap, and my oil cap looks like total crap (probably the original) and the gasket isn't too impressive either.

I agree that the excessive leaking (assuming one has a new gasket and a good oil cap) has to be caused by an underlying issue. Could be excessive blow-by, but I really think that a majority of the problems could be caused by faulty aftermarket PCV valves. I was going to change mine one day just for the heck of it, I bought two different aftermarket valves and both leaked when pressure was applied to the side that shouldn't allow air to leak by. I ended up testing mine and it was fine, so in the end I just left it on the car.

Bottom line: I dont think these aftermarket valves are built with boost in mind. I'm not sure if the OEM PCV valves are still available, but if they are I would try changing that before you do anything.

 

[doctor_shock10]

i haavent found a dsm that its dipstick doesnt pop the only problem with that is it could turn into a boost leak so just watch out. and its not going to hurt anything if the oil cap leaks so just clean it everytime you check you oil and move on hahahaahah

 

[steve]

i haavent found a dsm that its dipstick doesnt pop

Just because you haven't, doesn't mean they don't. Mine doesn't. If the seal drys out it's time to replace the dipstick just like the cap gasket.

To quote Hal, "No, the fix is to reduce the crankcase pressure that's forcing the oil out".

 

[KKneipper]

both my oem and aftermarket cap were leaking. i went to napa and the guy there suggested rtv... i used it, and it worked. my oil pressure gets up there, but it doesn't get too high. if you fix the leak and your pressure starts getting up to a dangerous level, then remove the rtv and find the source of your problem. pcv valves go bad over time, just like everything else, so you may want to replace it.

as for me, fixing the leak DID fix the problem.

also, (this will sound dumb but...) it may be time for an oil change, or you may have too much oil in your car.

 

[Hal]

How does the oil cap, leaking or not, cause a change in oil pressure?

 

[KKneipper]

if your oil cap is leaking, its caused by the oil pressure pushing the oil out of the top of your valve cover. if you fix the leak and you have something else causing oil pressure to build up, you'll notice a spike in oil pressure. possibly only when you really let your turbo spool up. if the oil can't vent pressure by leaking out of the cap, you may cause yourself a lot of problems.

as for me, fixing the leak didn't give me any oil pressure problems.

this is a common problem for most 2nd gens. i know 6 guys with 2nd gens and 5 of them have problems with the cap leaking.

 

[steve]

if your oil cap is leaking, its caused by the oil pressure pushing the oil out of the top of your valve cover.

You should stop digging this hole. It's already too deep for you to get out of.

Your confusing oil pressure with crankcase pressure. Oil pressure has nothing to do with crankcase pressure except that the air causing the crankcase pressure has oil vapor in it.