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Discussion Starter · #1 ·
So I've been enjoying the high compression life fairly well until the last 2 weeks.
It seems that my trusty Del Sol has developed oil leaks. Mainly the front and rear main seal and the oil pan gasket.

I installed a catch can whilst building my engine and as my luck would have it during a drive it must've kinked a hose. I noticed a very small pool of oil underneath my car and I opened the hood to find that hose kinked. Mind you I routed it from the valve cover > catch can > intake piping.

As of the last 2 weeks the oil leaks have grown exponentially. It's so bad right now that when the car just idles it gets a fairly constant drip.
If I floor it there's just so much smoke from the oil hitting the manifold.

I started testing things and when I took off the oil cap, there's a noticeable "wind" coming from it at idle.
At 2000rpm (or any throttle really) the "wind" goes away.
It seems as if its only there at idle or vacuum.
I did a compression test to see if my rings could be bad and I got 250psi, yes 250psi, across the board (not surprising as the engine has roughly 3000km on it)
I also took the line off of the valve cover expecting there to be the same noticeable "wind", but it was waaaaaay weaker than through the oil cap. I took the valve cover off and cleaned that part out but there was nothing in it. I could easily blow through that.
Tested the PCV valve, that still works.
Ran the engine without the pcv valve (did plug up the hose to the intake or else it would rev to 3000rpm) and me and my dad couldn't really notice any air coming from the hose towards the breather box.
With the PCV installed and everything connected as it should, pinching the PCV hose shut makes the car idle a tiny bit lower, other than that no difference.
It did tear my oil pan gasket somehow, gonna replace that with a brand new OEM one, same with the crank seals

The car runs and pulls fine. Plenty of power especially with those P29 pistons.

Currently I'm at a total loss of what this could be. It's not burning oil at all, yet I have this crankcase pressure issue.
Could anyone help?
I've attached a video showing the air being pushed out the coil cap: D16Z6 high crankcase pressure
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Id start by just replacing the sump gasket and following the correct procedure for installation. If you've still got your original gasket laying around don't forget to swap over the little metal spacers. Follow the torque sequence and review where Honda recommends putting the sealant ie: not on the top and bottom of the seal around the whole perimeter.
 

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4d EG manual rack/trans low n slow
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Vacuum line going to the intake pipe or manifold? If you have a large free flow intake pipe maybe you're not achieving enough vacuum, I know my skunk manifold has extra ports, and post throttle body is higher vacuum.
I'd put a little Marvel's mystery oil or a little ATF (1/8 oz) on top of the pistons and spin it without plugs in, see if you have sticking rings
 

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93 4d lx, z6,ported, port matched, compression bumped, balanced, manual swap
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Is your vc baffle still in place? Sometimes with a high compression build the vacuum signal is actually too strong at the manifold, keeping the pcv valve closed at idle, or mostly closed, not allowing enough flow to keep pressure low until vacuum drops with part throttle. Having the baffle still in the vc in these cases will cause high crankcase pressures at idle and at high throttle when vacuum signal drops and pcv valve closes.
 

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93 Civic HB SI, 95 Civic HB CX
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Is this a Z6? Do I spy a double gasket? Meaning, did you put:

Red RTV ----> Oil Pan Gasket <---- Red RTV

If so, can't tell you how many times I've seen this leak. RTV on two sides of a gasket is BAD PRACTICE, it is not needed!! The oil pan gasket should only need a little RTV at the block seams by oil pump and rear main holder, then around the crankshaft main 180's. Anything more is compromising the intended seal of the oil pan gasket rubber.

Clean and DRY surfaces (use copius amounts of brake clean and compressed air to remove oil before install) is all the pan gasket needs to seal effectively, with RTV only along the places specified in the manual.

Also, red RTV blows. It seriously has no place on an engine. I've never personally used it in my 15+ years as a tech, after fixing an unbelievable amount of previous work that leaked from other shade tree techs using the stuff. Get some Permatex Ultra Black, stuff made specifically for oil resistance. Red RTV naturally balloons when exposed to oil, not a good trait for an oil seal.

Fix this, then continue diagnosing. If you really have high crankcase pressure after this, your pan gasket wont leak, but your crank main seals will push out and let you know, making it seem like you have leaks from those seals, but will fix itself when the pressure dissapates. Although, main seal push out is HARD to do in NA form, unless the cylinder seal is seriously compromised.

More than likely, your double gasket job simply leaked and has failed. Your engine is probably fine.
 

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Id start by just replacing the sump gasket and following the correct procedure for installation. If you've still got your original gasket laying around don't forget to swap over the little metal spacers. Follow the torque sequence and review where Honda recommends putting the sealant ie: not on the top and bottom of the seal around the whole perimeter.
This :)
 

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Most common cause of crankcase pressure, especially with higher compression, is bad valve stem seals, next is valve guides in addition to stem seals.

Pull the intake manifold off, grab a small mirror, and remove the valve cover. SPray carb cleaner at the valves and see if anything makes it into the intake port
 

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Discussion Starter · #8 ·
Vacuum line going to the intake pipe or manifold? If you have a large free flow intake pipe maybe you're not achieving enough vacuum, I know my skunk manifold has extra ports, and post throttle body is higher vacuum.
I'd put a little Marvel's mystery oil or a little ATF (1/8 oz) on top of the pistons and spin it without plugs in, see if you have sticking rings
Could sticking rings still be an issue even though I still have an expected amount of compression?

Is your vc baffle still in place? Sometimes with a high compression build the vacuum signal is actually too strong at the manifold, keeping the pcv valve closed at idle, or mostly closed, not allowing enough flow to keep pressure low until vacuum drops with part throttle. Having the baffle still in the vc in these cases will cause high crankcase pressures at idle and at high throttle when vacuum signal drops and pcv valve closes.
Yeah that baffle is still in place. And the difference of air being pushed out of the valve cover hose connection vs the oil cap is huge. Could the baffle really restrict it that much?

Is this a Z6? Do I spy a double gasket? Meaning, did you put:

Red RTV ----> Oil Pan Gasket <---- Red RTV

If so, can't tell you how many times I've seen this leak. RTV on two sides of a gasket is BAD PRACTICE, it is not needed!! The oil pan gasket should only need a little RTV at the block seams by oil pump and rear main holder, then around the crankshaft main 180's. Anything more is compromising the intended seal of the oil pan gasket rubber.

Clean and DRY surfaces (use copius amounts of brake clean and compressed air to remove oil before install) is all the pan gasket needs to seal effectively, with RTV only along the places specified in the manual.

Also, red RTV blows. It seriously has no place on an engine. I've never personally used it in my 15+ years as a tech, after fixing an unbelievable amount of previous work that leaked from other shade tree techs using the stuff. Get some Permatex Ultra Black, stuff made specifically for oil resistance. Red RTV naturally balloons when exposed to oil, not a good trait for an oil seal.

Fix this, then continue diagnosing. If you really have high crankcase pressure after this, your pan gasket wont leak, but your crank main seals will push out and let you know, making it seem like you have leaks from those seals, but will fix itself when the pressure dissapates. Although, main seal push out is HARD to do in NA form, unless the cylinder seal is seriously compromised.

More than likely, your double gasket job simply leaked and has failed. Your engine is probably fine.
I'll admit it was a desperate last resort when I did that. I know its bad practice and I'll remove that stuff anyways. The leaks where already there. I dont think an oil pan gasket would fix everything because even when I first installed the pan and the gasket was fresh, when the problem occurred I could see oil seeping through it at the top part of the gasket, as if it was forced out.

My crankcase pressure is defenitely not normal

Most common cause of crankcase pressure, especially with higher compression, is bad valve stem seals, next is valve guides in addition to stem seals.

Pull the intake manifold off, grab a small mirror, and remove the valve cover. SPray carb cleaner at the valves and see if anything makes it into the intake port
Wouldn't I get oil consumption as well? It doesn't burn any oil. I've had the valve guides checked by a shop during the build and those are fine. I also used high quality valve stems. I will give it a shot, but taking my Skunk2 Pro IM off is a real PITA now

Vacuum line going to the intake pipe or manifold? If you have a large free flow intake pipe maybe you're not achieving enough vacuum, I know my skunk manifold has extra ports, and post throttle body is higher vacuum.
I'd put a little Marvel's mystery oil or a little ATF (1/8 oz) on top of the pistons and spin it without plugs in, see if you have sticking rings
It's a 3 inch intake pipe going from the OEM airbox (for stockooks) to the Skunk2 manifold.

Basically my setup is this
Valve cover > catch can > intake tube

And the pcv is just
Engine > breather box > pcv valve > intake manifold

Its probably not the best way for a catch can system to work (first time I installed one, before this build my car was burning a lot of oil and it came through the valve cover into the intake)
 

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Most common cause of crankcase pressure, especially with higher compression, is bad valve stem seals, next is valve guides in addition to stem seals.

Pull the intake manifold off, grab a small mirror, and remove the valve cover. SPray carb cleaner at the valves and see if anything makes it into the intake port
Could certainly be an issue, most machine shops will just take a gnurled bit to "refinish" a d guide, it only works for a short time.
Could sticking rings still be an issue even though I still have an expected amount of compression?
yes, especially if ring gaps are a bit too tight or p to w clearance is too high.
Yeah that baffle is still in place. And the difference of air being pushed out of the valve cover hose connection vs the oil cap is huge. Could the baffle really restrict it that much?
Most definitely, even 6 7mm holes drilled in that baffle in the correct places should alleviate the excess pressure that can be caused by a high cr build with too high a vacuum signal at pcv port, causing the pcv valve to shut at idle or cruising loads.
 

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Discussion Starter · #10 ·


Could certainly be an issue, most machine shops will just take a gnurled bit to "refinish" a d guide, it only works for a short time.

yes, especially if ring gaps are a bit too tight or p to w clearance is too high.

Most definitely, even 6 7mm holes drilled in that baffle in the correct places should alleviate the excess pressure that can be caused by a high cr build with too high a vacuum signal at pcv port, causing the pcv valve to shut at idle or cruising loads.
Okay thanks for the info

The shop didn't refinish them. They just checked them over and measured the tolerances if I'm not mistaken. Could still be a botchjob shop.

P/W was pretty good I thought. Don't know what it should be. Rings were gapped to 0.25mm on the 1st rings and 0.35mm on the 2nd rings

Where would you suggest to drill those holes in the baffle?

Some more info regarding vacuum that I just thought of. Whilst driving, if I come to a standstill with the engine still cold, the idle lightly surges between 1300 and 1500rpm. Doesnt do it warmed up. Sometimes warmed up it does take longer for the rpms to come down again when I'm stopping.
I not an expert on vacuum or anything but I feel like this has something to do with it
 

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Discussion Starter · #13 ·
My current guess is that the PCV system isn't doing its job seeing as disconnecting the pcv valve and feeling the hose leading to the breather box doesnt nearly produce as much air as the oil cap does. AFAIK where the breather box goes in there's a passage that leads to the valvetrain and the crankcase. So I would guess that the crankcase would push the air out the pcv system.

Any guesses on this? Ill remove the breather box and possibly revamp the oik catch can system. If anyone has any ideas on how to route it, please let me know
 

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Discussion Starter · #14 ·
Hi all.

On another thread discussing my high crankcase pressure I said that I don't think that my PCV system is working as it should

Its a high comp d16z6 p29 build with about 12.7:1 compression (250psi on all cylinders)

I've installed a catch can but since I've never done so I probably messed it up.

I've drawn my current setup and some idea's. I need the best possible way to get rid of the crankcase pressure, as its pushing oil out of every seal in the lower half of the block.

Rectangle Slope Font Parallel Design


How does this look? What would work the best?
At idle the line coming from the breather box barely has any air coming out of it, but when I take the oil cap off theres quite a bit of air being pushed out of it. Only at idle tho. At some throttle it stops and the pcv system seems to do its job.

Any help on this would be awesome
 

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Do like Joe said, increase the breathing of the baffle of the valvecover.

Would not hurt to put a pair of barbs on the exhaust side of the valvecover as well. Run em to the intake tubing or catch can.
 

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😱😱😱 i meant to take pictures of the modified one I had off today that solved this same issue, stupid time crunches and blazing hot sun reflecting off shiny shyt distracted me.
 

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Discussion Starter · #18 ·
Do like Joe said, increase the breathing of the baffle of the valvecover.

Would not hurt to put a pair of barbs on the exhaust side of the valvecover as well. Run em to the intake tubing or catch can.
Yeah I will look into that. Need to be a bit careful or else the mot guy or police will start moaning that its too modified and take me off the road. A stock-ish looking solution would be best since the motor looks mostly oem from the outside

Edit: I know that the port on the valve cover can release excess pressure, but why is my breather box on the back of the engine doing nothing at all? Like barely to no air is coming through there despite that thing being connected to the passages that go to the head and valve cover. Very weird, or it could be normal and I just don't know enough yet.

😱😱😱 i meant to take pictures of the modified one I had off today that solved this same issue, stupid time crunches and blazing hot sun reflecting off shiny shyt distracted me.
Ah no worries. If you have the time and want to take a pic feel free. It would really help

Throw a vacuum gauge on the intake at idle. Let’s see what vacuum you’re making.
Gonna do that. Ordering a vacuum gauge now with my new oem pan gasket, front and rear main seals
 
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