Why are my intake ports oily?
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Honda-Tech Member
Joined: Aug 2001
Posts: 1,937
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From: Brooklyn, NY, USA
Why are my intake ports oily?
Some background- just rebuilt, fully built engine. Headwork (with new valve seals), new pistons/rods/etc.
Engine starts up and runs fine, no problems.
First oil change after 20 minutes of idling- oil comes out looking the same as it went in.
Second oil change, again after 20 minutes but with some reving to 5K to check for water leaks- oil comes out black.
The car does not smoke either time.
I happened to be changing the thermostat housing and the IM and say this-
Notice the oily intake ports, with black oil.
Next I inspected the IM- it was clean up top, but the bottom near the ports was oily.
I'm not running a PCV valve- just a slash cut tube on the intake tube to the valve cover as well as a catch can setup. The catch can isn't connected yet, just have the two tubes venting as I figure out a place to put the catch can.
Here is the $64,000 question- how can I have oily intake ports with a clean intake manifold? And why is my oil so dirty?
Thanks
Ben
Modified by Bnjmn at 1:17 PM 12/24/2003
Engine starts up and runs fine, no problems.
First oil change after 20 minutes of idling- oil comes out looking the same as it went in.
Second oil change, again after 20 minutes but with some reving to 5K to check for water leaks- oil comes out black.
The car does not smoke either time.
I happened to be changing the thermostat housing and the IM and say this-
Notice the oily intake ports, with black oil.
Next I inspected the IM- it was clean up top, but the bottom near the ports was oily.
I'm not running a PCV valve- just a slash cut tube on the intake tube to the valve cover as well as a catch can setup. The catch can isn't connected yet, just have the two tubes venting as I figure out a place to put the catch can.
Here is the $64,000 question- how can I have oily intake ports with a clean intake manifold? And why is my oil so dirty?
Thanks
Ben
Modified by Bnjmn at 1:17 PM 12/24/2003
Honda-Tech Member
Joined: Nov 2000
Posts: 8,388
Likes: 2
From: Rochester, NY
Re: Why are my intake ports oily? (Bnjmn)
why?
you got your answer already... you are not running a PCV setup.
so I guess crankcase pressure is forcing oily air vapor into your valvecover area and into the intake tract.. thus into the intake manifold.
Also bad rings could do this too...
you got your answer already... you are not running a PCV setup.
so I guess crankcase pressure is forcing oily air vapor into your valvecover area and into the intake tract.. thus into the intake manifold.
Also bad rings could do this too...
Thread Starter
Honda-Tech Member
Joined: Aug 2001
Posts: 1,937
Likes: 0
From: Brooklyn, NY, USA
Re: Why are my intake ports oily? (owen_the_soyboy)
I would think the plenum area of the IM would have much more oil on it if there was oily vaport coming in through the intake tract- no?
Also, why didn't it have any of these issues the first time?
Also- there shouldn't be any oil vapor coming from the valve cover and into the intake tube because I am using a slash cut tube- it should be forcing fresh air into the valve cover. This is what should be happening.
Whether the catch can is connected or not shouldn't make a different since it will just hold whatever precipitates out from the crankcase vapor- the catch can isn't tied into the intake section in any way. (My catch can setup = slash cut tube in intake area to valve cover to provide fresh air, then the crankcase is vented into the catch can).
The rings are brand new, but I guess that could be a possibility.
Thanks
Ben
Also, why didn't it have any of these issues the first time?
Also- there shouldn't be any oil vapor coming from the valve cover and into the intake tube because I am using a slash cut tube- it should be forcing fresh air into the valve cover. This is what should be happening.
Whether the catch can is connected or not shouldn't make a different since it will just hold whatever precipitates out from the crankcase vapor- the catch can isn't tied into the intake section in any way. (My catch can setup = slash cut tube in intake area to valve cover to provide fresh air, then the crankcase is vented into the catch can).
The rings are brand new, but I guess that could be a possibility.
Thanks
Ben
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