240sx - Oil in the intake???

I have a 89 KA24E. .040 over, IT built motor. The last couple of races have had the high RPM go lean and start to overheat. The problem does not start until about 4 or 5 laps of hard driving.

At LRP, when the problem started, I immediately pulled into the paddock and took a look at the car. I found oil leaking out from between the upper and lower intakes. I took it apart this week and found what I believe to be excessive oil in the lower intake (there are pools of oil in each runner). I found that the breather from the valve cover also had a lot of oil, so it appears that oil is being drawn into the intake from the breather.

Now, how much is too much? I plan on changing the breather line to go to an overflow and measure how much is coming out in a race, and see if this helps my problem (maybe too much oil getting into the intake?).

Just wondering if others have had this issue and can point to any other cause for oil in the intake (other than a blown motor - which really fills the intake with stuff).

Jeremy
:figo:

I think oil pools in the runner would be excessive.
Definitely have to get the catch can on there to keep things cleaner.

I'm gonna take a guess and say those of us with "IT-prepared" engines, probably are using a catch can, so we shouldn't have anything in the intake.

Good luck,
Michael

Jeremy,
First, a question, was the oil actually coming out of the seam where the two intake manifold halves meet? IF oil can leak out of there, air can get in there. (other than possibly a miniscule seepage or wicking through a fibrous gasket) If this was happening, that could be part of the lean condition.
I had a one quart catch with a breather in my 240, and I never got more than a few drops when I drained it. Be sure you pull both hoses and T them together. I agree with Michael, It shouldn't be puddling in the intake. IF it is drawing a little while the engine is running, I would think that it would pull that amount on through and burn it off. How do the plugs look?
Joe H might have soem better advice though. He knows alot more about these Nissans than I do.

Jim

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Originally posted by its66@Aug 9 2005, 01:40 PM
Jeremy,
First, a question, was the oil actually coming out of the seam where the two intake manifold halves meet? IF oil can leak out of there, air can get in there. (other than possibly a miniscule seepage or wicking through a fibrous gasket) If this was happening, that could be part of the lean condition.
I had a one quart catch with a breather in my 240, and I never got more than a few drops when I drained it. Be sure you pull both hoses and T them together. I agree with Michael, It shouldn't be puddling in the intake. IF it is drawing a little while the engine is running, I would think that it would pull that amount on through and burn it off. How do the plugs look?
Joe H might have soem better advice though. He knows alot more about these Nissans than I do.

Jim

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Well start with a leak down on the motor first. I had a major issue with my 12.5:1 engine. (stock piston deal) pushing oil out that breather and it turned out to be broken ring lands in 2 pistons. Strange break cause ther were both exactly the
same. I had an issue with a race fuel I bought and some signs of rust in the bores. (not from a head gasket issue) The other place it can com from is the PCv system but that is up near the head so I would guess you would have a bigger issue in the cylinder than anything. Keep is informed cause I like to know what to look for. Also How much time is in this engine?

Thanks for the responses.

There is oil coming from the seam between the two intakes. When I took the upper intake off, it appears that the gasket was torn (well, it's torn now, but if that was from removing or if it already was is hard to know for sure). So, I'm guessing that is where some air was getting sucked in. If oil can leak out, air can leak in.

I'm going to vent the breather to a catch can and see how much is coming out. I'm wondering if on WOT there is enough of a draw/vacuum through the vent tube to draw oil from the top of the head (mostly from splashing around the valves and such).

Of course, I'm always looking for other causes, as the obvious one is not necessarily the correct one.

I'll try a leak down test, if/when I can find the right tools.

Oh, and I have about 6 race weekends on this motor (maybe 5-6 hours).

Jeremy

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Originally posted by 7racing@Aug 10 2005, 01:30 PM
I'm wondering if on WOT there is enough of a draw/vacuum through the vent tube to draw oil from the top of the head (mostly from splashing around the valves and such).

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Yet another reason to use the catch can.

It's been a while since I poked around, but isn't there another black-box type PCV/vent on the engine? It's somewhere underneath where the water temp sending units are, but it's an opening on the front cover of the engine.

Like I said, I don't remember where it comes/goes as OEM, but we have two hoses T'd to the catch can: that one from underneath, and the one from the valve cover.

Good luck,
Michael

Jeremy, it sounds to me like you've got excessive blow by due to broken piston ring lands. This occurs when the engine goes lean and you have severe detonation. If you have gotten a leak down tester you'll know right away if this is your problem. Good luck with this- it took me a long time to fix this issue on my KA24DE. Mike

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Originally posted by 7racing@Aug 9 2005, 08:50 AM
I have a 89 KA24E. .040 over, IT built motor. The last couple of races have had the high RPM go lean and start to overheat. The problem does not start until about 4 or 5 laps of hard driving.

At LRP, when the problem started, I immediately pulled into the paddock and took a look at the car. I found oil leaking out from between the upper and lower intakes. I took it apart this week and found what I believe to be excessive oil in the lower intake (there are pools of oil in each runner). I found that the breather from the valve cover also had a lot of oil, so it appears that oil is being drawn into the intake from the breather.

Now, how much is too much? I plan on changing the breather line to go to an overflow and measure how much is coming out in a race, and see if this helps my problem (maybe too much oil getting into the intake?).

Just wondering if others have had this issue and can point to any other cause for oil in the intake (other than a blown motor - which really fills the intake with stuff).

Jeremy
:figo:

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Originally posted by mcovello@Aug 21 2005, 05:15 PM
Jeremy, it sounds to me like you've got excessive blow by due to broken piston ring lands. This occurs when the engine goes lean and you have severe detonation. If you have gotten a leak down tester you'll know right away if this is your problem. Good luck with this- it took me a long time to fix this issue on my KA24DE. Mike

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So how did you fix it? I have braoken ringlands in the past but on engines with lots of hours on them. I did not find the normal signs of detonation that I would have expected. But these things do turn into a big freaking oil pump whrn they loose them.

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Originally posted by mcovello@Aug 22 2005, 12:15 AM
Jeremy, it sounds to me like you've got excessive blow by due to broken piston ring lands. This occurs when the engine goes lean and you have severe detonation. If you have gotten a leak down tester you'll know right away if this is your problem. Good luck with this- it took me a long time to fix this issue on my KA24DE. Mike

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Hmmm.....

I haven't done a leak down test yet (don't have the tools, need a shop, yadda, yadda, yadda....). I went to the races over the past weekend. I ran a catch can from the valve cover breather and I changed the upper intake and gasket. The original problem of overheating/loss of power went away and I was able to run my previous best time at the track. In the 17 lap race on a drying track I won the race and didn't have any problems.

There is some oil in the catch can, so there is some blow by, but it seems to be worse in left hand turns. Made for some extra smoke in the oval before finding the original catch can fell apart and leaked oil all over the place. Oops.

I'm still not sure if there is a problem. Eventually I'll get a leak down test done and see what the results of that are. Probably won't happen for a few weeks though (vacation the next week and racing 9/10-9/11). So far, so good!

Jeremy

Initially I thought my problem was a fuel issue - I thought we were getting an intermittent lean condition. The engine would run fine for 2-3 hrs and then just explode. What i finally realized was that the crank angle sensor (distributor) would heat soak to the point of failure and then the ignition timing would become erratic. All i did was to make some heat shielding to protect the CAS from the header heat and the engine has been bulletproof ever since.

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Originally posted by Joe Harlan@Aug 21 2005, 10:57 PM
So how did you fix it? I have braoken ringlands in the past but on engines with lots of hours on them. I did not find the normal signs of detonation that I would have expected. But these things do turn into a big freaking oil pump whrn they loose them.

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Originally posted by mcovello@Sep 11 2005, 08:05 PM
Initially I thought my problem was a fuel issue - I thought we were getting an intermittent lean condition. The engine would run fine for 2-3 hrs and then just explode. What i finally realized was that the crank angle sensor (distributor) would heat soak to the point of failure and then the ignition timing would become erratic. All i did was to make some heat shielding to protect the CAS from the header heat and the engine has been bulletproof ever since.

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That's an awesome point, and one i hadn't thought of. We had some problems with odd timing irregularities blowing up our engines (two engines in two different cars, one long weekend :( ). We haven't (i'm knocking on something right now) had that problem in my car, but i've got heat coated headers. And the problem seems much worse on hot days, and under heat soak. I appreciate the observation and will take that into our prep list.