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The part load breather will suck more oil vapor than you might imagine. I was surprised at how much there was when I took my intake off too. It will pretty well coat everything.
When I did the twin screw I added a catch can on the part load breather. In a 5000 mile oil change interval it accumulates maybe a cup or so of oil vapor. There is no noticeable change on the dipstick and the engine does not use any oil that I can tell, but now the intake is dry and clean.
If you don’t use oil between changes then I’d wager what you are seeing is normal. You could add a catch can if you wanted to keep the intake clean and were up for the trouble but it won’t improve performance or anything like that.
One of the important feature of engines is how to relieve pressure in the cam covers. The purpose of our Positive Cam Ventilation PCV) system is to direct the pressure into the air intake tunnel (full load breather) or the throttle body ( part load breather).
Our cam cam covers are fitted with oil baffle plates that should keep the bigger crap, from blow by, out but aerosoled oil vapour will go through hence the fine coating you see in the intake.
Heresay by Some Ford and VW owners say Catch Cans are necessary mods but that’s not something I’ve heard of with our AJ-V8 engine.
Maybe this in the realm of a “solution looking for a problem” as someone else on this forum said previously.
I did originally look at installing a catch can, and there is an old thread on that here for the X100, but poking around I found my full load breather is dry. Also my throttle body was recently cleaned as I wasn’t getting the high end pull at WOT at 160kph. Maybe this is the cause and putting in a catch can on the part load breather would prevent it... but cleaning a throttle body is an easy fix.
As I didn’t have a blue smokey exhaust, the oil in the air intake isn’t causing me any problem, so I forgot it .
i think you mean positive crankcase ventilation .
note not only under high load does the PCV vent . its under vacuum from the intake also , so there is always some flow .
reason, the vacuum helps seal all the oil seals .
it is well documented that the supercharged AJ-V8 requires an oil catch can to stop/reduce oil mist going through the intake .
and coating the charge coolers and blower internals.
i have read this multiple times in these forums .
i would not have thought the N/A version would have as much of an issue .
ether way a catch can will fix it .
my catch can separates about 50-80mls per 1000km.
Last edited by Datsports; May 26, 2019 at 11:32 PM.
+1 to Datsports - prevention is better than a cure
Agree with Datsport above esp. considering I have a 4.0L na engine so I run lower pressures.
Was a previous member of Porsche club and there was always talk of oil in air intakes and their air/oil separators esp. in the turbo cars.
If a simple catch can, as part of a maintenance schedule, stops this in a S/C Jag, it’s a simple mod. Big price differences I noticed from simple cans or baffled. I wonder if the size is restricted by the lack of space in the X100 engine bay. Do you need to fit both on the full and part load breather?
i went baffled as a further preventative .
i have worked on both the x100 XKR and the STR . i can tell you there is more room in the XKR eng bay than the STR .
mine is a mishimoto baffled catch can , it's quite small truthfully . finding vacuum proof piping is the hard bit . mine is excavator hydraulic hosing .
Regardless how much oil you have in the air intake, it seems to me that the quantity is very much related to how much load/pressure is put on the engine vigorous driving. IMHO if you are an "old Jag racer" type (not sure the criteria on that >4500rpm), I'm pretty sure you'll be checking the car after a vigorous drive, so emptying a catch can shouldn't be a big deal in terms of additional maintenance.
this is why engines with direct injection only will severely carbonize the valves. we do not have this issue. perhaps this oil helps with the lubrication of the valves and their seats and should not be considered a bad thing. it might even be protective if any dust gets past the air filter. fix one problem, cause another . . .
My engine does not consume a significant amount of oil and I am sure that this is the first time this area has been opened for inspection after 97K miles.
Other than cleaning up the very thin puddles of oil and checking the breathers I am not going to take any other action.
I'll consider the intake to be the intended catch can and remove that front plate at the next oil change for another look.
I agree with you Rothwell, My N/A xk8 had 120K miles and had a coating on the intake when I removed the cover to do my coolant pipe replacement . Thought it looked ICKY, but decided to leave it be. Now at 144K and no evidence of problems. Last oil change I changed to Syn (closeout Havoline $12/5qts) rather than Dino and doing the 10K miles change interval. Had to add a tiny amt. so I guess it is misting the intake valves as suggested.
Oil in intake manifold 4.2L
