I suppose this one is for the techs or those with solid experience.

Today, I was cleaning my MAFS and throttle body, and I was cleaning a few parts while I was at it. I've had some oil coming into my air filter...not a lot, but noticeable, and as I took apart the intake tube and MAFS, there was a bit of oil present there, as well. This of course has also led to a dirty throttle body, which is now squeaky clean.

During all of this, I unhooked my full-load breather tube from the crankcase cover. Looking into the hole on the cam cover, I could see mechanicals...I suppose the camshaft. I wondered, with an open hole like that leading right into an active oiling area...how could there NOT be oil coming through the full-load breather tube, and into the intake.

This afternoon, I read over the "AJ-V8 Engine and 5HP24 Transmission Introduction" that is available in the FAQ section on this forum. On page 35 of the document (which is page 40 of the pdf), it says that "the full load breather is a flexible composite hose connected BETWEEN THE OIL SEPARATOR in A bank camshaft cover and the air intake duct." Then it says "the oil separators consist of wire gauze packed into an open ended enclosure below the breather outlets." It also shows a drawing of the oil separators.

So here's the question (finally): is my A bank oil separator MISSING? According to the illustration in the technical guide, it would seem that if my oil separator was in place, I would not be able to see the camshaft if I look down the hole where the full-load breather tube is connected. I would just see the wire gauze of the oil separator. Right?

And if it's missing, it seems that I would get some oil sucked into the air intake, which would then get into the MAFS, air filter and throttle body.

What do you guys think? I'll pop the camshaft covers off to have a look when I have time, but would sure appreciate some knowledgeable opinions. You guys know who you are...

NOTE: This early XK8 has been checked for Nikasil and blow-by issues...no real problems there.

 

The S-Type 4.0 (AJ28) has a mesh for the full load breather but the AJ26/27 has NO mesh on many (all) of the cam covers I have looked at. The 'Full Load' breather is where the crankcase ventilation ENTERS the engine. The 'Part Load' breather is where the gasses are purged through a fixed size orifice to the negative pressure side of the throttle valve.

The orifice could be clogged (see Service Action S474) or the convoluted tube to the intake could be damaged.

If the part load system is intact and oil is getting to the air filter housing, then pressure is building in the crankcase and it has to go somewhere!!!!!!!!!!!!!!

The Part Load system is designed to handle normal blowby. If the blowby is excessive, then it carries oil in reverse of the intended direction.

A little oil is normal in the intake system but liquid dripping is evidence that something is wrong.

bob gauff

 

Bob,

Thanks very much for your help. My tech replaced my valve cover gaskets recently, and didn't mention an oil separator, so I guess that explains it. They're definitely shown in the technical guide I referred to...I guess the Jag engineers changed their mind.

My part-load orifice has been recently cleared (and was checked again today), but I don't know about the rest of the tubing to the throttle body.

My tech doesn't seem to be concerned about the small bits of oil in the intake...not too much rattles him. Maybe it's just at normal levels and I should chill out.

One other related question, though. Although my tech has inspected the engine (at least some) and isn't concerned with a blow-by issue, when I asked about a compression test he said it wouldn't really tell him much. So he didn't do it. With my "intermediate" level experience, I thought a compression test would the BEST way to determine whether I had a blow-by issue.

What is the best method for determining whether the engine has normal or excessive blow-by?