My 98 XJR has a bad case of oil blow-by - oil is coming from the crankcase ventilation (full load breather) into the air intake. This creates problems because 1) oil coats the air filter, blocking flow and 2) oil gets past throttle, screwing up air/fuel mix. If you've got an "R" model, you might want to check your air intake for oil - it's pretty common with the supercharger because of high compression.

There's a few air/oil separator DIY websites where guys will weld metal together to form a box (or even use a paint can) and stick dish sponges in it to stop the oil, but allow air to get through. I thought about this for a minute......and then decided, do I really want an ugly piece of scrap metal, or used paint can under the hood next to my lovely supercharged V8? No. Here's the route I took. I bought an air and oil separator from the "air tools" section of Menards ($6). I assume Lowe's, Home Depot, etc. have the same thing. It's basically used to stop water and oil from getting through an air gun - it's about the size of a fuel filter. I took off the crappy plastic tube that jaguar uses for crankcase ventilation (JTIS calls it a "full load breather"). I replaced this line with a new rubber hose with the oil separator in the middle (hose from crankcase vent to oil separator, hose from oil separator to air intake). It took some time a creativity to get it to work and look nice. So far so good - oil is accumulating in the separator and not my air intake. I haven't used it long enough yet to need to drain it, but it looks like there's a little drain valve on it for when the time comes.

 

Very creative skanoski. I'm familiar with air compressors, that should work.
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I presumed air compressors were just for inflating tires,*****,cleanin and so on
lol

 

After about 70 miles it seems to be working. Air intake is bone dry. Here's a pic of the separator.

[IMG]local://upfiles/2329/9A70FA62E6CD419AA67F4338714DCA09.jpg[/IMG]

 

Supercharged engines have a lower compression ratio than N/A engines. If you have a high mileage engine(I've seen some as early as 60K) and having a 98' you have nikosil coated cylinder liners and what happens is this coating wears down therefore creating blow by situation. One thing a would check is the PART LOAD breather wich is located on the drivers side cam cover towards the front, remove the vacuum tube and checkif its cloggedwith a fairly small drill bit. Jaguar got rid of this engine on 01" or 02" models.

 

Like JHE2003 said, check part load breather for blockage. Size below a 1/8th inch bit should do it. Nicasil lined blocks were crap. Sorry to say unless yours was replaced, you have one. Mid '99 was when Nicasil was phased out. Sounds like you have blowby. Sounds like you are pretty handy, so I would do a compression test. Should be around 120psi on all cylinders.

 

I have a 2000 XKR and I think it still has the original Nikasil engine. I'm upto about 76k miles now. The only problem i have is very occasionally (like once every month or two) I get a sudden "limp home mode" which goes right away on restart. Its very irregular but its kinda scary that it could happen at any time, say in the middle of a busy freeway. The dealer says I need a new throttle body but at $3500 (even a recon one is $1200) I think I'll look for second opinions first.

I've also noticed that I have oil coming out of the full load breather into the air intake. Its not a lot but over time its coating the whole inside of the big black plastic air intake pipe and making the throttle body dirty. I've also already checked the part load breather, as far as I can tell it seems to be clear.

I've been told by the dealer and some other people that its normal for a little oil to come out of the full load breather. Is this true or have I been fed a line? Does this mean I must have the dreaded Nikasil problem? I mean, does every XK8/XKR have sticky goo on the inside of the air intake pipe? If its normal, then it seems particularly stupid of Jaguar to have decided to pipe oil back into the air intake.

Actually what is the point of the full load breather anyway?
This is probably a dumb question, but what would be wrong with just allowing it to vent to the atmosphere (via a vertical pipe so the oil just runs back into the engine), or even (gasp) just putting corks in it and the air intake connector?

 

Stickly oil-based goo in the inlet manifold is common to most engines with a few miles on them, it's just that the Nikasil-engined Jaguars get more than most due to excessive blow-by the piston rings and valve guides, hence the block modification and replacement program Jaguar undertook to correct the problem. I saw the most awful goo on my previous car, a Rover 75 2.5 V6, but all was well after a clean out, in fact all was well before, to tell the honest truth !!

 

No oil in air intake. I make a oil catch tank between air intake and breather.

 

A lot of Rover 75 owners with the v6 engine have also fitted oil catch tanks, as the normal breather trap is very poor, and the oil gets into the Variable Inlet Manifold and makes the flap valves in there stick so the actuator motors fail.

 

The intent of the full load breather is to NOT vent the oil into the atmosphere but recycle it into the engine for a second chance at combustion. I think they put PCV valves on cars sometime in the '60's and they have gummed up since then on less that optimum condition engines.

 

Back in the 1970s, "blow-by" was a common problem on many engines that had done a big mileage under bad circumstances, e.g. a lot of cold running. Technically speaking it is due to the way the bores and pistons wear. They don't wear "straight" -- the bottoms of the cylinders wear more than the top, and more on the 'thrust' side, i.e. in the direction of the crank motion. The pistons when examined show black marks on opposite sides in the thrust direction. The only real way to fix unf. is a rebore and new pistons -- expensive. A partial fix was to slit the pistons and 'stretch' them so they were a bit wider at the bottom than the top, plus new rings and a special oil control ring. The top ring was 'stepped' to accommodate the 'wear-ridge' at the top of the bore. I think this idea was called "Koetherizing". Of course, it didn't last that long. Another cheaper panacea was to simply put some very thick oil into the sump as an additive such as STP, still available today. It was so thick it took half an hour to come out of the tin! But it DID work, and it WAS cheap and best of all, you could do it yourself. The downside was hard cranking in cold weather and poorer mpg. figs.
Fortunately, if you're in the process of test-driving a car prior to purchase, checking this is easy. Get the engine to full temperature and while idling, carefully lift the engine's oil filler cap a tad (some will squirt black oil at you if you just take it off), and check for a big wind coming out -- this is obvious, no quibble. If you find this, walk away. You have a high-miler here, despite what is says on the clock, and it's done its miles under bad conditions. 98% of the time with this you're looking at a recon. engine -- expensive. It makes sense also to check how the car has been used before. Not listening to the salesman, but seeing the previous owner. If he/she has only had it a couple of months themselves, be suspicious!
Leedsman.
Forgot: Up to about 2000 the Jag. engines had the "Nickasil" coating on the bores, a german idea along with "Alusil" another coating idea, also used by Porsche. This was a hard coating direct on the aluminium bores instead of the much more expensive steel liner. No-one realized at the time it was introduced that high-sulphur petrol/gasoline would erode this Nickasil coating, resulting in massive bore wear after a moderate mileage, say 50,000. This error cost Jaguar dear since the engines had to be replaced -- hugely expensive. Jaguar promptly went back to steel liners. Under good conditions, linered engines easily do a quarter of a million miles and more without heavy oil consumption. Be VERY careful if the the car you are about to buy has Nickasil coated bores!

 

but it gums up the throttle body and injectors.

My question was really why does there even need to be a breather at all? what would happen if you just closed it off?

 

The oil slump is under pressure due to the piston ring blow by. If you close off the breather tube it will just blow out somewhere else, like your front and rear crankshaft seals. Pick one.

 

ahh so its whole function is only to relieve blow-by pressure then. I didn't know that.
So presumably you could tell how much of a blow-by problem you have just by measuring the airflow going through the breather?

So whats the difference between the part load breather and the full load breather? Presumably because of the different naming, they aren't actually just the same with one for each half of the engine?

 

The full load breather, right side, is to vent the crankcase. The part load breather is for throttle body function.

When the Nikasil problems surfaced Jaguar provided blow by test equipment to WOW dealers to measure the amount of cylinder bore/ring wear. Apparently not many made it to the US.

 

Thanks! Its so good to have knowledgeable people here!
Could you explain a bit more about the function of the part load breather? I'd like to completely understand what its doing.