I had the same problem a few years ago. Never managed to find the real root cause. But it disappeared and it never happened. Now, to be true, the conditions under which it happens are a bit extremen. Only when doing well over 100 MPH. Here in Europe that can only be done on unrestricted speed sections on the German Autobahn. We happened to be in Germany yesterday. Unrestricted stretch of Autobahn, very little traffic so it is pedal to the metal. I have driven at very fast speeds several times since the problem occurred first, no problems, none whatsoever. So whatever it was, was intermittent at best it seems. This seems to be the second time it happens.

At about 110 MPH the engine starts to lay out a complete smoke screen. It is really bad. When the speed drops to below 100 MPH all is normal. No unusual sounds or anything. Car drives completely normal otherwise. I can’t replicate the problem by just doing a lower speed, but in a higher gear. So it is not (just) engine RPM related, but really load it seems.

This morning I checked the codes, nothing. Then I dug up the load breather bulletin. I checked this last time as well. According to this procedure you need to disconnect the full load breather, start the engine and hold a small piece of paper over the breather pipe. If the paper is sucked to the stub pipe proceed the clean the part load breather. The piece of paper did get sucked in, so I followed the procedure and used a 2,5mm drill to clean the part load breather. I don’t think there was anything blocking it, though.

I checked again, and the piece of paper still gets sucked against the stub pipe! Cant recall the outcome of this test last time. But the way I read it, if all is well the little piece of paper should not be sucked against the stub.

Where does the hose from the part load breather go to? It disappears under the supercharger coolers somehow and I have not been able to find anything in the workshop manual.

Can there be a blockage further up the part-load breather. How to get at it? Can I try a blowing a bit of compressed air into that hose.

This problem seems to be intermittent, the car has done tens of thousand kilometers between these two occurrences, drives really well, no excess oil usage, passes it emission test every years, colours flying.

Jeroen

 

If you're sucking air in a breather it's not caused by a restriction, it's caused by the breather valve not closing when it should. Usually because it's worn out. It's a one way valve that's only suppose to let crankcase pressure out, not suck more air in. Sucking air in increases crankcase pressue and blowby.
Breathers should never be routed back into the intake where this mixes with the intake charge. It's an emissions mandate that's not good for the engine, causes excessive carbon build up of the combustion chamber and pistons, and dilutes/contaminates the air/fuel charge with hot oily air. Valves start sticking. Not a pretty sight.
Now when your breathers start to malfunction you're blowing excessive amounts of oil in the combustion chamber.
Sooner or later that carbon build up will glow red and cause pre-ignition/detonation.
I vent to atmosphere but you will fail an emissions test. Easy enough to switch back for a test tho if you have to.

 

One possibility:

Some years ago I had a 1986 Daimler Double Six and there was a note in the Owner's Manual which said something like this: "Sometimes, at high highway speeds, you may notice whitish smoke coming from the exhaust. This is perfectly normal and is no cause for concern." It also explained that this was due to the carbon deposits, formed during stop-go city traffic, being burned-off.

If this is what is causing the smoke from your car, it should not be continuous while you are at a high speed on the highway but it should stop after some time.

 

I have a similar experience, but my issue was very specific so it is unlikely to be the same as yours. Maybe impossible if your have a naturally aspirated engine as mine is a supercharged and it is related to the gearbox, which is not the same on both. But just in case...

I had my gearbox serviced in a garage and they put too much oil back in. Under normal load everything was good, but under high load the oil expanded enough that it dripped out of the gearbox... Just above the right side exhaust pipe. Which created a cloud of smoke. I had the garage reajust the level for free and the issue immediately disappeared.

 

Those carbon deposits are more from the routing of the crankcase breathers as explained above. The carbon you're talking about is from fuel and as lean as these things run now days is hardly likely to occur. The pics are pretty damning proof of the internal engine damage that can be done by this treehuggers mandate. I highly suggest routing breathers to atmosphere if you care about the long term health of your engine. It also increases power albeit by a small margin as proven on a dyno.
As engines get older and blowby increases from worn rings, this becomes even more of an issue. Worn breathers themselves make it worse by increased crankcase pressure.

 

Leave the emission equipment alone (jail sucks). I think you were seeing carbon being cleared from the valves.

 

Thanks everybody. Not sure what it is,

So where are these breather valves on my engine? there are two load breather. The full load breather is connected directly to the intake air (just behind the air filter). The part load breather has a restrictor, but no valve either as far as I can tell.

Jeroen

 

Where do you think valves are located? Have you ever seen one? Where do you think the carbon comes from? The 14.7 AFR? I Hardly think so. It comes from oily mist routed back to the intake. Geezus.

 

Seen it in a movie once this guy named Bond had one that was variable

 

Actually the paper should be sucked in the valve cover hookup for the full load breather during low and part load. It means the part load breather is NOT clogged and the vacuum is sucking fresh air in thru the full load breather and venting out thru the intake.
There are no pcv valves on the 4.0. Just restricted passages. People assume it's a pcv system but it's actually a ccv system.
At some point the full load breather apparently reverses flow when the part load breather can no longer keep up venting the crankcase and pressure builds as vacuum decreases with load.
If you were to unhook the part load breather hose from the left valve cover and plug the end of the vacuum line you'll notice the full load breather hookup in the right valve cover no longer sucks the paper in. As pressure increases the blowby will passively exit thru both valve cover holes. You could just put filters on both valve covers. This is how it was vented back in the days before the treehuggers got crazy stupid about venting to atmosphere.
The are advantages to the pcv and ccv systems in that they create a vacuum which allows the pistons and crank to move freely and not fight the drag of positive pressure. The downside is venting that nasty crap back into the intake diluting the charge, lowering octane, carboning up the combustion chambers, and causing detonation/pre-ignition.
The best way to evac the blowby is with a vacuum pump to atmosphere. This provides the vacuum beneficial to making power and actively venting the crankcase without all the negative side effects of pvc and ccv systems I noted.
Hope this helps explain things better as the subject seems to be avoided here except for the treehuggers saying leave it alone or you're going to jail which is ludicrous unless you live in parts of Europe maybe where you're not not allowed to so much as speak out against the government or question it.

 

Thanks!

The Jaguar procedure is not entirely clear on this. It says


I assumed it meant that when all is well, breather wise, the paper should not be sucked in?


I have lived in the USA and in Europe ( and various other places) and I can vouch for the fact that you are much more likely to go to jail in the USA than in most, if not all of Europe. People here speak out and question the governments of the European states every second of the day. I have not seen anybody being thrown in jail for that. In fact, speaking out as such, is not questioned at all. We have them all, the flat-earthers, the greenies, the anti-vaxers, vegans, the mooonlanding-deniers, the right- and the left- wing loonies and any loony in between. All speaking out, none of them in jail currently as far as I am aware. Not quite sure how many European politician are banned from Facebook or Twitter? In fact, when a US politician/president was banned by various social media, almost everybody in Europe felt, yes the guy is a nut job, but that is no reason to ban him. Most European politician spoke openly about being against any form a banning!

We are lucky though. We have not seen extreme right wing nut cases storm, armed and all, our parliamentary buildings because they don’t agree with the current government. But then again, some of us used to chop off heads of those in power, but that was quite some time ago. Has not happened recently I think.

Back to cars and breathers!

Jeroen

 

Yeah, I'm not going to argue about emissions mandates anymore. We've been bypassing these forever here in the Midwest.
But that full load breather sucks fresh air in at idle and part load providing the part load breather has vacuum and is sucking crankcase pressure out. The problem comes from when vacuum drops at the part load breather under load. The full load breather then ceases to suck fresh air in and this is when you get oil in the air filter and tubing.
I've come up with a solution to this that will keep a steady vacuum on the part load breather at idle as well as full load and keep the full load breather sucking fresh air in all the time. You might want to check out my crankcase breather mod thread Here.

 

i've had this problem twice, one on my str at around 120 which was complete valve cover gasket failure, and another on my x308 when it gets to 135 not 132 or 125 but always when it hits that magic number. that one has a light leak. personally, i'd check the valve covers

 

Thanks, I replaced my valve covers not too long ago. But how do you see a leaking valve cover causing exhaust smoke at high loads? How would that work?
Thanks Jeroen

 

at least in my case, the oil got on the exhaust and started burning off, x308 never smoked just a strong oil burning smell

 

thanks, but my smoke is definitely coming from the exhaust. And not just a little bit. People actually had to brake as they drove into a black cloud pouring out of my two exhaust. So a very different issue I think.
Since I have had my engine flushed. Havent been back into Germany yet, but will get to go on the Autobahn later this summer

Jeroen

 

good luck, ya'll have an amazing landscape out there. went to Germany many times from the 80s-00s

 

Is the smoke screen just speed depdendat or can it reproducted by keeping the engine at same rpm at stand still ?

 

Thanks

No, only at very high speeds. I tried it by revving engine, by keeping engine in low(er) gears and giving it the beans. But only on the unrestricted Autobahn will this phenomena occur. I think at these high speeds the wind resistance is very considerable, so the engine gets really loaded up big time across the rev band.

Jeroen

 

I would separate the full load breateher from the intake pipe, block the intake pipe port so there is no intake leak and lead the breather to lets say 1.5l soda bottle with breath holes poked in to. Then hit the road and drive casually and stop to see is there any oil in the bottle at regular basis. If the bottle is empty as it should, then go with the full speed. If there is no smoke at the smoke screen speed. Don't stay there for a long. Just because if the engine spits out oil fast it will fill up the bottle. If there is still smoke from the tail pape, oil is gettin in somewhere else.
Please note that engine breathing to the outside air stinks strongly. Especially when engine oil is hot. And because when oil is hot it wil have a steam so it is normal when steam is oming out from the bottle.