Hey my loves, so this is an ongoing issue I am seriously struggling with.
When I start up, I get a tonne of white smoke from the tailpipes. it'll be a big cloud followed by a nearly invisible little stream, which will continue for a minute or so and then stop. I do get quite a bit of moisture in the tailpipes BUT... and here's what's making this hard to diagnose..

1. I can't tell if the smoke is blue or white.
2. it dissipates pretty quickly, so could be coolant steam
3. IT'S SUMMER HERE AND SUPER HUMID, NO WAY IT CAN BE WATER VAPOR.

My oil is fine and my coolant is fine, so we don't have cross contamination (phew) but this has been going on for months.

I am dreading the idea of a head gasket issue, esp since my engine was pretty much reconditioned 100K km ago according to old service history.

this issue only presents itself if the car has been sitting for a while- couple of hours. and it's just that cloud on startup- so I feel something is leaking while it's sitting.
what are all the possible things that could be leaking into exhaust while sitting that AREN;T head gasket?
I am definitely thinking coolant but hoping there's another explanation which may be more simple to work..
there is a slight smell to it, but it is not that offensive burning oil smell which makes me think coolant- though sweet is definitely not how I'd describe the scent.

once again, the smoke does not continue while driving, only on startup. though I have been told once by a fgriend who was driving behind me, that when accelerating out of a corner there was a little foof of white smoke for a second.

thanks guys xx

 

Hi Beck,

An XJ40 that doesn't smoke a little at startup is the exception rather than the rule. A very common issue is that the rubber valve stem seals harden and lose their seal, allowing oil to seep down the valve stems into the combustion chambers. While the engine is running, combustion pressure slows down the process. But when the engine is off, oil that pools on top of the cylinder head drips down the valve stems, especially on the exhaust side due to the tilt of the engine. At startup, the oil that has made its way into the cylinders burns off, producing smoke from the tailpipe.

From your description, it sounds like your case may be worse than normal, which makes me wonder.

You say your oil is fine and your coolant is fine, but you don't mention whether the level of one or both seems to decline more rapidly than you would expect.

One possibility that comes to mind is that if the crankcase breathing system is clogged, excessive pressure could develop in the crankcase, forcing oil upward, past the piston rings, into the combustion chambers.

Another thought is that there is a restrictor in the fitting of the air intake elbow where the breather hose attaches It is there to limit the vacuum created in the crankcase. If the restrictor was left out at some point when the elbow was removed, the intake could pull too much vacuum and inhale excessive oil vapors from the crankcase. There are some photos that show the restrictor in the albums at the links below (sorry again that the large images are still down at the Jag-Lovers forum):

Air Intake Plumbing & Crankcase Breathing Part 1 of 2
Air Intake Plumbing & Crankcase Breathing Part 2 of 2

I'll try to think of some other possibilities - perhaps someone else will have some better ideas.

Cheers,

Don

 

Don you're amazing as usual. Wish I could get you you to come have a look! I checked and I do have a little doohickey which I assume is an intact restrictor, though in diagrams the small end is pointing upward however it's seated pointing down in mine. Is that right?
The restrictor is also oily as hell. What's causing that? What are the next steps sarge? Xx

 

Beck how about a video clip? The other fluid that needs to be checked is the brake fluid.
I cannot see how that can get into the combustion area due to the power brake system used. If it was a normal vacuum booster set up then I can see that that could happen, I had it on a Rover 3.5 I ran in the UK.
BF burns white BTW.

 

Hi Beck,

That's how the restrictor was mounted in my XJ40s also, so that's good. But it is definitely time to remove the air intake plumbing and crankcase breather hoses and wipe the oil out of every hose where your hand will fit and flush the rest out with brake cleaner spray or some other suitable mild solvent. Over time the oil from the crankcase breather system accumulates throughout the intake and continues to be inhaled into the intake manifold. In bad cases, it can pool so deep in the intake manifold that it leaks forward, through the mass air flow sensor (MAF), and into the air filter. Which reminds me, have you checked your air filter?

Another thought is that your engine could also be running rich. Are the insides of the exhaust pipes coated with black soot? Common causes of rich running are failure of the coolant temperature sensor (CTS), a clogged air filter, a failing MAF sensor, oxygen sensor (O2S) or intake air temperature sensor (IATS, just to the left of the restrictor in your photo), a stuck-open carbon canister purge valve, or a failed diaphragm in the fuel pressure regulator (FPR). To test the latter, pull the vacuum hose off the FPR fitting, turn the key to position II (Run/ON) and look for signs of wet fuel at the FPR vacuum fitting, which indicates failure of the diaphragm that allows unmetered fuel into the intake manifold.

Have you checked the Vehicle Condition Monitor (VCM) for any stored diagnostic trouble codes (DTCs)? Some DTCs can be flagged by some of the issues noted above.

Cheers,

Don