White smoke from AJ6 on startup

[SimonR]

Hi all,

This is a characteristic of my Jag that I find a little worrying but I can't really explain it.

Nearly everytime I start it I get a puff of white smoke out of the exhausts. It isn't blue like oil smoke and doesn't smell like oil and clears immediately but I'm wondering what it can be. Is it possibly overfuelling or do I need to start worrying about the condition of my engine?

It's done 100K and apparently was taken apart at 97K and everything was found to be within the correct tolerances. There was no smoke evident when I bought the car (and it was started from cold) but it has had an oil change since then so maybe it's the wrong grade of oil or something. As far as I can tell it doesn't use any oil but I haven't driven many miles in it so far so I can't really tell.

I'm trying to establish a pattern to as to when it smokes and will report one if I find it until then, has anyone got any suggestions?

[Martin]

White smoke is usually associated with brake fluid. At least that's what happens on older cars when fluid leaks from the servo into the inlet manifold. Is your brake fluid level going down?

[SimonR]

Thanks for the advice, Martin.

I've been looking at this problem today and can report the folowing:

1. The brake fluid level is not going down
2. Over about 2,000 miles the oil level has remained the same
3. There is a very slight lumpiness when idling
4. The smoke doesn't smell or look like oil smoke
5. There's an initial puff of smoke on startup and then nnothing more, even at high revs
6. It doesn't smoke everytime I start it and there seems to be little pattern to it.

Could it be unburnt fuel? Could I have a leaky injector or something?

At the moment I can live with it as it doesn't seem to be causing any real problems but any ideas you have would make a good starting point. The only real embarrasing bit is thatthe smoke escapes through the slightly-blowing exhaust at the front! May be the exhaust is the reason for the lumpy idle?

Cheers

Simon R.

[cljxc50]

HI JUST A THOUGHT BUT IS THE HEAD GASKET OK? MY FRIEND HAD A PROBLEM JUST LIKE YOURS IT SEEMS THAT WATER WAS SEEPING INTO THE BORES AND WHEN STARTING HE WOULD GET THE WHITE SMOKE,BUT WHEN THE CAR WAS WARM IT WAS FINE. TRY CHECKING OIL AND WATER TO SEE IF THERE IS ANY LOSS OR MIXING OF FLUIDS, THAT MAY INDICATE H G F..

[SimonR]

H there,

Thanks for the reply.

Well, I took the cap off the coolant and thankfully it was a nice non-oily green colour, just as it should be. Then I pulled the dipstick to check the oil level. There was a slight trace of yellow mayonnaise at the very bottom but I'm trying to put that down to a short journey in the cold causing emulsification in the breather.

Recently, notably as the weather has got colder I have been getting some really poor fuel consumption figures. For example I did a 120 mile trip to the NEC and averaged about 17mpg Although I was making very good progress I wasn't booting it or driving like a maniac. Added to that I only got about 320 miles from my last tank-full so I think my Cat is over fuelling somewhat. In the warmer weather I was easily getting 400 miles from a tankful.

Added to that my heater never actually gets what I would call hot.

Now, I'm going to replace the thermostat this week but it is reasonable to suggest that my car is running rich and therefore the smoke could be fuel? It blew a perfect smoke ring at the weekend, much to my friends' ammusement.

Whatever happens I should get better MPG figures than that. What do you lot get at a constant 70ish(!) miles an hour?

Any other suggestions after the thermostat?

Cheers

Simon R.

[cljxc50]

HI SIMON IF IT IS OVER FUELLING, BEFORE WORRYING ABOUT THE CAT LOOK AT THE LAMBDA SENSOR AND THE TEMPERATURE SENSOR THEY CAN FOOL THE ECU INTO ENRICHING THE MIXTURE. IF YOU ARE WORRIED ABOUT THE MAYONNAISE YOU COULD ADD SOME K SEAL (LIKE RAD WELD) TO THE COOLING SYSTEM THIS SEALS THE SYSTEM AND IS SAFE WITH ANY ANTI-FREEZE. (A TRICK THEY USE IN GARAGES) PLUS ITS ONLY £8 A BOTTLE.....

[SimonR]

Oops, I think I have caused some confusion! When I said Cat, I meant Jaguar, as in Kitty in America

My Cat doesn't have a cat, so to speak.

Anyway, if my temp sensor were faulty would it alter the reading on the dash? - I'm consistently getting a very low reading, just above min on the scale so maybe that's another area to investigate.

I bought a thermostat today and will change it tomorrow lunchtime so lets see if that makes any difference.

SR.

[Martin]

Simon - reading through this you mentioned a slight bit of emulsion on the dipstick. It suddenly reminded me of a problem that is fairly common on these engines on the XJ40. There is a rubber crankcase breather pipe system that runs from the oil filler tube to the air inlet. Can't remember the exact details but it gets blocked and causes moisture to collect in the oil filler tube. It's easy enough to clean out. Might be worth a look.

[SimonR]

Thanks for that Martin. I'm going to do the thermostat tomorrow lunchtime so I'll take a look at this at the same time.

I guess if the thermostat doesn't solve the problem I'm looking at replacing the temp sender and then hollering if that doesn't do it.

You can rest assured that I'll be back if I'm still having problems ;¬)