4.8 white smoke

[Andy Collings]

Seem to have excessive white smoke coming out of exhaust. Does it when cold but carries on when normal temperature but not as bad. Read some forums and lots of idea's. Could be Crank vent hoses need changing, Valve seals gone, etc. Anyone had this on a 4.8 N62 engine ? How cured?
Read about related high oil consumption but not really experienced that. Will adding Lucas oil treatment help? Read a test to do, warm up engine let idle for 5 mins then throttle it hard, if white smoke valve seals gone, would that be right? Some have said replacing Crank vent hoses fixed it, others added the Lucas additive. Any opinions? Would adding additive be a good place to start?

[henrym3]

Had the white smoke problem with my 4.6 when I bought it some years ago. Especially noticeable coming off the throttle at speed, anyway, renewed the PCV system, cleaned out the inlet manifold and cured some vacuum leaks. Haven’t had a problem since. I know the 4.8 is prone to valve stem seals failing but going down that route would be a last resort. A recent car I got (Alpina b3 1999) had a problem of using oil, ran perfect or so I thought until I built a smoke machine and used the Alpina to test it. There were 2 very obvious areas where it was leaking, cured these and the oil usage improved to be not noticeable. I mention this to try and encourage you to get a smoke test done on your 4.8. Ensure your PCV system is in tip-top condition. If your PCV is good and no vacuum leaks at least you can say with reasonable confidence that it’s the valve stems. If you smoke test make sure you do it on a cold.engine.

[Andy Collings]

Thank you very much for your post. I will try your suggestions and see where to go. Hoping nothing too serious, spent a lot of money on the car already. Will post update soonest. Thank you.

[marti]

Normally a split in the PCV.

[Andy Collings]

Thanks. What do you classify as PCV ?

[henrym3]

D2008A4E-F4A2-4653-B51E-C49ECC2861B0.png (284.97 KiB) Viewed 3014 times

This is the PCV
Also have you got any oil leaks, even minor. If you have an oil leak then you have a vacuum leak

[Andy Collings]

Very grateful for the picture and the oil leak info. I do have an oil leak somewhere even though minor. The level doesn't seem to go down but every now and again I get a burning oil smell in cabin. Doesn't happen on a long run and mostly when car on an angle. Already had rocker cover gaskets replaced and a timing cover seal changed, both were leaking bad. Must be another one somewhere. Putting car in garage for a Heater control valve change soon, so will get them to do a smoke test and check for oil leaks and the PCV. Today I will do the warm up engine, idle for a bit and throttle it test. Very grateful for your help I will reply back with any findings. Much appreciated.

[rehan]

Hi (again!)

I had the same problem on mine to a greater degree than it is now. Others have suggested PCV Valve splitting which is the most common and cheapest fix. On mine, they were fine, although I could see that there was oil inside the inlet manifold (need to take throttle body off to check). This puzzled me as I couldn't see how oil could get there otherwise, even with a valve stem leak.

As it turns out, although the dealer said it had a service before I bought it, the air filters were filthy. My theory was that as they were so dirty, the engine was sucking in more oil via PCV system than normal.

Symptoms on my car that if it is idling more than 10 or 15 minutes, and I then rev the engine, I would see blue smoke. It would be fine when driving, so it's something that is collecting in the inlet manifold when it is idling. Although changing the air filters helped, I still suspect something along the PCV system on mine. I might take another look at it at some point. The PCV Valves are orange rubber diaphragms (if they fail, this is what splits), but there are other bits supporting them in place (spring, o-ring etc) that I suspect may not be optimal.

If it turns out to be valve stem seals, this is a big job, so I would exhaust the above first.

[Andy Collings]

Hi Rehan,
thank you for more useful information. I have had a quick look under the car and under the bonnet with a torch and also gone around with a clean white cloth, can't find any signs of an oil leak but some places are very hard to get to. Oil on dip stick was still where it should be. Tomorrow will do the white smoke blue smoke test. If I can't find anything I'll get it all checked out by garage when they do the HCV. Be glad to get to the bottom of it! Thanks again, will post updates.

[Andy Collings]

OK so done the warm up engine and idle test, quite a bit of white smoke came out of exhaust, used the rear view camera and mirrors to confirm it. Car booked in for PCV valve replacement and smoke test and crankcase hose and other bits once over. Also got some Lucas Stop leak additive to put in oil. Will get all these things done and see if any improvement. Need 1.6 litres of additive which for 2 litres was around £18 on Ebay. PCV repair kit, which was 2 covers and diaphragms was £10 also on ebay. Cheap first tries. Fingers crossed. Will post more updates after another garage visit and diagnostics.

[Andy Collings]

Put the additive in oil a couple of days ago, can take a few hundred miles to work. Additive is very gloopy and couldn't get it down dip stick hole easily even when warmed up. Had to put it in oil fill point, messy stuff. Managed to take some old oil out of dip stick tube with a syringe and small pvc tubing, worked ok. Put car in garage yesterday and had PCV valves changed, the orange diaphragms etc. Crank case hoses and smoke test checked, a couple of minor oil leaks found and a slight air leak from passenger side rocker cover area but a sod to get to. Will drive around for a while and see if any improvements. HCV changed for my heating problem too, see how that goes.
Another fault now though, picked up car and suspension symbol came on, on start up. Went away on next start but came on this morning when driving. Diagnostics said timing error right rear, cleared code and will see if it happens again.

[henrym3]

You said you had a small leak from the rocker cover gasket, if it was the same garage that you said recently replaced them i hope they didn’t charge you for fixing it.

[Andy Collings]

Good news was they didn't. Did some other bits for free too.