White-ish smoke hot overrun 300tdi

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Wicklaman

Member
Posts
22
Location
Wexford Ireland
hi all. 300tdi has a whiteish smoke problem when hot and more so when very hot after high load driving. the jeep starts easy and no smoke. the smoke appears when hot and when off throttle going down gears, the smoke starts to puff and then applying throttle again it comes in abundance. it clears soon after and doesn't reappear until off throttle again. if tipping about without putting high load (hills, towing or speed above 55mph) it isn't as bad (still smokes though). It will engulf the environment if i come to a stop at a junction after high load. i did a sniff test on coolant bottle, but negative. i am not convinced as i think it might not be positive unless the engine is suitably stressed. the smoke does linger so maybe that is more likely to be diesel rather than water. power is good. bit of black smoke when pushing up steep hills, but not too worried about that. no leaks that i can see on diesel train. generally very dry engine. head was replaced recently by a previous owner. turbo possibly? i cant make the link to injector trouble based on symptoms. landrover mechanic that did the sniff test think valve clearances are ok and best to try injectors and turbo. the gent that sold me the jeep is giving me a spare engine to help diagnose. Any ideas welcome. might save me some tinkering time. btw it appears to be whitehish greyish smoke but may be some blue...i need to get behind it to be more convinced of colour.
 
Update on my problem solving. I pulled off hoses on either side of turbo, all nice and dry, approx 1/2mm sideways play in turbo. inlet manifold pipe has only slight trace of oil. EGR is blanked. oil cap does a little dance when loosened but no real pressure here. oil was slightly overfilled so i dropped out 1/4 litre. fuel side all looks very dry, no water in filter. checked lines to tank, all look ok. leak offs appear good. cyclone breather pipe to sump has a weep and it is probably the tiny splits at end of hose (i will replace but not an urgent worry). if i go for a short hot run, it smokes when i get back to my gate but has generally stopped by the time i drive into yard and reverse into garage. I am leaning towards a tiny crack in head or head gasket, and it needs to have been under high load to open up the crack enough...hence why sniff test failed. Has anybody experienced similar, not easy to diagnose without stripping head and pressure testing. Thanks in advance for any help.
 
Did the oil you let out smell of diesel ?
hi freelance, cheers for reply. nope...oil is perfect. I took a measure of coolant in reservoir 2 days ago at cold and checked again this morn, it has dropped 3-4mm. The smoke at every junction is bad now, if i were a betting man I would put my money on the head gasket and each way on the head. possibly minor injector issue in the middle of it which might explain a minor diesel smell from the smoke but predominantly it smells like an over heating engine. also the smoke cloud has dissipated by 5-10 seconds. it is a thick smoke.
 
He doesn't appear to understand!
It horrifies me
5490BC57-BD80-4C46-8664-6889D9D9CC41.jpeg
 
hi all. 300tdi has a whiteish smoke problem when hot and more so when very hot after high load driving. the jeep starts easy and no smoke. the smoke appears when hot and when off throttle going down gears, the smoke starts to puff and then applying throttle again it comes in abundance. it clears soon after and doesn't reappear until off throttle again. if tipping about without putting high load (hills, towing or speed above 55mph) it isn't as bad (still smokes though). It will engulf the environment if i come to a stop at a junction after high load. i did a sniff test on coolant bottle, but negative. i am not convinced as i think it might not be positive unless the engine is suitably stressed. the smoke does linger so maybe that is more likely to be diesel rather than water. power is good. bit of black smoke when pushing up steep hills, but not too worried about that. no leaks that i can see on diesel train. generally very dry engine. head was replaced recently by a previous owner. turbo possibly? i cant make the link to injector trouble based on symptoms. landrover mechanic that did the sniff test think valve clearances are ok and best to try injectors and turbo. the gent that sold me the jeep is giving me a spare engine to help diagnose. Any ideas welcome. might save me some tinkering time. btw it appears to be whitehish greyish smoke but may be some blue...i need to get behind it to be more convinced of colour.

Could be your valve stem seals. Contrary to what oil "should" look like, in this situation the oil can create a whiteish-light grey smoke which can be a bit James Bond smoke-screen stuff.
 
hi discomania.
appreciate the genuine effort to help.
i think if it were valve stem seals i would expect a smoke screen also at startup as oil would pass down by seals overnight.
i may be wrong, but that is my understanding. i dont have smoke on cold startup.
 
Hi Wincklaman, I'm not great on engines but have you ruled out bad fuel? Although I'm sure your fuel filter should negate that.... just trying to think obscure.
 
hi Gymmaniac
thanks for your help.
i have not drained the tank to rule out fuel completely, which is probably the only true way to exclude. would it be the case that fuel issue would cause smoke continuously rather than just on/after overrun? i am.using the same fuel (from same garage) in the 535d and no issues. I think it is a good point, on a learning curve here so it's on the list of potential root causes. thanks again
 
hi discomania.
appreciate the genuine effort to help.
i think if it were valve stem seals i would expect a smoke screen also at startup as oil would pass down by seals overnight.
i may be wrong, but that is my understanding. i dont have smoke on cold startup.

I will suggest you are wrong yes. In early stages of seal deterioration it is the vacuum of the over run that pulls the oil down the valve stem - yet the seal will offer enough sealing properties to stop oil leakage under non-vacuum conditions.
 
Hi Discomania.
you have my attention. would you expect same on light throttle then just after overrun? and subsequently no smoke when back on medium/high throttle. the smoke at junctions is significant (when ticking over, and will plume with short bursts of throttle at junction).
 
Hi Discomania.
you have my attention. would you expect same on light throttle then just after overrun? and subsequently no smoke when back on medium/high throttle. the smoke at junctions is significant (when ticking over, and will plume with short bursts of throttle at junction).

I have re-read your original description of the problem just to help with this remote diagnoses and you made the following points.

No issue starting and no smoke at start.
Smoke only appears when the engine has warmed up.
Smoke appears when you come off the throttle - puffing smoke at this point and then when you apply throttle you have a lot of smoke.
It clears soon after this episode until you repeat.

Looking at that data I can surmise that the issue is not fuel related - it starts fine, it runs fine and with no loss of power and nothing happens until it is warm - therefore I will assume the fuel and the fuel system are OK - if you had a fuel issue then even at cold you would see added smoke or wisps of smoke from cold. Starting would possibly be affected.

There are two stories here, the intake and the exhaust. Both sides behave differently during different engine situations. So to paint a rough picture lets take the inlet side, you are going to have a bit of vacuum, usually boost and about atmospheric pressure at some stages. On the outlet you have pressure from exhaust gasses exiting, however immediately after the valve closes and when you let off the throttle this changes for a split second where the momentum of the exhaust gases will actually pull a slight vacuum. Imagine, going along with high revs, lots of air going in, air and gasses and heat and sparks and flames shooting out the exhaust valve, you then take your foot off the throttle the engine starts to slow, but the outgoing gasses don't get this message, they want to batter on and create a vacuum behind a now slowing engine and of course, a closed exhaust valve.

The fact it only happens when hot suggests things to us here too, the expansion of the valve guides is greater than the moly-chrome alloy of the valves, so the gap opens up a bit with a wonky seal you end up with more oil bypass. It gets sucked in under the circumstances described above and you end up with a squirt of oil above your exhaust valve, nice hot oil, it smokes, give it some throttle, burning fire and gas picks up the oil, ignites it all, blasts it through a turbo and before you know it, you have a nice stream of smoke, once you get the engine rolling again it burns if all out fairly quickly, on light throttle with the turbo sitting on the edge it is possible more oil is being fed in or it just takes longer to burn it up, if the leak is not too severe then it may have no smoke at light throttle. A tiny amount of oil can make a LOT of smoke. As someone who has spilt chainsaw bar oil onto a red hot chainsaw exhaust I can attest to this.

So how to proceed... you would need to get it hot(the reason for this will become apparent), then without removing your fingerprints loosen off your exhaust manifold and pull it back (I would bet on this one first) and have a look, if the valve stems look oily and wet then that is a good indicator, start her up (why you want her hot) (be careful!) and have a look, at idle with the vortex the exhaust gas will create it will pull on the valve stem you may actually be able to hear a sort of wet oily noise and see oil splashing about.

You can change the seals insitu - the problem is the guides are probably shot if the seals are leaking, but for £5 for some cheap ones (I would not recommend long term) you could change them all out, and see if that fixes it for a day, week month etc. If it does then I would suggest head off, order up new guides and good seals, take the lot to an engine shop (I always use a marine diesel place) and have them fit the replacements. The procedure for this head is to heat it up to I think 120°C if I recall correctly.

That is from my thinking and personal experience with Land Rover engines - sitting behind a laptop and not getting hands on with your engine always puts us at a disadvantage and it could easily still be injectors or turbo (but your sort of ruled that out) but there is some food for thought.
 
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Firstly, thanks for taking the time to respond. secondly, well done on technical detail here. it all stacks up to make the most sense per symptoms. I am collecting a spare engine next week so will rule out low hanging fruit (injectors turbo etc) albeit i am not convinced these are root cause. i am monitoring coolant loss currently, by using the defender more often (even though coolant loss does not currently stack up as root cause), that said i want to ultimately rule it out. I am also monitoring oil loss, however based on you analysis the oil loss is negligible if root cause is per your indication. I will complete checks per your recommendation also and report back in a couple of weeks on progress. I really appreciate the guidance as nothing else has really stacked up thus far as potential root cause. cheers
 
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