Blue smoke on start up!

[mr rooney]

Hi chaps! My pd 130 asz puffs out a cloud of blue ish smoke on cold start ups. It's done this for the last 3 years but is particularly bad as the weather turns colder. In the summer the smoke is minimal if not no existent on start up.  

My first thought is worn valve guides as the car has done 138k miles but i'm told if you drive and then decelerate you would get some blue smoke if your valve guides are worn. I don't get smoke in this situation. 

Is it possible my 138k mile old glow plugs could cause this problem? Car starts instantly every day even in cold weather but is a bit rough for a few miles. It use to run smoothly straight away years ago.

Thanks!   

 

 

[KenONeill]

Diesel smoke on start-up is normally white, and if you stand behind the car and sniff it smells of diesel fuel. So I'd discount cold cylinders as the cause of the blue smoke. Having said that, if you get rough running for literally miles on a cold day you probably should check for open-circuit glowplugs anyway.

 

Blue smoke is usually oil, but as you say most causes of that give you a puff of smoke when you pick up the throttle after time on over-run. About the only thing left wuld be oil leaking past the exhaust valve seals when the car's standing overnight.

[cheshire_cat]

the decelerate thing only applies to engines with a throttle which creates a vac    but it may be oil seals or just oil in ever joint in the intake system --- I know mine has

[stevobeavo]

I'd go for valve stem seals personally. Easy enough to change if you have a few hours free

[KenONeill]

the decelerate thing only applies to engines with a throttle which creates a vac    but it may be oil seals or just oil in ever joint in the intake system --- I know mine has

Er, engine braking always creates a vacumn in the intake.

[cheshire_cat]

Er, engine braking always creates a vacumn in the intake.

not on my boost /vac gauge   ;-)

[KenONeill]

not on my boost /vac gauge   ;-)

So how does engine braking work then?

[cheshire_cat]

compression of uncombusted gas ie: (fuelless air)   drawn in thro' a relatively unrestricted inlet system -- I guess at what point you consider to be a vac,  certainly not sufficient to be a major pull on the stems of open inlet valves --  just as the exhaust of same is no more than a gas moving machine ---does this constitute hijacking a thread ?  - sorry      

[sepulchrave]

A big part of the reason diesels are so much more efficient than petrols is that they don't have a throttle and therefore don't suffer the same suction losses at part throttle.

 

Edit: So yes, it could be valve guide stem seals leaking.

Edited 3 December, 2014 by sepulchrave

[mr rooney]

Thanks for the answers chaps! 

I thought worn valve seals could be a possible culprit but I popped in to a local garage and they recommend changing the glow plugs first as they believe the unburnt diesel left in the cylinders caused by faulty glow plugs will give a big puff of blue ish smoke.

It's also rough on start up when it's cold which indicates worn glow plugs.

It would be nice if it's just case of new glow plugs and not valve seals lol!  

@Stevobevo you say it's a simple job to change the valve seals ? How much time/ labour would a garage charge for this service?

[KenONeill]

compression of uncombusted gas ie: (fuelless air)   drawn in thro' a relatively unrestricted inlet system -- I guess at what point you consider to be a vac,  certainly not sufficient to be a major pull on the stems of open inlet valves --  just as the exhaust of same is no more than a gas moving machine ---does this constitute hijacking a thread ?  - sorry      

 

 

A big part of the reason diesels are so much more efficient than petrols is that they don't have a throttle and therefore don't suffer the same suction losses at part throttle.

 

Edit: So yes, it could be valve guide stem seals leaking.

Cheshire Cat appears to be arguing that engine braking is just pumping losses on a closed throttle. At this point any engine without a throttle valve or anti-lag is running atmospheric (the throttle plate imposes an additional loss as air is sucked past it and anti-lag is the only way a turbo will be doing more than windmilling). I can sort of see the sense of that, but for a turbo engine the pressure in the manifold will be at least 0.5 bar (for a diesel it could easily be 1 bar or more) less than when on boost and power. This means there's a fundamentally lower pressure stopping oil going down the vavle guides.

 

sepulchrave - I agree the above; how does the reasoning about changes in pressure across the valve stem seals grab you?

[KenONeill]

Thanks for the answers chaps! 

I thought worn valve seals could be a possible culprit but I popped in to a local garage and they recommend changing the glow plugs first as they believe the unburnt diesel left in the cylinders caused by faulty glow plugs will give a big puff of blue ish smoke.

It's also rough on start up when it's cold which indicates worn glow plugs.

It would be nice if it's just case of new glow plugs and not valve seals lol!  

@Stevobevo you say it's a simple job to change the valve seals ? How much time/ labour would a garage charge for this service?

Why? Glow plugs (aka combustion chamber pre-heaters) play no part in the fuel supply, and no direct part in the Otto cycle (hint in the name "compression ignition"; you compress the air, then add fuel which is ignited by being sprayed into hot air). I've almost never seen blue smoke from a diesel, and when I have it's never been identifiably unburnt fuel. (see #2 for a cold engine; on a hot engine the smoke tends to black as excess fuel means the reaction fails to go to completion and instead of cetane + oxygen -> CO2 + H2O you get cetane + oxygen -> CO2 + H2O + Cn. It's been 35 years since I actually calculated reaction rates so please just accept it as true that the H+O - > H2O reaction goes to completion more easily than the associated C+O -> CO2 one).

[_Jim]

Both of my vRS's, my girlfriends SE and a friends vRS have all done this on a cold morning. Between them the cars have ranged from 60k-135k miles.

One puff on start up from stone cold first thing in the morning then nothing else for the rest of the day.

None of them have ran rough however.

Edited 4 December, 2014 by _Jim

[devonutopia]

Mine puffs out white smoke for a few seconds on cold start which is just consequence of big nozzles and cold weather so harder to keep engine running initially. Never seen real blue smoke.

[cheshire_cat]

I guess a "throttle" is just the negative version of a Jake Brake :sun:  :sun:  :sun:  

[sepulchrave]

sepulchrave - I agree the above; how does the reasoning about changes in pressure across the valve stem seals grab you?

 

The mechanism for blue smoke only when first started in the morning would be gravity, the valve guides on a PD are completely vertical, any oil pooled under the lifter could leak past the hardened seal very slowly overnight leading to quick burnoff with no further loss, in any event it's an insignificant problem, some valve guide lubrication is actually beneficial.

[KenONeill]

The mechanism for blue smoke only when first started in the morning would be gravity, the valve guides on a PD are completely vertical, any oil pooled under the lifter could leak past the hardened seal very slowly overnight leading to quick burnoff with no further loss, in any event it's an insignificant problem, some valve guide lubrication is actually beneficial.

Put in those terms, agreed, and it's been an issue with some engine designs since the 1980s.

 

What I don't understand is how, out of certainly hundreds of thousands of 1.9TDis (maybe millions?) made (all tunes and perhaps we should include the 1.9SDi since it uses the same block and head?), this issue only seems to occur on a few of the PDs.

[sepulchrave]

Put in those terms, agreed, and it's been an issue with some engine designs since the 1980s.

 

What I don't understand is how, out of certainly hundreds of thousands of 1.9TDis (maybe millions?) made (all tunes and perhaps we should include the 1.9SDi since it uses the same block and head?), this issue only seems to occur on a few of the PDs.

 

I would guess that the additional heat generated by the higher output engines could lead to further seal hardening than simply age alone, also cylinder heads which may have been overheated during a vehicles lifetime will suffer premature valve guide stem seal hardening. Most French cars seem to suffer this fate since they commonly seem to overheat and blow gaskets at some point in their life 

[mr rooney]

Put in those terms, agreed, and it's been an issue with some engine designs since the 1980s.

 

What I don't understand is how, out of certainly hundreds of thousands of 1.9TDis (maybe millions?) made (all tunes and perhaps we should include the 1.9SDi since it uses the same block and head?), this issue only seems to occur on a few of the PDs.

 

Why? Glow plugs (aka combustion chamber pre-heaters) play no part in the fuel supply, and no direct part in the Otto cycle (hint in the name "compression ignition"; you compress the air, then add fuel which is ignited by being sprayed into hot air). I've almost never seen blue smoke from a diesel, and when I have it's never been identifiably unburnt fuel. (see #2 for a cold engine; on a hot engine the smoke tends to black as excess fuel means the reaction fails to go to completion and instead of cetane + oxygen -> CO2 + H2O you get cetane + oxygen -> CO2 + H2O + Cn. It's been 35 years since I actually calculated reaction rates so please just accept it as true that the H+O - > H2O reaction goes to completion more easily than the associated C+O -> CO2 one).

I'm no expert on these matters but my local garage reckons the glow plugs heat the combustion chamber on cold starts to allow complete combustion of the fuel on start up. If the glow plugs are not working correctly this doesn't happen and a big puff of smoke comes out and they also say unburnt fuel can look blue ish.

My lumpy cold start is due to incomplete combustion for a few seconds.

This morning I start up with the usual puff of smoke then 5 minutes  later I start it again to be greeted by yet  another puff of smoke. Surely this can't be oil passing the valve seals in such a short time?  But according to my garage it's unburnt fuel?

As soon as I get the chance to change the glow plugs i'll know if  that's the issue.

[trundlenut]

Based on previous experience (and that of my neighbours 50 yards along the road) knackered glowplug equals white smoke, no hint of blue.

[KenONeill]

I'm no expert on these matters but my local garage reckons the glow plugs heat the combustion chamber on cold starts to allow complete combustion of the fuel on start up. If the glow plugs are not working correctly this doesn't happen and a big puff of smoke comes out and they also say unburnt fuel can look blue ish.

My lumpy cold start is due to incomplete combustion for a few seconds.

This morning I start up with the usual puff of smoke then 5 minutes  later I start it again to be greeted by yet  another puff of smoke. Surely this can't be oil passing the valve seals in such a short time?  But according to my garage it's unburnt fuel?

As soon as I get the chance to change the glow plugs i'll know if  that's the issue.

I've never, repeat never, seen smoke from a cold start look blue, always repeat always white (white). Having said that, I'd agree that oil shouldn't be passing the valve seals that fast, but have you drained the intercooler?

[cheshire_cat]

mine is always blue :sun:   and I have a catch can and clean the lower pipes and drain the IC every year and it's only done 50 odd K from new --am sure my oil seals are still good -- only first start of the day

[mr rooney]

I've never, repeat never, seen smoke from a cold start look blue, always repeat always white (white). Having said that, I'd agree that oil shouldn't be passing the valve seals that fast, but have you drained the intercooler?

The intercooler is pretty clean as I did the elephant mod some time ago and there's very little oil left in the pipe work. I use 1 litre of oil every 8k mile btw.

 Seems odd I get the big puff of smoke within 5 mins of the first cold start ? This can't be oil draining past valve seals that quick?

When I get the chance to have new glow plugs fitted i'll report back.

How easy is it to change glow plugs on the ASZ pd 130 ?

Cheers!

[devonutopia]

Easy to change.  Whip loom off, then a deep socket and wrench.

 

When my gopro arrives next week I'll do a little video of mine starting up from cold.

[SEVrs]

My BLT engine (50K miles) always blows out black smoke on first start up then nothing else (whether ambient temp is warm or cold).  It has always run smoothly, never uses much (if any) oil and runs fine. It used to bother me that something wasn't quite right but as it only does this on start up and never on the move, I've given up worrying.  I'd not be impressed if the valve seals were worn on a FSH car at just 50K miles, but I'd also expect oil use if the valve stem guides were worn and I'm not getting any.  The smoke always smells strongly of unburnt diesel so my thoughts are that it might be a faulty glowplug.