W124 E36 blue smoke on startup..

[joeywarren]

Hi all,

hopefully someone can help!

I have a genuine E36 W124 estate, with 91k.

It has an issue on cold starts whereby it takes a few turns to get going, then basically throws out blue unburnt fuel smoke from the rear - for about 30 seconds, then it's fine after that - no other issues.

I have had coils, plugs, HST etc all replaced as a matter of course.

Any ideas where to go next would be appreciated!

thanks!

 

[Dieselman]

Blue smoke or black.
Blue means oil, black means fuel.
If oil suspect valve guide seals.

 

[joeywarren]

Hi - well it's blue smoke, smelling of fuel ;( Cold starts only though - does that make a difference?

 

[rf065]

Strange?
I answered your post, same answer as Dieselman, but it has disappeared, how did that happen?

Russ

 

[280gee]

Sorry if I misunderstand here but, if the smoke is blue immediately after starting then that's oil burning. Can you also smell petrol when this happens?

 

[joeywarren]

Hi yes indeed it is. Blue smoke with a very strong smell of fuel.
It then runs lumpily for about 30 secs, then it all clears to running very well.

Hmm!

 

[joeywarren]

Hi Russ thanks - I didn't get an email or notification about your original reply, so thanks for posting again...

To clarify - blue = fuel and black = oil ?

Trouble is - I have plumes of blue smoke at cold startup smelling *very* strongly of fuel. Does that contradict Dieselman's thinking?

 

[280gee]

Did you observe this in good daylight? Assuming so then I'd suggest that you may have worn valve guides or possibly defective valve stem seals or both. The oil seepage will affect the starting performance so that you'll have to wind the engine over to get the mixture 'clean' enough to ignite. Or put another way to let the spark plug 'spark' properly. Until that happens the engine will puke out unburnt fuel and oil vapour. as soon as it catches the oil will burn with a blue smoke. Probably more than you needed to know.... )

 

[joeywarren]

Hi again, yup in good daylight each morning! That all makes total sense. OK so what are we looking at - I assume this is quite a long job to get this looked at & diagnosed - any ideas who might be good at this kind of work, and who isn't about to rip me off? I have heard good stories about some folks... I may just put out a "who wants to take a look / quote / make a recommendation" note to the forums to see where people gravitate to in terms of opinion.

Sounds expensive.

 

[Ade B]

Is the ABS light on?

Would eliminating the OVP relay causing an issue with cold starts before getting into the oily bits be sensible?

Ade

 

[Sp!ke]

Threads merged.

 

[280gee]

Diagnosis could follow the lines that I suggested so that's experience and a bit of time required.

From there if it is -just- valve stem seals then it may even be possible to replace those in situ without too much dismantling. With valve guides it's a remove the head job, a wise man would also do the seals at that time too.

Where are you located, (roughly will do) it'll help for recommendations.

 

[joeywarren]

(Thanks Sp!ke)..

Hi Ade - no the ABS light is ok..

280gee - Good point! I am in North Essex, but happy to travel to someone well recommended and willing to take on the ongoing relationship with my good self plus AMG baggage

 

[kth286]

The 104 engine is not known for valve stem seal problems, or the guides, especially at only 80k miles.

My own at 165,000 miles has never had that problem.

The previous generation 103 engine does have the problems.

So, be cautious and tread slowly and carefully.

 

[kth286]

Thinking about your problem for a few minutes it could be an injector/s leaking overnight.

If all the spark plugs are removed first thing in the morning and you shine a torch into each cylinder in turn you should be able to see some petrol glistening on the top of one (or more) of the pistons perhaps.

The problem can escalate and if severe leakage occurs can cause hydraulic lock in a cylinder when next attempting to start, with expensive consequential damage.

Been known to happen and engines written off.

 

[280gee]

Someone that knows what they are doing would have this diagnosed for you quickly.

You might want to try this simple test for yourself however.

Find a stretch of road with a long hill or slope that you can descend with no one immediately behind you. Make the car pull hard as you ascend the slope/hill then coast down the other side with no accelerator applied.

After a few tens of metres, (a hundred would be good) push down on the accelerator and keep an eye out in your rear view mirror for signs of smoke (blue) A non windy day helps, as does daylight for this test and hopefully no one breaking their neck to get by you...

 

[joeywarren]

Thinking about your problem for a few minutes it could be an injector/s leaking overnight.

If all the spark plugs are removed first thing in the morning and you shine a torch into each cylinder in turn you should be able to see some petrol glistening on the top of one (or more) of the pistons perhaps.

The problem can escalate and if severe leakage occurs can cause hydraulic lock in a cylinder when next attempting to start, with expensive consequential damage.

Been known to happen and engines written off.

Thanks for both of these posts - I will be having a look this week to see if I can see anything like leaking fuel on top of the cylinders. Should I be driving it?!

 

[joeywarren]

Someone that knows what they are doing would have this diagnosed for you quickly.

You might want to try this simple test for yourself however.

Find a stretch of road with a long hill or slope that you can descend with no one immediately behind you. Make the car pull hard as you ascend the slope/hill then coast down the other side with no accelerator applied.

After a few tens of metres, (a hundred would be good) push down on the accelerator and keep an eye out in your rear view mirror for signs of smoke (blue) A non windy day helps, as does daylight for this test and hopefully no one breaking their neck to get by you...

Thanks again, even a couple of "specialists" I'm afraid haven't been so easily forthcoming with such simple measures to try & diagnose the issue. I'll do this today and see what happens. I will report my findings!

I do appreciate the help! We're not all engineers on the forums, just real enthusiasts...

 

[Dieselman]

You might want to try this simple test for yourself however.

Find a stretch of road with a long hill or slope that you can descend with no one immediately behind you. Make the car pull hard as you ascend the slope/hill then coast down the other side with no accelerator applied.

After a few tens of metres, (a hundred would be good) push down on the accelerator and keep an eye out in your rear view mirror for signs of smoke (blue) A non windy day helps, as does daylight for this test and hopefully no one breaking their neck to get by you...

That won't show much because the car is an automatic so will coast downhill.
That testing will show ring wear when the engine is under load up the hill though.
I understand what you were suggesting, and the only thing the Op needs to do is to lock the gearbox into a lower gear going downhill on the over-run causing the engine to rev which in turn increases the intake vacuum, let it over-run for some time then apply power again and look for the smoke.

 

[ray_hennig]

I think the 'overrun' test does work ...

Our old 280TE had top end wear but virtually no bore wear.

We spent a lot of time at high speeds (100+ mph) on motorways and when I released the accelerator at high speed on a long downhill stretch, there would be a very pronounced 'chuff' of blue smoke as the oil was sucked down the valve stems by the high overrun vacuum.

Under heavy, high speed acceleration, often to the red line with 7 people on board and 2 heavy roof boxes and bikes on the back, no smoke.

I all respects, the car performed like dream but the rear end by the exhaust was pretty greasy and I checked oil level at EVERY fuel fill. I remember I often just bunged in a litre of oil knowing that we'd burn it during the next two fuel tank's worth. Happy days.

So, I recommend finding that long downhill and try to get to, say, 80 or 90 at the top, then drop it into 3rd as you coast down - WATCH THE MIRROR.

Do let us know how you get on as that sounds like a mighty interesting motor.

RayH