J

James6

New Member
Hi all!

I have an unusual problem, wondering if anyone can help…

My 300tdi blows a lot of white smoke in the morning. And I mean a lot! It can fill a lane!

It only blows when coming off the throttle (so essentially under engine braking) and only when the engine is cold. It completely stops smoking after about 60 seconds of driving.

Has anyone else had the same issue? Any suggestions?
 
James6 said:
Hi all!

I have an unusual problem, wondering if anyone can help…

My 300tdi blows a lot of white smoke in the morning. And I mean a lot! It can fill a lane!

It only blows when coming off the throttle (so essentially under engine braking) and only when the engine is cold. It completely stops smoking after about 60 seconds of driving.

Has anyone else had the same issue? Any suggestions?
Click to expand...
Welcome to LZ.

Is this a recent development, or been going on for some time?
 
James6 said:
I’ve been trying to diagnose it for a few years!!
Click to expand...
OK. Was wondering if it was in fact steam, which was visible in cold weather, but not in the summer.
I assume you live in the UK? Or somewhere else with cold winters.
 
James6 said:
Yeah, but it’s not a cold weather issue… it happens throughout the year.
Click to expand...
My only other guess would be diesel vapour from excess fuel injected and unburnt.
But not sure why it would only be an issue for a short time after start up.
Does the coolant level hold pretty constant over time?
 
Turboman said:
My only other guess would be diesel vapour from excess fuel injected and unburnt.
But not sure why it would only be an issue for a short time after start up.
Does the coolant level hold pretty constant over time?
Click to expand...
A ‘professional’ suggested it could be glow rods, so I changed those. Someone else suggested injectors, so I changed those. Coolant does go down, but I’ve had the car for 20 years and it’s always needed topping up, no more now than usual.
 
James6 said:
A ‘professional’ suggested it could be glow rods, so I changed those. Someone else suggested injectors, so I changed those. Coolant does go down, but I’ve had the car for 20 years and it’s always needed topping up, no more now than usual.
Click to expand...
Glow plug change and injector service never does any harm, even if it hasn't dealt with the issue.
If the coolant goes down, it must be going somewhere. And if there are no external leaks it could be going into the engine, possibly via a cracked head, and down the exhaust.
Have you smelled the "smoke"? Or tried to condense some on a cold metal plate?
 
Turboman said:
Glow plug change and injector service never does any harm, even if it hasn't dealt with the issue.
If the coolant goes down, it must be going somewhere. And if there are no external leaks it could be going into the engine, possibly via a cracked head, and down the exhaust.
Have you smelled the "smoke"? Or tried to condense some on a cold metal plate?
Click to expand...
No. Not sure how I’d do that?!
 
If I start the car at the top of a hill and engine brake all the way down… it’d blow loads of white smoke the entire way!

Normally, it’s just when approaching a couple of junctions on my street.
 
I’m starting to worry about a cracked head, but it seems odd that the problem completely goes away after 60ish seconds.
 
James6 said:
No. Not sure how I’d do that?!
Click to expand...
If you have a nose, just smell what comes out of the exhaust.

And for the other, get someone to start the engine and rev it up a few times, and hold the metal plate near the end of the exhaust.
The liquid that condenses on the plate may be water, which identifies the vapour.
It will in fact be a mix of both, but one may be more in the mix.
 
James6 said:
I’m starting to worry about a cracked head, but it seems odd that the problem completely goes away after 60ish seconds.
Click to expand...
If it is steam, it will go away when the water clears from the cylinder.
If it is a cracked head, it must be a very small crack, so you could go on topping up, and get the head pressure tested when you have to take it off anyway for head gasket, etc.
 
If not using any fluids, I would suggest it is an injector pump issue, some 300tdi had a cold start widget on the side of the inj pump, think it was engine side and looks like a little lever with external springs.
This is from memory of my old 94 300 disco.
 
See pics stolen from ebay.
Ist pic extra lever.
2nd pic no lever.
I am not sure which way it moves when cold/hot etc, but a bit of nosing around might give you an idea.

Screen Shot 2023-12-17 at 20.25.27.png
Screen Shot 2023-12-17 at 20.26.12.png
 
lynall said:
If not using any fluids, I would suggest it is an injector pump issue, some 300tdi had a cold start widget on the side of the inj pump, think it was engine side and looks like a little lever with external springs.
This is from memory of my old 94 300 disco.
Click to expand...
That’s about the only part that hasn’t been changed!!
 
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