Ford Transit Custom - suspected wet belt failure

facade

Alanp said:

I think the newer engines are chain driven 

Even chains are not safe, it is perfectly possible to engineer a chain, running in what should be a perfect environment to fail- e.g. BMW, Audi/VW, Vauxhall.....

sevenhills

facade said:

Popular rumour has it that the wet belt fails because of diesel in the oil from DPF regens.

If only there was a way to block regens............

Surely the waste from the regens would not be piped back into the engine block?
If that is the case, is that common in other engines?

WellKnownSid

sevenhills said:
Surely the waste from the regens would not be piped back into the engine block?

If that is the case, is that common in other engines?

Many manufacturers achieve regeneration by adding fuel into the cylinder during the exhaust stroke.  Multiple failed regens means lots of fuel seeping past the pistons diluting the oil, in some engines raising the oil level so high that the engine goes bang.  That's why there's usually a big X on the dipstick - the point of no return...

Barkin

sevenhills said:

facade said:

Popular rumour has it that the wet belt fails because of diesel in the oil from DPF regens.

If only there was a way to block regens............

Surely the waste from the regens would not be piped back into the engine block?
If that is the case, is that common in other engines?

Deisel in the oil from failed DPF regens - yes. 

sevenhills

WellKnownSid said:

Many manufacturers achieve regeneration by adding fuel into the cylinder during the exhaust stroke.  Multiple failed regens means lots of fuel seeping past the pistons diluting the oil, in some engines raising the oil level so high that the engine goes bang.  That's why there's usually a big X on the dipstick - the point of no return...

So the fuel would need to get past the pistons.

Goudy

Yes and it's becoming rather a common problem.

Diesel particulate filters are active, they need a fuel source to raise the temp inside them to turn the large particles of soot to much smaller particles of ash, which the filter then stores.
This burn process requires something like 600c in the filter but the normal exhaust is only around 400c or so at best.

The fuel source to achieve this is normal diesel which is added to the combustion chambers post combustion, so not on a combustion stroke to burn in there but pass through into the filter to burn in the filter instead.

If the regen process fails to complete it then tries again as is it still detecting it needs to regen, then if fails to complete again and so on and on and on means the post combustion injected diesel seeps past the piston rings and into the engine oil. 

Over time this means the oil level in the engine rises, though it's no longer just oil. It's been diluted with diesel which obvious has different properties to engine oil.

Some engines like this Transit ,run the timing belt in engine oil as it reducing friction, trouble is it is now no longer running in just engine oil.
The diesel weakens the belt where it will eventually shred and snap.
The shredded material effects the oil system, clogging up the oil pump and oil galleries and a snapped belt, well the results of that are pretty obvious.

Ford and a few other manufacturers have also had trouble with some petrol engine belts in oil which obviously don't use post injected fuel. So perhaps this system isn't as robust as it should be to start with.

Even if it had a different timing drive arrangement like a chain or dry belt, the increase in oil and diesel in the sump can in extreme cases cause diesel runaway.
This excess oil/diesel in the sump gets thrown out of the engine via the crankcase vent and as that is plumped into the air intake to burn off the normal blowby gases, the engine runs away on it until it's used up all it's engine oil, then goes bang in a big way.

The normal way to stop a diesel engine is by cutting the fuel off, as you can't stop it eating it's own engine oil, you can't stop it.

If you want your diesel to regenerate properly, it needs time and the right temps.
People say floor it in a low gear, but that isn't the ideal conditions as the exhaust gases tend to be richer/cooler and more saturated with soot.
Getting it up to a good speed and feathering the throttle lightly will produce less soot and cause the engine to lean out and exhaust temps to increase. Time will do the rest.

More and more petrol cars have particulate filters but they are passive, so inject no post combustion fuel.
They just rely on the increase in exhaust temps which peak on the over run to burn the soot. So it regens more often and they don't produce the same levels of soot as a diesel engine anyway. 

ontheroad1970

I think it's time that there was a physical indication that the vehicle is on a regen like a light on the dash.

sevenhills

ontheroad1970 said:

I think it's time that there was a physical indication that the vehicle is on a regen like a light on the dash.

I believe there is on my Zafira, because it's there to warn you not to switch the engine off. I am still not convinced that any excess regen fluid would get past the pistons, if they are firing every milli-second.

Goudy

Post injected fuel will stick to the cylinder walls as it is not injected on a compression cycle to be burnt in the cylinders, it's timed to push down the exhaust and create a flame front in the filter to reach the desired temp needed to burn the soot to ash.

Fuel normally would be just fired in as the piston starts to crown with the valves closed, but this post injected fuel is injected with the piston rising on the exhaust stroke, so the exhaust valve is open so there no combustion.

The cylinder is not a perfect seal, fuel runs past the rings and into the engine.
Heat in the oil will usually evaporate some fuel but trouble starts because of short tripping.

Short trips tend to create more soot as they generally use more fuel.
More soot means repeated attempts to regens and oil not getting enough to evaporate the fuel leads to dilution.
Rise and repeat for month after months and you now have a problem.

You can search for oil dilution DPF and see for yourself.

Ectophile

Goudy said:

The normal way to stop a diesel engine is by cutting the fuel off, as you can't stop it eating it's own engine oil, you can't stop it.

Having once owned a model of Land Rover that was notorious for running on its own engine oil (though mine never did), I did look up ways to stop a runwawy engine.

One is to block the air intake.  That's not easy on most cars, but on Land Rovers the air intake was in through the wing..

The other is to stall it by ramming it into high gear with the brakes firmly on.  I don't suppose that's possible on an automatic, though.