Biodiesel woes

[TVRTASMIN]

Hi.
I'm new to this website forum and hope i can get some friendly advice.

I have a W124 300 six cylinder diesel estate .
Anyway, since filling with biodiesel several compression leaks have started from near to the injector bodies.The leaks (sounds like a chuffing noise) are from the same place.
There appear to be small holes in the head just next to the steel inserts that take the plastic heat shrouds, and the leaks appear to be coming from there.
The following link best dewcribes the situation regarding the location of the leaks;
http://www.mercedesshop.com/shopforum/showthread.php?t=120712

The engine is running badly with plenty of smoke from the exhaust.
I also noticed that the coolant temp went higher than normal and i get a lot of clatter on tick over.
My thoughts on this are that the biodiesel is causing pre-ignition. The mixture is igniting in the pre-chamber for some reason.

The metal injector washer type seals were replaced but this did not cure the problem.

Any help greatly appreciated.

 

[Flying Scot]

exactly what did you fill it with? tell all

 

[Bolide]

Need more info. Which engine? Turbocharged or not? How long have you been running Biodiesel?

And exactly what do you mean by Biodiesel?

Nick Froome
www.w124.co.uk

 

[TVRTASMIN]

The engine is a 603.912 non turbo.

I filled with my first tank of biodiesel (refined WVO to EN 14214 standard) less than 10 miles prior to the problem.

If you followed the link, this is where the pre ignition leak is coming from.

 

[Parrot of Doom]

What happens when you run it on normal diesel?

 

[TVRTASMIN]

It ran fine on normal petro diesel but the problem only arose after filling with Biodiesel.
I changed both filters and found no obvious cause for concern but the pipe to the pump from the pre filter was slightly loose.

Are you the same Parrot of Doom from Pistonheads?

 

[Parrot of Doom]

Aye, that be me

A complete guess would be that the oil is a bit too thick for the engine to handle.

On the upside, you may have identified leaks that would eventually have occured on normal diesel anyway.

 

[Bolide]

My reply from last night has disappeared...

I can only think that you have a batch of bad fuel or that using Biodiesel has resulted in lots of sludge & crud blocking the fuel system. I've read that this can occur but have no direct experience of it

I'd try draining the tank (keeping a decent-sized sample), flushing through the pipework, replacing the fuel filter & prefilter, refilling with a couple of gallons of fresh diesel and trying again. If it doesn't run well after a few minutes I'd take it to your local diesel specialists for diagnosis

Is the return fuel pipe blocked? You could try disconnecting the fuel leak-off pipe from the frontmost injector, feeding it into a container and running the engine. If the problem goes away the return may be blocked

EN 14214 is a tough standard and the differences between that and pump diesel don't seem to be that great. But it does seem logical that the problems are related to the fuel changeover

Nick Froome
www.w124.co.uk

 

[TVRTASMIN]

Thanks for the input chaps.

Nick, i changed the fuel filters which looked OK, plus syphoned 50% of the Biodiesel out and put thirty some litres of fresh petrodiesel back in and went for a run. No change though.

I had the injectors tested today and they were all fine with only a few psi between them.

I'm going to change the hoses for biodiesel proof stuff anyway, and i've ordered a new tank strainer filter.

I was going to try the engine on some fresh petrodiesel using a short pipe from the prefilter inlet to a five litre 'petrol' can full. I'll also try the return hose too.

I have two twenty litre containers of biodiesel which i bought at the same time so this could be used for testing the fuel quality if required.
I've heard it costs a couple of hundred quid though!

What i am most annoyed about though, is the fact the selling agent for the biodiesel has not replied to my latest email or phoned me as kindly requested.
After all he sold me the stuff with no advice other than to change the filter after 1,000 miles.
I've been told by another garage selling biodiesel that i should have started on a 50/50 mix.

 

[TVRTASMIN]

I've still heard nothing from the biodiesel supplier despite a couple of emails.

As i have said earlier, the car ran absolutely fine before i filled with biodiesel.
I've spent time and money trying to get to the bottom of this but i've had no response from the supplier.

I'm reluctant to go any further as it seems the biodiesel has caused all the prechambers to leak, so reverting back to petrodiesel will not cure that.
I'm looking at big expense, but i really need some cooperation from the supplier as legal action will be my last resort.

Does anybody have any views on this. Do you think the biodiesel supplier has some liability here?

Cheers

 

[Parrot of Doom]

Is there a metal gasket between the engine block and the cylinder head that perhaps needs replacing?

To my mind it sounds very much like going from mineral oil to fully synthetic, and discovering leaks - the leaks were always there, its just that they've been identified by the change.

Could you perhaps post some pictures of exactly the spots where its leaking?

 

[TVRTASMIN]

There is a head gasket yes, but the chuffing noise (the sound the leaks make),
is from the prechambers.
These are small chambers fastened into the head that contain the glow plugs to which the fuel charge is injected into.
I'll have a go at adding a diagram or link to.

http://www.detali.ru/cat/oem_mb2.as...GM=717.433&CT=M&cat=503&SID=01&SGR=065&SGN=07

It is item 600 on the drawing plus the bits above to form the prechamber for the injector to screw into.

 

[Parrot of Doom]

Is it leaking from the point where the prechambers screw into the head, or from the prechambers themselves?

Is it possible that there are some seals missing (previous work where they haven't been replaced by a former owner)?

Have you removed them to see whats up? Are they torqued to the correct amount?

 

[TVRTASMIN]

The prechambers do not usually need replacing.
The leaks are from the outside of the prechamber .
The prechambers themselves protrude into the cylinders a bit like long reach spark plugs, so if you can imagine the spark plug body as being the prechamber and the ceramic bit as the injector, the leaks are as if all the spark plugs are leaking from the head around the thread.

The prechamber retaining collars are tight but obviously the sealing rings in behind the collars have failed due to the excess heat and preignition brought on by the biodiesel.

I checked the pump timing last night and it is ok.

 

[Parrot of Doom]

Change the failed collars. Perhaps new ones will be better able to hold against the heat?

 

[TVRTASMIN]

Change the failed collars. Perhaps new ones will be better able to hold against the heat?

Easier said than done.

There are two seals for the prechambers and to replace them requires removing the head. This is the easy part.

Getting the prechambers out is extremely difficult i've been told.
A local well known engine reconditioners once had to send a head to Mercedes they were stuck so bad.

There are also three thicknesses of seal depending on whether the head needs to be skimmed or not.

Still no word from the fuel supplier.

 

[Parrot of Doom]

Well, they're leaking, and the leaks ain't gonna go away. Swallow hard and get it done mate.

I would imagine the fuel system was sold to you without warranty covering your engine, just the parts you bought.

Check out www.dronsfields.co.uk or www.mercman.com for scrap parts, maybe a new head?

 

[TVRTASMIN]

Not sure what you mean by fuel system.
The fuel can be bought around the country dispensed from your standard style forecourt fuel pump.
No modifications are required and the stuff is supposed to mix properly with petro diesel.
The fuel is supposd to be made to EN14214.

Anyway i have now put everything back together and ran the car up on petrodiesel and it runs a hell of a lot better.
There are now only two prechamber seals leaking and the clattering has gone.

So it is quite obvious to me that the fuel was to blame.
Surely you don't expect me to foot the bill for rectifying this.:?

Still nothing from the fuel supplier.

 

[Parrot of Doom]

Apologies, I'd presumed that you'd done some kind of SVO conversion.

All I can say is that I've run mine on pure vegetable oil, straight from the bottle, and nothing leaked.

Personally I reckon all you've done is expose leaks that were already there - diesels can run on pretty much anything without issues.

 

[TVRTASMIN]

I would agree with you, but there is obviously a problem with the biofuel to cause the preignition and increased combustion temperatures and the resulting damage this has caused.

Like i said, when i switched back to normal petrodiesel, the engine ran a lot better but is still leaking from two out of the six prechamber seals due to the fact that they have been damaged .
Every single prechamber was leaking when running on the biodiesel.
They were'nt leaking prior to filling with biodiesel or i would have noticed it.

From what i can gather from the experts and what i have read, there is contamination of the fuel, more than likely the methanol or something else used as part of the refining process which has caused the fuel to burn quickly.