Strange buildup

[xud9te]

Hi,

I was wondering if any of you guys have any idea why i have a buildup of 'stuff' around the pre-chamber hole on my cylinder head.  I have never seen this before.  I will post a pic when i can take a decent one in focus.

Its kind of limescale looking about 2 mm deep, I can only assume it is some knid of glycerin - by product of using rape seed oil?  Or possibly water residue from a leaking gasket?

Has anyone seen this before?

Cheers
Greg

[jtanguay]

Hi,

I was wondering if any of you guys have any idea why i have a buildup of 'stuff' around the pre-chamber hole on my cylinder head.  I have never seen this before.  I will post a pic when i can take a decent one in focus.

Its kind of limescale looking about 2 mm deep, I can only assume it is some knid of glycerin - by product of using rape seed oil?  Or possibly water residue from a leaking gasket?

Has anyone seen this before?

Cheers
Greg

i've heard some things about using straight oils like SVO, WVO, etc.  if the oil isn't heated properly, and the injection system isn't up to par, it will form some really really hard residues that will ruin the motor.

another thing to consider is the viscosity of the fuel.  since it is thicker than regular diesel, the pop pressure will actually be higher than stock, and so timing may be affected, possibly causing inadequate burn...

[xud9te]

So it could be the veggie.... :?

Last time this engine was apart was only like 15000 miles ago.  Only running up to 50% veg.  Injectors and pump were new/reconditioned, have high flow lift pump.  Timing set to 1.0mm/ .0041"

I wonder if the injectors themselves are allowing fuel to run down the prechamber iteslf due to incomplete atomisation beacuse of the thicker fuel?  If each time the engine was shut off there was still a trickle of veg/diesel running into the cylinder, it would hang as a droplet in exactly this spot, and the deposits do kind of look like little stalagtites!!!

Maybe my new bigger nozzles will cure this?  One thing i am sure of is that I am glad it is not a si engine as the hotspots generated would cause huge detonation!!

How much does an endoscope cost?  Could run the engine on veg again and take out an injector and look inside in a few thousand miles....

[jtanguay]

So it could be the veggie.... :?

Last time this engine was apart was only like 15000 miles ago.  Only running up to 50% veg.  Injectors and pump were new/reconditioned, have high flow lift pump.  Timing set to 1.0mm/ .0041"

I wonder if the injectors themselves are allowing fuel to run down the prechamber iteslf due to incomplete atomisation beacuse of the thicker fuel?  If each time the engine was shut off there was still a trickle of veg/diesel running into the cylinder, it would hang as a droplet in exactly this spot, and the deposits do kind of look like little stalagtites!!!

Maybe my new bigger nozzles will cure this?  One thing i am sure of is that I am glad it is not a si engine as the hotspots generated would cause huge detonation!!

How much does an endoscope cost?  Could run the engine on veg again and take out an injector and look inside in a few thousand miles....

hmmm not good my friend.  that is why veggie kits come with a purging system to clear out the veggie before turning the engine off.  please tell me you're at least heating the fuel!!!

also what kind of car are we talking about??? i've heard some mercedes can take straight unheated veggie, but i can't imagine it being any bit good for the motor.

[745 turbogreasel]

Personaly, I think the purge system is about as necessasary as a dome light minder module or key buzzer.
I pulled my head afer about 20,000 miles of WVO burning, and neither the oil or combustion side of the head had any unusual deposits, I'd even describe the lifter valley as unusualy clean for an old diesel.  Injectors had typical high miles wear, and 2 glow plugs were still operational.  Head gasket had failed where previous head installer stripped out one of the bolts, and presumably left it loose.
 Is the oil residue in your lifter valley thick and gooey, or worse unremovable?
I feel both would be consistent with unheated Veg, or possibly polymerised or glycerine contaminated fuel.

[xud9te]

Hi,

No i dont have any  additional preheating, but it doesnt get that cold over here!!  Any colder than 10deg c and I dont fill up with veggie anyway.  My car has a built in fuel heater which allows the fuel to swirl aroung a water passageway in a spiral before being sent to the pump.  This keeps temps at about 5 deg below the water temp unless there is low fuel in which case it is higher.  

745, my valvegear and top of the head are not affected, it is just around the opening of the prechamber on the head face (combustion side).

Here is a bad pic but i cannot get a better one now as i have got rid of the deposits!!!





Any other ideas?

I still have a 10% feeling that it may be water ingress, but on all cyls?  Never seen that before.

I am getting it pressure tested, maybe all the prechambers have burnt out, cracked and are letting water in.  They dont appear o be too bad on the surface.  The car was running an awful lot of boost and fuel for a while which could have raised temps too high.  Unfortunately my egtg was not working at this time so cant tell you how hot it was getting.  I would still assume a valve to go before the precups though.  Still cant believe it would happen so uniformly anyway.  Gotta be the veg I say!! :?

[burn_your_money]

It's kind of hard to tell from the pictures but I think I had a similar buildup in one of my engines I took apart. It only ran 100% diesel and it was not a turbo

[dave friday]

mine was the same, it also had cracks on the same pre-combustion chambers[all four] also all eight valves had cracks between them.the injection pump timing was way out[too far retarded] clouds of smoke on start up!.i do'nt think its been run on veg ect and i put the build up down to the injection timing.the head gasket did have some cracks in it though,i changed it because it was leaking water from the outer edge around  no 7 head bolt[it had snapped]
 regards