This van has 280k miles and is totally stock except the last 100k were running a V3 Vegistroke system. Almost all miles are highway, but owner admits alot of idle time (both on diesel and VO). The heads are off after bending a 2nd pushrod in a couple months.

Can we have a discussion about what this is or has done to the pistons and the rest of the engine? If this is evidence of advanced timing, could this have contributed to the recent pushrod failures? Should this guy use this bottom end and just rebuild the heads? Or is this evidence of damage in the form of fatigue and is a tell-tale sign of eminent doom? What can he do to prevent this from happening again? (There was no chip or tuner and it was never run hard cold...)

 

Is it the same connecting rod Jason? If so we could be looking at hydrolocked in that cylinder, bad wrist pin or something with the lower end. I would not chance it and on top of that curiosity would get the best of me to pull it apart to see what I could find.

 

I'm subscribing, but don't have any ideas to offer as to the cause of the star pattern.
Is it only on one piston? Or on all of them?

 

Idle time. I have seen the star pattern before on engines with high idle time.

I suspect that during extended idle on VO, there is some tar/coke condencing on the exhaust valves and sticking them when the engine cools down. Is it an exhaust pushrod that is bending? I would do a valve job just to clean any deposits off the valve stems and instruct owner to keep the idle time down.

I do not switch to VO unless I am at highway speeds.

 

Clean the top of the piston so we can really see that star pattern

 

The PCM calculates timing from several sensors like oil temp, engine temp, etc.

I believe if any of those are whacked out, this could possibly happen.

It is my speculation that is what has happened before when people see this that don't run a tuner.

 

I've asked him to do that.

It was exhaust valve on 2 different cyls.

We are schooling him regarding the idle time - especially on VO.

 

Where did I get connecting rod from ........
I would have to agree with Paul on this one then

 

I wouldnt idle at all on WVO.

Do all the pistons have that pattern?

 

If my memory is still working that is about the same pattern that was on your old engine running a tuner

 

Trippy, huh? I had more evidence of heat/fatigue in the form of cracks - but I admit I drive it like I stole it. This guy drives like a granny, he said 'I never floor it' - too funny. Meanwhile his 'mechanic' told him he was working the engine too hard and bending pushrods...

I'm sure my old engine had quite a few hours of idle time as well. Although the bulk of my mileage is on the highway, it is common for me to pull over and take a nap - running HVAC as dictated by outside temps. The last 100k or more I had hi-idle on my chip and would use that - dunno if that still counts as 'idle' or not??

As far as idling and VO - definitely not recommended. Primarily because a PSD's coolant temp drops very fast when there is no load on the engine and if using coolant to heat VO - then fuel temps also drop and poor atomization thru the injectors is a danger (y'all don't buy into the idea 'the heads do enough heating, right? ). But also because as combustion chamber temps fall, incomplete combustion can occur resulting in coking/carbon build-up. I don't think 'extended' (hours) idling at 600rpm on diesel can be very good either. The same poor combustion happens, although the effects are probably nowhere near as damaging as from VO.

I guess I never considered how or why idle time would produce this pattern. That would explain the pattern found on some ambulance pistons - maybe better than 'run hard when cold' (ie. advanced timing). Can someone help me understand how idle makes this happen?

Man, sometimes I swear the more I learn - the dummer I feel...

 

I'm having a brain fart right now.

Where does your coolant loop return from the WVO heat exchanger?

Reason I ask, cause I think theres a coolant temp sensor, and if it thinks the engine is cooler than it really is, that would advance the timing, I think.

Is it possible the coolant returning from the heat exchanger has been coming back cooler than the motor, and causing the PCM to think that the motor is colder than it really is?

 

I always thought it was poor spray pattern/atomization from a combo of weak hpop, worn injectors, idling, etc.

 

Do single shot injectors cause that star pattern at all, I wouldn't think so.. I know Jason's friend has splits but just wondering.

 

I'd like to know what the timing is during idle (stock, tuned, etc.). I idle for llooooong periods too. What I'm suggesting is that if there is some kind of advanced injection timing at idle, then it would "explain" the star patterns that have showed up on stock engines when this question came up. Tuning CAN cause the star, but if long idle times cause it on stock engines too, then it might be interesting to see if there are differences in what the star looks like in tuned engines vs. long idle stock engines (if there *are* any differences).

Just brain dumping here...... Interesting thread. Reps coming....