Mcrafty1

On 08/28/2016 at 3:08 AM, Timmyb said:

I'm NOT a mechanic. But could you have swapped that injector with say, no 6 injector? Then if problem still occurs then may not be injector. And if no 6 piston melts like previous no 5 it could be injector issue?

Just thinking outside of the box. 

Thanks, the injector was swapped around and even relaced the last time

On 9/11/2016 at 4:09 PM, Hobert62 said:

The biggest perc is not having to deal with check engine lights and emissions crap.  And the BMT family is right along with it.   

I guess I should have stated my question a little differently and included 'other than the obvious' lol, I couldn't agree more, not having to deal with those things is perks enough to keep on with the old Mack.

5 hours ago, farmer52 said:

If you license it as an "antique", most states restrict the usage (i.e. parades, shows, etc.) but cannot be used "for hire" or commercial service.  Check with your state BMV to be sure.

OK Thanks, I am reasonably sure my state has restrictions but I'll check to be sure.

   I have an 1986 Mack RD685S is it considered antique now? I work the truck every day and have since I purchased it in 2002 so it just doesn't seem 'antique' to me. If it is are there any percs to owning and working an antique truck? ie: licensing fees, insuring and such?

On 09/03/2016 at 0:06 AM, m16ty said:

Kind of OT but why does everything you read these days have to mention "global warming"? Seems everything these days is linked to the global warming hoax. Fires- global warming, too hot- global warming, too cold- global warming, too much rain-global warming, drought- global warming.

Its called 'indoctranation'

5 hours ago, gearhead204 said:

I understood that the cooler nozzle  was aimed , my question is ..... has its proper operation been verified!  as for the boost on the 350's  that would explain why the 4 or 5 I ever ran I liked so well..... could always make a 400 cummins look sick!

I can't say for sure that it was......but would it go for two years between pistons if it were not working? I talked with a man yesterday that has a 400 and has the same experience with his......since he cranked it up, #5 every time, I'm hoping between my old turbo not up to par and cutting the fuel back that I am going to be running this motor longer than the last two.

7 hours ago, Dirtymilkman said:

Has this motor always had the same head on it over #5? Maybe the injector hole is drilled at a wrong angle? Just brainstorming.....

No, the head was changed two pistons ago.

2 hours ago, theakerstwo said:

Another ideal about the piston cooler,It may have been aimed at some time but that would be with the piston out.It would be easy if the cooler is still in the block to get bent bythe rod when installing the piston.

The cooler is aimed right, I have been on my back guiding the connecting rod down by the nozzle the last two times so I'm sure it is still right. I do believe the fuel pressure was to much and I also believe that number five must be the 'hot hole' in these engines. Time will tell, I cut the fuel back enough so I haven't seen the pyrometer go above 875 degrees....before I turned it back I could run it up into the 1000s without much effort.

9 hours ago, gearhead204 said:

a couple of thoughts here is there any thing different in the intake runner of the #5 cyl.? also I have never been around a 250hp e-6 but 19 lbs. of boost sounds low to me, I know a e6 350 will do 28 -32 ish,  so do you have a cooler issue?  also did any one pre oil this engine before installing the pan to verify that #5 cooling nozzle is performing correctly? also did you check the rocker arm travel on #5 verses the other cyl's?  i'm  thinking bad cam lobe on the intake could cause it to run hot of not getting enough air.

  

No, nothing different with the intake....141/2 to 17 is the norm for boost, the cooling nozzle was checked and aimed to spec, rocker arm travel was checked and a visual of the cam lobes confirm its condition to be like the others.  

Well, shes back together and running sweet....on less fuel, and with the new turbo its making 19lbs boost so more air and less fuel may mean less of a chance of a reoccurring piston issue. Im hoping this is the last time im into this engine in my working life.......time will tell. Thanks to all for the pointers on possable reason but i found no smoking guns this time.

I agree but the question is...why? Deck is perfect and all liners are fine.

For sure....but im out of ideas so back together she goes

If, during re-installation of the head I find something that we've overlooked I'll be sure and post it up for all to see. Thanks to all for the help and suggestions. 

...It doesn't bother me so much that it is doing what it's doing, as it does that I can't figure it out. lol

Well, The head is done...and checked for double sealing washers, nothing there. The fuel line was changed on that cylinder the last time we replaced that piston so no smoking gun there either. Looks like I'll be putting it back together without having a fix for the ongoing problem....sigh, I suppose I'll just pull that head and replace no. 5 every spring before I start using the truck and minimize my losses do to down time. I don't have anywhere else to turn.

On 8/12/2016 at 1:53 PM, 41chevy said:

So 70 +  Republicans are sending a letter to pull funding and support for Trump and only concentrate on the Senate and House seats. In reality giving the Presidency to Hillary with no Republican candidate for president. Apparently the wishes of the people mean nothing when it comes to preserving the status quo.

Now 41chevy come on, You KNOW 'the will of the people' don't mean jack...... the Washington elite, and most state elected officials aren't going to get filthy rich of the backs of the people if the people have anything to say about it.

It's always about the revenue first....and control of the masses second....wait, maybe it's the other way around? 

On 8/22/2016 at 10:13 PM, Dirtymilkman said:

I know this sounds stupid but I'd replace the injection lines. Or at least number  5. If a previous owner put a wrong line on that can throw off injection timing on that cylinder. They all gotta be the same length. 

Actually I believe that line has been replaced sometime during this whole ordeal....just when I can't say but I'm certainly going to look into it. I think when I do find the culprit it's going to be some stupid little thing like that. Thanks for suggesting that....you have me thinking about now.

On 8/22/2016 at 4:41 PM, fjh said:

Obviously, Liking and proving are two different things ,Ya need to re install the injectors on the bench and see if they protrude differently on the failed hole! Sounds like you've tried everything else!The washer is the thickness of a dine you likely would have noticed but worth looking!

The nozzles are out of the head now, when it comes back from the machine shop I'll check and make sure the sealing washers are not doubled up. Thanks, Allan

5 minutes ago, farmer52 said:

Have you checked the spray pattern of the nozzle?  If it is burning in a small area outside the piston bowl, that might indicate a poor spray pattern.

Thanks, Yes we checked that the first time and replaced the nozzle the second time just because that was all we could find to blame it on then but I guess that wasn't it because here we are today.

21 minutes ago, fjh said:

If a guy were to compare piston tops you would likely see if you have doubled up on washers by the spray pattern the spay usually hits right at the bowl corner. If it was fueling you would think you would have had pound (fuel knock) but ya never know!

The tops of the pistons look comparatively the same, what happens is it burns down by the side in a small area and melts the ring landings which are a different material (steel of some sort maybe? IDK) and then that tends to work around the piston within its own grove until finally pieces of it works it's way back up on top pf the piston and then the noises start, other than that the truck runs ok but develops blow-by. Last time I shut it down at the first signs of a problem and replaced that one piston and liner and this time it had done a lot more damage to the piston before any significant signs of trouble showed up other than the blow-by. The head on that end had to go to the machine shop and I decided I would do the other 5 holes and rods and mains this time so I'll be starting out with a new engine again....and I Will be cutting the fuel back a bit but I doubt it will be the answer to this specific problem.

  I'm still liking the two washer theory although I worked on that head yesterday myself. I was checking the valves and can specifically remember comparing that nozzle to the one on both sides of it and can't believe I wouldn't have noticed a difference in the protrusion of it in reference to the surface of the head since I was inspecting it for damage then.

2 hours ago, theakerstwo said:

It would sure be good to know if the pump  shop just repaired the governor and did not calibrate the pumpor or if they did all of the pump plus the calibration.If # 5 was over fueling due to bad calibration then this may follow you around for a longtime.years a go i saw a 711 do this for maybe 5 times before the pump was checked and repaired.

Thanks Glenn, The pump rack was overhauled and was re-calibrated the last time this happened,   and the governor was repaired this time and they said although it wasn't new by any means, it was right and would be fine for a while....or so they said, it is a very reputable diesel fuel specialty shop in Bangor, Maine that does many, many of the surrounding area truck shop and personal owner fuel work. I believe them when they say the pump is right.....however, I have no way of checking their work.

2 hours ago, theakerstwo said:

Also have you changed the piston cooler nozzle?It could be stopped up or bent.I always pull them out before the piston comes out.The rod may miss it coming out but can hit it going back in.

Yes, nozzle has been check any clogging and has been checked for proper aim. Thanks

Will do

Wow, that's a possibility I hadn't considered and it is doing it in the same spot each time...If that were the case wouldn't it be noticeable on the underside of the head? by that I mean wouldn't that injector protrude  a enough less below the head compared to the other two to be noticeable? or would it be such a small difference that one wouldn't notice it if they weren't looking for it?  If what you say is the case it would explain the whole sorted affair with this engine's problems. I'm for sure going to check it out, Thanks a lot! that might just be the answer.

  I've discussed this here before to some degree but my 86 mack E6 250 has burned down around no five piston yet again (third time in 3700 hrs. ) my question to the mack gurus here is this: although I have the fuel turned up on this engine and drive it myself can anyone explain why the same number 5 piston is the only one that fails? the other 5 piston have been in the truck three times as long as the one that failed yet show no signs of over fueling or excessive heat. Some history...The first engine failure was 10,000hrs. broken ring which ended up on top of the piston (which now looks a lot like the same failure that I keep having) the engine was inframed, fuel turned up at this time and new heads were installed(all mack parts) same nozzles, 2000hrs later same piston failed replaced that piston and liner only and replaced the nozzle thinking that that was the culpert. Started to notice some blowby around 3600 hrs.and the pump failed at that point (governor issues) so I sent it (the pump) to a reputable diesel fuel systems shop and had it rebuilt and last week at 3740hrs. no 5 has failed again...I'm really at a loss as to why the same piston is the problem every time and I'm hoping some here has had the same issue and found out how to correct it. Thanks for any and all insight into this that you have.