NHC 250 head gasket problems...

[wrenchturner6238]

On the injector it could be scored plunger or if you had them out an on re-torque it is very important to get the hold down nice and square if you had the injectors out loosen the hold down and see if it frees up. If it is scored and will not move free you will need to replace injector.
On the gaskets may not be to big of a deal they have not been on long.
While the plug is out can u see if oil has ran out of the plug? If you see oil could have been your leak. There is a set screw in the middle of the top take it out and replace the o-rings both ends of shaft slide the shaft out one way a little and then slide the other way just enough to replace o-rings and if the plug fits tight put plug back in with some silicone.

 

[Carlo]

Good news. Looks like you have some possibilties. I wish I lived closer to you and I would give you a hand.

 

[DW818]

I'll re o ring the rocker box and loosen up the hold down on that injector...hope its not scored because its a brand new set of injectors...when installing them I made sure I torqued them 4 ft lbs evenly per side till I got to the 12 ft lb end torque value...I pulled the pluger up a little and all of them return to there neutral position...moved freely up and down with out restriction...Thanks for all the help...gonna try and get some pics tonight.

 

[DW818]

Injector is toast...they came with a warranty thankfully...Here some pics of my findings. The rear gasket and deck surface where it was leaking...and just a pic of the rig itself.

 

[DW818]

My next question is...why would a brand new injector hang like this??? And when I go to re install the heads, can I keep the injectors in the heads??

 

[wrenchturner6238]

Well there could be many reasons for the injector to fail: a slug of water, some dirt, is hard to say it also could be the hold down did not go down square. Are the bolts for the hold downs bolts with nylock on them? They are hard to get even. When I test to see if the injectors are in even i lift the plunger almost all the way up and let loose to see if it will go down to its static position.

Yes you can keep the injectors in the heads and not mess with them as long as you are careful not to damage the tip sticking through to the bottom of the head.

 

[DW818]

...I drained the tank...new fuel...new filter new fuel lines..made sure the cups for the injectors were spotless...and yes the bolts have what's left of the nylon on them...I did as you said when I first installed all the injectors...made sure they would move freely through the injector body...thought I covered all bases...I still have my old set of injectors...would it be acceptable to re install one in its place ...or will this cause imbalance in the fuel delivery...if not I'll hafta wait to get my replacement...

 

[wrenchturner6238]

Well it is hard to say why the injector failed it might have had to close a fit for the parts.
Did you have a miss or heavy smoke if you did not have these problems you can use one of the old injectors with new o-rings they most likely were ok or well enough to run longer

 

[DW818]

I'll try one of the original ones with new o rings...and hopefully exchange the hung up one for a new one for a spare...I took it out on two test drives after I finished flushing the coolant system and it seemed to run pretty well ...but now that you mention it ..it did have to seem a sort of stumble when increasing the throttle just past idle...I can see why now. I'm going to go over my block deck with a fine tooth comb and check over it again for anything out of place....get everything cleaned off real good and try it again...hopefully with a better outcome...really trying to get her back to a safe running condition...Thanks for the help...All you guys have been a big help.

 

[WillWagner]

Just be careful when using one of those cleaning pads on the deck. If you look at the liners, you'll see a little raised bead. DON'T knick it, hit it with the buffing wheel, nothing. That bead is the only thing that seals compression. Remember, it doesn't need to be all shiny to be clean. You'll need to find another freeze plug for that rocker box.

 

[DW818]

Thanks for the advice Will. I was as careful as I could be around the liners...Figured I would just spray some brake cleaner on a rag and wipe the deck and head mating surfaces before I put the new head gaskets in place over my locator studs...Gonna track down a new freeze plug tomorrow hopefully...Thanks again.

 

[350TacoZilla]

I have heard a few "old timers" say not to buff the block to a clean shiny state like it looks like you have because there is nothing for the gasket to grip then. Basically the surface has to have small imperfections for the gaskets to seal up proper, I'm not too sure on it but I was always careful to only clean off old gasket material and try not to clean the deck too much with the scotch pads.

 

[DW818]

Thats a valid point...I tried not to get too crazy on it just enough to clean the old gasket material ..hope I didn't go to far..is there a preferred method to slightly roughen the surface with out causing harm? Thanks for the help.

 

[wrenchturner6238]

I have buffed off a lot of blocks and heads with a die grinder with a roto lock buffing pad without problem.

 

[DW818]

That's reassuring thank you...I used very light pressure and always stayed moving just enough to remove the old stuck on gunk from the old head gaskets....

 

[350TacoZilla]

I have also used the air powered die grinder with the buffer pads and lightly went over it to remove old gasket, just looked like your deck was polished almost smooth. (maybe just pictures doing that)

 

[DW818]

The deck still had fluids all over it from removing the heads...maybe that combined with the flash/)
Lighting...thanks for input...hard to say what this hobby would be like with out this site...and the people that make it tick most importantly.

 

[DW818]

Update: first off I'd like to give thanks to all the members that chimed in when things didn't work out the first time through my head gasket project...I was finally able to fire her up this Sunday...and ...Success!!!... No more coolant/oil leaks...hit the back roads to test her out...runs good...put about 4 hrs on her and not a problem...thanks again everyone!!!

 

[wrenchturner6238]

I am glad to hear you had success with you truck project.

 

[m16ty]

Changing head gaskets on a Cummins isn't a walk in the park. I just got done doing a N14.

Not only do the heads weigh a ton, you have three of them and you have the rocker boxes to deal with.