1998 Cummins N14 525 Rebuild

[Frank C. Brants]

I just purchased (at an extraordinary price) a "rough" 1998 Signature, knowing that it needed a lot of work.

The previous owner installed an ECU kill switch to prevent the ECU from draining the chassis batteries.

I tried starting the engine (using the rear starter switch...) before I remembered the ECU kill switch, so I inadvertently had the opportunity to listen to the engine crank, but not fire.

This revealed a very distinct knock that's not audible when the engine is running.

I will mark the crank pully with paint to confirm the knock happens at the same point during the engine's rotation, but I'm preparing myself for an engine rebuild.

So, can anybody recommend a really good engine rebuilder, preferably in Texas?  Also, any shops to "avoid at all costs" would be tremendously helpful as well.

If I'm going to rebuild an N14, I think I would rather pull the (now 25 year old) engine & do a complete rebuild.

Thanks in advance!!

Franko

[vito.a]

Wow, that's a great find.  How many miles are on your N14?

It wouldn't be that difficult to remove the oil pan and roll new rod bearings in.   You could also check the main bearings but they are probably fine. 

But removing the engine is a tough job in these motor homes and will be expensive.  

I'd start by backing it up onto some homebuilt ramps made from stacked 2"x10" boards.  Drain the oil.  Remove the oil pan and then start checking and changing rod bearings.  

You may have to remove the trailer hitch and starter for access.  

Best of luck!

[CAT Stephen]

Hello Frank,

Before you consider a rebuild, power on the  ECM, then crank the engine to determine if the ECM is throwing a code. The most common issue with the N14 is that can cause the noise that you described is when an injector isn’t grounded. 

[Ivylog]

I would send off a oil sample before assuming the worst. 

[Frank C. Brants]

4 hours ago, vito.a said:

Wow, that's a great find.  How many miles are on your N14?

It wouldn't be that difficult to remove the oil pan and roll new rod bearings in.   You could also check the main bearings but they are probably fine. 

But removing the engine is a tough job in these motor homes and will be expensive.  

I'd start by backing it up onto some homebuilt ramps made from stacked 2"x10" boards.  Drain the oil.  Remove the oil pan and then start checking and changing rod bearings.  

You may have to remove the trailer hitch and starter for access.  

Best of luck!

Thanks Vito, I will definitely do that - the previous owner had (and I kept) a great storage location that was converted From an old workshop with cement floors, air & 50 amp service everywhere, so 'up on the jack stands she goes...'

I will definitely check the rod caps first, after taking an oil sample & cutting the oil filters open.

It's a bit more work than I anticipated, but I signed up for a "project" & the Sig delivered 😉

3 hours ago, CAT Stephen said:

Hello Frank,

Before you consider a rebuild, power on the  ECM, then crank the engine to determine if the ECM is throwing a code. The most common issue with the N14 is that can cause the noise that you described is when an injector isn’t grounded. 

Thanks Stephen, I will give that a try, thank you!!

1 hour ago, Ivylog said:

I would send off a oil sample before assuming the worst. 

Absolutely, thank you!!

Edited February 13 by Frank C. Brants
Fat Fingers...

[Frank C. Brants]

4 hours ago, vito.a said:

Wow, that's a great find.  How many miles are on your N14?

~120,000 - it's actually in great shape, but with some significant (think Mr. Magoo with pliers...) problems.  It will take some sorting...

[Jdw12345]

Was the previous owner willing/able to share any info on the engine condition? 

[Frank C. Brants]

On 2/14/2023 at 7:53 AM, Jdw12345 said:

Was the previous owner willing/able to share any info on the engine condition? 

Not to put too fine of a point on it, but he told me 6 polar opposite stories on a single topic, every one of which was mutually exclusive (it could be one or the other, but not both), so I don't believe anything he told me in the past, nor would I believe anything he said going forward.

[dl_racing427]

Wow, I'd be very reluctant to believe that engine needs a complete rebuild.
If it's not knocking when running, I'd take an oil sample and see what it says.
If they just changed the oil, I'd drive it a few thousand miles before sampling.

[Gary Cole]

Frank if you only hear it when its cranking you might consider having your wife start it for you.  Then you can go out.  My wife always complains that the engine is too noisy and the fan blows so much air that  it messes her hair up when she stands at the rear.

Edited February 16 by Gary Cole

[Jdw12345]

He should be able to start it from the rrb.

[Frank C. Brants]

It's a pretty serious knock... I'm working with an experienced mechanic (will share his info if he gives me permission) to troubleshoot.  We're about 95% certain it's in the overhead - possibly a broken injector spring.

1. Cold, first crank, no air pressure in tanks:
   1. https://share.icloud.com/photos/064RZEQmBd0dJoE0i_Hh21chw
2. Cold crank + cold start:
   1. https://share.icloud.com/photos/024ELf-0ofDKakHa34i0IFXMA
3. Hot crank, air tanks full & compressor unloaded:
   1. https://share.icloud.com/photos/0923hGoNPzfZAI9hoiYd2fXNw
4. Hot crank, chasing the knock:
   1. https://share.icloud.com/photos/0c5lxQj6QGkTV0-7o0gWI3zXg

[Jdw12345]

Maybe a broken bridge……

[dl_racing427]

I'm gonna say that's definitely in the valvetrain or the Jake brake.  The knock is every 2nd crank revolution.  I could also hear it after it started.
I'm not sure what ratio the air compressor is driven at, but if it's at camshaft speed that's another possibility, but I'd start by pulling the valve cover and checking for anything broken or loose.
Also a good opportunity to check and adjust valve clearance.

At any rate, I doubt this is a serious or particularly expensive repair, especially if you caught it before metal shavings were spread around the engine.  The bottom end sounds really good to me.