Diesel Engine Cummins N14 Rebuild Kit | Highway and Heavy Parts

We're discussing some inexpensive additional pieces you should think about changing when you rebuild your Cummins N14. The Cummins N14 is a strong, reliable engine that will just keep on going if you treat it right. Depending on how much weight you're pulling, the average rebuild is needed around 800k to 1 million miles. The standard N14 inframe kit will come with nearly everything you need to rebuild the engine. Here's a look at some of the additional pieces that are a good idea to change while performing the rebuild. The nice thing is, they won't break the bank.

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What Additional Parts Should I Change When Rebuilding My Cummins N14?


1. Engine Brake Gaskets

Engine brake gaskets are the one necessary item that all N14 inframe rebuild kits leave out. If your Cummins N14 came with engine brakes, you're going to need the gaskets anyway! So, don't forget to ask for a set when you're ordering parts. You'll need three brake engine gaskets. We have them available on our website at up to 50% off OEM prices!


2. Piston Cooling Nozzles

The N14 piston cooling nozzles are located on the right hand side of the block. They are spaced out just enough to hide behind everything that can get in your way such as the oil filter, coolant filter, alternator, etc. In most cases you can still wiggle them out without removing these items. The N14 cooling nozzles are made of plastic and can get brittle from the heat of the engine. If one happens to break, you will typically have a noticeable drop in oil pressure.

The worst case scenario is that the lack of oil to the underside of the piston could cause a piston failure or cause the wrist pin to seize in the rod. Either way, this is something you definitely want to avoid. The cost of these nozzles is low and it is highly recommended to install a new set after you put the pistons and rods back in the engine. This eliminates the possibility of hitting the nozzle with the rod when dropping the piston & rod assembly back into the liner.

You'll need six of these nozzles for your engine. You can purchase them from HHP here.


3. Thermostats and Seals

Thermostats are the most expensive item on this list, but it's still a good idea to change them when you're only working a couple of bolts away. The N14 thermostat seals are one item that are often forgotten about, overlooked, or even skipped because they can be a pain to change. Cummins makes a special installation tool for the job, but if you pay attention to the seal depth prior to removing them, it isn't necessary.

If the seals are bad, they allow coolant to flow around the outside of the thermostat and lessen how effective they are. Changing both the thermostats and seals when rebuilding your engine will help protect against overheats and slow warm-ups.

You'll need two thermostats, as well as two thermostat seals. These parts are built to strict OEM specifications, so you can rest assured that you're getting the best quality for your money.


4.  Oil Pump Pressure Regulator Plunger & Spring

The N14 Lube Oil Pump is a heavy duty unit. Sure, it's possible for them to go bad, but it's unlikely. If you want to save some money and not change the entire pump, just change the spring and plunger. The spring and plunger can be accessed with the pump still installed.

There is a single bolt that holds a plug on the bottom side of the pump. Removing this plug allows easy access to the spring and plunger. If you note the length of the old spring compared with the new spring, most times you will see a significant length difference. This is because engine heat, pressure, and time causes the spring to relax. This can cause your oil pressure to go down.

The plunger gets scored up from particles in the oil getting caught between it and the body of the pump. If scored bad enough, it may cause the plunger to stick, causing the engine oil pressure to jump erratically.

For this replacement, you'll need two seal rings, a regulator plunger spring, and a pressure regulator plunger.


5. Front Cover Accessory Drive Bushing

The front cover or the accessory drive aren't normally taken off during an inframe rebuild, but it's worth mentioning. If you've reached a million miles on your N14 and haven't ever had the dreaded giant oil leak caused by the accessory drive bushing, consider yourself lucky. What happens is that the accessory drive bushing spins in the front cover blocking off the oil feed hole that keeps the accessory drive lubricated. The bushing and drive heat up from the lack of oil and cause the accessory drive seal to fail. This results in any and all remaining oil in the area to run down the front of your engine until the problem is fixed.

Unfortunately, the fix is a new front cover, accessory drive, and all the labor needed to change them. A simple solution to this is installing a new bushing when you have the accessory drive out. To better help the bushing stay where it should, a light coating of large diameter sealing Loctite can be used.

The bushing you'll need for this job can be found here.


6. 90-Degree Fuel Elbows

A trick to help you remove the cylinder head closest to the cab is to take a hammer and break off the 90-degree fuel elbows at the back of the head. The fuel lines can be very difficult to loosen up and many times the line is damaged beyond repair in the process. By simply taking a hammer and breaking the fittings off, it allows for the removal of the cylinder head.

With the cylinder head out of the way, the elbows can be taken off the lines. The fittings on the lines can then be worked free to allow for easy installation. The broken part of the elbow will need to be removed from the cylinder head, but a quality bolt extractor usually takes it right out. There is also a 90-degree fuel elbow in the front cylinder head, but this one is usually easier to access. If it's not, just grab your hammer.

Youll need two 90-degree elbows for the job, you can purchase them here.


These few inexpensive fixes can help keep your N14 engine running trouble-free for its second life. If you need to know more about any of the parts mentioned or just have a N14 question in general, contact Highway and Heavy Parts (HHP) at 844-304-7688 and speak with one of our ASE Certified Technicians. Or, you can always request a quote online!

Originally Posted July 14, 2014; Edited February 1, 2020