Inline Radiator Coolant Filler Necks - The Last Piece Of The Engine Cooling Puzzle.

A radiator filler neck is a cap opening that is installed in between the upper radiator hose fitting and the fitting on the engine. It allows  you to fill up the cooling system with coolant by removing the cap. It usually has a pressure cap and is secured with hose clamps.

You have finally finished that sweet engine swap, everything is assembled and you are now in the testing and tuning phase. You now have one last problem to diagnose - OVERHEATING!.

You have the big aluminum radiator, the good fan or fans, everything seems ok. But wait, what about the possibility of an air bubble? Yes the elusive air bubble in the system.

When you were hacking away and fabricating you’re engine swap; a situation occurred. The radiator hose routes higher than the top of the radiator filler cap. Because fo this; A bubble you cant see is at the top of the radiator hose. This is where a inline radiator hose filler comes in. Inline radiator filler necks are Tee fittings allow you to splice in a inline radiator cap into your upper radiator hose. This is in order to relocate the radiator fill cap to the highest point of the cooling system. This allows you to fill the coolant up to enough to eliminate the possibility of air bubbles In the cooling system.

There are both very expensive and inexpensive ways to remedy this. In order to navigate your options; there are companies out there like http://ipgparts.com. IPG Parts has a ton of bolt on inline radiator filler necks that will work with many popular engine swaps. These radiator fill kits feature tig welded billet aluminum construction that use factory bolt holes. If they do not have your application; go the less expensive approach and Visit the Filler Neck supply Company website. Here you will find tig welded universal inline radiator filler necks that into you’re factory upper radiator hose. What if your upper radiator hose has a bigger filler neck on the engine; than it does on the aluminum radiator? Filler Neck Supply Stocks Inner Diameter Hose reducers to get a larger diameter at 1 end of your inline coolant filler neck. Many times the intake neck is 1-½ and the radiator nipple is 1-¼”. With an Inner Diameter Reducer you can get the perfect fit.

Now that you have chosen the perfect Inline radiator hose filler neck, now comes time for installation.

The basics include

1. Find the highest point on the upper radiator hose.

2) Cut a section out of the upper radiator hose.

3) insert hose clamps on both sides of the hose.

4) insert both ends of the inline radiator filler neck Tee Splice.

5) Tighten down the hose clamps.

6) Insert the cap and you’re done.

See The Many Radiator Filler Neck Sizes 

For more engine cooling mistakes and problems see this great article CLICK HERE