Radiator Banjo Bolt

1990 XJ-S and 1991 XJ-S Classic Collection Coupes (US Spec, 5.3L V12)



Radiator Banjo Bolt/2 Copper Washers

5/8” Socket/Wrench

A little Coolant/Water


Having read about dropped valve seats from overheating, and a clogged banjo bolt potentially causing overheating, I thought I better change the bolt on both my cars as one of my first maintenance jobs.


A banjo bolt has a hole in the middle of the bolt cylinder and a hole right through (across) the bolt near the top to allow liquid to flow through.  The Radiator banjo bolt is on the right side of the top of the radiator, bolted into the thin metal tube going across the top of the radiator cover plate and to the hose connected to the center coolant fill hole.  It is part of a scheme to try to trap any air in the cooling system into the top of the filler necks.


As per nearly everybody, I got a replacement bolt from Ron Kelnhofer (e-mail Ron) for $18.88 including the appropriate copper washers.  He is responsive and was very helpful when I wanted to talk with him on the phone.  There is a picture of the bolt at Garage Engineering, but they do not sell it directly.


You might want to put a container under the car near the bolt to catch any dripping coolant (don’t worry, it won’t be much if any at all).  I had my car facing up a considerable slope on my driveway, and no coolant came out.  With the engine cold, remove the old bolt with the 5/8” socket.  Carefully lifting the metal pipe, remove the old washer underneath it (its copper, so a magnet won’t help).  Put a new washer in its place, lay the pipe back down, put another new washer on top, and install the new bolt.


Open the crossover tube filler cap (the cap nearest the center of the engine, and top it off with appropriate coolant/distilled water.  Next project…


Radiator Banjo Bolt (Center of Picture)

(Viewed from Right Side-Front)



Questions/comments: Email me.