• Hi Guest!
    If you appreciate British Car Forum and our 25 years of supporting British car enthusiasts with technical and anicdotal information, collected from our thousands of great members, please support us with a low-cost subscription. You can become a supporting member for less than the dues of most car clubs.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Oil cooler hose fittings - 5/8 UNF versus 3/8 NPT

Share this page

DanLewis

DanLewis

Jedi Trainee
Offline
I'm trying to install a thermostatic oil filter sandwich to use with an oil cooler on a 1275. The sandwich has two female 3/8" NPT ports, but my hoses have 1/2" BSPT fittings. Victoria British sells some adapters designed to connect these BSPT hoses to the engine by removing the oil pipe that runs between the oil filter head and the rear of the block. The threads at the filter head are 1/4" NPT and those at the rear of the block are 5/8" UNF.

I know I can use brass bushings to reduce the 3/8" NPT ports on the sandwich to 1/4" NPT and connect to the bushing using the VB adapter that would normally connect to the filter head. However, I've noticed that the other VB adapter and the sandwich port both have 18 threads per inch. That adapter is a close fit to the 3/8" NPT port on the sandwich even though the two parts conform to different thread standards. Both are shown in the photo below.

My question is this: Would the solution that does NOT use the brass bushing actually seal if the threads were wrapped in Teflon tape and a brass crush washer used as shown at the bottom of the photo, or is that just asking for trouble? I ask because eliminating the bushing shown at the top reduces how far the fittings extend beyond the side of the sandwich.

Dan

IMG_6143.JPG
 
Dan
Before you get too far into this check that you have the room to fit that 1 3/8" thick adapter in place.
Last time that I checked it won't fit.
BillM
 
Hi Bill,

Billm said:
Dan
Before you get too far into this check that you have the room to fit that 1 3/8" thick adapter in place.
Last time that I checked it won't fit.
Click to expand...

Actually, the sandwich fits with plenty of clearance. :encouragement: No problem getting the filter in and out at all. I decided to go with the 3/8" NPT to 1/4" NPT bushings rather than take a chance on mixing thread types. I routed the hoses forward from the sandwich, under the motor mount, and then up and around the fresh air intake hose.

However, I guess it's always "one step forward, one step backwards": Since the oil cooler is mounted in front of the radiator, I knew that I would have to cut an opening in the rectangular shroud that directs air into the radiator so that it would clear the hoses. I decided that the best way to know where and how much to cut would be to lower the bonnet and see where the interference would be. I didn't realize that the bonnet would be pressing so hard against the 90 degree elbow where it attaches to the cooler. The weight was so great that it bent the intake port on the cooler enough to cause it to leak where it mates to the sheet metal of the cooler. :confusion:

I'm hoping I can get the cooler repaired by having someone re-weld the male fitting to the cooler so it doesn't leak any more. The cooler is brand new, so it would really be sad to have to buy another!

Dan
 
Back
Top