Thread size of front brake bleeding nipples

[Mephistopheles]

I am interested in replacing the brake bleeding nipples of my E Type Series III by non-return valve bleeding nipples. One supplier claims metric thread size for front brake bleeding nipples: M10x1x16mm. Is this correct?
Thanks and best regards
Holger

[abowie]

I can't speak with certainty about S3 cars but I would expect that they are 3/8" 24tpi UNF like earlier cars.

Be aware that M10 1mm is very similar. A 3/8" fitting will screw into a M10 hole quite convincingly. M10 is slightly larger in diameter and I don't think an M10 fitting will go into a 3/8" hole.

[vee12eman]

Hi Holger,

Andrew is correct. The thread of most Girling calipers on UK cars at the time (including the Series 3) was UNF and the bleed nipples are 3/8 UNF. Aftermarket units often differ - you can check by running a bolt into the caliper, the vast majority of 3/8 UNF bolts have a 9/16" head.

UNF 3/8" thread has 24 tpi.

Regards,

Simon

[mgcjag]

Just for info Jaguar used M10 on the brake fittings on the later S3 XJ6 models..so possibly some confusion there....Steve

[abowie]

Just for info Jaguar used M10 on the brake fittings on the later S3 XJ6 models..so possibly some confusion there....Steve

I found out about this when installing Volvo 244 calipers on my E Type. Even though they are Girling all the holes and threads are metric. So when I tried to fit 3/8 UNF fittings they went in but leaked.

The only sure way to tell them apart is by measuring them with a vernier. From memory the 3/8" are about 9.35mm in diameter, the M10 are around 9.8mm. There's only one TPI difference in thread pitch and it is very hard to differentiate them by this.

[Mephistopheles]

Hi Andrew, Simon and Steve
Thanks; I understand: I will order non-return bleeding nipples with both thread sizes to make sure that I can install them directly after removing the old nipples. The supplier has already agreed to take the non-fitting parts back.
Regards
Holger