FB/EK versus FE/FC rear brake hose

[Harv]

A year or so back I pulled the spare diff out from under the house, had it overhauled and the LSD fitted. I had some spare time last weekend, so threw the diff into the FB. All fitted well, except the rear brake hose (the one that goes between the brass tee on the diff and the steel brake line that runs the length of the car).

Eyeballing the brass block, the one on the spare diff (all cleaned up and shiny now) looked the same as the one on the FB diff (covered in a half centuries worth of grease and crud). I reused the rear brake hose off the FB, but it is too long in the thread - bottoms out on the brass block before the copper crush washers deform. Stupid me put the old diff waaaaaay under the house, and I am trying to avoid pulling all the stuff out to get at it again.

I'm wondering if the spare diff (and hence brass block) might have been FE/FC. Masterparts says there is a difference in the brass block and rear hoses between FE/FC and FB/EK. By some chance, is the FE/FC brass block not drilled and tapped as deeply as the FB/EK (and hence causing my FB/EK hose to be too long in the thread)?

Cheers,
Harv

[EK283]

Harv,

Can't help with the technical questions you have asked but I do know some brass fittings have a taper at the bottom which can seal with the right type of rubber hose fitting. The copper washer in this case is deleted.

Greg

[Errol62]

If it is an FE FC diff the axle bearings use the separate seals like everything bar FB EK. Also the backing plates would be slightly different due to the narrower brakes. Very much doubt the hoses would be different. Dr Terry question.

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[ardiesse]

In the absence of a reputable authority, here goes -

One of the many engineering changes for the FBs was to use smaller brake pipes - 3/16" instead of 1/4". At the same time, the rear wheel cylinder bore was reduced to 1.000", and the brake shoes were widened from 1-1/2" to 1-3/4" (and drums modified to suit). And the change of rear wheel bearing too. And the rear springs were widened to 2-1/4".

You could install an FE-FC rear axle housing into an FB, but you'd notice the differences. Did the rear spring mounting pads on the rear axle look too narrow for the springs? If you then attempted to install FB rear brake components, they would almost, but not quite fit.

As for brake hoses, my '57 master parts catalog says that all brake hoses are the same, but a copper washer is only listed for the front brakes. (I'd need someone with a later catalog to confirm part numbers for FB-EK brake hoses.) The hose's "male" fitting has both a flat shoulder at the hex, and an internal flare at the end. When connected to a front wheel cylinder, sealing is effected by the copper washer between the cylinder and the flat on the brake hose. When connected to the rear axle, sealing is effected by the internal flare in the brake hose into the distribution block, just as if the hose were a brake pipe.

In short, Harv, the brake hose is supposed to bottom in the brass block. But I seriously doubt that you fitted an FE-FC rear axle to your FB.

Rob

[gpi]

you could get a reducer for the chassis hose and use an fx-fc brake hose? ...i have a feeling the diff might be coming back out...

[Errol62]

That's right, forgot about the change in fluid tube diameter.

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[Harv]

Interesting.

The diff bolted up beautifully. I put rebonded FB/EK shoes into it without a drama while it was still out of the car. So more likely than not an FB/EK housing. I bought the housing years ago along with a front end from a bloke at Holsworthy. It came out of one of Steve Jackson’s ex-cars that the bloke was hotrodding.

The hose was originally in my FB. My cloudy memory says that I got it replaced 10 years ago because the old one had rub marks. Can’t remember what I thought it was rubbing on, but the replacement hose got some split rubber tubing cable-tied over it. I have a spare hose in the spare parts department that is rubbed, so is likely the old hose. I think I got Pirtek to make the new hose up. It is identical to the old rubbed one.

The hose has a square-cut nose (no inverted flare), and a shoulder that would happily take a copper washer. It had no washer on the FB. Grace’s ute has no washer either. Without the washer, it bottoms out but the nose does not seal inside the brass block. I tried a copper washer, but the hose bottoms out before the washer crushes. I tried two copper washers, stood back and cursed myself for doing something so dodgy on a brake line (they didn’t seal either).

I’m leaning towards the new shiny brass block being scratched/scored/dinged at the seat. I’ll pull the old block out over the weekend and swap it over. May need a stick to fight off the spooders under the house. I figure it’s the same block and hose that just did ten years of daily service in the FB... has to work.

For some light entertainment, I went to add oil to the diff yesterday. Filler plug had rounded corners... someone had tried and failed to get it out. Got a socket on it and proceeded to really round all the corners off using a breaker bar. Worked my way up through the stillsons from “tap repair” size to the 2.5’ “oil rig roustabout’s helper” set... plug did not budge, and I nearly pulled the car off the stands. Laid into it with a cold chisel, and finally got it out. For Sale: one genuine early Holden diff filler plug. Some signs of wear, easy repair. Rare.

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Cheers,
Harv

[gpi]

this is why we do it

for the sake of 40 bucks i would get a new hose, especially if youve still got single circuit brakes, not fun pressing on the pedal to find it go to the floor...

[In the Shed]

Yep, them diff plugs can be a headache to get out. Why the hell did they make a hex headed plug so slim that is so easy to round off and smash your knuckles?

[Errol62]

Hexagonal socket on old school impact driver plus bfh. Jack body up so axle hangs down. Rattle gun with feet wedged so you can push against diff. Tried them all. Oh yeah, dads old footprint stilsons.

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[ardiesse]

The plug is slim, because replacing a burred-over plug is less trouble than dealing with a stripped thread in the rear axle housing. Think of it as a mechanical fuse.

Rob

[Harv]

Fuse is close to the word that I used, but I think you pronounce it differently.

Cheers,
Harv

[Harv]

Got under the house, and pulled out the original FB brake block. The retaining clip groove is different, but otherwise identical to the leaky one.

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The hose connection port is 7/16-20UNF, drilled to 0.34” deep, and has a raised flat seat to mate up to the hose.

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This is different to the two pipe connection ports, which are 3/8-16UNF and have a 45-degree inverted flare seat ready to accept 3/16” tube.

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The hose is threaded 0.47”, 0.11” longer than the 0.34” deep brass block (i.e. the hose bottoms out with a 0.11” gap). A typical 70-thou crush washer will not fill the 0.11” gap. Instead, the square hose nose seats on the internal flat seat. This is different to the front brakes (for FB/EK the rear hose and two front hoses are same same). The front brake cylinders are threaded 7/16-20UNF ready for the hose, but drilled 0.63” deep with no seat. The hoses thus bottom out with no seat to land on and need the copper crush washer.

I could find nothing wrong with the hose, nor either brass block. Put it back together with the FB block, and it appears to be holding tight. Maybe there is a non-obvious flaw in the first block, maybe one of the flares was not right and leaked by dripping off the hose, or maybe the FB got a little scared when it saw me lay into the diff filler plug with a cold chisel. One for Scully and Mulder

Cheers,
Harv