Tracing a brake system lea

[argiopeweb]

I've been noticing that the brake system loses fluid when the car sits. It's worse when the front is lifted. Last night I left the right side up, and this morning I'm almost totally drained of brake fluid on both sides of the canister.

Presumably whatever is leaking is affected by having the right side higher than the left. It's definitely in the brake system, because it drains well below the level of the clutch line. I don't see any visible leakage. The car doesn't seem to leak when driving, so it's presumably not in an area of the system that would be pressurized when the car is on.

Any recommendations on how/where to start to trace this down?

Edit1: Well, I apparently can't spell, and I can't edit the title... Woe is me.

[sjv]

I would check the clutch slave cylinder the brake canistor feeds the clutch hydrolic's slave cylinder is next to starter

[mytrplseven]

A flourescent dye kit from the auto parts store will help a lot, if you can't find it. They're cheap and you'll need to bleed the brakes with the dye in the master reservoir to push the dye throughout the system. After you've found and repaired the leak, flush and re-bleed the system with new fluid.

[argiopeweb]

Ooh, hadn't thought of fluorescent dye. I know the local places have it for A/C systems. I'll look around and see if I can find it in a non-pressurized form.

Definitely not the clutch system, sjv. For one thing, the master and slave are new, but, even if they weren't, they can only drain the system down to the level of the line from the canister to the clutch master. This consistently drains much lower, and refilling the system fixes the problem without a clutch bleed. Leakage this dramatic in the clutch would definitely leave air behind.

[mattdavis11]

The braided hose would be the culprit.

[Bradical]

Mine was doing this, small drip on the floor under the master cylinder every few days. It was the rotted resevoir grommets. They can be replaced by just turkey-basting the fluid out, no bleeding needed. Id start there?

[argiopeweb]

Yep, reservoir grommets and a new master cylinder o-ring are in the Pelican shopping cart. Hopefully they will help.

I still can't decide how it would leak an entire reservoir overnight without me noticing fluid somewhere... I'll check the driver side floor more carefully in the morning.

[argiopeweb]

I replaced the reservoir grommets/sealing plugs. The old plugs were definitely bad, as the rubber humps were crushed flush with the rest of the plug. The new plugs fit snug, allowing neither rocking nor up/down motion (a clear improvement over the ones they replaced).

The unfortunate portion of this is that the improved sealing plugs has caused the elusive blue hose to leak under pressure (which it never did before). So, kudos and apologies to sjv and mattdavis11; you've been vindicated by new sealing plugs.

Now to wait another 2 days for new blue hose to come in so that I can bleed the clutch so that I can install the starter and get back on the road...

[mattdavis11]

That hose isn't under pressure, it'll just fail, for no reason, other than age.

[argiopeweb]

I have a Motive power bleeder, so the blue hose was most certainly under pressure. It visibly (and rapidly) leaked at 10PSI, which implies it probably has failed less dramatically at ambient pressure.

It has the OE hose clamps on it, so unless it was replaced with the original clamps it's almost 30 years old. As you said, failure due simply to age.