Brake fluid seen in the catcher near the cap

[wowly]

Recently acquired a 77 911s. Saw overflow of brake fluid in the picture. Any suggestion the cause of this? I don't drive hard on this car and no track days.

[GaryR]

Likely an overfill or a spill...

[pete3799]

If you did a brake job recently could be that when you compressed the calipers it over filled it.
Make sure the cap is not leaking. Excess fluid should go out the vent hose.

[AlistairWallace]

A less likely scenario, but its possible:

If you have a full reservoir and water in the system and do some hard driving the expansion from the hot fluid will push it out. But All things have to perfectly align for that to happen.

[dannobee]

Here's how it happens. Brake pads wear through normal driving, someone sees the brake fluid level low and tops it up, not knowing that the low fluid level was due to the worn out pads causing the caliper pistons to move further out of their bores. When time for the brake job finally comes, the pistons get pushed back in their bores to make room for the new brake pads and the brake fluid has nowhere to go, so it goes back through the master cylinder, into the reservoir, then out through the top after the reservoir is full.

[SCadaddle]

I just spent the past few weeks working on the calipers, hoses, pads and bleeding the brakes on my SC.

The first thing I did was to remove that cloth sheathed vent line from the fluid reservoir and blow compressed air into the line to make sure a dirt dauber wasp hadn't made a home in the far end of it, supposedly behind the front valence. I should think an overflow situation would go out that vent line once connected. And you'll see the line has a slight incline between the plastic tap on the reservoir and the metal clip on the backside of the reservoir. So I'd chock that one up as sloppy pouring.....which by the way, I found a 8 oz. plastic dosing cup from a previous hospital stay by someone in my family was THE ticket in transferring the fluid from the 1 litre can to the reservoir without making a mess.

[smadsen]

Clean up the overflow tray with a paper towel. Make sure the fluid lever is below max and above min. Should solve the problem.

[SCadaddle]

Originally Posted by smadsen

Clean up the overflow tray with a paper towel. Make sure the fluid lever is below max and above min. Should solve the problem.

And that's really the odd thing, as in at least on my SC I could find no discernable markings on the reservoir for max and min level, so knowing the overflow line might take on a bit of fluid if filled just below the neck of the reservoir, it would have to go higher than almost the level of the top of the cap to travel further down the vent line because of the metal clip holding the line to the top of the rear of the reservoir.

[Solamar]

Originally Posted by SCadaddle

And that's really the odd thing, as in at least on my SC I could find no discernable markings on the reservoir for max and min level, so knowing the overflow line might take on a bit of fluid if filled just below the neck of the reservoir, it would have to go higher than almost the level of the top of the cap to travel further down the vent line because of the metal clip holding the line to the top of the rear of the reservoir.

From the SC Owners manual -

"The brake fluid should always be at the top mark"

What's the matter? Can't find your top mark? I certainly can't either

[SCadaddle]

Originally Posted by Solamar

From the SC Owners manual -

"The brake fluid should always be at the top mark"

What's the matter? Can't find your top mark? I certainly can't either

Well, I couldn't put my hands on my owners manual to see what you've noted, and I don't suppose the relative topic in the manual was accompanied by a photo? I used the "advanced search" function of this forum to find out where the "top mark" would be, and for what it's worth even Google didn't know either!

That being said, and until I remove the strainer screen and stick my finger in and over into the reservoir to try and feel the vent part of the reservoir for it's depth or flush mounting situation, I'm going to go on the same concept of never leaving a general aviation aircraft sitting on the tarmac without a full tank of fuel, because doing so just invites condensation in the tanks that you do not want. So fluid up to the vent tap is how I'm going to roll.

[Locker537]

Originally Posted by SCadaddle

Well, I couldn't put my hands on my owners manual to see what you've noted, and I don't suppose the relative topic in the manual was accompanied by a photo? I used the "advanced search" function of this forum to find out where the "top mark" would be, and for what it's worth even Google didn't know either!

That being said, and until I remove the strainer screen and stick my finger in and over into the reservoir to try and feel the vent part of the reservoir for it's depth or flush mounting situation, I'm going to go on the same concept of never leaving a general aviation aircraft sitting on the tarmac without a full tank of fuel, because doing so just invites condensation in the tanks that you do not want. So fluid up to the vent tap is how I'm going to roll.

If you drive it hard - track hard - it will pee pee out of the vent. Not a big deal as that's why the vent is there.

[Walt Fricke]

And why the reservoir has a sort of fluid catch fence around it, where the spill sits harmlessly until you see it and mop it up.

[jgurnari]

I read DOT 3 OR DOT 4 for my 1985 911 coupe. What if I use DOT 3 but DOT 4 is already in the system or visa versa?..that a problem?

Anyone have a photo of the maximum / max line on the reservoir ..I cant see to the MIN / MAX line.

[Walt Fricke]

There is no max/min line. Fill to the top, or just a bit under to account for some thermal expansion. The reservoir is vented, so your brakes won't lock up. However, as long as you have fluid over the internal separator (one side for front, one side for rear) you are OK. Time to worry if the fluid is below the metal strap around the reservoir. Call that the min line.

DOT 3 and DOT 4 mix just fine. But it might be good practice to flush the system, which will get rid of all the old stuff and replace it with new. Then you know what's in there.

[jgurnari]

thanks