Leaking brake fluid but I don't see it on the ground

I have been adding brake fluid but there has been no change in my braking… still very strong. I do not see any fluid leaking on top. Last year the brakes were changed and a new accumulator was installed. The only hose that was changed was the left front. I notice the brake warning light…red…on the dash being activated, and then going off. More on turns, right…but was on a straightaway, the New York State Thruway this afternoon and it stayed on most of the time. Filled to max line and red light still goes on, thus it’s not a matter of not enough fluid.
Please advise and thanks in advance.

Leaking into the brake booster.

R&R the brake booster and M/c.

The OP mentioned replacing accumulator, which indicates TEVES III.
If that’s the case, there is no vacuum booster. If the electrical pump that provides the boost is leaking, it should be very obvious.

It is not an excessive leak, but it is leaking. The accumulator was installed 1 year ago. Brakes are perfect the only reason I notice is the dash light going off.
What is TEVES III? Is there anything I can do here at home?

There are two brake fluid level switches in the Reservoir and the combination pressure switch which can turn on the Red Brake Failure light. In either case - failure of a brake fluid level switch, or the combination pressure switch, you will need to replace the combination pressure switch or the brake fluid reservoir - they are not repairable. You will need to check the circuits with you VOM. A Schematic for the Teves III system is attached.

Teves III ABS.pdf (294.9 KB)

Yes please, fill your profile so people that respond would know what model year is your Jaguar.

TEVES III is a brake system with an electric pump and accumulator to store pressure.
Was introduced in 1988 and lasted until 1995.
VIN break point is 198335 (1995 models).

HI. I looked up TEVES…could there be a leak in the hoses?

Hi. The brakes work well…very solid when applied. When reservoir is filled the light won’t go off. It appears I am losing a tad of fluid and that’s when the light lights. It’s odd though…I have the reservoir filled to max and I would think the light would go on only if the fluid dipped below the minimum mark.

Poking around on top. I see no leaks and as mentioned the vehicle stops on a quarter, as a dime would be too small for such a large engine.
My concern is this. Yesterday, I had coffee with a colleague who lives in the valley section of Syracuse. To get to him one must go down a very steep hill and directly go up another one. If there is an issue at either time, especially go down said hill…not much I can do but look up and in Fred Sanford’s words…”Elizabeth honey, here comes the big one."

Hello Richard - try this - unplug the brake fluid low level indicator connector, check to see if the brake warning light goes out; plug back in and then move the float a few times to make sure the contacts are not stuck, then luck at the light and see if it goes out when you operate the contacts - check the black/yellow wire to see if it has bad insulation and is being grounded anywhere - this is just to test the circuit for the light, not the leak problem - Tex Terry, II - 1991 XJS V12 Classic Coupe, 1986 XJS V12 Coupe - sent 10/17/2020 1211hrs. EDT USA.

Hi. Will do but out of three connections, which one am I chequeing? I have been looking under the vehicle as best I can and find no leaks from the brake hoses. By the by, where is the float?
Please advise and thanks in advance. This is a good day to do this, a beautiful fall day in Syracuse, and no sense listening to the Syracuse/Liberty football game as the outcome is not favourable to Syracuse.



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How much are you topping off per week?

The fluid is going somewhere…if your brakes are still strong, then its not in the brake lines or else air would get into system and cause spongy brakes. So it must be reservoir.

Could be trickling down to exhaust and burning off?

Chequed under the vehicle and all brake hoses are intact with no leakage. I am assuming we are now looking upside. As mentioned, the accumulator just celebrated it 1st birthday, and I see no fluid around it, and for that matter none around the reservoir as well.

I would check all four calipers.

You need someone to press brakes while checking underneath. Fluid could be leaking while driving/using brakes.

If I am on level ground, I fill the reservoir to the max line. There is a small knobby extension on the right hand side as you, or I, look into the reservoir…I am using that as a guide post. I has been that the dash light fires when it goes below that knobby extension. I am curious why the light would go on when it drops below “max” as it would make more sense if the light went on if the fluid went below “min.” I have looked around the reservoir and I see no leakage whatsoever.



Would it need to up on a lift to do so? And wouldn’t I find something on the ground?

Jackstands, wheels off for front.

I assume you have rear inboard brakes? Jackstands, wheels can stay on, but you’ll have to crawl way in there.

Old calipers can easily have slow leaks that only happen when braking. One of first things I did on mine was flush with couple quarts of brake fluid, inspect, flush again, and inspect. So far so good.

If you’ve never inspected your calipers, you should. Hopefully you’ll be ok and know they’re good. You can at least see if theres any wetness in there without having someone pump brakes.

Rear inboard brake calipers are susceptible because of location.

Enclosed is what has been done…I have no idea why they are posted upside down. My apologies in advance.




Folks. Is it possible that the accumulator did not have correct precharge and brake fluid is slowly filling in the accumulator? Until the brake system pressure isn’t strong enough to push more fluid in that space?