the light goes on because fluid is low refill and light goes out.now I refilled and light stays on,brakes seem fine but this is a new issue.could it be the rings in the brake booster going flat and bad....just thinking if any 240 owner has had this prob. thanxs

On some volvos, the switch plunger falls into a valley and it will not reset until the switch is raised so that the piston can return to its normal position.

so this plunger problem would lead to loss of fluid ? how can I access this plunger? thanks

Never mind. The plunger that needed reset was last used in a 140 volvo. Really is best if you would confirm what year your car is to avoid the guesswork we are doing.
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Art Benstein near Baltimore

A woman has twins and gives them up for adoption. One of them goes to a family in Egypt and is named "Ahmal." The other goes to a family in Spain; they name him "Juan." Years later, Juan sends a picture of himself to his birth mother. Upon receiving the picture, she tells her husband that she wishes she also had a picture of Ahmal. Her husband responds, "They're twins! If you've seen Juan, you've seen Ahmal."

thanks art ...91 245 wagon 3.1 engine.my bulb failure light also stays on but the fact remains I am losing fluid slowly

One of the most difficult mistakes to correct is the Juan/Ahmal syndrome. While Juan and Ahmal are identical twins we might be pretty safe to say if you've seen one you've seen them all. Now I have a couple sets of identical twins in my extended family, and I can assure you similarity in looks is indeed superficial.

Problem is, people new to Volvo get this idea one 245 is just like another, and don't bother telling us what year, trim, transmission, etc. figuring they're all the same. But they're not.

Model years 75 to 90 had a pressure differential sensor (brake failure warning switch) to trigger the brake failure light. 91 through 93 used a float level sensor in the reservoir.

A torn seal in the master cylinder might leak out through the booster to be eventually burned in the engine -- a brake fluid leak well hidden from view. You'd have to separate the cylinder from the booster to confirm this. However there are many other places fluid could leak and not be noticed without a diligent inspection. You need to get your mechanic to do a thorough inspection to find the leak and fix it.
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Art Benstein near Baltimore

If you have any trouble sounding condescending, find a UNIX user to show you how it's done. -Scott Adams

oddly enough I started getting leakage a couple of weeks after my mechanic replaced the brake booster

"I refilled and light stays on,brakes seem fine "
Why are you losing brake fluid?

I'd suspect that the piston in the brake junction block is stuck to the side which is losing fluid.
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1980 245 Canadian B21A with SU carb, M46 trans, 3:31 dif, in Brampton, Ont.

"I'd suspect that the piston in the brake junction block is stuck to the side which is losing fluid."

It could very well be what Trevor is suspecting above.

After the brake system is well purged, I would try to pump rapidly and hard in order to free the piston in the junction box.

It is spring loaded at both ends and it should return in the center of the junction box.

That should apply on 1986 and older version of 240 in my opinion.

I checked back on some of the OP's other posts. He posts about a '91. 1991 was the year they did away with the octopus in all 240 models ABS or not. The brake failure light is activated by a float switch in the reservoir. Normally, when it lights, it is time to change brake pads, and if it isn't, it is time to look for the leak.
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Art Benstein near Baltimore

Pilfered from Eric:

The Parts Man Prayer

I work behind the counter
In an auto parts store
Sometimes I'm called a genius
Sometimes I'm called much more.

I say I'm no mechanic
But when their job goes sick
Everyone comes in and asks me
What makes the damn thing tick.

I'm supposed to know the number
Of nuts and bolts and gears
For every machine ever made
For more than a hundred years.

I'm supposed to have the answer
For everything unknown
To every Tom, Dick, and Harry
For all their questions thrown.

My life would be a pleasure
And I'd grin from ear to ear
If only they would tell me
Their Model, Make, Year

Many thanks Art, I have a 1991 and that is good to know for me.

thanks,good info.i do see evidence of fluid below the brake booster which is brand new put in by my regular mechanic

Depends on the year.
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Art Benstein near Baltimore