hey folks --
i have a 1987 245 and am trying to figure out a mysterious brake fluid leak. i have checked all lines, around the calipers, at the distribution box, below the master cylinder and the resevoir. all seems okay. i also just bled the brakes and flushed the system with fresh fluid. in doing so i used my power bleeder and didn't find any loss in pressure through the system there.
i think i may have found some fluid, but i'm not sure if it's even brake fluid though it's light and slightly oily. i found it just under the car where the firewall meets the floor pan under the driver's seat. thing is i can't figure out where it might be coming from if it is brake fluid. nothing drips down the engine compartment side of the firewall and i pulled up the carpeting inside the car to see if i could get a better look from in there, but nothing.
my hunch is that it could be coming from the brake booster, but that's really just a guess. i'm hoping someone here has experienced similar problems and can help point me in the right direction. are there any known problems with a seal in the brake booster?
thanks in advance.

 

Is the fluid in the reservoir going down at all?

When you pressure bled the system did you spill any fluid in the area of the master cylinder?

Also check where the fluid reservoir sits on the top of the master cylinder for leaks. It is just a push fit into the cylinder with two seals to stop the fluid coming out.

There should be no brake fluid in the brake booster, it is there to assist the driver to apply pressure to the master cylinder by vacuum. If fluid is getting in there it will be leaking from the rear seal of the master cylinder.

 

Bill, thanks for your response. You saw I cross listed this question elsewhere.

"Is the fluid in the reservoir going down at all?"

Yes, that's why I believe there's a leak.

"When you pressure bled the system did you spill any fluid in the area of the master cylinder?"

No.

"Also check where the fluid reservoir sits on the top of the master cylinder for leaks. It is just a push fit into the cylinder with two seals to stop the fluid coming out."

I see no leaks here either. Before I started bleeding the system with the pressure bleeder I pressurized the system at the resevoir to 10 psi and didn't see any pressure loss after 10 minutes or so.

"There should be no brake fluid in the brake booster, it is there to assist the driver to apply pressure to the master cylinder by vacuum. If fluid is getting in there it will be leaking from the rear seal of the master cylinder."

My thought exactly. So you suggest I look into replacing the rear seal of the master cylinder? Not that I can see into the booster to tell if there is any fluid in there, but maybe it's around that seal where the leak is?

 

If the leak appears to be coming from the booster area it is a fair bet that it is coming past the main seal.

When you use a pressure system to bleed or flush the brakes you actually put pressure on the master cylinder seals in the reverse direction. In view of the age of the car and assuming that the seals are the originals this reverse push could have been enough to upset one or more of them.

 

The junction block under the car is also known to leak where the electrical sensor is in the block.

To see if the master is leaking loosen it from the booster and slide it out and see if it is wet.