Brake fluid mystery

[Ronski]

Have 1999 3.9 V8 D1.
Have spent last 6 months building new engine. Installed the block last weekend and will put on heads this week.
While getting the engine back in car, I noticed the reservoir for brake fluid was completely empty.

I double checked all wheels and no leaks at calipers, no leaks anywhere tracing along brake lines.
All was good before removing engine, so my question is;
Where has all the brake fluid gone? It does not evaporate, Is it possible it has drained into the servo? If so, how to get it out?
Am I looking at rebuilding the master cylinder. ie leaking rear seal?
Any insight welcome.

Ron.
183599

edit: picture cut off and does not show brake master.

[Tins]

Have 1999 3.9 V8 D1.
Have spent last 6 months building new engine. Installed the block last weekend and will put on heads this week.
While getting the engine back in car, I noticed the reservoir for brake fluid was completely empty.

I double checked all wheels and no leaks at calipers, no leaks anywhere tracing along brake lines.
All was good before removing engine, so my question is;
Where has all the brake fluid gone? It does not evaporate, Is it possible it has drained into the servo? If so, how to get it out?
Am I looking at rebuilding the master cylinder. ie leaking rear seal?
Any insight welcome.

Ron.
183599

edit: picture cut off and does not show brake master.

Reckon you'll be pulling the servo and m/cyl. Unusual for both reservoirs to be empty though.... Are they? The reservoir might have got damaged in the engine removal process.

[Ronski]

On closer look, the larger front is completely empty, the smaller rear is a little down.
If I need to remove both master cylinder and booster, I will do it before fitting heads and everything.
makes it easier.
I don't want brake fluid being sucked into new engine through vacuum hose, if that's even possible.

No, I was very careful removing engine.

Should I refill and check to see if there is damage.


What do you think?



183602

[Lintz]

In the event that all possible external fluid system leaks have been eliminated, then the missing fluid can only be leaking into the controlled vacuum chamber (forward section) of the master cylinder booster from the rear seal of the brake master cylinder.
If the master cylinder fluid reservoir is continuously topped up and the escaping fluid level reaches the level of the vacuum connection point it will transfer into the engine oil sump through the vacuum pump.
Pull out the vacuum connection elbow and use a 300mm long black cable tie to confirm the missing fluid in the lowest part of the controlled vacuum chamber.
I would recommend a complete brake master cylinder with reservoir replacement ($300) rather than a brake master cylinder kit ($100) due to the age of the vehicle together with a vacuum leak-down test for the servo.
Expect the master cylinder to ABS pipe connections to be very tight and use a little heat on the master cylinder body (which will be discarded) to allow unthreading of the soft metal connections without deformation.
It would be great to hear your feedback to assist others in the future with the same issue.

[AK83]

....
If the master cylinder fluid reservoir is continuously topped up and the escaping fluid level reaches the level of the vacuum connection point it will transfer into the engine oil sump through the vacuum pump.
....

I think this section refers to the tdi. But the OP has a v8.

Just clarifying.

[Tins]

I think this section refers to the tdi. But the OP has a v8.

Just clarifying.

IOW, the fluid will enter the engine via the inlet manifold, with accompanying billows of white smoke....