Losing brake fluid

[Jon K]

Ok guys - didn't drive the car for like 2 weeks, and it said brake fluid low. Topped it off. Drove about 300 miles. Brake fluid low. Where should I start?

It's a 1992 525i. Any known problem areas?

[BigKriss]

grommets underneath the resouviour

[Brandon J]

Yeah, known problem areas. Obviously the first place are around the caliper hoses and connections. Then check the reservoir by the o-rings. These can begin to leak from age, from rough handling the reservoir, and from pressuring it too much while brake bleeding.

[bahnstormer]

any wet spots when its parked?

[Jon K]

any wet spots when its parked?

Yes. The car pisses oil (lifting head gasket from 15 psi of boost). Hm..


Grommets eh? I don't notice and pressure loss when holding the brake when idling. I jam the pedal down hard and everything seems right - the pedal doesn't slowly leak down.

I will check the grommets. Where exactly are they? Are they the things that the ETK shows the res sitting on between the res and the master cyl?

[Turbo Ready]

Yes.

Grommets eh? I don't notice and pressure loss when holding the brake when idling. I jam the pedal down hard and everything seems right - the pedal doesn't slowly leak down.

I will check the grommets. Where exactly are they? Are they the things that the ETK shows the res sitting on between the res and the master cyl?

You won't loose pressure if those grommets are leaking, they are as you realized, the ones which holds the reservoir onto the master cylinder and not part of the pressurized braking system. They provide fluid which is gravity fed into they master cylinder.

Incidentally, I pulled a brake booster with the master cylinder today out of an e34 535i and it was wet at that spot and along the boot at the firewall.

[BigKriss]

also maybe the pipe from the intake manifold to the brake booser is leaking. when i changed my headgasket the grommets were leaking then but since the car is running now it deosn't happen anymore. just a though.

[Jon K]

You won't loose pressure if those grommets are leaking, they are as you realized, the ones which holds the reservoir onto the master cylinder and not part of the pressurized braking system. They provide fluid which is gravity fed into they master cylinder.

Incidentally, I pulled a brake booster with the master cylinder today out of an e34 535i and it was wet at that spot and along the boot at the firewall.

I understandt hats not pressurized - thats why I think that could be it, though unsure. I can hold the pedal down and I don't feel it sink. Hmph. Do you think I can see the whole potential leaky area from above with a flash light?



Kriss the connection from the intake manifold to the booster is a vacuum line. Nothing to do with the brake fluid really.

[ryan roopnarine]

you probably want to pass your hand along the underside of the MC and see if it wet or if your hand ends up smelling like brake fluid. in that scenario, either the grommets (sp) are leaking, lines are leaking, or the mc is leaking from the seal. disappearance without accountability would be either a hard to find leak or a tear in the booster that allowed the fluid to be sucked into the engine from the mc.

[Turbo Ready]

you probably want to pass your hand along the underside of the MC and see if it wet or if your hand ends up smelling like brake fluid. in that scenario, either the grommets (sp) are leaking, lines are leaking, or the mc is leaking from the seal. disappearance without accountability would be either a hard to find leak or a tear in the booster that allowed the fluid to be sucked into the engine from the mc.


^^^ It's the best method for checking for grommet leaks.

What you can do as well is make up a brake fluid pressure rig to trouble shoot, it won't go to waste because you can use it for bleeding the brakes as well.

Make a pressure rig using another reservoir cap and an external pneumatic pressure source, I am sure you know about this, pressurize to 5 psi and look for the leak.

[Jon K]

Checked under the resevoir and though I couldn't see the grommets, I saw that the master cylinder housing is a nice clean silver all around and didn't see fluid on it at all.

****, now what

[Ferret]

Checked under the resevoir and though I couldn't see the grommets, I saw that the master cylinder housing is a nice clean silver all around and didn't see fluid on it at all.

****, now what

Clutch leak? Arent they fed off the same reservoir in some cars?

[Jon K]

They are - I think I will get under the car real quick tonight with a flashlight.

[Dave M]

Clutch leak? Arent they fed off the same reservoir in some cars?

The clutch feeds from the brake res. in the M50.

Barring any obvious leaks along brake lines or at the wheels, a leak somewhere in the clutch system might just make sense (as you aren't experiencing a lack of brake pedal pressure). In case you don't know, your clutch slave is on the drivers side of the tranny. and can be reached from below to check for wet spots. If its leaking into the bell housing you can remove the two (10 or 13mm bolts??) to check the cylinder. Its a bit of a contorsionist manouver, but I'm sure you're more than capable ;) Otherwise, what about the primary (master) at the clutch pedal?

In either case, I'm not sure why you wouldn't have a dead clutch pedal, but its worth checking in lieu of other obvious symptoms.



Dave

[Jon K]

I would say that my clutch doesn't feel as "jerky" as it did before being 6 puck ceramic. But, I did just drive a REALLY touchy M3 for a while so maybe I am just not used to my own car... but I think we're on to something with the clutch. Yeah I've done the whole clutch so I know where the slave is. I will get under there and check it out tonight real quick and see if I can see anything. Worst case is I will be on a lift on Saturday

[Ferret]

I would say that my clutch doesn't feel as "jerky" as it did before being 6 puck ceramic. But, I did just drive a REALLY touchy M3 for a while so maybe I am just not used to my own car... but I think we're on to something with the clutch. Yeah I've done the whole clutch so I know where the slave is. I will get under there and check it out tonight real quick and see if I can see anything. Worst case is I will be on a lift on Saturday

As well: any weird smells in the cabin? You might miss it if your engine's blowing oil everywhere I suppose. Check the carpet around the master cylender and see if it's full of brake fluid.

:D

[Jon K]

no weird smells granted i smell fuel and exhaust because no cat and a lot of fuel :)

Otherwise no the car runs fine and no funky smells.

I wish i had someone around here that could just go under the car for me while I am at work :)

Any takers!!? Haha

[bsell]

Kriss the connection from the intake manifold to the booster is a vacuum line. Nothing to do with the brake fluid really.

If the rear seal on the brake master cylinder leaks, it can fill the vacuum booster with brake fluid which tends to make a mess of the valve system in the booster. This mess can migrate down the vacuum line and into the intake manifold in extreme cases. I can't imagine how many cans of brake fluid this would take, but I have seen a car or two like this. Makes you wonder about some folks' idea of safe driving!

Brian

[bsell]

The clutch feeds from the brake res. in the M50.

Barring any obvious leaks along brake lines or at the wheels, a leak somewhere in the clutch system might just make sense (as you aren't experiencing a lack of brake pedal pressure). In case you don't know, your clutch slave is on the drivers side of the tranny. and can be reached from below to check for wet spots. If its leaking into the bell housing you can remove the two (10 or 13mm bolts??) to check the cylinder. Its a bit of a contorsionist manouver, but I'm sure you're more than capable ;) Otherwise, what about the primary (master) at the clutch pedal?

In either case, I'm not sure why you wouldn't have a dead clutch pedal, but its worth checking in lieu of other obvious symptoms.

Dave

If the hose from the reservoir to the clutch master is pissing fluid slowly (two weeks or 300 miles to get a brake fluid low light) there may be no clutch symptoms as the connection to the clutch master stayed covered with fluid.

Most clutch systems that share the reservoir with the brakes has the take-off point for the clutch in an area where a leak in the clutch circuit will not suck all of the brake fluid out of the brake side, causing a lack of braking action. So I figure Jon caught this fluid loss before any ports/tubes got uncovered by the brake fluid.

Brian

[Jon K]

on thing i noticed is that yes the fluid dings low but its not empty nor is it really all that close. It was at this same level last weekend. I wonder if it will keep leaking itself, or if its only leaking to a certain point... hm

[Elekta]

Dot 3 brake fluid will toast those grommets. No need to ask me how I know that.

Stick with oem fluid after you change out the grommets and you should be fine.

[Jon K]

I use ATE Super Blue

[bsell]

on thing i noticed is that yes the fluid dings low but its not empty nor is it really all that close. It was at this same level last weekend. I wonder if it will keep leaking itself, or if its only leaking to a certain point... hm

If you had a crack pretty high on the plastic tank, you could get the same symptoms but would have a mess underneath the master cylinder. I'm betting on the hose that connects the tank to the clutch master. (No money, only pride on the line:D )

Brian

[Jon K]

Well I did some testing - the reservoir area looks dry really. I couldn't see any considerable moisture that brake fluid would leave. I backed out of my oil soaked parking spot and started pumping the brakes. I am not convinced the pedal is losing pressure - it seems pretty firm.

However, was 2 drops about 2" apart (along with oil drops too) when I moved the car forward. Like an idiot I didn't mark where the car was so I can't be sure where it came from. I am going to top the fluid off tonight and drive it and get it on a lift Saturday and have my friend pump the brakes like I did until it drips with cardboard under it on the lift and see where it's coming from. I guess its good news that it's dripping externally, or so I think.