Riddle me this...

#1

Hoping the Spec E30 family can help me get to the bottom of an odd braking issue.

Symptoms

Topping off brake fluid to the max line results in “draining” back to a level just below Max. The fluid level drops back to the original lower level and holds. “Draining” is in quotes because the fluid is going somewhere, we just don’t know where that somewhere is. The level the reservoir drains to is just below the lower lip of the opening (I’ll take some pics and post shortly).
I’m also noticing the front calipers are sticking - they are relatively new remans.

Troubleshooting to date:

We removed the mater cylinder. It was dry at the shaft seals and the brake booster looked dry as well.
We checked the braided and hard lines at the four corners (next we’ll trace each hard line back to the master).
We checked the clutch slave cylinder
We checked the lines around the ABS system
There are no puddles of brake fluid anywhere.
We bled the system several times. And have since poured one Full bottle of ATE Type 200 into the reservoir - it’s going somewhere, perhaps Narnia?

Mid-Ohio is looming and I’d quite like to slow the car down at the end of the back straight.

I’m welcome to any thoughts at this point. Thanks in advance for the help.

#2

Is there any fluid on the frame rail below the booster?

#3

Drivers footwell, if the soft line to clutch MC leaking?

#4

No fluid on the frame rail below the booster.

#5

Drivers footwell is dry. Though I’ll dig through the wiring under the dash this evening as I wasn’t able to get eyes on the clutch master. The is a small section of factory sound deadening still on the bulk head that may be soaking up some fluid. But not large enough to consume a whole can.

#6

Come to think of it, we did isolate the clutch hydraulics altogether. We disconnected the soft line on the drivers side of the reservoir and capped it off. We re-did the same fill test and the fluid level still “drained” to the same low level.

Here’s a shot of reservoir. If we fill it to the brim, it will eventually drain to the level you see (about 1/4’ below the small relief hole in the dirt screen basket).

#7

Only idea I can come up with is to keep pouring fluid into it. Maybe get some cheap brake fluid at the local autoparts store if you’re tired of paying $15/can. Eventually a puddle of fluid has to show up somewhere. Has to. Has to, has to.

Be darn careful not to spill a drop as you pour fluid in. Otherwise, when a little puddle appears the following night under the MC the uncertainty will be painful.

#8

Am I the only one thinking normal? He isn’t saying that the entire reservoir is emptying itself, then looking at his picture that looks pretty normal to me. I mean we are talking about draining from max to just below max.

#9

I’d agree except that he apparently put in a full can and sees this same behavior each time.

OP, let me wax poetic re. how the last bit of fluid behaves when you pour it in. Consider if you are seeing the same thing, just seeing a bit more of the behavior (a can of it).

When you pour the last couple of tablespoons of fluid into the cylindrical opening of the reservoir, it will fill to the top even tho you can see trapped air in the reservoir below. It takes a while for those couple tablespoons to drop away and for some of that air to gurgle out. Sometimes those couple tablespoons will be devilish and won’t drop because air doesn’t want to come out. Then when you put the cap on, the cap’s float, pushes fluid out of the reservoir on to the ground. Other times you just have to be patient and fill the cylinder with fluid over and over again as the trapped air comes out in fits and starts.

The problem with fitting your situation with the above behavior is that you’ve gone thru a whole can of fluid apparently doing exactly what I just described. I could understand a half-cup, but there’s not going to be a can of trapped air in the reservoir so the fluid has to be going somewhere.

#10

are you saying that you have to keep adding fluid after driving or after it sits?

#11

Hmm, seems pretty odd. Anyone think the fluid could be getting sucked into the booster and consumed by the engine?

If not, that seems like a pretty small volume of fluid, basically the volume of the filler neck. I could believe it is weeping out through the cap slowly enough that you don’t see much residue on top of the plastic reservoir.

My final thought is, if hitting yourself in the foot with a hammer hurts, but it feels better when you stop, maybe you could just stop.

As in, don’t fill it beyond the fill mark on the side of the reservoir, which I believe is below the level of the filler neck entirely, and move on.

#12

I’m putting my money on inside the booster

#13

[quote=“bedmonds” post=80581]are you saying that you have to keep adding fluid after driving or after it sits?[/quote

Here’s the play-by-play:

The issue started during a Practice session. The brake light came on during the session despite braking performance feeling completely fine. To play it safe, I brought the car in to have a look-see. We found the brake fluid a little low. I thought this was odd because I had just replaced the front calipers and did a four corner bleed. Pedal was firm. So we went to top of the fluid and then proceeded to watch it drain slowly to just below max. We added more fluid, it would drain to the same spot. We repeated this about 4 or 5 times. Then we re-bled the brake at all four corners. The brake pedal was rock hard the entire time and braking effectiveness was fine. Before doing what Ranger suggested (keep adding fluid), we isolated the clutch hydraulics to rule out clutch master and slave, plus clutch line leaks. The issue continued. We pulled the brake master cylinder which was dry and checked the brake booster for fluid. It too was dry. At that point we resolved to keep adding fluid to see if we could make it pool up somewhere and finally the reservoir stopped exhibiting the "draining’ behavior, holding right at Max. We poured in nearly an entire can of fluid. With shaky confidence in my braking ability, I took to the track and qualified the car for the race. There were no issues with braking. Pedal remained rock hard for the entire session.

During the race, I was tagged in the passenger quarter/rear wheel and spun. We recovered from spin and finished the race. However, after the hit I started getting an intermittent and soft pedal. It got worse as the race went on finally resulting in the pedal going to the floor every 4th or 5th braking attempt. In each case I could pump the brakes up prior to hard braking. I slowed significantly to basically keep testing the pedal for the last couple laps. After the race, the reservoir was right back at the same low level. I added fluid, it “drained” to points unknown. The key difference now is that the pedal is soft and basically goes to the floor every 3rd or 4th braking attempt.

On our Great Lakes message board, a fellow competitor recommended disconnecting the vacuum line to the brake booster to test. I’ll try that next. I’m going to go ahead and swap in new braided lines (they’re older and it’s always good to replace them from time to time). I’m also going to replace the master cylinder and swap in new calipers. I’ll also re-trace each hard line. But at this point I’m basically guessing and throwing parts at the car.

Thanks for your posts and questions. I think this is a good discussion and with your help we’ll get this sorted.

#14

Disconnecting the booster isn’t a useful test for this. Nothing about the booster is going to cause the symptoms you described.

I figure that either it’s a leak, or you’re looking at the normal behavior of trapped air in the reservoir. You have a 2nd issue now, soft brakes. Maybe wherever it’s leaking (which isn’t proven) allowed some air into the system when the car got banged.

I would suggest doing a good bleed to get the brake pedal hard again. Then keep pouring fluid in. But don’t focus on the cylindrical port at the top of the reservoir. Just fill it to the Full mark on the side of the reservoir and see if it stays there. If you have to keep pouring in fluid, that’s fine…eventually the leak will show up.

#15

I think you are losing fluid on track and the fluid is not “disappearing” but rather replacing the lost fluid. The soft pedal would support this theory. Are you using a pressure bleeder to bleed the system?

#16

It’s going somewhere for sure. And we are certainly replacing what is being lost. Ranger’s air in he system theory did occur to a friend’s IT car a few years again. He was hit, it prang’d the brake distribution block at the rear of the car. While no fluid leaked out, it would draw in air over time. I fear finding the cause will be a challenge.

I’ll do another bleed when the new brake lines arrive and report back. In the meantime all ideas are welcome.

#17

Kyle,
Check out the portioning valve. We have not had the problem, so no first hand information. Dave Harrington chased phantom brake problems for a year. He took apart, inspected, cleaned every piece of the brake hydraulic system.I think he finally found partially clogged or stuck valve - not sure. Try reaching out to him for suggestions.
Good luck.

#18

[quote=“SGrace” post=80600]Kyle,
Check out the portioning valve. We have not had the problem, so no first hand information. Dave Harrington chased phantom brake problems for a year. He took apart, inspected, cleaned every piece of the brake hydraulic system.I think he finally found partially clogged or stuck valve - not sure. Try reaching out to him for suggestions.
Good luck.[/quote]

I did order a new proportioning valve to swap in while I have everything apart. I’ll reach out to Dave as well. Thanks!

#19

For those who may read this post later. I ended up swapping the following parts in the order listed. We tested the pedal feel in between most of the parts replacement trying to isolate the issue.

Master Cylinder (Good bleed, fluid level holds at this point - we checked the brake booster, it was dry as a bone and had good vacuum - pedal was no longer going to the floor).
Front calipers, lines and pads (After another good bleed the pedal was still soft - we cycled the ABS pump and ran each of the 3 solenoids and bled some more)
Brake proportioning valve
Rear calipers and pads
Another good bleed

After replacing the brake proportioning valve, rear calipers and pads we did notice a bit better pedal feel. Still lower than before but consistent. I should say we switched to manual bleeding as we didn’t want to introduce air with the pressure bleeder.

Since we swapped nearly everything, I will adjust the brake pedal itself next using this post. That should have us back to normal.

#20

Did you figure this problem out? I have had what I thought was a slow leak for a while, just no evidence, and pedal will slooooowly go to the floor if you stand on it. Well the car was sitting at the shop for two weeks, and it has lost all the fluid in the reservoir. No sign of fluid leaks anywhere. Grrrrr.