Isolating a brake leak - Tilted Forum Project Discussion Community

belkins · 03-23-2005, 03:22 PM

I'm trying to isolate a leak in my brake system. There is not any fluid on the floor but I think there might be a small enough leak that air is getting in.

What I wanted to do was plug the port for the rear brakes on the master cylinder and only bleed the front brakes to see if I can get a solid pedal. I'm having a VERY difficult time getting all the air out of the system.

Is there any chance of damaging the seals inside the MC if I plug the port at the MC?

The car is a '71 Lotus Europa.

Thanks.

belkins

grumpyolddude · 03-23-2005, 07:27 PM

When do you get the mushy pedal? All the time? On hard braking? Can you "pump up" the brakes?
Have you tried gravity bleeding the system? Make sure the master is full, then crack open all 4 bleeders and let gravity do the work for a couple of hours. Pay attention that the master stays full. If there's air in the lines, that should purge it.
If you still have a soft pedal, consider that fluid may be bypassing inside the master due to a worn seal between the chambers. A rebuild kit should solve that.
Have fun!

belkins · 03-23-2005, 07:46 PM

grumpyolddude,

Thank you for the reply. Yes, I have the mushy pedal all the time and no, I cannot pump up the brakes.

The position of the master cylinder will not allow me to gravity bleed because the lines go up from the master cylinder (in other words the master is not the highest point in the brake system).

It's a brand new master so I don't think it needs to be rebuilt yet unless all the pumping I've had to do has worn it out! I'm only on about my 28th gallon of brake fluid now or it feels like it anyway!

If this car is a hobby why is it so damn aggravating at times?!

cj2112 · 03-23-2005, 07:59 PM

pull off your drums, look for a leaking wheel cylinder....I'd look there first.

grumpyolddude · 03-23-2005, 08:03 PM

Then I'd suggest a MityVac brake bleeding kit. It's a hand-operated vacuum pump to draw the fluid through the system... comes with a variety of rubber nipples and a cup to catch the fluid. Start with the wheel furthest from the master cylinder and finish with the nearest. The tubing is clear so you can see any air bubbles that you draw through. Keep an eye on the fluid level in the MC ( i keep on saying that, don't I?).

Have fun!

(I'm concentrating on bleeding... no evidence of leaks, right?)

cj2112 · 03-23-2005, 08:10 PM

Quote:

Originally Posted by grumpyolddude

Then I'd suggest a MityVac brake bleeding kit. It's a hand-operated vacuum pump to draw the fluid through the system... comes with a variety of rubber nipples and a cup to catch the fluid. Start with the wheel furthest from the master cylinder and finish with the nearest. The tubing is clear so you can see any air bubbles that you draw through. Keep an eye on the fluid level in the MC ( i keep on saying that, don't I?).

Have fun!

(I'm concentrating on bleeding... no evidence of leaks, right?)

I definitely agree on the MightyVac, I'll never bleed brakes without one ever again. The reason I said to check out the wheel cylinders for leaks, is he mentioned that he's losing fluid. that fluid HAS to be going somewhere.

stingc · 03-24-2005, 05:55 AM

I have a corvette from the same vintage which tends to suck air through the piston seals if the rotors have any runout. Maybe your car has the same issue?

Anyway, I don't think that plugging the MC should be a problem, but you probably shouldn't listen to me

.

belkins · 03-24-2005, 08:00 PM

Thank you for all the replies. I really appreciate all the help that has been extended.

Quote:

I definitely agree on the MightyVac, I'll never bleed brakes without one ever again. The reason I said to check out the wheel cylinders for leaks, is he mentioned that he's losing fluid. that fluid HAS to be going somewhere.

No, I'm not losing fluid. If I mentioned that I was I made a mistake but I don't see where I may have mentioned it.

Edit: I see where I said that! What I meant is an air leak. Yeah, I wasn't real clear on that point.

I've rebuilt the front calipers and the wheel cylinders on the rear drums are new as well. The entire brake system is brand new except for the brake lines, rotors, drums and backing plates on the rear drums. I've been having the bleeding problem since replacing the brake system.

I purchased an Eezibleed system. Some people have told me that if there is a lot of air in the system (which I'm pretty sure there is) that the MityVac won't work as well as doing a pressure bleed (which is how the Eezibleed works).

I did borrow a MityVac from a friend as well just in case!

I'll keep you informed as to what the outcome is.

james t kirk · 04-02-2005, 06:45 AM

If you are not losing fluid, and you are not getting bubbles coming out of the bleeders, then you definitely have a defective master cylinder.

New or not, sometimes even a new part can be bad.

I installed a brand new clutch on my car once and the clutch ended up with a a jerky feel to it. After replacing just about every other clutch componet (master, slave, pedal bearings, actuating mechanism) I finally bought another new clutch and voila, problem solved.

03-23-2005, 03:22 PM	#1 (permalink)
belkins Tilted Location: Salt Lake City	Isolating a brake leak I'm trying to isolate a leak in my brake system. There is not any fluid on the floor but I think there might be a small enough leak that air is getting in. What I wanted to do was plug the port for the rear brakes on the master cylinder and only bleed the front brakes to see if I can get a solid pedal. I'm having a VERY difficult time getting all the air out of the system. Is there any chance of damaging the seals inside the MC if I plug the port at the MC? The car is a '71 Lotus Europa. Thanks. belkins

03-23-2005, 07:27 PM	#2 (permalink)
grumpyolddude Deliberately unfocused Location: Amazon.com and CDBaby	When do you get the mushy pedal? All the time? On hard braking? Can you "pump up" the brakes? Have you tried gravity bleeding the system? Make sure the master is full, then crack open all 4 bleeders and let gravity do the work for a couple of hours. Pay attention that the master stays full. If there's air in the lines, that should purge it. If you still have a soft pedal, consider that fluid may be bypassing inside the master due to a worn seal between the chambers. A rebuild kit should solve that. Have fun!

03-23-2005, 07:46 PM	#3 (permalink)
belkins Tilted Location: Salt Lake City	grumpyolddude, Thank you for the reply. Yes, I have the mushy pedal all the time and no, I cannot pump up the brakes. The position of the master cylinder will not allow me to gravity bleed because the lines go up from the master cylinder (in other words the master is not the highest point in the brake system). It's a brand new master so I don't think it needs to be rebuilt yet unless all the pumping I've had to do has worn it out! I'm only on about my 28th gallon of brake fluid now or it feels like it anyway! If this car is a hobby why is it so damn aggravating at times?!

03-23-2005, 07:59 PM	#4 (permalink)
cj2112 Unbelievable Location: Grants Pass OR	pull off your drums, look for a leaking wheel cylinder....I'd look there first.

03-23-2005, 08:03 PM	#5 (permalink)
grumpyolddude Deliberately unfocused Location: Amazon.com and CDBaby	Then I'd suggest a MityVac brake bleeding kit. It's a hand-operated vacuum pump to draw the fluid through the system... comes with a variety of rubber nipples and a cup to catch the fluid. Start with the wheel furthest from the master cylinder and finish with the nearest. The tubing is clear so you can see any air bubbles that you draw through. Keep an eye on the fluid level in the MC ( i keep on saying that, don't I?). Have fun! (I'm concentrating on bleeding... no evidence of leaks, right?)

03-24-2005, 05:55 AM	#7 (permalink)
stingc Psycho Location: PA	I have a corvette from the same vintage which tends to suck air through the piston seals if the rotors have any runout. Maybe your car has the same issue? Anyway, I don't think that plugging the MC should be a problem, but you probably shouldn't listen to me .

04-02-2005, 06:45 AM	#9 (permalink)
james t kirk Junkie Location: Toronto	If you are not losing fluid, and you are not getting bubbles coming out of the bleeders, then you definitely have a defective master cylinder. New or not, sometimes even a new part can be bad. I installed a brand new clutch on my car once and the clutch ended up with a a jerky feel to it. After replacing just about every other clutch componet (master, slave, pedal bearings, actuating mechanism) I finally bought another new clutch and voila, problem solved.