Glazedham42

iTrader: (4)

Okay guys, this should be a fairly easy one. I was working on putting in the new brake master cylinder last night. I was cleaning off the black plastic cap that goes on the reservoir and noticed that there was a hole in the top of it. Nothing big, it's a very small hole. It is about the size of a pencil point. If your cap is really dirty, clean it off and let me know if your has a hole in it. It may be clogged up with grime.

Is the hole supposed to be there or is that why my brakes have been so spongy always? Just thought I'd make sure. Sometimes it's the little things that count in the end....

Jamie

Pele

iTrader: (28)

It's just the vent incase you overflow the resivour when returning fluid backwards through the system. (IE, pushing caliper pistons back in.) Or to let air in as the fluid goes down.

Keep grime out of it, but I'd say it's not causing your problem.

IanS

iTrader: (4)

I have same problem. Happened after I replaced the front brake pads. I thought it was air in system so I bled the entire system starting at the back and working my way up front. I bled at least 2 reserviors (sp) full of fluid and still same problem. 1 pump and then it feels like it should when braking. Let me know how you fix it.

ddewhurst

Guys, your inline master cylinder is just what the word inline means. The master cylinder is two separate cylinders that are in a straight line. The rear cylinder is for the rear brakes. The forward cylinder is for the front brakes. When you do the brake bleed process by starting with the longest brake line first & the shortest brake line last after you bleed the longest two lines & you have a very stiff pedal when the pedal is pushed half way down. That stifness is coming from well bleed rear brakes. The issue after you have finished bleeding the front brakes & still have a spongy pedal is that while you are steping on the brake pedal bleeding the front brakes the brake pedal stops because of the well bleed rear brakes. The brake fluid is solid from the rear cylindrer of the master cylinder through the rear brake cylinders & you are not allowed to compress the front cylinder of the master cylinder far enough to bleed ALL the air out of the front brakes.

With the brake system on my 1st gen race car I installed a Speed Bleed valve within the brake line that travels to the rear of the car. The Speed Bleed valve is installed very near the Master cylinder with a hose connected to the Speed Bleed valve that travels to the un-caped Master Cylinder so that while I'm bleeding the front brakes with the Speed Bleed valve cracked open the fluid from the rear brake line flows back into the Master Cylinder allowing full stroke of the rear cylinder of the Master Cylinder & full stroke of the forward cylinder of the Master Cylinder so the the air is flowed out the front wheel cylinder bleed valves. A Speed Bleed is about the same size as a normal cylinder bleed valve excpt that a Sped Bleed valve has a built in check valve that allows fluid to flow out but no air to flow in. I also have Speed Bleed valves at each wheel cylinder so the the brake bleed job is a one person deal.

You can also accomplish the same bleed process by having two helpers. while someone pumps the brake pedal have a person at the front bleed a wheel cylinder while a person is at the rear opening a rear cylinder bleed valve at approx the same time. Again this process will allow you to get full pedal/front/rear
cylinder travel to flow the air to the front bleed valve.

Works for me
David

Pele

iTrader: (28)

You can also pressure bleed.

Jack the car up and remove all four wheels.

Cut up an old bicycle inner tube. (Leave maybe 6 inches on one side of the valve stem so that you can tie it in a knot. Leave however much you want on the other end.)

Stretch the tube over the mouth of the resivour. Pump the tube up to a couple PSI and loosten bleeders at the closest wheels first (Driver's front, Passenger's Front, Driver's Rear, Passenger's rear... In that order, RHD or LHD.)

Remember to check the tube pressure and fluid level regularly.

Works well and no pedal pumping necessary. Sometimes a good rubberband or zip tie holds the inner tube on the resivour well.

jimmdog

Sweet *** Garage trick. I have a Vacula Bleeder but I wish I had herd of this Inner tube trick before