Hello everyone,

Well, I thought I needed a master cylinder, but now Im not so sure. I own a 1989 C4 coup. I noticed a high pitch squeal..not from the rotors and calipers, but from the area of the master cylinder. I was also going through a cup of brake fluid in the rear reservoir every other day...So after some examination, I noticed that the master cylinder was loose on one side from the brake booster. Consequently fluid is leaking through the brake sensor hole...weird. I took my baby to the chevy dealership and they thought a new sensor should fix it..hopefully....I have tightened the master cylinder back up to the brake booster and a new sensor will be here tomorrow. What Im wondering is if I even need that? What are the chances that due to the loose connection with the booster, air got in the cylinder and it was expelling it from the path of least resistance?...Im not sure...but with the economy being what it is, and there seems to be a shortage of reman master cylinders..( all the box stores tell me they are back-ordered for even their vendors) .....I cant at this time afford a new one....any thoughts, ideas or suggestions would be welcom....thanks in advance..Sean:banghe ad:

 

If you are getting a whissle type noise from the booster chances are you are going to need a new booster. The booster has a bladder and it is in no way sealed by the Master Cly. As far as the fluid leak may be sensor but may be cylinder. just a opinion

 

the whistling was probably caused by fluid in the vac check valve and made noise as you stepped on the pedal and vac entered...I'd bet the vac line is wet inside from sucking fluid thru into the plenum. ...Thats got to be odd..car smokes when you step on the brakes....weird.

Don't try to disassemble the booster...it has a large spring that hurts alot when it jumps out and hits you in the face......

Shop the usual Vette catalog stores for a MC. Also look at EBAY for any of a thousand sellers that offer reman, used with warranty or even new. Lots of Vette parts stores there that nobody has ever heard of.

 

Remove the nuts that hold the master on and pull the master forward an few inches. First look at rear of master to see if any fluid is leaking out the rear into the booster. If it is the master is probably bad. If it is not, then masters seals are probably good and you just need that one part.

From that point you can decide if fluid is going thru the check valve.

If all is dry maybe the booster is bad, but it usually makes a whoosh or a vacuum leak noise if the bladder in booster is bad.

 

i have a booster from a 92 im pretty sure its still good if it works/fits u can have it for the shipping cost pm me

 

Thanks Trackman, Ill let you know.

Well, after tightening the master cylinder to the brake booster, where it had loosened up,..the squeal is gone,and I have pedal again..Ill know tomorrow whether I'm still loosing fluid...Ill give it a few days and then update you guys...thanks for the advice

 

I'm pretty sure replacing the brake warning indicator will not fix the problem. Once the front/rear bias shuttle moves, it triggers the brake warning light. Fluid is then un-contained and will spew from the indicator.

If the fluid is still leaking from the indicator you can try to move the shuttle with a pick until the groove is centered. You may also need to crack open a front and rear brake bleeder to relax the line pressure before attempting to move the shuttle. Remember to bleed the brakes afterwards.

I blew a caliper seal and had to reset the shuttle in this fashion. It was a PITA but saved the cost of a replacement MC.

Try looking for parts online at Rock Auto and other vendors/sponsors on this forum.

 

If you're leaking brake fluid at the sensor switch you have bad seals. The switch area should be dry inside. You need to rebuild or replace the master cylinder.

 

After a long search of all vendors and ebay I finally came up with a new Raybestos M/C for my 85. Maybe the 89 wont be a one year model and it will be easier to find. Sorry tho, none of them are cheap.