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Hey guys, I've got a strange problem with my 1987 300zx. For a long time I've noticed it slowly leaks brake fluid, so i have to top it off every once and a while, but last night after a drive, I noticed a strange noise. Coming from right around the Master Brake Cylinder, I could hear what sounded like macaroni and cheese cooking on the stove lol. It was very liquidy bubbling sort of noise, and what I assume this to be is a damaged seal and the noise of the pressure escaping the cylinder, bubbling through the liquid. I hope that it isn't anything more serious than that! I've posted a video on my YouTube channel of the noise and you can find it here:
Any help on this crazy noise would be greatly appreciated! Thanks. -Retro
 

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My best guess is that either you have a dragging brake that's heating and boiling the fluid, or you have a bad master cylinder.

Have you checked the brakes on each corner after driving to see if one is significantly hotter then the others (careful - it would be very hot.)
 

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My best guess is that either you have a dragging brake that's heating and boiling the fluid, or you have a bad master cylinder.

Have you checked the brakes on each corner after driving to see if one is significantly hotter then the others (careful - it would be very hot.)
Ahhh, I haven’t actually checked that, I know that the brake calipers in the rear of the car tend to stick, and on occasion I have to tap them with a rubber mallet to loosen them up, I didn’t even think about that, don’t know if that’s what would be doing it. Also I had to replace both clutch cylinders because of bad seals, so I probably need to replace the brake cylinder as well whether it’s bad or not. I don’t know exactly how to check to see if the cylinder is bad though other than to just replace it and see if the problem persists. Thanks for the help though! I’ll have to keep investigating. Also any testing information for those issues would be very useful and appreciated! Thanks! -Retro
 

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If your rear brake calipers are hanging up occasionally, I suggest that you replace them. You could easily get stranded by that. I've had a caliper on a Jeep decide to hang up and start heating, and it took me two hours to nurse the vehicle to Denver, stopping every few miles to find water I could pour on the caliper and wheel to cool them off. I barely made it, and if I hadn't caught it I could easily have had a fire.

How often have you changed brake fluid? This can be caused by water accumulating in the brake fluid and corroding the caliper bores. That's nothing to fool with. The test is: does the caliper hang up? If it does, you've done the test and determined the problem. Most of us don't do it often enough, but brake fluid should be replaced every 3 years or so.

You can also pull the calipers, hone out the caliper bores and rebuild the calipers, but that's more than many people want to mess with and I've never looked for rebuild kits. EDIT: yes, the kits are easy to find with a Google search. Not too expensive either.
 

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Discussion Starter #5
If your rear brake calipers are hanging up occasionally, I suggest that you replace them. You could easily get stranded by that. I've had a caliper on a Jeep decide to hang up and start heating, and it took me two hours to nurse the vehicle to Denver, stopping every few miles to find water I could pour on the caliper and wheel to cool them off. I barely made it, and if I hadn't caught it I could easily have had a fire.

How often have you changed brake fluid? This can be caused by water accumulating in the brake fluid and corroding the caliper bores. That's nothing to fool with. The test is: does the caliper hang up? If it does, you've done the test and determined the problem. Most of us don't do it often enough, but brake fluid should be replaced every 3 years or so.

You can also pull the calipers, hone out the caliper bores and rebuild the calipers, but that's more than many people want to mess with and I've never looked for rebuild kits. EDIT: yes, the kits are easy to find with a Google search. Not too expensive either.
Ahhhh gotcha, I’ve only had the car for about a year now and I’ve had to change the brake fluid twice due to it leaking and the cylinder draining. I’m not sure sure how often but was changed before I owned it. Also I definitely need some new calipers, the ones on there are rusted and definitely stick to the brake disc. I’ll look into replacing those calipers, I hope that’s whats wrong with it! Thanks for the help, -Retro
 
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