Need to replace the master cylinder... I think. - ZR-1 Net Registry Forums

JT ZR-Won · 01-08-2022

I recently noticed a little tiny puddle of brake fluid coming from underneath the master cylinder area. While running my hand and some clean rags around the entire master cylinder area, brake lines, etc, everything is completely dry except for a very slow drip coming from the bottom of the brake booster. It's been quite a while since I've turned a wrench on these cars and I'm definitely no mechanic, but maybe the back of the master cylinder is leaking into the booster? I'm guessing I need a new master cylinder and possibly the booster as well.

I know the master cylinder on the '90's came with 2 reservoirs on top but mine has only 1 reservoir. The car is modified and I'm thinking the master cylinder could be from a '92 or later? If so, what would be the advantage of that? I attached a couple photos of what is currently on the car.

Thanks in advance for any input.

Jay

GOLDCYLON · 01-08-2022

Quote:

Originally Posted by JT ZR-Won

I recently noticed a little tiny puddle of brake fluid coming from underneath the master cylinder area. While running my hand and some clean rags around the entire master cylinder area, brake lines, etc, everything is completely dry except for a very slow drip coming from the bottom of the brake booster. It's been quite a while since I've turned a wrench on these cars and I'm definitely no mechanic, but maybe the back of the master cylinder is leaking into the booster? I'm guessing I need a new master cylinder and possibly the booster as well.

I know the master cylinder on the '90's came with 2 reservoirs on top but mine has only 1 reservoir. The car is modified and I'm thinking the master cylinder could be from a '92 or later? If so, what would be the advantage of that? I attached a couple photos of what is currently on the car.

Thanks in advance for any input.

Jay

Jay it might have been the only option for the previous owner because I noticed the booster in your picture is a two bolt vs four bolt booster where it mates to the fire wall. He may have simply changed it all out because the lack of availability of the replacement booster. I am not tracking any difference performance as the J55 brake system remained the same throughout the entire ZR-1 production run. The 90 and 91 used the dual reservoir system not sure when the change occurred but maybe 94.

HAWAIIZR-1 · 01-09-2022

The PO might have also upgraded the hose and the slave to later model as I did when I had my 90. Like GC said the 90 booster was hard to find so they changed to later model style. I still have an extra 90 booster that I need to sell. I believe you will find no problem with your booster and it is the master cylinder leaking from behind.

http://www.zr1.net/forum/showthread.php?t=29293

Bleeding the Clutch Hydraulic System (CHS):

There are two versions ('89-'90, '91-'96) of clutch hydraulic Actuators (slave cylinder) for the C4 Corvette. The '89-'90 Clutch Hydraulic System actuator has the feed tube located at 12 o'clock and bleed tube at 10 o'clock. The '91 - '96 Clutch Hydraulic System Actuator has the feed tube located at 12 o'clock and bleed tube at 6 o'clock. This redesign makes the bleed fitting more accessible. Unfortunately, the bleeder horn repositioned to the 6 o'clock position complicates the bleed process due to the fact that air bubbles rise therefore rendering the reverse bleed method as being most effective approach to bleeding the '91 - '96 CHS.

http://www.zfdoc.com/clutch_hydraulic.htm

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32valvZ · 01-09-2022

Quote:

Originally Posted by HAWAIIZR-1

The PO might have also upgraded the hose and the slave to later model as I did when I had my 90. Like GC said the 90 booster was hard to find so they changed to later model style. I still have an extra 90 booster that I need to sell. I believe you will find no problem with your booster and it is the master cylinder leaking from behind.

http://www.zr1.net/forum/showthread.php?t=29293

Bleeding the Clutch Hydraulic System (CHS):

There are two versions ('89-'90, '91-'96) of clutch hydraulic Actuators (slave cylinder) for the C4 Corvette. The '89-'90 Clutch Hydraulic System actuator has the feed tube located at 12 o'clock and bleed tube at 10 o'clock. The '91 - '96 Clutch Hydraulic System Actuator has the feed tube located at 12 o'clock and bleed tube at 6 o'clock. This redesign makes the bleed fitting more accessible. Unfortunately, the bleeder horn repositioned to the 6 o'clock position complicates the bleed process due to the fact that air bubbles rise therefore rendering the reverse bleed method as being most effective approach to bleeding the '91 - '96 CHS.

http://www.zfdoc.com/clutch_hydraulic.htm

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I think youre confusing the clutch hydraulics with the brake hydraulics...

HAWAIIZR-1 · 01-09-2022

Quote:

Originally Posted by 32valvZ

I think youre confusing the clutch hydraulics with the brake hydraulics...

Ha ha! You are right. I shound have just went to sleep!

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secondchance · 01-09-2022

JT ZR-1,

What is pictured does not look like later C4 master cylinder. Master cylinder as well as the reservoir don?t look right and may be from other GM product.

JT ZR-Won · 01-10-2022

Thanks for the input everyone. When I get a little time I'll see if I can't pick up another master cylinder. Hopefully there is not a lot of fluid sitting in the brake booster and it is still good. I was going to take the vacuum line off the booster and run a zip tie to the bottom of the booster to check and see how high the fluid is on the zip tie.

JT ZR-Won · 05-28-2022

UPDATE: I reached out to Marc Haibeck who pointed me in the right direction as far as what master cylinder is on my car. Turns out this master cylinder is from a '97 Camaro SS with a 1" bore.

I just ordered one so hoping to put it in next week sometime. Hoping it will bolt right in (keyword: hoping).. fingers crossed.

Jay

WARP TEN · 05-29-2022

Quote:

Originally Posted by JT ZR-Won

UPDATE: I reached out to Marc Haibeck who pointed me in the right direction as far as what master cylinder is on my car. Turns out this master cylinder is from a '97 Camaro SS with a 1" bore.

I just ordered one so hoping to put it in next week sometime. Hoping it will bolt right in (keyword: hoping).. fingers crossed.

Jay

Great to hear Marc helped you out. Can't go wrong with his advice! --Bob

Young1 · 06-08-2022

Rock auto. $140.99

01-09-2022	#3
HAWAIIZR-1 Join Date: May 2010 Location: Japan Posts: 3,543	Need to replace the master cylinder... I think. The PO might have also upgraded the hose and the slave to later model as I did when I had my 90. Like GC said the 90 booster was hard to find so they changed to later model style. I still have an extra 90 booster that I need to sell. I believe you will find no problem with your booster and it is the master cylinder leaking from behind. http://www.zr1.net/forum/showthread.php?t=29293 Bleeding the Clutch Hydraulic System (CHS): There are two versions ('89-'90, '91-'96) of clutch hydraulic Actuators (slave cylinder) for the C4 Corvette. The '89-'90 Clutch Hydraulic System actuator has the feed tube located at 12 o'clock and bleed tube at 10 o'clock. The '91 - '96 Clutch Hydraulic System Actuator has the feed tube located at 12 o'clock and bleed tube at 6 o'clock. This redesign makes the bleed fitting more accessible. Unfortunately, the bleeder horn repositioned to the 6 o'clock position complicates the bleed process due to the fact that air bubbles rise therefore rendering the reverse bleed method as being most effective approach to bleeding the '91 - '96 CHS. http://www.zfdoc.com/clutch_hydraulic.htm Sent from my iPhone using ZR-1 Net Registry __________________ Craig "ZR-1 NO KA 'OI" "ZR-1 ICHIBAN" 1995 #228 Black/Black with Dunn Heads ZR-1 owner since September 2003 ZR-1 Net Registry Founding Member #0074 NCM Lifetime Member #2048 Last edited by HAWAIIZR-1; 01-09-2022 at 03:16 AM.

01-09-2022	#6
secondchance Join Date: Aug 2006 Location: McLean, VA Posts: 3,703	Re: Need to replace the master cylinder... I think. JT ZR-1, What is pictured does not look like later C4 master cylinder. Master cylinder as well as the reservoir don?t look right and may be from other GM product.

01-10-2022	#7
JT ZR-Won Join Date: Aug 2021 Location: Bradenton, FL Posts: 134	Re: Need to replace the master cylinder... I think. Thanks for the input everyone. When I get a little time I'll see if I can't pick up another master cylinder. Hopefully there is not a lot of fluid sitting in the brake booster and it is still good. I was going to take the vacuum line off the booster and run a zip tie to the bottom of the booster to check and see how high the fluid is on the zip tie.

05-28-2022	#8
JT ZR-Won Join Date: Aug 2021 Location: Bradenton, FL Posts: 134	Re: Need to replace the master cylinder... I think. UPDATE: I reached out to Marc Haibeck who pointed me in the right direction as far as what master cylinder is on my car. Turns out this master cylinder is from a '97 Camaro SS with a 1" bore. I just ordered one so hoping to put it in next week sometime. Hoping it will bolt right in (keyword: hoping).. fingers crossed. Jay

06-08-2022	#10
Young1 Join Date: Sep 2016 Location: Ocala, FL Posts: 870	Re: Need to replace the master cylinder... I think. Rock auto. $140.99 __________________ Steve Young 1991 ZR-1 Quasar Blue Metallic/Black #729 Second Owner 1991 ZR-1 Dark Red Metallic/Black #2040 SOLD 1990 ZR-1 Dark Red Metallic/Saddle #1670 SOLD Double your happiness.....complain half as much.