Issues with master cylinder cap? - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

young51 · 07-11-2019, 08:25 PM

Guys please tell me I'm just being paranoid but my master cylinder cap seems a bit on the "cheap" side in material and operation. I swear it takes only a quarter turn or so to loosen or tighten it. It seems like I barely touch it and it wants to come off. anyone else have this issue? Is there a good fix or a replacement cap that works better? I come from a hotrod/custom background and am used to all billet/metal MC's and caps, the plastic ones kinda make me cringe...is this normal or should I replace it? Thanks in advance.

BUBZ28 · 07-11-2019, 10:53 PM

Just checked mine. There's a little tension but not much. Not enough to make me worry about it coming off.

John_C · 07-11-2019, 11:02 PM

Mine has started slightly leaking actually.

Only 50k miles on the car....

D2M · 07-12-2019, 08:28 AM

I cut out a thin round cardboard shim to put between the rubber boot and plastic cap. It tightens up the cap nicely and prevents any leakage even when on track. I used a USPS envelope, about 1/16 thick cardboard. You can stack 2 shims if needed. I have done this on many of my previous cars without any issues.

Katech_Zach · 07-12-2019, 10:21 AM

There was a TSB on these awhile back. Be very careful when replacing brake pads if you did a fluid change while the brakes are worn. Compressing the pistons back into the caliper can cause the fluid to overflow out of this cap.

young51 · 07-12-2019, 03:10 PM

D2M, rubber boot? The cap just threads to the plastic reservoir tank. Do you mean place the shim into the cap and then thread it on? or remove something from the cap, then put in the shim and then replace other part and thread on? thanks

havelegs · 07-12-2019, 10:00 PM

I bent the tabs on the cap down so the cap fits snug when on.

Mgizzle · 07-13-2019, 09:53 AM

All caps are a small turn to open close like a quarter turn or so. Dont put anything in your cap, brake fluid eats about everything and any contamination can wreck havoc in the abs and other seals. Just buy a cap band for it, I bought these brembo ones and put around the cap. Every cap also has a vent hole so the rubber membrane works to relieve pressure as well.

https://www.ebay.com/p/Sweat-Band-Bl...SABEgJenvD_BwE

D2M · 07-13-2019, 10:37 AM

The cap consists of 2 parts, a rubber boot and plastic cap housing. Remove the boot and place 1 or 2 thin round shims inside the cap and replace the boot. This is a spare cap for my bleeder. I have had this same setup on my Z/28 since new and previous cars, not a drop of fluid seepage. I did also use the external cloth sock just in case but it never got a drop on it.

young51 · 07-17-2019, 12:56 PM

D2M, great, thanks for the tip!

pat_t · 07-17-2019, 02:03 PM

Great tips on this thread! Why I love this forum. Mine has been bugging me for a while now! I'll try shimming it

07-11-2019, 08:25 PM	#1
young51 Drives: 2015 z/28 Join Date: Apr 2018 Location: Bay Area Posts: 39	Issues with master cylinder cap? Guys please tell me I'm just being paranoid but my master cylinder cap seems a bit on the "cheap" side in material and operation. I swear it takes only a quarter turn or so to loosen or tighten it. It seems like I barely touch it and it wants to come off. anyone else have this issue? Is there a good fix or a replacement cap that works better? I come from a hotrod/custom background and am used to all billet/metal MC's and caps, the plastic ones kinda make me cringe...is this normal or should I replace it? Thanks in advance.

07-11-2019, 11:02 PM	#3
John_C LSx FTW!!! Drives: 2010 Camaro 2SS RS Join Date: Jan 2017 Location: TN Posts: 767	Mine has started slightly leaking actually. Only 50k miles on the car.... __________________ 2010 2SS RS A6 781rwhp on E85 Stage 2 ProCharger D1X Circle D 3400 Triple Disc Kooks Jet Hot Headers Kooks Full 3in exhaust Trick Flow GenX 255's Polished PAC .660's & Ti-retainers TSP VVT 3.2 cam kit w/DoD Delete Smith Bro's Trunnion kit AEM X-Series OBDII Widebands FIC ID1300x Injectors GM ZL1 High Output Fuel Pump DSX Tuning Flex Sensor DSX Auxiliary Fuel System Tim King Stage 4 Max Effort CTSV 6L90 DSS 1 piece aluminum driveshaft JRE 6L80E / 6L90E Dipstick NGK Iridium IX spark plugs #7 heat range Mighty Mouse Camaro 5 Wild w/-12an and Billet Black HP Tuners VCM Suite

07-12-2019, 10:00 PM	#7
havelegs Drives: '23 LT1 A10 Join Date: Oct 2015 Location: Austin Texas Posts: 1,005	I bent the tabs on the cap down so the cap fits snug when on. __________________ 24 LT1 M6 Sharkskin Metallic 14 Mazda Mazda3 S Grand Touring (Daily)

07-13-2019, 09:53 AM	#8
Mgizzle Drives: 2013 Camaro 1LE 1SS Join Date: Aug 2012 Location: Detroit Posts: 1,252	All caps are a small turn to open close like a quarter turn or so. Dont put anything in your cap, brake fluid eats about everything and any contamination can wreck havoc in the abs and other seals. Just buy a cap band for it, I bought these brembo ones and put around the cap. Every cap also has a vent hole so the rubber membrane works to relieve pressure as well. https://www.ebay.com/p/Sweat-Band-Bl...SABEgJenvD_BwE __________________ I work for General Motors and am not an official spokes person for General Motors. My views and opinions are my own and not those of General Motors.

07-13-2019, 10:37 AM	#9
D2M Drives: Z/28 Join Date: Oct 2015 Location: NJ Posts: 538	The cap consists of 2 parts, a rubber boot and plastic cap housing. Remove the boot and place 1 or 2 thin round shims inside the cap and replace the boot. This is a spare cap for my bleeder. I have had this same setup on my Z/28 since new and previous cars, not a drop of fluid seepage. I did also use the external cloth sock just in case but it never got a drop on it. Attached Images

07-11-2019, 10:53 PM	#2
BUBZ28 Drives: '15 Z/28 #0270 Join Date: Jan 2017 Location: San Pablo, CA Posts: 85	Just checked mine. There's a little tension but not much. Not enough to make me worry about it coming off.

07-12-2019, 08:28 AM	#4
D2M Drives: Z/28 Join Date: Oct 2015 Location: NJ Posts: 538	I cut out a thin round cardboard shim to put between the rubber boot and plastic cap. It tightens up the cap nicely and prevents any leakage even when on track. I used a USPS envelope, about 1/16 thick cardboard. You can stack 2 shims if needed. I have done this on many of my previous cars without any issues.

07-12-2019, 10:21 AM	#5
Katech_Zach Drives: 14 Camaro SS 1LE Join Date: Feb 2019 Location: Clinton Twp, MI Posts: 483	There was a TSB on these awhile back. Be very careful when replacing brake pads if you did a fluid change while the brakes are worn. Compressing the pistons back into the caliper can cause the fluid to overflow out of this cap.

07-12-2019, 03:10 PM	#6
young51 Drives: 2015 z/28 Join Date: Apr 2018 Location: Bay Area Posts: 39	D2M, rubber boot? The cap just threads to the plastic reservoir tank. Do you mean place the shim into the cap and then thread it on? or remove something from the cap, then put in the shim and then replace other part and thread on? thanks

07-17-2019, 12:56 PM	#10
young51 Drives: 2015 z/28 Join Date: Apr 2018 Location: Bay Area Posts: 39	D2M, great, thanks for the tip!

07-17-2019, 02:03 PM	#11
pat_t Drives: . Join Date: Jun 2016 Location: . Posts: 589	Great tips on this thread! Why I love this forum. Mine has been bugging me for a while now! I'll try shimming it