Weird brakes? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

sixty8chev · 11-29-2003, 02:07 PM

Ok heres the problem
My brakes work well 90% of the time, as well as 4 wheel drums can, but about 2 or 3 times a day the pedal will go slowly to the floor, it comes back up then works fine again.
Its not losing any fluid and I replaced the rear wheel cylinders last month and the fronts in the summer, new shoes at the same times, andits probably been bled about 20 times since to try and get rid of the problem.

SO I'm gonna go out and grab a new master cylinder this morning, but just in case that doesn't do it or if somebody has a suggestion that can save me the drive I would really like to hear it.

*67Fleetsidedream* · 11-29-2003, 02:09 PM

I would think that it is your master cylinder......

Injected68LS1 · 11-29-2003, 02:20 PM

I had the same problem. A new master cyl. fixed it right up.

Hotrod70C10 · 11-29-2003, 02:21 PM

I third that, I had the same problem and a new master cyl. did the job.

sixty8chev · 11-29-2003, 02:37 PM

Thanks guys,
Always good to know somebody else has had the same problem and that it can be fixed.
NOW is there anything i could be lookin out for puttin in the new one?
If i remember correctly a couple have had trouble with the thrust rod fallin out on them , but i think that was only those lucky ducks who've got power brakes.

cableguy0 · 11-29-2003, 08:14 PM

i agree rebuilt master cylinders are junk get a new one and save yourself the aggrevation 6 months or a year from now

**old Rusty C10** · 11-29-2003, 09:41 PM

now i tend to agree with these guys but if ya have a power booster on it it may lose vacuum and cause the pedal to sink i had that with an old chevelle cant remember if there was drums all around or discs up front

gmc67swb · 11-29-2003, 09:44 PM

JUST DID MINE 3 DAYS AGO. MANUAL 4 WHEEL DRUMS. REBUILT UNIT COST ME 16.00 BUCKS WITH LIFETIME WARRANTY AND IT CAME WITH A BLEED KIT. 2 BOLTS HOLD IT ON AND 2 HARD LINES. REAL SIMPLE. THERE IS A GASKET THAT GOES BETWEEN IT AND THE FIRE WALL.

lukecp · 11-29-2003, 11:42 PM

Very simple job. Just make sure to bench bleed it first. I haven't had any problems with rebuilt MC's.....i have a $15 one in my truck and it works great.

The job shouldn't take more than an hour, more like 30 minutes

SWINGSAX68 · 11-30-2003, 12:13 AM

Easy...but make sure you bleed thouroghly!!!!Bench bleed....THEN bleed the cylinders. Check the brakes and give them a good adjustment just to double check. 30 mins and a buddy to pump the brakes.

dinnut · 11-30-2003, 04:16 PM

mine came from autozone for like 17 bucks. works good so far but i need brakes

Injected68LS1 · 11-30-2003, 10:35 PM

I've always wondered how you actually bench bleed a master cylinder. Can somebody enlighten me? I'm sure it's something simple. Thanks.

11-29-2003, 02:07 PM	#1
sixty8chev The Sauz Join Date: Mar 2002 Location: Chilliwack BC, Canada Posts: 149	Weird brakes? Ok heres the problem My brakes work well 90% of the time, as well as 4 wheel drums can, but about 2 or 3 times a day the pedal will go slowly to the floor, it comes back up then works fine again. Its not losing any fluid and I replaced the rear wheel cylinders last month and the fronts in the summer, new shoes at the same times, andits probably been bled about 20 times since to try and get rid of the problem. SO I'm gonna go out and grab a new master cylinder this morning, but just in case that doesn't do it or if somebody has a suggestion that can save me the drive I would really like to hear it. __________________ 68 lwb 2wd (spread between 3 garages) 72 Burb - Flat Deck 92 Yukon 3" lift - 33's - the new bush pig 01 Sierra - Daily Driver (for now)

11-29-2003, 02:20 PM	#3
Injected68LS1 Registered User Join Date: Jul 2003 Location: So. Cal. Posts: 389	I had the same problem. A new master cyl. fixed it right up. __________________ 1968 Chev SWB with 1998 Corvette LS1 305hp and 320 ftlb to the wheels (stock engine!) AEM EMS and wideband O2 sensors Bowtie Overdrive's 700R4, stage 3 Baer 4 wheel discs and 20s http://iciclelanding.com/aperture?album=2049&view=album

11-29-2003, 02:21 PM	#4
Hotrod70C10 Low & Slow Join Date: Dec 2002 Location: Oklahoma Posts: 1,047	I third that, I had the same problem and a new master cyl. did the job. __________________ 70' C-10 LWB Fleetside 4.5/6 drop

11-29-2003, 02:37 PM	#5
sixty8chev The Sauz Join Date: Mar 2002 Location: Chilliwack BC, Canada Posts: 149	Thanks guys, Always good to know somebody else has had the same problem and that it can be fixed. NOW is there anything i could be lookin out for puttin in the new one? If i remember correctly a couple have had trouble with the thrust rod fallin out on them , but i think that was only those lucky ducks who've got power brakes. __________________ 68 lwb 2wd (spread between 3 garages) 72 Burb - Flat Deck 92 Yukon 3" lift - 33's - the new bush pig 01 Sierra - Daily Driver (for now)

11-29-2003, 08:14 PM	#6
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,948	i agree rebuilt master cylinders are junk get a new one and save yourself the aggrevation 6 months or a year from now __________________ Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member.

11-29-2003, 02:09 PM	#2
67Fleetsidedream Wiseass secured himself a BAN Join Date: Nov 2000 Location: MOON!!! Posts: 2,282	I would think that it is your master cylinder......

11-29-2003, 09:41 PM	#7
old Rusty C10 Robert Olson Transport Join Date: Oct 2002 Location: recent transplant to NC USA Posts: 20,310	now i tend to agree with these guys but if ya have a power booster on it it may lose vacuum and cause the pedal to sink i had that with an old chevelle cant remember if there was drums all around or discs up front __________________ Bob 1951 International running on a squarebody chassis "If a man's worth is judged by the people he associates himself with, then i am the richest man in the world knowing some of the fine people of this board" http://67-72chevytrucks.com/vboard/a...t.php?f=25&a=9 (you can review the site rules here!) PM Me for your vehicle/parts hauling needs in the North East US or see my Facebook page Robert Olson Transport Live each day to the fullest.. you never know when fate is going to pull the rug out from under you... I hate cancer!!

11-29-2003, 09:44 PM	#8
gmc67swb Registered User Join Date: Feb 2003 Location: Mesquite, Tx Posts: 396	JUST DID MINE 3 DAYS AGO. MANUAL 4 WHEEL DRUMS. REBUILT UNIT COST ME 16.00 BUCKS WITH LIFETIME WARRANTY AND IT CAME WITH A BLEED KIT. 2 BOLTS HOLD IT ON AND 2 HARD LINES. REAL SIMPLE. THERE IS A GASKET THAT GOES BETWEEN IT AND THE FIRE WALL. __________________ GM 330HP/350, Magnuson 122HH, Tremec TKO 5spd

11-29-2003, 11:42 PM	#9
lukecp Formerly yellow72custom Join Date: May 2001 Location: Austin, TX Posts: 7,531	Very simple job. Just make sure to bench bleed it first. I haven't had any problems with rebuilt MC's.....i have a $15 one in my truck and it works great. The job shouldn't take more than an hour, more like 30 minutes __________________ '72 Chevy C10 Mild 350/TH350/3.07. Ochre/White. Old high school ride. '70 GMC C2500 '62 327 4bbl/SM465/4.56-geared Dana 60. White/White. Project or parts truck. '97 Saturn SL DD. 1.9/5-speed. 40+ highway mpg

11-30-2003, 12:13 AM	#10
SWINGSAX68 Now the others dig........ Join Date: May 2002 Location: San Antonio, TX Posts: 1,520	Easy...but make sure you bleed thouroghly!!!!Bench bleed....THEN bleed the cylinders. Check the brakes and give them a good adjustment just to double check. 30 mins and a buddy to pump the brakes. __________________ 68 Chevy C10 Stepside Black Primer 78 GMC Longbed White 09 Chevy Silverado Shortbed Granite Blue *LOOKING FOR A 67 4 DOOR IMPALA!!!Just like Sam and Dean Winchester!! 'Cause Mustangs are for p^#$ and you can fit a body in the trunk of a 67 Impala* MEMBER OF THE DRUM BRAKE CLUB Bachelor of Music in Jazz Studies Texas State University-San Marcos, TX Certified Music Educator I hope Mom is up there watching and being my Guardian Angel "I've got a fever.....and the only prescription.....IS MORE COW BELL" -The Legendary: Bruce Dickenson "F#$@ 'em up!!!!!!" -The Legendary: Rogelio Escobar TRUCKY LINKS** http://67-72chevytrucks.com/vboard/s...d.php?t=457750 http://67-72chevytrucks.com/vboard/s...d.php?t=461184 http://67-72chevytrucks.com/vboard/s...d.php?t=472848 http://67-72chevytrucks.com/vboard/s...d.php?t=417541 http://67-72chevytrucks.com/vboard/s...d.php?t=477788

11-30-2003, 04:16 PM	#11
dinnut Registered User Join Date: Apr 2003 Location: missouri city, tx Posts: 4,486	mine came from autozone for like 17 bucks. works good so far but i need brakes __________________ 70 longbed 496/th400/Ford 9"

11-30-2003, 10:35 PM	#12
Injected68LS1 Registered User Join Date: Jul 2003 Location: So. Cal. Posts: 389	I've always wondered how you actually bench bleed a master cylinder. Can somebody enlighten me? I'm sure it's something simple. Thanks. __________________ 1968 Chev SWB with 1998 Corvette LS1 305hp and 320 ftlb to the wheels (stock engine!) AEM EMS and wideband O2 sensors Bowtie Overdrive's 700R4, stage 3 Baer 4 wheel discs and 20s http://iciclelanding.com/aperture?album=2049&view=album

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