Brake Master Cylinder Upgrade GMT 400 '88-'98 Trucks

[@cyclingfan2010]

I have a 1988 C1500. I’ve changed the front calipers and hoses, rear wheel cylinders, all new lines and a master cylinder. Brakes are still soft and pedal travel is long. I’ll be doing this upgrade along with the rear ABS delete this weekend. Thanks for posting the video! Todd

[@MOE13576]

Update ?

[@KableTac]

I put a gmt800 mc on mine a few years ago and i can confirm that this will undoubtedly make your gmt400 stop on a dime, no squish at all on the pedal. Nothing else in the brake system matters if you're trying to get rid of the soft pedal. You don't need to make new lines or anything if you're careful with the original lines and slowly bend them in a way that it'll route to the shorter mc connections. All you need is 1 adapter that's commonly found at auto stores

[@Busadventures72]

I just did the upgrade this morning Friday March 24 2023 the brakes are so much better

[@pantherplatform]

Did this yesterday on a 1994 suburban. Had to make custom lines from the MC to the proportioning valve since the 1/2 20 inlets were a little closer to the booster than the old rectangular shaped one. Used the pressure bleeder to bleed the mc, abs modulator valve and all four wheels. Now it has a rock hard pedal, stops right away and the abs works!

[@Blugiatos]

I was about to do mine until I ran into that problem do you have a video of you doing it or a picture of it so I can see what you did?

[@HiredGun5]

Will be doing this on my '94 C-1500 this afternoon. Picking up parts on my way home. I pull heavy trailer and loads with mine, and it's not a fun feeling when you make the last twenty miles of a run stopping with just the trailer brakes!!! THANK YOU!!

[@whiterose7909]

I'd already thought about this conversion so I went to a junkyard and picked up a master cylinder. That's when I found out oh s*** I need an adapter. That's all the information I needed but I end up watching the entire video. Great information and great presentation

[@vehdynam]

Thank you ; I have been chasing this issue for years.

[@jessphuqette1716]

Thank you for making a clear concise video. So many people making these vids are so inept that it makes me question their mechanical abilities. Keep up the good work. I just subscribed

[@ITSNOTMEITISYOU]

Hate to sound unoriginal here but thanks for taking the time to share this. Just inherited my Dads pretty clean 97 GMC and it definitely has that low pedal…..but not for long!

[@playsportfun3356]

My 03 dmax pedal was horrible from the factory. Improved it a little. But always a you say spongy. I have 2 05s and a 88 and those pedals are right up there firm, very little travel. I would do the opposite, I would put a OBS master on a NBS.

[@alansand7116]

i changed my brake booster & the new style master Cylinder, & i have good brakes but they are going almost to the floor, after bleeding twice. I cant figure out why i have no pedal. I gave up & put the OE master Cylinder back on. Works great...

[@compassionate_scum4637]

Maybe you just got a bad unit

[@donaldsposatojr1521]

With this change does the proportioning valve need to be updated aswell?

[@markoconnell9219]

Great Info! I have a 1988 Suburban and Just ordered a 2002 Master cylinder. Excited to install. I did just like you and replaced everything, including getting rid of the assembly valve at the back that was connected to the rear axle.

[@9thGenAccord]

Right on!

[@TXPRODUCT]

Thanks for the video. I just swapped out mine. For some reason my factory line won’t bottom out to the adapter. Any thoughts or suggestions? Thanks in advance

[@CoolCarsKJ]

Is that a hydrooboost unit? why does it have that nipple poking out the front? did you just cap it?

[@Generalpurpose702]

I’m going to do that upgrade because I have a power master brake bleeder adapter that fits the upgrade master cylinder

[@JedediahBryant]

Does this work on hydro boost trucks/suburbans? And does proportioning valve need changed since going from disc drum to disc disc MC?

[@gtuttle4]

Great video, I may do this on my 89 Chevy K1500!

[@flyntmyrick6291]

Was it worth the effort? What changes did it make on your truck if any?

[@gtuttle4]

@@flyntmyrick6291 Unfortunately I haven't had a chance to make the upgrades.

[@chrisstockert7926]

Thanks for the video! The how to is straight forward. Got a Master Cylinder for an 02 and the adapter and it worked as you said. Just a note for others who still have their ABS in line, make sure you bleed it as well. This needs to be done wether or not you still use the electronics. Mine is functional but it does not have to be. There is a Schrader like valve under a cap. Should be located at the steering wheel side, aiming at the driver side wheel well. It’s fun to get to but has to be done. Depress it to release air from system. ABS System. Pump brakes just as your doing a caliper or wheel cylinder. Redo until confident you have no air in it. This mod literally changed the way my truck drives. Well worth the few dollars spent.

[@freetoride003]

there are two schrader like valves depending what kelsey hayes abs module you have depending on year. and two more on all abs modules no matter what abs module you have. on the kelsey hayes they are side by side just under the in and out lets of the brake line connections

[@avitiatiger]

Im gonna try this tomorrow. Do I have to do the rear ABS delete??

[@Roni-sp8zt]

Any updates thinking of doing this today?

[@mikegarcia1117]

Thank you I will try it I have a 97 Chevy 2500 brakes suck

[@derekrugby]

Did it work on your 2500?

[@mugizoro47]

I was reading that you can't do this because of the low drag calipers on the GMT400 1988. What calipers do you need to pair with this?

[@freshbutplain1144]

Did you have to add a different proportioning valve for the disc/drum brakes? The nbs Mc is disc/disc right?

[@roughneck2204]

I bought this cylinder for mine. Why are some people using the smaller 2001 mc?

[@100016]

So the original thread size for the 1/4in brake line(furthest to front of truck) is a 9/16th?

[@pi_is_awesome_3.144]

Hi! When you performed this swap, did your stock proportioning valve cause any headaches? I see the button on the front mine moving now, and I'm not sure if it's normal.

[@brandondingle6594]

Do I still need to do the abs system delete ? I have a 1998 k1500

[@blakedismuke3656]

I am wondering about if my abs isn't messing up because my pedal feels different everytime I press it

[@stevelassetter6954]

Great information. Thank you sir!👍🏼

[@marmadukepickthall4128]

So basically the problem with OBS trucks breaking is primarily poor master cylinder design? I have 98 2wd Silverado with bad brake booste. Btw awesome content thank you

[@bluesteeljay9343]

Thanks, your vid is a clear perspective to a vote of confidence on reference on a upgrade. Mine decided to leak at the res 2 days ago. Im also gonna drop the anti lock off. Ill be doing the bleed on a vice, other than that ill replicate your good works 👍

[@Angelo-qy5ht]

Anyone know if it's the same part # for a 1996 OBS with the 6.5L diesel? My brake booster looks different but it looks like it'd probably fit. The NM4073 isn't coming up for a 2006 6.6l diesel so wondering if it's different

[@joeymullins3859]

I have a 94 k1500 I don't think it has a valve like that one,can you still do the upgrade on it.

[@patrickbodine1300]

Tip: replace the cap after bleeding m/c.

[@Mr.boxxchevy]

Can this be done on a 94 GMC Vandura/G20.

[@vincentsanders3312]

Thanks, I needed this. HATS OFF TO YOU SIR.

[@dustinvarnum1302]

Have you had any problems with your upgrade as in has it been pumping air into the system or have you not have any problems whatsoever out of it?

[@backyardbuilttrucks1]

Or just put a master for a 3500 on it. I have hydraboost from a 95 C3500 on my 94 K1500 that is setting on a 1976 K20 chassis with disc brakes on 14 bolt rear axle and on Dana 44 front axle.

[@NERDSLAYERPRIME]

How's the dana on yours? You have to replace the whole hub when you're doing the front rotors?

[@bobchristie346]

I have also replaced everything but still have excessive air in my master cylinder when i push the pedal. Any help?

[@dyer2cycle]

Going to try this on my '90 that has crappy brakes..the "Brake" light has been staying on for a long time, don't know why, brakes were pretty good up until recently. Light's still on, but now, the pedal goes way down..not losing fluid, though. BTW, I don't know why or how the GMT 400 got the "OBS" moniker...stupidest thing I've ever heard..if it's "old body style", then so is the GMT 800, 900, and whatever the '14-'18's were, since they are no longer being produced and not the "current" body style...not crazy about the term "squarebody", either, not sure when that term started to be used, but I remember when the GMT 400's first came out...the "squarebody" was still in production at the same time, and the 400's and '73-'87 body style were produced alongside each other through 1991, as the Blazer, Suburban, and certain styles 1 ton trucks continued to use the '73-'87 body style... During this time, I actually remember most people around here calling the '73-'87 style "Old Body Style", and the GMT 400 "New Body Style" to differentiate the two...

[@dennissmith2560]

Great video Russell! Will this work on my 1994 GMC Yukon, 5.7 TBI? I plan on deleting my entire ABS, run new brake lines and would love to upgrade my MC. Thanks

[@jordan7290]

How did bleeding the ABS go?

[@pkennedy4256]

Keep seeing k1500 does it work on the c1500? It does seem like a dumb question to me as well.

[@angelmeza8445]

Yes should work

[@mikegarcia1117]

I did use the adaptor but the line leak in the middle

[@scratchy331]

I tried this on a 98 silverado. The fitting with the adapter leaked. I tried thread tape then an o-ring and it still leaked. The other fitting did not leak. Any suggestions?

[@cj599]

Dont use Teflon or a oring either tighten it more or get the right fitting you more than like have the wrong one or a damaged fitting or line or master cylinder seating surface

[@pjnegale8082]

U prbly cross tread the part

[@gerardolopez5875]

Would that work for square body 84???

[@kCI251]

I would note that this brake master cylinder is for a C1500, not a 2500 or 3500 truck. They HD trucks use a larger bore than 1/2 ton trucks.

[@ELBertoProductions]

Please respond to us boss man , in order for this to be a true upgrade do we have to delete the abs ??

[@bluesteeljay9343]

No. Unless your anti lock is an issue from the rear, usually you can tell if it is. Example i have a c3500 warmin up my brakes sensitive,but when shes at temp my brakes are spongy as heck, night and day feel. The reason why he upgraded is that the master is shorter in tale it makes for a more sensitive brake like newer trucks.

[@ELBertoProductions]

@@bluesteeljay9343 I’ve been trying to locate the issue, replaced front pads and rotors , the master cylinder , bled all lines , bled the cylinder and I’m still having a super spongey brake pedal.. do you think If I didn’t replace rear brakes ( shoes ) or vacuum booster this issue will continue ?

[@ELBertoProductions]

@@bluesteeljay9343 my next test was going to be bleeding out abs

[@bluesteeljay9343]

@@ELBertoProductions im assuming this is a gmt400 style truck. Does it have rear drums? And do you have a brake booster or hydro?

[@bluesteeljay9343]

@@ELBertoProductions gonna ramble on just incase i get too busy and forget to respond back. *Drums: failed cylinders, brake pads toast or not aligned, a bad brake booster and yeah the dumper* all can add to spongy brakin. Start with inspectin the drums first and replace if they're old. Cheap on rockauto.com. still issues than you know all brakes are good. If you're losing fluid you got a bad booster valve or crack or leak allowing bubbles. I think a bad valve youll see fluid raise and lower. Honestly your almost half done on a full restore it sounds like.

[@jmapalmer94]

Will this work with a 93 k2500?

[@christophernava6685]

Yes

[@moneymone414]

Was this with an vacuum or hydraulic set up

[@christophernava6685]

Vacuum

[@toothbrothers262]

This upgrade did not help my brake pedal. Any other ideas? New brake booster? Bleed my abs module?

[@jordan7290]

More than likely bleed the ABS, it’s a pain in the ass.

[@bonnieclyde100]

do you know if this will work on 97 3500 with hydroboost

[@toyotat100rules]

I wonder the same thing have you try it?

[@bonnieclyde100]

@@toyotat100rules no not yet I'm going to start looking into it when spring comes around

[@MikeSmith-nu9wt]

Nope , and if your steering gear box is leaking , thats why your brakes are goofy , hydro brakes suck on them heavier vehicles , but they had to do something to help stop all that weight ..hook it to the power steering pump and the steering hear box , great design aint it ..lol

[@catdakman1273]

NOTE:: Gravity bleeding will NOT work with a Bad Rear ABS system.

[@freetoride003]

hmmm maybe because your valve is stuck shut...

[@catdakman1273]

@@freetoride003 ? the original proportioning valve ?? could be. ABS valve has been removed. The rest, all new, wheel cylinders to master cyl.

[@isaacstone9331]

Would this same upgrade work for a 93 GMC 1 ton?

[@Willy3Sticks]

Yes

[@blakedismuke3656]

Is it a 9/16 by 1/2

[@stephenmerritt5750]

I have all the parts just haven't done it.

[@MiamiWebDesign]

I’m so disappointed! I did this same mc swap and can’t hardly notice a diiference, maybe the pedal is a tad less spongy now. Yesterday i got off a turnpike exit a little fast and almost could not stop at the traffic light off that exit. Freaked me out! Can this possibly all just be air in the system?

[@davin24]

Can you cut that barb sticking out of plastic reservoir looks horrendous

[@catdakman1273]

Long throw pedal..... the master cylinder you used is the same throw as the OEM 88' 95' master cylinder. I used the 2002 silverado M Cyl. the short one. Now hard pedal, .....NO POWER BRAKES!!!!!!

[@GMT400Chevy]

No it is not the same throw, that is the whole reason to swapping the master cylinded🤦‍♂️

[@catdakman1273]

@@GMT400Chevy SO, NO POWER BRAKES ANY MORE WITH SHORT MASTER CYLINDER ???????

[@XPFTP]

the bottle feed you had. just pumping peddle will get rid of air as you see. ten pumps per wheel. done deal. i do it all the time. no grav needed but hey who am i .

[@littlescottiesadventures9480]

Heard this the other day, definitely going to try this when I do the upgrade

[@freetoride003]

no need. i have never pumped a pedal for one cylinder or caliper more then 4 times to bleed the air. i start rr with 4 pumps and move to lr down to 3 pumps while opening the bleeder at each pump. 2 on the fr and 1-2 pumps on the fl. never had an issue

[@armandosaenz5588]

Do you turn the key on?

[@christophernava6685]

for bleeding you do not need to.

[@catdakman1273]

Did You Still Have Good POWER Brakes ?????????

[@catdakman1273]

DO YOU STILLL HAVE "POWER" Brakes?????

[@cj599]

The booster makes the "power brakes" work not the master cylinder

[@donniedixon5013]

I could use some help. I have a 89 c1500 I did the master cylinder swap with the same parts you used. And deleted my ABS and I have absolutely no petal. Goes straight to the firewall.

[@blakedismuke3656]

Bleed it and watch for leaks

[@catdakman1273]

?? Will the SHORTER Master cylinder 2000 silverado Work on a 1991 ??? and still have POWER Brakes???

[@rene5861]

My dumbass never thought of doing 2 at a time

[@catdakman1273]

Gravity bleading did NOT work a on a 91 silverado. No fluid would flow.

[@freetoride003]

you either have a clogged line, broke line, or clogged bleeders.

[@MikeSmith-nu9wt]

Proportioning valve could be stuck in one side , did you blow a line , the proportioning valve will shut off the side that blew , usually front or rear , open the other side bleeder and have someone hit the brakes hard , panic stop with one bleeder opened on the opposite line of what blew , either front or back , tighten bleeder before releasing the pedal ...now see if you got pressure on that other line ( usually the rear for me is the ones that blow out , so a panic stop the front bleeder , it flips the proportioning valve to both sides , kind of recenters it

[@Midwestmodifiedtoys]

I woulda just re flared the line

[@FSEVENMAN]

I don't understand why would you bypass the dump valve and not remove it from the vehicle? what the hell's the matter with you?🤓