Bolt size confusion and stuck master cylinder

[Frankenchevy]

I wasn’t planning on shipping. Only if you were close enough. Just saw your screen name and thought northern CA.

Tbh, a new master cylinder for my truck was $60 maximum after tax. Yours will likely be in that ballpark.

 

[R8rPhan]

I wasn’t planning on shipping. Only if you were close enough. Just saw your screen name and thought northern CA.

Tbh, a new master cylinder for my truck was $60 maximum after tax. Yours will likely be in that ballpark.

Ahhh.. Where are you?

I just talked to the auto parts store, and a brand new MC with lifetime warranty for a '79 is about 38 bucks plus the guvna's cut...

He said if I bring the MC from the 88 down, we can make sure I get one that fits the same push rod and is for a chevy truck with disc/drum of the same year range as mine.. He said he shows the same part for like 10 years worth of similar trucks.. lol

Chassis appears to be a C10 so we should probably be able to figure it all out... Hope I don't have any issues with the prop valve...

and I can pick up some nuts, and a plastic enclosure for the little intermittent wiper circuit board I bought... Have had the part for probably a year so I'll be doing that while I have the gauge cluster out.. No more 'keeping my hand on the wiper control' to fake like I have intermittent wipers.. YAY!

 

[Frankenchevy]

Ahhh.. Where are you?

I just talked to the auto parts store, and a brand new MC with lifetime warranty for a '79 is about 38 bucks plus the guvna's cut...

He said if I bring the MC from the 88 down, we can make sure I get one that fits the same push rod and is for a chevy truck with disc/drum of the same year range as mine.. He said he shows the same part for like 10 years worth of similar trucks.. lol

Chassis appears to be a C10 so we should probably be able to figure it all out... Hope I don't have any issues with the prop valve...

and I can pick up some nuts, and a plastic enclosure for the little intermittent wiper circuit board I bought... Have had the part for probably a year so I'll be doing that while I have the gauge cluster out.. No more 'keeping my hand on the wiper control' to fake like I have intermittent wipers.. YAY!

Okay...I’m not an expert but I think an early c10 will be vacuum or non boosted. Pretty sure won’t work with a hydro native MC. $40 is definitely worth it.

 

[R8rPhan]

Good news is, the nuts that held the MC on are the same ones I need to finish mounting the booster bracket.. So now I have a nut to take with me...

 

[R8rPhan]

You didn't state that in your initial post and your profile says you have a '73. That's all we have to go on.

When I established my account here, that's all I had to go on too.. But when I rewired the truck I quickly found out that there was something fishy going on, because none of the 73 schematics matched what I was seeing.. Then I found a different VIN plate on the dash than what is on the door post... When I used 'that' to find schematics, suddenly things matched up.. Then I did an engine search, and then a tranny search, and lo and behold nothing matched... and you can tell the bed didn't come from the same truck as the cab and front clip, by just looking at it, from like half a mile even..

Soooooo here we are..

BTW, the nuts that hold on the MC itself are the same ones I need for the firewall studs where the booster bracket mounts, so now I have one to take with me...

 

[R8rPhan]

PS, the pictures of the maroon/burgundy 73 K10 in my gallery, is not the truck in question.. That's a truck I had like 30 years ago (and wish I still had)..

Had some pictures of this truck I thought, but they're somewhere else I guess.. I need to go to my build thread and steal some from there..

This is an old beater long bed pickup, 2wd...

 

[Goldie Driver]

That's essentially what I did, only on the truck.. I don't have a vise, so using the truck as one is my only way...

So which one do I get? I know the cab isn't a 73.. I 'think' it might be from a 79 1 ton farm truck.. Bed, chassis, engine, cab, transmission, all from different vehicles..

I know this power brake drum and bracket fits better then the drumless one that was on it..

Trying to avoid taking any of the nuts back off ... They were a royal PITA to install.. Between the bracket and the drum, a short socket was too short to adequately reach things inside the bracket and a deep socket couldn't fit in there.. Plus there was extremely reduced range of motion for the ratchet.. I probably spent an hour and a half just getting the three of them on there are now..

Was hoping someone knew what was typical so I could avoid taking one off again..

I know EXACTLY what you mean by PITA, but mine had studs mounted on the firewall so I did not fight that battle!
I used a "cool tool" from Craftsman.

You must be registered for see images attach

Hollow ratchet and socket set !
I forget the Craftsman name for them.

Anyway, good luck !

Britt

 

[R8rPhan]

I know EXACTLY what you mean by PITA, but mine had studs mounted on the firewall so I did not fight that battle!
I used a "cool tool" from Craftsman.

You must be registered for see images attach

Hollow ratchet and socket set !
I forget the Craftsman name for them.

Anyway, good luck !

Britt

Nice! I think I'm gonna stop by Harbor Freight while down there and pick up a cheap flex handle ratchet.. That should help a 'lot!'

 

[bucket]

Do you own a C-clamp? There must be some vertical object like a garage stud or sawhorse that you could use to clamp the MC and try to bench bleed it. Do you have a combination wrench? I'm sure it's tedious, but it can't be that hard to bolt up a vacuum booster.

bucket is probably right about the stud size, but all of a sudden you're changing the story. Your profile says you have a 1973 truck, and I promise you there was no metric hardware on a 1973. So now the story changes to a 79, which probably still isn't metric since GM only went metric in 1980 and then we get a hodgepodge truck that came from twenty different vehicles. There's probably some people here that can help you, but not without proper information. Especially when you ask what was "typical" for Frankenstein's monster.

I'm not trying to be a d-bag about this even though I come across that way, but you're asking for a golden bullet to kill this werewolf in your driveway, but that magic solution doesn't exist. We'll need a LOT more engineering information to try to find the right pieces to keep you from killing yourself and the people on the road around you.

GM actually did start using some metric fasteners here and there, in '79. But if the truck is made from multiples, it's anyone's guess as to what parts are correct, without having the truck in front of them for inspection.

Pictures would help though.

 

[R8rPhan]

Well, got a ride into town, got a remanufactured Master cylinder...

Went in well, fit perfect... bled it... cleared snow away from the rear tires, jacked it up, pulled the wheel, the drum, fashioned up something I could use to do the 'one man bleed' method.. Then proceeded to break the zerk off of the wheel cylinder...

So.. here I am, needing to get another ride into town to get new wheel cylinders.. Day is shot... Now to finish the brakes and the thermostat, the wiper control, and the turn indicators, I'll be forced to finish all this in the rain sometime next week..

Oh well, I tried... Gonna buy cylinders for both rear wheels, as it's a long way into town, and the extra 12 bucks is well spent insurance against having issues on the other side too... and I guess it can't hurt to go ahead and replace them both..

Sheesh.. Nothin is ever easy... Even when it's supposed to be...

At least my money supply will be replenished somewhat by the time I get down there.... So I won't be having to get 'creative'

 

[Rusty Nail]

Sux dude, sorry bout the luck. You'll get her all fixed up..maybe even post a pix.
Thanks for the update!

 

[R8rPhan]

Sux dude, sorry bout the luck. You'll get her all fixed up..maybe even post a pix.
Thanks for the update!

It's all a test! That's what I keep telling myself to stay sane anyway..

 

[MikeB]

You'll have measure to see if the studs are coarse or fine thread. These nuts have 17mm hex heads, as mentioned above.

https://www.boltdepot.com/Product-Details.aspx?product=4789

https://www.boltdepot.com/Product-Details.aspx?product=6875

Here is a pack of 10 nuts with 15mm hex head, but the thread pitch isn't mentioned.

https://www.autobodytoolmart.com/10...k62sH6KpJ6S_5OsEapmpOqfl9guicfV8aAm4WEALw_wcB

You should be able to buy the nuts with 17mm hex heads at Lowes or Home Depot. An industrial supply house might carry the nuts with 15mm hex heads if the 17mm heads have a clearance issue.

 

[R8rPhan]

So, put the new master cylinder in, bled the brakes, and hooked up the vacuum.. Have brakes in reverse, but barely in forward.. I had to back the adjuster off on one side some to get the drum back on, so adjustment might part of that problem...

Still pulls to the right.. I forgot to check how much pad was left on the left front brake, but all the others had lots of meat.. So I gotta pull that wheel again.. If that side's pads are good too, I might have a stuck caliper issue...

So now I'm reading on line that power brake push rods need to be adjusted, and the description of what they act like when they need adjusting sounds exactly like how my pedal is performing...

I'm 'hoping' that the push rod for this 88 chevy booster is adjustable.. Anyone know if the chevy trucks (tahoe/suburban) had adjusters on the end of the push rods? I'd hate to have to unbolt that booster and deal with disconnecting the push rod under the dash again...

But there's a lot of pedal travel before any braking happens right now.. Not safe enough to take out on the road yet.. Stops, but takes a lot of pressure/travel.. a 'lot'...

As far as pulling to the right, can the proportioning valve cause that?

There's a little rubber cap on the side of it, that when pushed, I felt a little click, and then whatever was in there didn't need pushing again (stayed in), so I think I reset it (I 'think' I was unable to bleed the rear brakes until then but bleeding the rears took a lot of pressure and a ton of pumping).. I had to pump the crap out (and hard) of things to get the rear brakes bled, but the fronts needed only a few pumps...

This proportioning valve doesn't appear to have two separate lines out for the front brakes though.. Just a front and rear. (Total of 4 lines connected, including the two from the MC)...

At least nothing is leaking now...

 

[Blue Ox]

Adjusting the rears may help with pedal height. The combination valve should not cause a pull. Maybe post a pic so somebody can ID why it doesn't split the fronts. Not a style I'm familiar with if it's a factory part. The thing with the boot should be the residual pressure valve (I think GM called it a metering valve) it normally only pushes out when there is pressure on the brakes. Maybe it was stuck, but I don't think that's a good sign. I would recheck it a few times to be sure it's working correctly. On mine the rears don't require any pressure to bleed, so there may be an issue with the proportioning side of that valve. Or something isn't hooked up right.