Clutch master cylinder and the Starter circuit

[Birdhouse]

Hi all
I moved the Birdhouse on Saturday.
It was a bit hair raising.

Turns out the hydraulic clutch went flat since last driven in August. It still had the tiniest hint of throw at the bottom. Just barely enough to disengage. Strangely, there was no lake underneath.

Its a 1983 front engine flat nose with 8.2 Detroit and Spicer 5 speed.
Has the clutch pedal that sticks up through the floor, and a fully cast iron master cylinder. Said master is rusted pretty good and the cap is very stuck. We rounded the nut head pretty good with a wrench, in the road before deciding to h³ll with it, we go now. Plenty of grinding gears. It was not inclined to speed shift, even with what was left of the clutch in.

Anybody have a line on a good original Mc or an idea what I can swap in there that might have a plastic tank, etc and won't get rusted again? Already checked ebay for Bluebird clutch. Lots of Nissan parts. Nothing for an old bus.




Also the starter would not crank with the key. I had started it like 3 days before with zero issue. I have been working on the tail light wiring, but did not disconnect anything that I know of. Of course it has 3 wires that go to said switch, a wad of switches and relays and wires internally.

Due to said 3 wires I can't figure out which to splice together at the front to be done with all that ham. Other option maybe just disconnect the ign switch or relay wires and run a new direct line.
Starter functions great when tripped. My buddy had to keep crawling under and bumping a bare twisted spot that some clown made on the trigger wire against the hot lug...


Any advice appreciated.


Thanks.

[s2mikon]

Post a picture of it.

[BeNimble]

I replaced the mc and slave in my 85 C700 with 8.2, the parts where cheap from rockauto, don't know if they might be able to make work, check rockauto it has pics of the parts. The cast iron design is better imo.

[Birdhouse]

Well at least the starter is no longer an issue.
I found the relay behind the headlight that all that ham feeds. I hooked both wires to the same post and presto. I can delete or ignore the rest of the ham. Cool.


I agree, iron seems superior but when the thing is 100% rusted to death it makes it hard to feel that way. Then again a plastic one from 1983 would probably be a zombie by now anyways.

I need to figure out where on the floor it is at. The guy that I bought this thing from planked over the access hole with oak. Shouldn't be too hard to cut a plug.
Still want to find a new one, even if I get it uncorked

[Birdhouse]

Originally Posted by BeNimble

I replaced the mc and slave in my 85 C700 with 8.2, the parts where cheap from rockauto, don't know if they might be able to make work, check rockauto it has pics of the parts. The cast iron design is better imo.

Well, strangely rockauto isn't even including master cylinders on the menu for said Chevy Medium duty truck with the 8.2. Or an 83 Chevy bus with 8.2.... any other idea what might be listed?

Probably better get a slave too while I'm at it
I'll check Napa tomorrow

[s2mikon]

This clutch master cylinder was used on many trucks, buses and fork lifts. They were made as clutch master cylinders and brake master cylinders. Single circuit. The only difference between a clutch and brake master cylinder is the check valve. Brake master cylinders have check valves clutch master cylinders don’t. Keeping the bore diameter the same is very important. Once you have it removed you need to measure the bore size and the piston rod depth. I don’t think that is rebuildable due to corrosion. How long is the rod from the pedal to the master cylinder? You may be able to re fab the mount and use a different master cylinder. How are your metal working skills? Just because it is obsolete doesn't mean you can’t use it.

[Birdhouse]

Common as dirt sounds good. Any ideas what vehicles to send me sniffing at?

As for fabrication, I'm pretty fair. Not quite a prototyping engineer but I can cobble pretty good. I'd rather not change it too much though

Dunno how long the rod is, but pretty long

[s2mikon]

Most all trucks of that size class will use a cylinder bore very close. Ford, IHC or GMC. With the long rod that makes it easy. If you change the mount you can shorten the rod. I would look to the Ford f600 4 bolt master cyl. https://www.ebay.com/itm/37345648144...cAAOSweWZblUrD
Try to keep the master and slave in the same ratio. And replace both of them.

[Birdhouse]

Cool. Got the master.
Now the slave.

Is it specific to the Detroit or to the Spicer?

[s2mikon]

No. Was your new master the same size bore?

[Birdhouse]

Honestly I have no idea. But it looks identical and I'm going with it

[Birdhouse]

I'm just trying to figure out which tree I need to bark at to find a slave cylinder now
I'm guessing the Spicer tree. What did this trans come in?

[s2mikon]

Post a picture of it please. I bet I'v seen one before. As one Dr said to another.

[Birdhouse]

I'll see what I can do when I get back.
I'll search the tranny number on ebay. See if it spits anything back

[Rucker]

Originally Posted by Birdhouse

Well at least the starter is no longer an issue.
I found the relay behind the headlight that all that ham feeds. I hooked both wires to the same post and presto. I can delete or ignore the rest of the ham. Cool.


I agree, iron seems superior but when the thing is 100% rusted to death it makes it hard to feel that way. Then again a plastic one from 1983 would probably be a zombie by now anyways.

I need to figure out where on the floor it is at. The guy that I bought this thing from planked over the access hole with oak. Shouldn't be too hard to cut a plug.
Still want to find a new one, even if I get it uncorked

Looks like you have a bleeder valve on the left (top, next to the slave cylinder). Have you tried just bleeding the slave?

I have an older pickup that needs bleeding once every few years.

[Jolly Roger bus 223]

for the slave cylinder look at flatbed and dump trucks of the same era.
c60/c70 models. with the same combination.
if its a thomas bus body PM me i have the thomas body wiring diagrams for 82 and up to at least my 96 for ford,chevy/gmc and international including some chassis manufacturer specific wiring.

[Birdhouse]

I haven't done anything besides fail to remove the cap.
Already bought a new master.
I'm in no crisis situation (it's a wonder it didn't drop dead in the middle of town)
Got a few bucks to my name
Just gonna replace both when I get it squared away as to what I need

[Birdhouse]

Oh no joke there really were on everything. 1960 suburban, 1985 box truck, some dodge....

I searched the casting number and found 3 models from Dorman that look the same but seemed to vary in diameter. I got one spec for a Pseries box van, 1 1/16 diameter I believe.

Drama solved.
Thanks guys.

[s2mikon]

The larger trucks used 1.5 inch bore and the smaller trucks used 1 inch to 1 1/8 inch. You don't have much ability to resize.

[Birdhouse]

Hmm I dunno.
In that case, it's too bad these things all look the same, if it's all wrong I'll send the sucker back. Considering I am shooting in the dark here, and have never seen a thing like this in the wild to know where to look. Lol I don't even know the truck series designators.

You wanna show me one with a 1.5 bore?