I Learned Somthing Today About S-10/Blazer Master Cylinders...

[69hurstolds]

They share the same casting number as an 83-88 G-body! Well, namely, ones that fit my G-bodies.

Just something I never bothered to look at before. Maybe y'all knew that, but I never checked out much on S-10s. I knew they had those RH drive style master cylinders for S-10s that everyone loves to get, but never knew the regular ones were the same. Makes sense since the S-10 was virtually a G-body steering and suspension parts (to a degree) toss into a small truck. I knew they had "different" master cylinders, but never thought that all they did was fit it with a different shaped reservoir.

So....if anyone knows anything about GM aluminum master cylinders, MANY people don't have a clue what part number their M/C was to begin with. For example, all my G-body Oldses use master cylinder GM p/n 18013429 (83-88 gas engines). Most other G-bodies use this p/n as well if not a diesel. Production part number was 18009816. Yours may differ.

Fortunately, there's a casting number on the bottom of the cylinders that may give you the tip you need. And that number is 18010023.

Always on the lookout for GM NOS stuff, I can hardly ever find brand new GM 18013429 masters on ebay. But for fun, I typed in 18010023. It showed me a bunch of master cylinders not even for G-bodies. In particular, an NOS master but was an SR code. It looked the same, but the reservoir is different.

This is the one I bought for $95. It was advertised as p/n 1810023 because of the cast in numbers on the bottom, but the SR code piece is actually service part number 18013433 for S-10/Blazer with power brakes. Original production part number was 18009879.

Here's a used one showing the 18010023 casting number.

I actually traced it down by using the repair (rebuild) kit part number 18010083. All the other guts parts are the same part numbers. Both the S-10/Blazer and the non-diesel Cutlass used the same master cylinder bores, just used a different reservoir. Even the lid/gasket interchanges. Just so happens I have an NOS reservoir and cover kit just laying around with nothing to do. So now I can just pop off the reservoir on this new one and pop my reservoir on it and have a brand new G-body Olds master cylinder. For much cheaper than the last time I saw an NOS G-body m/c.

If anyone wants an NOS "SR" reservoir by itself for your S-10 or Blazer, I'll give it to you. I'm never going to use it. Just hope I can pop it off without tearing it up. The way the grommet and resi nipple fit in there, it can be a PITA to get them apart.

 

[69hurstolds]

Oh, and for reference, the 18013429 I bought many years ago at the dealership cost me around 159-ish with a discount, IIRC. I'll dig it out and take some side by side comparo pics when I get this new one.

 

[1983calais]

Not that I paid attention to the casting numbers but on my 1950 Chevy truck, I retrofitted a g body brake pedal and brake booster to the firewall. The g body master cylinder wouldn’t work beca of the angle the plastic tank is at. The firewall on my truck is basically 90 degrees from the frame. A g body is on an angle ( I’m sure you all know that). The s10 master tank is straight. Bolted on and worked perfectly. Maybe if I look at the numbers on the bottom, they might be the same.

 

[69hurstolds]

Exactly. The G-body angle makes the reservoir lid only level because it's such an upward angle the way it mounts.

According to all tertiary support information, the S-10/Blazer w/J50 uses the same master as the 429 for G-bodies. Just the reservoir was changed to protect the innocent. Also to level it up properly, I guess. 🙂

 

[69hurstolds]

So, I got the new S-10/Blazer master cylinder. It's just as I suspected. A G-body master with the different angle reservoir because of the way it mounts in the truck.

Here's the comparo pics:
Sh*t wasn't cheap even 27 years ago. 197 list, I paid 157.60 plus tax.

These are some rare birds.

Comes with the decal on it already. Note too the code is etched into the end of the master cylinder aluminum piece as well.

Other than the resi, same ol' same ol'.

With both master caps "level" you can see the upward angle the G-body version mounts. Quite significant.

It's just optics if they don't look it, but these ends are exactly the same size as each other. One is sitting slightly forward of the other.

And here we are. Same engineering "part number" 18010023. Date stamps I haven't figured out. The top one, the G-body version is dated 3306 (I suspect Tuesday, Nov. 2, 1993 with an "07" out there for whatever reason). Bottom one says 7 156 16. To which I believe it translates to Thursday, June 5, 1997 with a "16" out there for reasons yet to be known. I'm only speculating on dates due to availability and things that may make sense for manufacturing dates.

 

[69hurstolds]

Got the reservoir kit ready to go to replace that S-10 resi. Kit comes with resi and two grommets. No cap though. That's separate!

But that is fixed with cover "kit" GM p/n 18006073. It's stupid to call it a "kit" when the cover comes with the rubber gasket already on it.

Note, too that the new cover does NOT come with the Delco-Moraine logo on the cover like the production version and over the counter G-body master cylinder cover. It's just flat there. Interestingly the S-10 master cylinder cover doesn't have the "D" on there either.

Check out the differences.

 

[69hurstolds]

Here's directions for master cylinder overhaul which includes how to remove/install new reservoir. Basically you pry it off and put a new one on. But, these guys are plugged in pretty well so it will take some effort. DON'T damage the reservoir removing it with a pry bar. Use even, slow pressure. And NEVER clamp the body in a vise. Only clamp it via the mounting ears (see drawing of the master cylinder in the vise below).

One thing to note in the instructions, and I can't believe I didn't notice this before, it says use brake fluid or silicone grease when installing the seals/resi. Brake fluid for these cars was DOT 3, glycol-based. You can use DOT 4 or DOT 5.1 as those are also glycol-based with higher temp ratings than 3, but DON'T use DOT 5 brake fluid unless everything in the brake system is brandy new. DOT 5 is silicone-based. Silicone and glycol-based brake fluids don't do well together and the DOT 5 may ruin OEM 80s type seals in the calipers and such. Newer seals are designed to withstand DOT 5. Raybestos is the only brake component manufacturer to state specifically their aftermarket seals and new/rebuilt brake components they sell at repair places can withstand DOT 5 requirements. Not sure of any of the others. Glycol and silicone fluids can also form a gelatenous mix. So I wouldn't recommend silicone grease for lubing the grommets. Do whatever you want, just saying.

 

[spongbob]

They share the same casting number as an 83-88 G-body! Well, namely, ones that fit my G-bodies.

Just something I never bothered to look at before. Maybe y'all knew that, but I never checked out much on S-10s. I knew they had those RH drive style master cylinders for S-10s that everyone loves to get, but never knew the regular ones were the same. Makes sense since the S-10 was virtually a G-body steering and suspension parts (to a degree) toss into a small truck. I knew they had "different" master cylinders, but never thought that all they did was fit it with a different shaped reservoir.

So....if anyone knows anything about GM aluminum master cylinders, MANY people don't have a clue what part number their M/C was to begin with. For example, all my G-body Oldses use master cylinder GM p/n 18013429 (83-88 gas engines). Most other G-bodies use this p/n as well if not a diesel. Production part number was 18009816. Yours may differ.

Fortunately, there's a casting number on the bottom of the cylinders that may give you the tip you need. And that number is 18010023.

Always on the lookout for GM NOS stuff, I can hardly ever find brand new GM 18013429 masters on ebay. But for fun, I typed in 18010023. It showed me a bunch of master cylinders not even for G-bodies. In particular, an NOS master but was an SR code. It looked the same, but the reservoir is different.

This is the one I bought for $95. It was advertised as p/n 1810023 because of the cast in numbers on the bottom, but the SR code piece is actually service part number 18013433 for S-10/Blazer with power brakes. Original production part number was 18009879.

View attachment 241170
View attachment 241187

Here's a used one showing the 18010023 casting number.

View attachment 241171

I actually traced it down by using the repair (rebuild) kit part number 18010083. All the other guts parts are the same part numbers. Both the S-10/Blazer and the non-diesel Cutlass used the same master cylinder bores, just used a different reservoir. Even the lid/gasket interchanges. Just so happens I have an NOS reservoir and cover kit just laying around with nothing to do. So now I can just pop off the reservoir on this new one and pop my reservoir on it and have a brand new G-body Olds master cylinder. For much cheaper than the last time I saw an NOS G-body m/c.

If anyone wants an NOS "SR" reservoir by itself for your S-10 or Blazer, I'll give it to you. I'm never going to use it. Just hope I can pop it off without tearing it up. The way the grommet and resi nipple fit in there, it can be a PITA to get them apart.

I when ther stuck you need to make ( saw) 2 oak wedges about a foot long and say 1 inch wide with a ramp of 1 & 1/8" pound them in from opposing sides under the tank near grommets if the skip reset them and pour some brake fluid around connection