GC Galant Hardtop and GD Galant Hardtop, Sedan and Wagon Brake Master Cylinder Replacement

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There's some confusion surrounding replacement brake master cylinders for GC Galant hardtops and the GD Galant line-up produced in Australia, by Chrysler, between 1974 and 78.  This affects at least two major suppliers' databases: those of the Australian Brake Service, better known nationally as ABS, and online parts retailer Automotive Superstore.

Both companies list only one master cylinder for 1970s rear wheel drive Galants on their websites.  This is incorrect; the 11/16th (17.48 mm) units that they state will fit Galants of that era are only suitable for GA and GB Galants, GC Galant sedans and wagons, and ‘76 GD Galants without boosted brakes.

GA and GB Galants were not sold in Australia with boosted brakes.  GC Galant sedans and wagons didn't have boosted brakes, either.  GC Galant hardtops did, however, come standard with boosted brakes, as did GD Galant hardtops, and the majority of GD sedans and wagons from early ‘77.  (Just check your car's braking system before ordering.) 

Automotive Superstore sell their 11/16th Galant master cylinder as part # DBADM1189.  It's not known what part number ABS markets its 11/16th master cylinder as, but staff at a capital city store told me that the replacement they supply is the only one that's listed as being for a 1970s rear wheel drive Galant of any description.  

This is the 11/16th Galant master cylinder supplied by Automotive Superstore that's NOT suitable for GC or GD hardtops, or boosted GD Galant sedans and wagons: 

This is NOT suitable for GC hardtops or non-boosted GD Galants.

The use of the master cylinder above on my GC hardtop resulted in a soft, spongy pedal that I initially thought was an indication that the brakes needed bleeding.  Two attempts at doing so failed to fix the problem.  Hardly surprising once the real culprit was identified! 

Reference to the master cylinders fitted to two separate GC Galant hardtops owned by members of a couple of Aussie Galant-specific FaceBook groups has proven that the correct size master cylinder for these cars is 13/16th (20.65mm), which is cast onto the master cylinder itself.  This size (bore) has since been confirmed by a second participant in one of those groups who has an original Chrysler Galant parts book.

Below is the Automotive Superstore's 13/16th master cylinder that IS compatible with GC hardtops and boosted GD Galants. 

This IS suitable for a GC hardtop and boosted GD Galants.
 
It's actually listed on their website as being for a Chrysler GE Sigma (the car that took the place of the GD Galant).  Other than the bore and part # (DBADM1292), it's ostensibly identical to the 11/16th master cylinders supplied by ABS and Automotive Superstore with the small exception that the product specifications describes the thread size for the incorrect unit as:

    Thread size 10 x 1 ball
    Thread size 1 10 x 1 ball,

and the specs for the correct one as: 

    Thread size 10 x 1 ball
    Thread size 1 10 x 1 inv,

with reader Kevin explaining that “inv” is the flare on the brake tubes.  

Hopefully, this brief piece will help any of you who are about to renew their CG hardtop's or boosted GD's braking system.  I know it would've saved me heaps of time and frustration!

Big thanks to the FB members - Loran, Pat and Sean - who referenced their own hardtops or bookshelves to guide me to the right master cylinder selection.  The contributions of other forum members was hugely appreciated, too.  Comments by Kevin, Allan and Stephen have also been helpful. 

Did you enjoy this post or find it useful?  If so, why not browse the rest of the uppermiddlepetrolhead site?  There are loads and loads of classic, sports and performance vehicles featured (several on Galants!), as well as stacks of car shows and motorsports events.  Even better, you can follow either the 'blog itself or do so via Upper Middle Petrol Head's Facebook page.  And please do like, comment and share!






U M P H

(uppermiddlepetrolhead.blogspot.com.au.)

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