Been doing some brake work on my Sister in laws car (85 GT-S coupe) and it is most likely going to need a new MC. Anyways that got me thinking about a brake problem that one of our members has had (
solution starting here-ish). In researching and verifying I have found info that is relevant to the forum but feel it would get lost in his thread, so Ive started a new thread (that will hopefully get stickied).
Celicas use a different M/C depending on whether they have drum or disc brakes in the rear.
Toyota P/N
47201‑14400 (08/1981 - 07/1983)
47201‑14470 (08/1983 - 06/1985)
Unfortunately the usual parts places have lumped all 3rd gen celicas together as far as master cylinders go. The problem is that MCs intended for cars with drum brakes are supposed to have a residual pressure valve on the rear outlet.
The valve is contained in a threaded piece that goes into the mc and the brake line attaches to. Here is the difference between an outlet with a valve on the left, and one without on the right. This is a view from the "inside" btw. Note: these pics are from a Landcruiser MC so might be different from what you see on a Celica MC, they are not pics of the P/N listed below.

These outlets have their own part numbers. I believe the distinction is with res valve and w/o res valve but I havent seen pics to confirm this
47218‑12040 (08/1983 - 11/1985)
47280‑30030 (08/1981 - 07/1983)
So, if you need to replace your master cylinder: Check the rear outlet! If necessary take the outlet off of your old MC so that your brakes will function properly.
Rear Disc= No valve
Rear Drum= Yes valve
If you have rear disc and the valve is left in, your rear brakes will drag, causing unnecessary wear on brake parts and reducing mileage
If you have rear drums and the valve is not in place you will be making the front brakes do all the work and wear them out prematurely...