Tandem master cylinder (1 Viewer)

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hello.
I have a 1978 FJ40, I have noticed that the car does not brake very well. I lookd at the master cylinder and noticed that there is only one reservoir. I have owned previous FJ40's and they have two reservoirs. I took the front wheels off and noticed that the drum brakes were replaced with disc brakes in the front. I had ordered a new tandem master brake cylinder. Can I use the tandem master cylinerd for this application or do I have to exchange it for just a one reservoir?
I attached some photos.

Thank you.
20200525_115326.jpg

20200518_201207.jpg
 

reddingcruiser

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Reservoir is not the issue if set up for dual circuit brakes. I run a NON-ABS FJ80 MC. One reservoir and it works fine. I'm not seeing a proportioning valve.
 
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Disc brakes were standard in the US in 1976.

Here is a picture from my 79:

20200525_125903.jpg


There is also a brake portioning valve to help balance braking between the front and rear.
 
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Thank you all. I forgot to mention that the car is a non US spec vehicle imported from Colombia.
 

Pighead

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That appears to be an 80 series dual circuit brake master. (Don't 80s have 4 wheel discs? I forget). Which may not provide enough fluid to move drum cylinders.
Perhaps adjust your rear drums tighter? Or add rear discs...
Edit: adjusting your rear drums tighter would be the cheapest easiest and quickest fix...
 

reddingcruiser

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Not mine, but a good explanation of why you NEED a proportioning valve:

"A Proportioning valve is required on vehicles that have disc brakes on the front wheels and drum brakes on the rear wheels. Disc brake pads are normally in contact with the disc, while the drum brake shoes are normally not in contact with the drum. If the pressure was not proportioned the disc brakes would engage before the drum brakes when you depress the brake pedal.


The Proportioning valve compensates for this, allowing the drum brakes to engage first before the disc brakes. The Proportioning valve does not allow any pressure to the disc brakes until a pre-determined pressure has been reached. The pre-determined pressure is low when compared to the maximum pressure in the braking system, this allows the drum brakes to engage before the disc brakes engage. Having the rear brakes engage first provides the control and stability needed to stop your vehicle safety.


The proportioning valve reduces the pressure to the rear brakes. Whichever type of brakes your vehicle has, the rear brakes require less pressure than the front brakes.


If equal braking force were applied to all four wheels during a stop, the rear wheels would lock-up before the front wheels. The proportioning valve only lets a portion of the amount of pressure to the rear wheels thus preventing rear wheel lock-up."
 

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