Welcome to our new home at previadiaries.com
First, I have to thank whoever left this pullback 3rd Generation Previa on my doorstep since the last update. It has lights and sounds, how cool is that!?
Thank you kind stranger!
Much of this past summer and fall were dedicated to resolving a brake issue on TRO (“The Red One” for new readers) wherein the brakes didn’t really stop the van.
As I mentioned here, it began with a burning smell emanating from somewhere on the van.
I did some investigating and found that the right front caliper was seized tight, and that smell was burning brake pad. I replaced that caliper and took the fresher pads and rotor from TGO to install at the same time.
I bled the brake and it was spongy, so I bled the whole system. That’s how I found out two things:
- the hoses (of which there are 7) were pretty dry and cracked, and likely expanding with fluid pressure
- The rear brakes weren’t working at all.
In went TGO’s rear brakes, which were in surprisingly good shape (big thanks to Jason M for helping out with this), and new hoses throughout.
I bled the system again, and still the pedal went right to the floor.
I stared at this diagram for days, trying to chase down the leak. I put in TGO’s master cylinder, replaced a couple of sections of line that refused to come out without a fight, and inspected other attachment points to no avail.
This was without a doubt the most upsetting mechanical bind I’ve ever dealt with, it made me doubt myself and question everything. It made me angry and frustrated. Instead of the magnificent feeling of accomplishment that comes with fixing something broken, this seemed an insurmountable challenge. I was pouring time, money, and effort at what felt like a sinking ship. I started to doubt it would ever work properly.
I decided to take Jason’s suggestion to go down the line and block it at all the connections using this neat line blocker he rigged up.
Finally, that led to some progress.
This rubber box to the left holds what’s called the “Load Sensing Proportioning Valve”
You can read about the basic idea of proportioning valves here, but the distinction on a “Load-Sensing” valve is that it can detect how heavily loaded the vehicle is and change the brake balance accordingly.
If the vehicle is riding lower as a result of more weight, an arm is pushed upward which in turn raises the amount of brake force sent to the rear wheel. It’s a clever solution to the problem of vehicles with such a wide range of potential weight on board.
You may recall, TRO was lowered, and in keeping with much of the other work the previous owner did, it was haphazard.
As far as I can tell, they didn’t bother disconnecting or adjusting that delicate arm, they just dropped the weight of the van on it. While the rear brakes were seized, a fragile stasis had been created. By reintroducing movement and replacing the chunky style fluid, I had brought to light a leaking valve.
I ordered a new valve from a Japanese parts vendor after triple checking compatibility (Japan’s Estima has a completely different rear suspension arrangement than the US one) and when it showed up I got to work extracting the old one and installing the new one.
After a few more bleeds and some tightening, I finally had brakes again.
Next time on previadiaries.com, the #weepreviadiaries post.
Thanks for reading
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