Ezrider_92356

i have not driven the toyota in about a month untill today and we have not gotten above freezing here in over a month 7 degrees out right now. i got the toyota moved out of the pile of snow it was in and took it around the block and the break pedal is real stiff. it was like this last time i drove it as well. i was thinking maby frozen moisture in the break booster? what are your thoughts? do you think it would help to pour a little rubbing alcohol in the break booster?

Ardent

I'm going through the same issue right now. If you search, you'll find a thread on the topic. Several people mentioned that it could be the "Brake Check Valve." I'll see if I can find the thread.

EDIT:

Well after searching through many pages, I can't find it... (I was reading it Wed.) Anyway, in the vacuum line that runs along the firewall from the Master Cylinder, there’s an in-line valve that is supposed to keep the brakes working for a while after the engine shuts off. On cold days it can stick open or closed and it doesn’t allow the power brakes to work until it warms up.

What I read said that it was around a $50 part.

If anyone else with more experience can confirm this for us, that would be great.

scope103

There IS a check valve in that line ("Valve Assy, Vacuum Check for Brake", 44730-24020), so that the vacuum stored in the booster doesn't bleed off into the plenum when the engine is shut off. I have no idea if it is a "known" cause of your problem, so I will defer to Ardent. My guess, though, is that is preventing the vacuum from reaching the booster, rather than the other way around.

As a quick check, start the truck, then pull the vacuum line off the booster. If you don't feel suction, then the line is blocked somewhere. (It's a big line; it will probably kill the engine when you pull it off, assuming it's working.)

Marc

I think this is the thread Ardent was talking about.
I've had the same problem twice when it was -30.

https://www.yotatech.com/forums/f2/9...w-10-a-161902/

Ardent

Yeah, that's it! Thanks Marc!

Ezrider_92356

thank you defently gives me some places to look at. ill probably take the toyota over to the shop tonight to put a new alternator in it, ill see if that is my break problem then.

Ardent

Just got my new Check Valve. Part # is 44730-24020 if you need it. I'll update if it gets cold enough to tell if this fixed it.

Good Luck!

Belize Off Road Team

What temp is your brake fluid good for?

Tofer

it may also be just a bad master cylinder... mine when out in my 94

thook

It doesn't really matter, per se. But, if you're going where I think you're going with this..........

Moisture in the brake fluid? Milky? Dirty/grungy?

Belize Off Road Team

Well actually, i had a 92 Isuzu PUP, it saw some really harsh weather, in the winter in Edmonton the Clutch would freeze cause of the fluid, same with the brakes, no matter what you could not press the pedals. So it is possible that the brake fluid is just cold.

Ezrider_92356

on mine i took the check valve out and cleaned it with electrical contact cleaner and re installed it with a quick shot of wd 40 in the check valve no more problems so far

thook

I guess what I meant was that the choices are only Dot 3 or 4. Temp wise they're only rated by the amount of braking heat they will tolerate. So, it's kind of a moot question. But, still...I have no experience with extreme cold like that. In other words, not challenging your point about the cold.

Ezrider_92356

it gets -30 to -40 degrees F here never any issues with break fluid if you were to get alot of moisture in your fluid you may run into a problem. the only problem i have had in the past is water freezing in the rear drums and recently an issue with the check valve, only two cold related problems i have had with breaks

abecedarian

DOT 3, 4 and 5.1 are all glycol based, DOT 5 is silicone based and not compatible with the others. DOT 3/4 is all that's needed for >95% of all on/off road vehicles and DOT 5.1 is only necessary for the most demanding race-oriented vehicles.

The primary difference between any brake fluid is the wet-boiling point of the fluid.
With respect to cold temps, the differences are negligible.
If the brake fluid has absorbed enough water to freeze, the DOT rating would not matter.

abecedarian

But glycol based brake fluids absorb water from the atmosphere so... if left un-changed for long enough, any one of those fluids would freeze simply due to the water they would absorb from the air.

PunchinPreacher

I had the same problem in my truck. However it's more of a stiff pedal.

I changed the master cylinder back in the summer in edmonton, and flushed the whole brake system and replaced it with DOT 5 (The silicone mentioned above)

The master was from a 92 v6 and mine was the 86 22r.

I moved the other day out here in -30 or worse, it breaked great but the peddle was stiff still. Not much more than before, but compared to my dodge, it's a rock.
Now however, my tranny that day did not want to shift... it was stiffer than the break pedal for sure!

Not to hijack, but anyone use ATF for tranny and diff fluids for our 5spds and diffs? or just go with a proper synth?

thook

(Consolidated for ya!)

Thanks for elaborating, Abe.

thook

Nope. You don't want to use ATF for diff's or the manual gear boxes. It won't hold up under the pressure for the diff, for one. And, it's simply not heavy enough for friction in either.

Search the forum for "MT-90" on your transmission, and any synth.....Mobil 1, Amsoil, Redline, etc....would be good for the diff. That is if you want a synthetic.

Anyway, run a search. Tons of info already.