Different grade brake fluid, different pedal feel?

[heypete]

Hi folks,

I recently changed the brake fluid on my 2006 Camry from the Toyota OEM fluid (presumably DOT3) to Prestone DOT4.

During the change, I had an assistant who pressed the pedal and refilled the reservoir while I loosened and tightened the bleeder valve. A tube connected to the bleeder valve drained into a jar that contained a small quantity of brake fluid, so no air could get back into the system. At all times, the fluid level in the reservoir was kept above the "minimum" line.

Maybe I'm hallucinating, but the pedal feels a bit softer than before. I wouldn't describe it as "spongy", which would indicate air in the system, but it seems like it needs to move just a hair further before the brakes start kicking in.

I've tested the brakes in both short, sharp stops and longer, gentler stops all without any problem. ABS works fine as well (tested by braking firmly on a loose gravel road).

Odds are that I'm just going nuts, but is there any difference in compressibility or pedal feel that would come about from switching from DOT3 to DOT4 fluid? If so, would there be any problem with such a change?

 

[Liquid_Turbo]

Check the compatibility in the owners manual.

 

[saaber1]

Dot 5 is the one that is not interchangeable. Dot3 and 4 are fine.

Starting the countdown for the guys to chime in who say butt conventional is imagination, noises are imagination, rev. differences are imagination, brake feel is imagination. 5... 4... 3...

 

[chrome]

Try re-bleeding the brakes again. One useful trick I learnt was to wrap a thin layer of teflon tape (plumbers tape) onto the threads of the bleeder screws. This prevents air from being sucked in via the threads.

 

[heypete]

Originally Posted By: chrome
Try re-bleeding the brakes again. One useful trick I learnt was to wrap a thin layer of teflon tape (plumbers tape) onto the threads of the bleeder screws. This prevents air from being sucked in via the threads.


Hmm. Good idea. Can I remove the bleeder valve without completely draining the system and getting fluid everywhere?

 

[DieselTech]

Pete, just making sure your starting from the furthest point from the master cylinder?

 

[heypete]

Originally Posted By: DieselTech
Pete, just making sure your starting from the furthest point from the master cylinder?


As far as I could tell, yes. I picked the rear-left bleeder valve first, followed by the rear-right. Then front-left and front-right.

 

[casper]

also try a rubber mallet to the caliper to ensure all small air bubbles are removed.

Also some good reading from a very good friend of mine who I only trust with my brakes.

http://zeckhausen.com/bleeding_brakes.htm

 

[HTSS_TR]

You should start right-rear(passenger-rear) first, then left-rear(driver-rear), then front-left(passenger-front) and last is front-right(driver-front).

When you remove the bleeder valve to wrap a layer of teflon tape and to re-bleed the system, you'll loose a couple table spoons brake fluid at most if you have a helper.

 

[nthach]

Rebleed the brakes, some Toyota systems can be pesky. I have a Power Bleeder just for this purpose at home.

 

[djb]

Some air may have been entrained as the fluid was being poured into the reservoir when flushing the fluid. The smallest bubbles takes a day or two to work their way to the surface.

Try bleeding again, just a tiny bit -- not enough to need more fluid. For the second round I usually bleed just a drop or two into a paper towel.

 

[postjeeprcr]

Originally Posted By: HTSS_TR
You should start right-rear(passenger-rear) first, then left-rear(driver-rear), then front-left(passenger-front) and last is front-right(driver-front).

When you remove the bleeder valve to wrap a layer of teflon tape and to re-bleed the system, you'll loose a couple table spoons brake fluid at most if you have a helper.


You mean front right(passenger front) and front left(driver front) right?

 

[mechtech2]

It is tough to synchronize a two man bleed job.
It works well, but you have to really be familiar with each other.

I suspect the bleeding is not right.

ABS systems require special fluid sometimes, and special bleed and pre-bleed techniques.

With a two man bleed, there is no need to have the tube immersed - it is a non issue. Fluid goes one way.
Also, teflon tape on the threads is useless. If the bleeder is open, you WANT it open. When closed, it seals on the tapered end, NOT the threads.

I really like a vacuum bleed. A Mity Vac or knock off is fast and simple. It's hard to screw this up, unless the reservoir gets too low and you have to start over again.