Dot 5.1?

[theophile]

In summer 2012 I bought several bottles of Motul DOT 5.1 brake fluid that I intended to put into a Honda Odyssey. I ended up letting a shop do the brake flush so I still have these bottles of brake fluid, which have never been opened.

Now I'm overhauling the suspension on the LS, and I have noticed that my brake calipers and brackets look quite unappealing, with some surface rust and other discoloration. I'm considering cleaning them up and painting them, which I would prefer to do off the car so I don't have to worry about overspray and so I can keep working on the suspension at the same time. As removing the calipers would likely result in at least some fluid loss, I'm wondering if it's worth doing a DIY brake flush and fill with the DOT 5.1 I've had for 3 years.

So that leads me to my questions:

1. Is it OK to use DOT 5.1 in these cars? My understanding is it should be OK because DOT 5.1 is glycol-based and can be mixed with DOT 4 and/or DOT 3.

2. If I do this, my plan would be to disconnect the brake lines at the caliper and just let them drip into a container, and then when I put the calipers back on, top off the master cylinder with the new DOT 5.1 and then use my Mityvac to bleed each line with the bleeder valve (making sure to keep the master cylinder topped off) until I see the new fluid coming out of the bleeder. Is this the right way to do it?

 

[Telco]

Yes. DOT3, DOT4 and DOT5.1 are compatible. DOT5 is silicone based, generally only used in military vehicles, and is NOT compatible as it will destroy the seals in the braking system.

I would not bleed the brakes that way. Use your Mityvac to suck all the old fluid out of the master cylinder and fill with the new fluid. Then use the Mityvac to draw the old fluid out and the new fluid through. Start at the right rear wheel (furthest from the master cylinder) and draw fluid through the bleeder until the new fluid comes through. Make sure to keep the MC topped up while doing this. Go right rear, left rear, right front, left front. This will bleed all but the ABS unit, which needs a scan tool to open the valves for bleeding.

 

[theophile]

Yes. DOT3, DOT4 and DOT5.1 are compatible. DOT5 is silicone based, generally only used in military vehicles, and is NOT compatible as it will destroy the seals in the braking system.

I would not bleed the brakes that way. Use your Mityvac to suck all the old fluid out of the master cylinder and fill with the new fluid. Then use the Mityvac to draw the old fluid out and the new fluid through. Start at the right rear wheel (furthest from the master cylinder) and draw fluid through the bleeder until the new fluid comes through. Make sure to keep the MC topped up while doing this. Go right rear, left rear, right front, left front. This will bleed all but the ABS unit, which needs a scan tool to open the valves for bleeding.

Thanks for the feedback. In that case, I guess I'll plan to plug off the brake lines to prevent them from dripping out while I have the calipers off the car, then after I reinstall the calipers. do it the way you suggested.

Do you happen to know how much brake fluid it takes to flush out the system?

 

[joegr]

You can get most, but not all of it flushed out, unless you have a scan tool that can cycle the ABS to clear out what is in the pump.

 

[Zr0]

Yes. DOT3, DOT4 and DOT5.1 are compatible. DOT5 is silicone based, generally only used in military vehicles, and is NOT compatible as it will destroy the seals in the braking system.

I would not bleed the brakes that way. Use your Mityvac to suck all the old fluid out of the master cylinder and fill with the new fluid. Then use the Mityvac to draw the old fluid out and the new fluid through. Start at the right rear wheel (furthest from the master cylinder) and draw fluid through the bleeder until the new fluid comes through. Make sure to keep the MC topped up while doing this. Go right rear, left rear, right front, left front. This will bleed all but the ABS unit, which needs a scan tool to open the valves for bleeding.

Funny you say that...maintenance guy was wondering why mail trucks go through so many master cylinders today. All the while he had a bottle of purple DOT5 on hand to fill it up after he replaced it...

 

[FDR]

I wish I had drained the master cylinder before starting. My lines never bled to clear fluid, just pale yellow. Or did I need to get a 3rd bottle of fluid? My reservoir is clear.

As far as plugging the lines, I didn't have much fluid come out provided you keep the reservoir cap on. But then again, I only opened one hose at a time. Obviously it's a safe bet to plug them, but for someone else worried about a hemorrhage-like flow, it won't happen.

 

[Telco]

Funny you say that...maintenance guy was wondering why mail trucks go through so many master cylinders today. All the while he had a bottle of purple DOT5 on hand to fill it up after he replaced it...

Heh heh... now you know.

I wish I had drained the master cylinder before starting. My lines never bled to clear fluid, just pale yellow. Or did I need to get a 3rd bottle of fluid? My reservoir is clear.

As far as plugging the lines, I didn't have much fluid come out provided you keep the reservoir cap on. But then again, I only opened one hose at a time. Obviously it's a safe bet to plug them, but for someone else worried about a hemorrhage-like flow, it won't happen.

There is a huge difference between old and new fluid, and it's quite obvious when you get the new fluid out. It won't be clear like water, it will depend upon what color the fluid you use is. I used to use a blue brake fluid from Germany before they apparently banned it in the US (don't remember the brand anymore). What's important is to get the nasty black crap out. Since your fluid is mostly clear you're OK until it's time to change it again.