Replacing DOT 4 with DOT 5 Synthetic Brake Fluid--What's involved?

[ilm65]

Has anyone replaced their DOT 4 brake fluid with DOT 5? Obviously you have to bleed the entire system--just how far do you have to go? Some have said bleed until the purple DOT 5 comes out, others say to go as far as disassembling each wheel cylinder, replace all rubber seals, etc. DOT 5 has many benefits to those of us who can't drive our cars year-round. Any advice before I tackle this on the Satellite???

 

[Hemi Rebel]

You need to make sure the system is completely cleaned of the dot 4. It does not mix with the 5. I would probably open the system and flush out with brake fluid and make sure it is clean and dry before putting in the 5. Then flush it through just to make sure.

 

[RustyRatRod]

The hell it won't mix. You just will NOT like the results. lol

 

[Belvedere-II]

I used to work at a high end performance shop and we had a lot of Carrera Cup racers that bought parts from us. The advice our techs gave to everyone who wanted to switch was to completely remove every brake line and flush them completely, and to install new calipers, and master cylinder so there wasn't a chance that the DOT 4 was still in the system.

Side note... There is a DOT 4 brake fluid made by Ate (German) that has a blue dye in it, they also have a gold dye. Racers who wanted to flush their systems completely while staying with DOT 4 would alternate between the blue and gold fluids - that way when the color of the fluid changed they knew that line was completely flushed of the old fluid.

 

[440+6]

I did mine when I had to replace a leaky master cylinder so the master only saw silicone then bled through everything twice, then put new wheel cylinders on the back then removed calipers and cleaned and dried then re installed, then bled everything twice.

One trick is to warm up the silicone (put in the sun on hot day) with cap cracked open, this gets the air out of it, and pour slowly as to not make air bubbles.
Silicone absorbs air kinda like dot 3 or 4 absorb water.

Did this over 10 years ago with no problems whatsoever and very firm pedal.
The guy that thought me the procedure is a good friend of mine and he did all his cars way before me and even he has had no problems to this day.

 

[adamst56]

I have a couple of my cars converted to DOT 5. I did it when I changed essentially every component of the system (lines, master cylinder, portioning valves, calipers). I have read both that flushing with alcohol and then blowing the lines out with air is good and I have read that you should just flush well with DOT5 and then repeat within a month with a second complete flush. I would suggest to rebuild your calipers as well.

 

[lewtot184]

the system has to be flushed out. dot 3 & 4 are not compatable with dot 5.

 

[ilm65]

I used to work at a high end performance shop and we had a lot of Carrera Cup racers that bought parts from us. The advice our techs gave to everyone who wanted to switch was to completely remove every brake line and flush them completely, and to install new calipers, and master cylinder so there wasn't a chance that the DOT 4 was still in the system.

Side note... There is a DOT 4 brake fluid made by Ate (German) that has a blue dye in it, they also have a gold dye. Racers who wanted to flush their systems completely while staying with DOT 4 would alternate between the blue and gold fluids - that way when the color of the fluid changed they knew that line was completely flushed of the old fluid.

Thanks Belvedere-II, For anyone else considering this, I've learned that DOT 3 and DOT 4 are hygroscopic (extract and hold moisture) which causes rust within the system. These two don't mix with DOT 5 and if residual amounts remain in the system (typically low spots within the lines or proportioning valves) can cause rust. DOT 5, being synthetic, isn't hygroscopic and therefore is best for those of us whose cars aren't driven a lot. What a pain this upcoming conversion is going to be, but should be worth it. Thanks for your input--I'll see if there's a color difference between the DOT 4 and DOT 5 to aid in the changeover.

- - - Updated - - -

I did mine when I had to replace a leaky master cylinder so the master only saw silicone then bled through everything twice, then put new wheel cylinders on the back then removed calipers and cleaned and dried then re installed, then bled everything twice.

One trick is to warm up the silicone (put in the sun on hot day) with cap cracked open, this gets the air out of it, and pour slowly as to not make air bubbles.
Silicone absorbs air kinda like dot 3 or 4 absorb water.

Did this over 10 years ago with no problems whatsoever and very firm pedal.
The guy that thought me the procedure is a good friend of mine and he did all his cars way before me and even he has had no problems to this day.

This is REAL helpful--thanks for the priceless input!!!