DOT5 or not to DOT5...that is the question?

[MarPar]

Story goes...I replaced all brake components in my Newport last year 'cept fer the metal lines, the booster and that pesky rear rubber line . It sat for a month and half this year and then the master decides to **** the bed (brand "new" NAPA unit. I went to NAPA today and I will pickup a "new" one tomorrow.) Anyways, so I says to myself, "self, maybe now is a good time to switch to DOT5 instead of DOT3."

Then I thought about it later...I reckon all the new components have had enough time to soak up DOT3 and if I switch over to DOT5 now, I will have problems. Dumbass me should have just switched over to DOT5 last year when I had the chance. Sound about right?

 

[live4theking]

Sounds about right...

 

[bluefury361]

DOT 5 is the best choice but the system needs to be completely flushed of DOT 3 as they are not compatible. Mineral spirits and air pressure through the steel lines will work. Master cylinder, wheel cylinders and the three rubber lines should be purged and cleaned thoroughly.

 

[3C's & a D?]

Which car do you have that napa has a booster for? I have over the years never had any luck going that route and had to have them locally rebuilt. Which isn't cheap. I have mulled over switching myself but decided against, due to the fact that they have always used dot 3 and the extra cost is better off being spent on 2-3 year system flushes.

 

[detmatt]

I switched to dot5 in my Imp and regret not doing it in my Vert.

 

[78Brougham]

I wouldn't worry too much about it Mario. Our cars have lived with DOT 3 for forty plus years. Why change now? You're not planning on taking it to Road America and running the Vintage Gran Prix are you?

 

[mr. fix it]

I run mostly for the “if it spills “ worries
You can upgrade to DOT4 without flushing with mineral spirits
Or you can flush ,blow dry, then switch and be ready to bleed the brakes twice to ensure that there is no bubbles in the system

You do have to flush the DOT5 more often since it doesn’t absorb water which is the biggest killer of brake wheel cylinders and calipers from the articles I have read due to rust build up
How or why there is rust I have no idea because in order for rust there also has to be air

Dot5 tends to hold microscopic bubbles of air not then dot3/4 fluids

It does have a slightly spongy feeling as well
More noticeable in some cars over others

 

[MarPar]

Which car do you have that napa has a booster for? I have over the years never had any luck going that route and had to have them locally rebuilt. Which isn't cheap. I have mulled over switching myself but decided against, due to the fact that they have always used dot 3 and the extra cost is better off being spent on 2-3 year system flushes.

1969 Newport

I wouldn't worry too much about it Mario. Our cars have lived with DOT 3 for forty plus years. Why change now? You're not planning on taking it to Road America and running the Vintage Gran Prix are you?

Well, ya never know. My brother does have some of that Blue DOT4 that Beemers use...some coilovers, frame ties, and 17x8's and im set. Maybe I should start a what's the widest tire I can fit on a Newport thread

Well, it looks like im sticking with good olde fashioned DOT3 or maybe 4.

Thank you Gents!

 

[Clover]

I’ve switched to DOT 5 in many cars over the years and never gotten a spongy pedal or had any problem whatsoever. It is a myth that DOT 3 and DOT 5 are not compatible. I guess the reason for the mineral spirits flush (which I’ve never done) is to remove every last bit of the DOT 3 but I’ve always just used DOT 5 to flush out the DOT 3. I have two cars running DOT 5 for 30+ years now with no flushes ever and no failures, except one wheel cylinder (that lasted over thirty years after the DOT 5 was added). Use the DOT 5!

 

[mr. fix it]

I’ve switched to DOT 5 in many cars over the years and never gotten a spongy pedal or had any problem whatsoever. It is a myth that DOT 3 and DOT 5 are not compatible. I guess the reason for the mineral spirits flush (which I’ve never done) is to remove every last bit of the DOT 3 but I’ve always just used DOT 5 to flush out the DOT 3. I have two cars running DOT 5 for 30+ years now with no flushes ever and no failures, except one wheel cylinder (that lasted over thirty years after the DOT 5 was added). Use the DOT 5!

Cool
Again learned something new

 

[bluefury361]

[QUOTE="Clover, It is a myth that DOT 3 and DOT 5 are not compatible. QUOTE]



Not quite true. DOT 3 will absorb and hold moisture, (condensation), DOT 5 does not.
If mixed in any degree then your defeating the purpose of using DOT 5 and the moisture issue is still present, although to a lesser degree.
The two will work together but system life will be shorter.

 

[Clover]

[QUOTE="Clover, It is a myth that DOT 3 and DOT 5 are not compatible. QUOTE]



Not quite true. DOT 3 will absorb and hold moisture, (condensation), DOT 5 does not.
If mixed in any degree then your defeating the purpose of using DOT 5 and the moisture issue is still present, although to a lesser degree.
The two will work together but system life will be shorter.

What you say here does not address compatibility. And my experience shows that for me, DOT 5 will give me at least 30 years of maintenance-free and trouble-free driving and storage. That’s a pretty good record in my book!

 

[Clover]

And for the record, DOT 5 and DOT 3 will not go into solution, so the DOT 5 will push the DOT 3 out and then you pump a few more squirts of DOT 5 through and voila!, no “mixed” fluid remains, to speak of.

 

[mr. fix it]

It’s a matter of doing it. Record the results and post for all to see

 

[Clover]

Also for the record, I’m not a fanatic on the subject of DOT 5- just a stickler for the facts on any subject. I have and have had cars that have never been converted. Technically, one could say that 3 and 5 are not “compatible” since they won’t go into solution. The way the word is bandied about makes it seem as if there will be major problems if the two ever touch, which is ridiculous. If anybody cares to experiment by “mixing” the two, help yourselves, as it’s perfectly safe. Or, for only $5 I’ll tell you the secrets of what happens when you do!

 

[MarPar]

Or, for only $5 I’ll tell you the secrets of what happens when you do!

 

[78Brougham]

Glad you're sticking with the DOT 3 or 4. Like they say... the more you over think the plumbing the easier it is to stop up the drain.
To me it's not worth the battle to jump through all those hoops to use DOT 5. Just sayin'

 

[detmatt]

Glad you're sticking with the DOT 3 or 4. Like they say... the more you over think the plumbing the easier it is to stop up the drain.
To me it's not worth the battle to jump through all those hoops to use DOT 5. Just sayin'

What hoops? I did as CLover said on my Imp.. when I changed the front calipers I just bleed the Dot5 through and was done with it. Now that was only a couple of years ago but I’ve had no fluid related issues since. Although I did spill some Dot3 on the new paint under the hood of my vert when I was changing out the booster last year...

 

[78Brougham]

Those other guys were making it sound like you had to flush the system with mineral spirits or something and changing hoses etc. Made it sound like a pain...

All the same I'll stick with 3 in my Mopars, 4 in the others as the manufacturer recommends. Been working for years.

 

[MarPar]

Those other guys were making it sound like you had to flush the system with mineral spirits or something and changing hoses etc. Made it sound like a pain...

Exactly why I wanted to stay with 3/4. **** if it's really as ez as flush it all through, then I would consider changing over to 5.