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Brake fluid dot4+

pano

pano

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Past Site Supporter
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Sorry if a duplicate, my phone is preventing me from the search function. I have an unopened can of volvo dot4+ brake fluid. Is dot4+ compatible with our GS brake systems? I plan on a complete rebuild and flush.
 
If you are doing a complete rebuild and lines, use Dot5. 3&4 is paint remover, 5 won't hurt your tank the next time you might spill some. That might cost you a lot more than a partial can of Dot4. You can only make the switch on virgin surfaces. Contamination between the types of fluid would be a problem. I've used it for over three years after a complete rebuild.
 
Interesting.....DOT5 you say,,,cool

Going to go and return the bottle I purchased, and get the DOT5 instead....

system is completely clean, new lines as well, so the change over is going to be OK

.
 
I use DOT 4. Dot 5 is not compatible with 3/4 so only use it on a complete rebuild, including changing the lines. 5 has a more spongy lever feel too for some reason.
 
I never noticed a "spongy feel", but one thing I do notice is that It stays clean a lot longer and is clear so you can see anything in it. I'm starting to see some tiny black flecks settling on the bottom of the reservoir, so I think it's time to flush it with spring maintenance.
 
A good article about brake fluid types here... http://www.motorcycleproject.com/motorcycle/text/cows-brakefluid.html

Another one...http://www.stoptech.com/technical-support/technical-white-papers/brake-fluid

"The original DOT 5 fluid specification was expected to be fulfilled by silicone based (SSBF) composition. It was designed for use in applications where its resistance to water absorption (and therefore low corrosion) was desired - like in military equipment. It has also found use in antique cars because it does not dissolve paint finishes. With SSBF, unfortunately, these characteristics were only achieved by unacceptably high compressibility. As such, the DOT 5 grade SSBF is of little value to any conventional automotive or high performance application."
 
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From that info that Ed posted:


The real way to compare brake fluids is by deciding what is important to you. Is silicone fluid's safety around paint and plastic more important than yearly changes and a softer action?
Its higher boiling point, the reason for its development and at one time its strong suit, is now academic, since D.O.T. 5 glycol (5.1) fluids are now widely available.
Glycol fluid therefore is, for most of us, the better brake fluid, and the best just may be the 5.1, if the highest boiling point, which is really a moisture tolerance measurement, matters.

On the practical side, beware that glycol and silicone brake fluids are hugely incompatible with each other. Mixing even small amounts will create a sludge that looks amazingly like
Italian salad dressing and is about as effective as a brake fluid -- meaning, not. Of further consideration is that, in some cases, the hardware designed for one fluid will not accept the other.
Brake caliper and master cylinder seals, hoses, and other parts won't always work correctly when the type of fluid is changed.
 
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