Is There An Easy Way To Tell If A Car Has Silicone Brake Fluid In It ? I Know I Can Flush The System And Start Over With All New Fluid But I Really Don't Want Or Need To Go That Far. I Just Want To Figure Out If The Car Has Silicone Or Not So I Can Add More To It When I Replace The Master Cylinder . Any Sure Fire Test Methods? Thanks For Any Help!
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Re: How Can I Tell If It's Silicone Brake Fluid?
If you have a small clear container -- a test tube would be ideal, but who has one of them? Draw off a few drops or a teaspoon of the fluid from the master cylinder. A turkey baster works well for this, but a straw will work better (and keep you on better terms with the wife). Put the straw in the master cylinder reservoir and put your finger over the top of the straw. Have a paper towel handy to keep it from dripping on your paint. Put the contents in the small clear container and add a like amount of water. Shake it up.
Edit add: One advantage of being an old fart is I have a lot of old empty Rx containers around for this kind of thing.
If you have a white milky fluid the master cylinder has glycol based brake fluid in it (DOT 3, 4 or 5.1). If you have two separate volumes of fluid your master cylinder has DOT 5 (otherwise called silicon) fluid.Terry -
Re: How Can I Tell If It's Silicone Brake Fluid?
Paul-------
Quite easy. Remove a small amount of the fluid from the master cylinder and place it in a clear glass vial. Add about an equal volume of water (or DOT 3 fluid) to the vial. Shake it up and let it stand for 10 minutes, or so. Observe the vial. If you note a phase separation (like "oil on water"), then the fluid is silicone. If there is no phase separation and the mixture appears "homogeneous" then the fluid is glycol ester-based fluid (i.e DOT 3, 4).
There is no way to differentiate DOT 3 from DOT 4 fluid, but it's not important. Both of those fluids are compatible.
You cannot reliably differentiate between DOT 5 and DOT 3 or 4 by color. OUT-OF-THE-BOTTLE, DOT 5 silicone is dyed purple. However, after some period of time in the car's brake system it turns yellow. DOT 3 and 4 are a very faint yellow. The DOT 5, after turning yellow, is a much more pronounced yellow. So, if you can tell the difference in yellows, you can also differentiate the DOT 5 from the others. However, the test I described above is a lot more positive and reliable.In Appreciation of John HinckleyComment
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Re: How Can I Tell If It's Silicone Brake Fluid?
Having used DOT 5 silicone in my 68 and 70 for over 20 years I can clearly see through the fluid to the bottom of my master cylinders on my cars through the original installation of the fluid. DOT3/4 had never stayed that clear when it was used for a long period of time.Comment
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Re: How Can I Tell If It's Silicone Brake Fluid?
If all the other tests, put some on the front fender's paint......Comment
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Re: How Can I Tell If It's Silicone Brake Fluid?
Thanks For Eveyones Help !!
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Re: How Can I Tell If It's Silicone Brake Fluid?
Loren;
That's not too funny. It often happens when bleeding brakes that some drops splash onto the cowl or fender - I know, you should cover them with plastic or something, but it happens. I just spent several hours taking a few spots of my cowl. That's what I get for having someone help me.
Stu FoxComment
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Re: How Can I Tell If It's Silicone Brake Fluid?
Stu
Who was it that helped? TomComment
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Re: How Can I Tell If It's Silicone Brake Fluid?
Tom;
I went to our local "Just Brakes" where a neighbor down the street works. They have the better equipment for bleeding brakes than I and I was having some trouble early on after installing my Matrix-Ceramic linings last year getting a good pedal. In the process, the master spit back a few drops onto the cowl. He wiped them off quickly, but it only takes an instant to do damage. I was able to rub them out ok last week.
Stu FoxComment
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Re: How Can I Tell If It's Silicone Brake Fluid?
Hi Stuart
I have used silicon brake fluid since about 1975,with excellent results.I've flushed the system on my one owner 66 one time in 35 years and found no evidence of rust or deterioration.The fluid I removed was surprisingly clean after 30 years of use.I've always thought that one of the greatests dividends to using silicon was that if you develope a leak or spash some you won't ruin the paint on your fender or chassis .I've been told that silicon fluid should never be use in an ABS brake system,because it will foam when the system palsates. Make sense to me.
Have a good one
Stephen Barrett (21558)Comment
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Re: How Can I Tell If It's Silicone Brake Fluid?
Stu
I am just glad it wasn't the young fellow who wanted to change the battery out for you!Comment
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Re: How Can I Tell If It's Silicone Brake Fluid?
Stephen------
I would not use silicone fluid in a car with ABS, either. However, I think the car manufacturer's admonition on this might be a matter of "over-caution". I've done some rather simple comparative tests on silicone brake fluid versus glycol-ester based fluids and I have not found any greater tendency on the part of silicone to aerate or foam. I found the two types of fluid to be virtually identical in this respect. Of course, the tests I ran were pretty simple and more comprehensive and sophisticated tests might reveal a difference. However, if there actually is any difference, at all, I expect it would be minor.
Still, I think it's wise to follow the manufacturer's recommendations and not use silicone fluid in a car with an ABS brake system.In Appreciation of John HinckleyComment
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