66 C2 DOT#5 Brake fluid "disappears" during Winter Storage

[Larry E.]

My car with manual brakes and DOT#5 brake fluid always seems to lose some of
it's volume(About 80% loss in the Master Cyl.) during Winter storage in a "Car Bag". (October To April)
Can not find any leak anywhere. When I add the proper level of fluid in the Spring (Used April to October)
every thing is OK during the Summer months. No leaks and car brakes work fine and no loss of volume The
brake pedal is used in the Summer but not in Storage. Found the below on a different forum:

So it does evaporate . . . . but it aint much and it aint fast.

When brake fluid is lost in stored vehicles it is generally "leaking" somewhere.
Not a major leak. Probably nothing you can even see. Rather it is a seepage.

If brakes are used regularly (even just stepping on the pedal once a month) the seals/cups are continually pushed out against the metal bores, if they sit, the seal lips will shrink ever so slightly and allow for a slight seepage.

Is this the answer to my mystery?? Comments and Thanks>Larry

[Edward J.]

Re: 66 C2 DOT#5 Brake fluid "disappears" during Winter Storage

Larry take a peak at the interior fire wall. For a master cylinder leak.that area is hidden from view.

[Gary B.]

[Larry E.]

Re: 66 C2 DOT#5 Brake fluid "disappears" during Winter Storage

Gary: Thanks for the response. I already have the next experiment already done. My "other 66 Vette is the Coupe" with the
exact same brake system(Manual) but with DOT 3 (Regular Brake Fluid). Car is stored in same building as the DOT 5 car and
with same identical bag type. Building is none heated so temps vary a lot from Fall To Winter then back to Spring. This car
with the DOT 3 DOES NOT LOSE ANY VOLUME FROM THE MASTER CYLINDER LIKE THE DOT 5 BRAKE FLUID CAR.
SOOO> I am thinking that the DOT#5 is more susceptible to have more storage problems in a Non-Heated building like
mine. Thoughts?? Comments?? Larry P.S. Don't forget that during the Summer Months(Same amount of Months) THERE IS NO
VOLUME LOSS ON EITHER CAR. Thinking that "Pedal" usage makes a difference.

[Patrick B.]

[Joe L.]

Re: 66 C2 DOT#5 Brake fluid "disappears" during Winter Storage

My car with manual brakes and DOT#5 brake fluid always seems to lose some of
it's volume(About 80% loss in the Master Cyl.) during Winter storage in a "Car Bag". (October To April)
Can not find any leak anywhere. When I add the proper level of fluid in the Spring (Used April to October)
every thing is OK during the Summer months. No leaks and car brakes work fine and no loss of volume The
brake pedal is used in the Summer but not in Storage. Found the below on a different forum:

So it does evaporate . . . . but it aint much and it aint fast.

When brake fluid is lost in stored vehicles it is generally "leaking" somewhere.
Not a major leak. Probably nothing you can even see. Rather it is a seepage.

If brakes are used regularly (even just stepping on the pedal once a month) the seals/cups are continually pushed out against the metal bores, if they sit, the seal lips will shrink ever so slightly and allow for a slight seepage.

Is this the answer to my mystery?? Comments and Thanks>Larry

Larry------


It's utterly impossible for any DOT-approved brake fluid to evaporate from a brake system. The brake system is a completely and necessarily sealed system. LEAKS could get by seals, of course, but that's not evaporation.

[Mark E.]

Re: 66 C2 DOT#5 Brake fluid "disappears" during Winter Storage

What Edward said.

[Mark M.]

Re: 66 C2 DOT#5 Brake fluid "disappears" during Winter Storage

I agree with Edward and Mark to check the back of the master. It may be leaking under the insulation and under the carpet.

[Larry E.]

Re: 66 C2 DOT#5 Brake fluid "disappears" during Winter Storage

[QUOTE=Gary Beaupre (28818);947579]Larry,

Is the bagged car stored in a high temperature, very low humidity environment? If not, proceed to the following:

Gary: The answer is no to your question. This is Illinois> Temps from 105 Degrees to 20 Below 0. Humidity all
over the spectrum. This is typically from Late September to April. Larry

[Larry E.]

Re: 66 C2 DOT#5 Brake fluid "disappears" during Winter Storage

Larry take a peak at the interior fire wall. For a master cylinder leak.that area is hidden from view.

Edward: Thanks for the idea and response. After a Thorough inspection (Behind Master Cylinder and Interior Firewall)
I have found NO EVIDENCE OF A LEAK ANYWHERE. Also some say that brake fluid gives off a "fishy odor" which I
also have not found. So I am still confused on the disappearance of the Dot#5 fluid only during storage months. Larry

[Larry E.]

Re: 66 C2 DOT#5 Brake fluid "disappears" during Winter Storage

Larry------


It's utterly impossible for any DOT-approved brake fluid to evaporate from a brake system. The brake system is a completely and necessarily sealed system. LEAKS could get by seals, of course, but that's not evaporation.

Joe Lucia/Patrick Boyd> Agree with you guys on the above statement when the system is completely sealed. BUT>
"When brake fluid is lost in stored vehicles it is generally "leaking" somewhere.
Not a major leak. Probably nothing you can even see. Rather it is a seepage. if they sit, the seal lips will shrink ever so slightly and allow for a slight seepage." QUESTION> WHEN THIS OCCURS DOES NOT THE "COMPLETELY SEALED SYSTEM
BECOME A INCOMPLETELY SEALED SYSTEM"?? Larry

[Patrick B.]

Re: 66 C2 DOT#5 Brake fluid "disappears" during Winter Storage

Larry- I have always stored my brake fluid in jars or cans with lids, but I do not think it would evaporate even if the lid was left off. How long have you had this car? Has it always lost fluid from the MC over the winter or only lately? I have had silicone fluid in my car for almost 50 years, and the only times the level in the MC changed during storage were as a result of leaks. I think that has been the experience of other DOT 5 users too. Maybe you should place an open container of the fluid you use in your garage and see if the level changes during summer or winter.

[Larry E.]

Re: 66 C2 DOT#5 Brake fluid "disappears" during Winter Storage

Larry- I have always stored my brake fluid in jars or cans with lids, but I do not think it would evaporate even if the lid was left off. How long have you had this car? Has it always lost fluid from the MC over the winter or only lately? I have had silicone fluid in my car for almost 50 years, and the only times the level in the MC changed during storage were as a result of leaks. I think that has been the experience of other DOT 5 users too. Maybe you should place an open container of the fluid you use in your garage and see if the level changes during summer or winter.

Patrick: Thanks so much for your comments. Let's begin with the Subject of Brake Fluid Evaporation. I have talked to local Chemist and have used"Google" to talk to best of Chemist and by almost 100% they say that "All Liquids will evaporate in time;some slower then others." So Brake fluid when in open atmosphere will indeed evaporate. Just throw some of it onto your driveway it will disappear just like gasoline/anti-freeze or any other liquid you may come up with. That being said there may be liquids out there made by the Government/NASA/or?? that are so exotic that will not evaporate. Brake fluid is not "exotic" so not in this category.

I have had this car since the mid 90's. It has always been "bagged" for Winter Months. I have added some DOT#5 on occasion since then but have added a lot more per year in the last 8 years or so. Since I can not
find any leaks I will go with the following theory unless someone else can come up with a better one. This applies
to DOT#5 only.

I believe that in the Winter Months and being bagged the seals at the wheels will shrink to some small degree
will let out some fluid so small it will not be detected when inspected. This moisture(brake fluid) WILL EVAPORATE DURING STORAGE IN THE BAG.

Since my car is a trailer queen I can live with this condition because I have no guarantee even with a brand new brake system it won't do the samething.JMHO Comments Always Welcome>Larry

[Gary B.]

Re: 66 C2 DOT#5 Brake fluid "disappears" during Winter Storage

Larry,

I prefer data to theory. Next time you bag the car do the open container of DOT 5 test and mark the before and after level. Regardless of the speculation of some, I believe the evaporation will be nowhere near 80%.

Gary

[David M.]

Re: 66 C2 DOT#5 Brake fluid "disappears" during Winter Storage

It doesn't take much (IMO) to pull the master away from the firewall and peek in the bore. My money is on the master bore. Synthetics will leak where dinosaur juice will not.

80% volume leak should show its ugly self visually.

Get it up on a lift and look.