Greetings!

Last week the concentric slave cylinder in my Ford F-150 went out. The seals blew due to the extreme cold up here (Fairbanks, Alaska). This is the third time that I have had to replace the slave cylinder because of this problem.

One solution that was recommended was to drain out all of the DOT-3 brake fluid and replace it with DOT-5 (synthetic). Another solution that a friend suggested is to simply add some denatured alcohol to the existing solution. He said this will thin it down and have no effect on the mechanism or seals. Come summer, the alcohol will evaporate out and then I will have to replace it with an equal volume of DOT-3 fluid.

Has anyone had any experience with "thinning" hydraulic fluid like this? Will the denatured alcohol have any effect on the seals and potentially cause the new slave cylinder to blow out faster?

Thanks for the input!

Doug
(dog_driver@hotmail.com)

Greetings!

Last week the concentric slave cylinder in my Ford F-150 went out. The seals blew due to the extreme cold up here (Fairbanks, Alaska). This is the third time that I have had to replace the slave cylinder because of this problem.

One solution that was recommended was to drain out all of the DOT-3 brake fluid and replace it with DOT-5 (synthetic). Another solution that a friend suggested is to simply add some denatured alcohol to the existing solution. He said this will thin it down and have no effect on the mechanism or seals. Come summer, the alcohol will evaporate out and then I will have to replace it with an equal volume of DOT-3 fluid.

Has anyone had any experience with "thinning" hydraulic fluid like this? Will the denatured alcohol have any effect on the seals and potentially cause the new slave cylinder to blow out faster?

Thanks for the input!

Doug
(dog_driver@hotmail.com)
Im just curious, is this a common problem in alaska? I know the extreme cold affects the oil, batteries, tires, and alot of other things. But i would think that if the slave cylinder failure was directly related to the temperature`s effect on the brake fluid, you would also have problems with the brakes! Seems like it would also be blowing the clutch master cylinder. I wonder if the seals are becoming brittle because of the cold, or theyre shrinking, allowing the fluid to bypass. Also, brake fluid is hygroscopic, and readily mixes with water. It will absorb moisture from the air. Maybe your fluid is contaminated with moisture, and thats causing the problem? I looked on some fluid containers, and couldnt find any reference to temp. related performance, except boiling point. As far as the alcohol, it wont attack most rubbers, but the synthetic fluid would probably be best to try. Or maybe a very light weight hydraulic oil. Maybe check with some of the trucking co,s , and see what they say. Theyve probably encountered most every cold related problem you could imagine.
I agree with you on the better idea. Hydraulic clutches are fine, but inside the bellhousing aint the place for the slave cylinder. This is automotive engineering ignorance at its finest. These people dont have to work on em. Good luck
Later
Ed
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