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#32409 06/02/2004 4:16 PM | Joined: Mar 2004 Posts: 71 Member | | Member Joined: Mar 2004 Posts: 71 | When I brought my truck (49 1/2 ton) home in mid Feb, it went straight into the garage for teardown. I drove it maybe a total of 5 miles. The brakes were pretty bad, about a 1/4 pedal and the rear axle seals were leaking. I put off any brake work while I did other stuff and agonized over whether to upgrade to dual M/C. Last week, I was in the cab and noticed that there was no pedal(to the floor). I cracked open the M/C and it was bone dry.
My question; is it possible that with this "open vent" system that enough fluid to give me a 1/4 pedal three + months ago has evaporated while the truck sat in a heated/ac garage? There are no leaks, the garage floor is (was) clean. The M/C, wheel cylinders, lines, hoses look to be in very good condition.
I'm going to replace the hoses, bleed the system and see what I've got but after reading posts about losing fluid due to evaporation in these systems, I'm curious. | | |
#32410 06/02/2004 5:05 PM | Joined: Aug 2000 Posts: 122 Shop Shark | | Shop Shark Joined: Aug 2000 Posts: 122 | I would say no, there is very little, if any, chance of evaporation of the brake fluid. There must be a leak of some sort in the system to cause the loss of fluid. I would pull the drums and check the wheel cylinders to see if they are leaking. Odds are you will find a mess of brake dust and fluid built up under the drums.
Steve
55 1st Series 3/4 ton
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#32411 06/03/2004 8:05 AM | Joined: Mar 2002 Posts: 990 Member | | Member Joined: Mar 2002 Posts: 990 | what steve sez. its no doubt leaked out on one of the wheel cylinders. | | |
#32412 06/03/2004 2:03 PM | Joined: Feb 2000 Posts: 988 'Bolter | | 'Bolter Joined: Feb 2000 Posts: 988 | if not all the wheel cylinders. My guess is that you were "low" to begin with and you have one or more "seeping" wheel cylinders. Pull the drums and see if any of the WC are "wet". Good luck
Brian Moore
1949 3100 5 window Deluxe
"Today is better than yesterday, but not as good as tomorrow"
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#32413 06/03/2004 2:05 PM | Joined: Jun 2001 Posts: 379 Shop Shark | | Shop Shark Joined: Jun 2001 Posts: 379 | Peel back the boot on the stock master. Inspect for rust and fluid residue. Often the bore in these is compromised by pits in the bottom, or the bore has been honed beyond the specifications. IMO the modern dual master is the way to go. Also the use of residual pressure checks will retard the introduction of moist air into the brake fluid. The dual master has a diaphragm in the lid which makes it a closed system, the stock mc has an air vent built in where moist air enters. It's funny, but a new dual master costs less than a new single shot stock master. The dual master bracket and linkage is a one time additional expense. Less than $100. Good luck.  | | |
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