Good Day all...I have a 56 Transtar 1 ton with Hydro-vac drum brakes & twice now since owning it the brake pedal has gone to the floor.The first time it did this I checked the fluid & found the M/C was empty so I filled it & no more issues,that was a year ago. This past Saturday I fired it up & noticed alot of white smoke while it warmed up.As I came up to a stop sign I discovered I had no brakes til the pedal almost hit the floor & then they grabbed hard. I checked the M/C & sure enough it was empty again,so I filled it & checked for leaks but could not find any obvious leaks or wet spots. Is it at all possible for the engine to suck or siphon fluid out of the Hydro-vac & be the cause of the white smoke I saw at start up? There is a check valve on the vacuum line,the crank case oil is full & after refilling the M/C the brakes were back to normal. [ATTACH=CONFIG]35667
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The Hydro-vac needs to be rebuilt. The check valve in the system prevents damage to the Hydrovac if the engine should back fire. In other words it does not prevent fluid from getting in the engine. The engine has to create a vacuum pull on the Hydrovac so it can function, along with that comes the chance fluid can be sucked into the engine as well, should a problem develop inside the hydrovac.Frank van Doorn
Omaha, Ne.
1962 GT Hawk 289 4 speed
1941 Champion streetrod, R-2 Powered, GM 200-4R trans.
1952 V-8 232 Commander State "Starliner" hardtop OD
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The Check valve only holds the Vacuum when the engine is shut down, to give you a couple pumps of Brake before the Boost fails. It should not have liquid brake fluid in it, so cannot effect your problem. A BAD booster Diaphragm will.
UPDATE: that was MY first thought also Frank, about a backfire as with a PCV Valve, but with more thought I realized that it's main function is to hold the Vacuum.Last edited by StudeRich; 06-17-2014, 09:05 AM.StudeRich
Second Generation Stude Driver,
Proud '54 Starliner Owner
SDC Member Since 1967
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It's not the diaphragm that is bad, On a Hydro-Vac the diaphragm is metal with a leather lip seal sandwiched between two metal discs, that make(s) up the diaphragm. Then it has a push rod coming off the diaphragm that pushes on the slave master cylinder. This rod passes through a leather seal on it's way to the slave cylinder, that is what is leaking.Bez Auto Alchemy
573-318-8948
http://bezautoalchemy.com
"Don't believe every internet quote" Abe Lincoln
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