Click on image for the lowdown. 
====
| | |
9 members (3B, Johnny Rib, baldeagle, 68ironhead, 2-Ton, 1955 1 Series, JW51, Guitplayer, walter74),
108
guests, and
2
robots. | | Key: Admin,
Global Mod,
Mod | | | Forums66 Topics128,038 Posts1,055,471 Members48,424 | | Most Online14,466
Apr 26th, 2026 | | AD Chevy Trucks  Over 6,000 pictures Brad Allen has an awesome collection of Chevrolet factory pictures that he has set up from film strips. Check them out!
Lots of work on Brad's part ... pure enjoyment (and references) for you!
| | THANKS!
For helping keep this great
old truck web site
on the Internet for over 30 years! and not clogged down
with Ads!  Again, thanks!
| | | | Joined: Aug 2010 Posts: 24 New Guy | | New Guy Joined: Aug 2010 Posts: 24 | So I have rebuilt my hydrovac with a rebuild kit from Cadillac parts and now I have no vacuum assist, so obviously I must have put something back in incorrectly. Does anyone have any advice on how to troubleshoot these units? I would like to know where I should be looking rather than a total disassembly. | | | | | Joined: Nov 2005 Posts: 6,100 'Bolter | | 'Bolter Joined: Nov 2005 Posts: 6,100 | Hy Jaredm, do you have any brake pedal at all? Does your engine run correctly? | | | | | Joined: Aug 2010 Posts: 24 New Guy | | New Guy Joined: Aug 2010 Posts: 24 | Brake pedal is hard and brakes work fine other than having to push as hard as possible. Engine runs and idles great. Any ideas of where to check would be much appreciated | | | | | Joined: Jun 2011 Posts: 5,096 Crusing in the Passing Lane | | Crusing in the Passing Lane Joined: Jun 2011 Posts: 5,096 | No vacuum assist, so, check your vacuum system.
Ed
'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
| | | | | Joined: Nov 2005 Posts: 6,100 'Bolter | | 'Bolter Joined: Nov 2005 Posts: 6,100 | Hy Jaredm, as EdPruss said you don't appear to have vacuum assist or your atmosphere line air filter or line are plugged. Try removing the rubber hose from the 1/2" pipe on the front of the Hydrovac and trying the brakes again, if they still don't feel boosted then you may have a vacuum supply problem or a leak although you say the engine is running as it should. The other thing may be that the atmosphere valve is not opening which could be an assembly problem, good luck, hope that helps. | | | | | Joined: Aug 2010 Posts: 24 New Guy | | New Guy Joined: Aug 2010 Posts: 24 | I have vacuum at the hydrovac, I will look at the atmosphere valve, maybe I have it in backwards or something.
Thanks | | |
|
|
