Loss of brake vacuum after 10 minutes

Oct 1, 2014
Silvan, Austraila
Darn annoying. Switch the truck off, ( 1995 80 series) and 10 minutes later you've lost that 1st 'free' brake application with vacuum assist. When you're a manual and on a steep hill, its disconcerting to have to jam your foot so hard on the pedal the truck doesn't roll along while you shift to neutral and key it. Soon as it starts pedal sinks and all is well, got great brakes again. What's the most likely suspect causing a loss of vacuum after a few minutes of not running the engine and how would you check.

Pic of my trusty LN106 bush rig as the 80 is in semi-retirement so it last another 30 years. .
hilux9 (2).jpg

Feb 23, 2011
El Segundo, CA
How is your hand brake?

The brake booster usually holds a vacuum pretty well but it is not perfect. I can count on mine to hold a vacuum for hours, but not days. The brake pedal is always hard before I start up after a week in the garage. 10 minutes is very short.

You could try replacing the little check valve where the hose to the intake connects. The check valve and rubber grommet are not expensive and it can be changed on the car in a few minutes.
Nov 9, 2012
Olathe, KS, USA
This will be the hose and check valve between the intake manifold and the brake booster or the brake booster itself.

Start small and cheap, go expensive.

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