Young Guy, Old Mack (B61 Dump Truck)

[mechohaulic]

that wouldn't be a valve NORMALLY associated with parking brake system / should be a regulator valve , question is = what system ?? suggestion would be to trace lines best possible, or what valve / switch do you move  to make a difference in valve leak.

[mechohaulic]

4 minutes ago, Mark T said:

Reversing relay for the puff limiter.

"stopped leaking when I set the brakes" == why a puff limiter ??

[Mark T]

It gets air when you release the parking brakes, then meters air to the puff limiter on the injection pump in relation to manifold pressure.

[mechohaulic]

8 minutes ago, Mark T said:

It gets air when you release the parking brakes, then meters air to the puff limiter on the injection pump in relation to manifold pressure.

possibly what's throwing me off (besides the long day/ Yukon Jack ) is the picture posted!! I remember  the intake manifold having an air cyl  1 in +- dia with line going to injection pump ; not the picture posted .

[Mark T]

6 minutes ago, mechohaulic said:

possibly what's throwing me off (besides the long day/ Yukon Jack ) is the picture posted!! I remember  the intake manifold having an air cyl  1 in +- dia with line going to injection pump ; not the picture posted .

There's a couple different types 

[Smoothy]

2 hours ago, Mark T said:

It gets air when you release the parking brakes, then meters air to the puff limiter on the injection pump in relation to manifold pressure.

Thanks Mark, that makes perfect sense to me now. I've managed to scrounge up the Mack service manual on puff limiters from another thread on the site. What I don't understand now is that if the reverse relay leaking/ bleeding air off into the atmosphere with the brakes released is normal, surely not right? There's no figure showing the different ports on the reverse relay, but it does mention a test port. Is that what is leaking on my relay and simply needs plugged?

 

The only other thing messing with my head on this one is that the control valve appears to be removed.

[Smoothy]

Well, it took some digging. But this problem was one I invented. Thanks again, BMT forums. 

[Mark T]

Looks like maybe someone tapped into the same fitting on the manifold for a manifold pressure gauge (?) .  Try explaining that leak to a DOT guy in 2025 🤔

[Smoothy]

3 hours ago, Mark T said:

Looks like maybe someone tapped into the same fitting on the manifold for a manifold pressure gauge (?) .  Try explaining that leak to a DOT guy in 2025 🤔

Yeah I'm not exactly sure what's going on with this thing. The plastic line coming off the fitting in the manifold is just dangling off not attached to anything and the puff limiter line from the injection pump that goes to the reverse relay is also removed. It seems the puff limiter has been disabled, but they didn't clean up their work. Wondering if I should just finish it off and cap the lines to the manifold and maxi brakes. I can't imagine the reverse relay is doing anything at the moment.