Manual Proportioning valve install

[LCAM-01XA]

If you can get to it, unplug the the vacuum pump hose from the vacuum tree, and shove the tester in that hose, this will tell you what the pump alone is doing. Then if that checks out plug that hose back onto the tree, and pull the vacuum hose off the brake booster (careful not to break that small valve at the end) and test that hose, this will tell you how much vacuum actually reaches the brake booster. Unplugging the smaller vacuum hoses off the tree to get them out of the way is fine, as long as you remember to plug them back on when you're done - I've noticed that once unplugged, the hoses usually need about 1/2" length cut off their ends before plugged back on, that removes the already stretched ends and exposes fresh hose that would make for a better seal to the vacuum tree.

 

[plywood]

If your actual vacuum pump is bad then the truck will shift at high rpms and also the Climate Controls won't work quite right as there will be no vacuum to power the servos.

 

[LCAM-01XA]

Not necessarily - my HVAC worked just fine even tho my pump was weak.

 

[plywood]

Just fine or just right?

 

[LCAM-01XA]

Perfectly fine, how's that? ;p You may be correct on the VRV thing for the C6 tho...

 

[plywood]

As for mine and his they use vacuum to power servos.

This can be used as a vacuum diagnosis.

I can't even see what kind of truck your talking about.

 

[TDW]

I've noticed that once unplugged, the hoses usually need about 1/2" length cut off their ends before plugged back on, that removes the already stretched ends and exposes fresh hose that would make for a better seal to the vacuum tree.

That makes sense.

I expect that getting fresh proper hose to barb fittings will be a preventative measure that will rule out small leaks in the vac circuit.

 

[TDW]

If your actual vacuum pump is bad then the truck will shift at high rpms and also the Climate Controls won't work quite right as there will be no vacuum to power the servos.

None of these symptoms have been experienced. Good to know.

 

[gonecrazyi]

When my vacuum pump started to go, the hvac controls would just cut out and I my brake reserve slowly dissappeared. But my cruise control continued to work.

The pump I have on there now wont pull the valve for the dash vents but will hold it when its pulled. It also will still run the cruise control without any problems. Seems every pump dies a different way.

 

[LCAM-01XA]

As for mine and his they use vacuum to power servos.

This can be used as a vacuum diagnosis.

I can't even see what kind of truck your talking about.

All of the IDI trucks and vans have vacuum servos for the air doors, mine ain't any different from yours in that department. My experience with the system has been that it requires very little vacuum to operate, as I drove with that mostly-dead pump for several months before I scored a good working one from Jeremy (Pipeliner86). I do have an E4OD tho, so I never got the late shifts you mention would be present with a C6.

When my vacuum pump started to go, the hvac controls would just cut out and I my brake reserve slowly dissappeared. But my cruise control continued to work.

The pump I have on there now wont pull the valve for the dash vents but will hold it when its pulled. It also will still run the cruise control without any problems. Seems every pump dies a different way.

Actually once you set your vents to where you want them the system don't pull any more vacuum, really it only needs the vacuum pump to replenish vacuum used by the servos moving the air doors, if your 1-way valve by the firewall and the vacuum lines behind the dash are in good shape you shouldn't see the system defaulting to defrost by itself, only when you use up all of its vacuum and before it builds up some to replace it. I actually installed a small vacuum canister in my truck for the HVAC servos alone, it's a vacuum reserve canister for the EGR valve of a fullsize Ford fuel-injected car (roughly the size of a tuna fish can) and I have it T-eed in the HVAC vacuum supply line with the factory truck 1-way valve between the canister and the vacuum tree on the firewall, and the factory donor car 1-way valve between the canister and the rest of the HVAC - this way even if my pump goes real weak I can still move my air doors for quite some time which allows the pump to build up vacuum again.

Now the cruise control, that can be a real hog on vacuum, and it needs the pump running all the time too! Heck if I know how yours kept working but the HVAC didn't, usually it's the other way around...

 

[gonecrazyi]

I don't really understand it myself. I just tied the valve under the dash into the on position. Ive got to go through the system and check for kinked hoses to see if thats the problem.

Mu vac pump is original to the truck and has about 180k on it. I figure I got my use out of it. Just need to track down another one.

 

[LCAM-01XA]

Yeah, finding one that is good and cheap seems to be quite an issue sometimes - like I said Jeremy on here bailed me out when mine took a dump, if it weren't for him I'd probably be running around with the old one for quite a while longer.

The vacuum lines under the dash are actually amazingly simple, being used to the automatic-temperature-control Panther HVAC systems I was expecting a rats' nest of lines under there, but there are only a few of them. Very easy to get to with the radio and the glove box pulled from the dash.

 

[TDW]

That may be an unrelated issue, it actually sounds like your vacuum pump is dying on you and you lose brake assist because of that- put a vacuum gauge on the pump line directly and tells us what numbers you see, should be well over 20"Hg at idle.

Well I just tested the vacuum coming off the pump at idle, and it's well below 20 It was actually just below 15"hg when I first started the motor, but then dropped down to around 12"hg.

Looks like a new vacuum pump is on my list. I guess I'll be spending some money on a new one since it seems like the best idea. Any ideas where I can find a decent pump at a decent price? Do you think one from the junkyard would be a viable option.

I'm glad to get to the bottom of this. ThANKS.

 

[LCAM-01XA]

Well I just found a good vacuum pump in the junkyard today, at least it feels like it's good cause if I turn the pulley by hand I can feel the vacuum at the end of the hose, so yes, junkyard is a feasible option IMHO, as long as you can find a pump.

 

[TDW]

Well I just found a good vacuum pump in the junkyard today, at least it feels like it's good cause if I turn the pulley by hand I can feel the vacuum at the end of the hose, so yes, junkyard is a feasible option IMHO, as long as you can find a pump.

Auto zone has a re manufactured pump for 110 bucks. Perhaps time saving and 1 year warranty is worth buying it. I'm going to call around and see if any u-pull its have any of these diesels sitting around, because it would be good to start collecting some extra parts.