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Topic: Air exhausting at firewall valve (Read 536 times) previous topic - next topic

Air exhausting at firewall valve

I'm not sure if the link will work to the video but I've attached a picture of the small valve (below the black cannister/accumulator). Whenever driving this small valve exhaust every 10 seconds or so, I don't recall this happening before. Anyone have this happen before?


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Re: Air exhausting at firewall valve

Reply #2 –
Like craneman posted it is a vacuum generator utilizing air pressure through a venturi to generator a vacuum.  Diesel engines don't have vacuum from the manifold like a gas engine does so they used a vacuum generator.

Re: Air exhausting at firewall valve

Reply #3 –
is it normal for it to vent like that (every 10 secs or so)? or does that mean there's a vacuum leak downstream causing it to work more than normal?

Re: Air exhausting at firewall valve

Reply #4 –
Quote from: len.barron –
...does that mean there's a vacuum leak downstream causing it to work more than normal?
Since this is "new" behavior, I would say your guess is a good possibility.  Check all the vacuum lines you can see or reach for cracks or loose connections.  There are some vacuum lines under the lift-up dash cover - attached to the heater/air conditioner controls.

Re: Air exhausting at firewall valve

Reply #5 –
I was pretty sure it was new, so, after reading through a bunch of the related threads I saw that heater controls position (setting static in one spot) might be the cause, sure enough after I cycled it through the different positions it cleared right up, now it only cycles after a couple of vent position  changes (from "off" to "vent" to "heat") then it will cycle a single time to recharge the canister with vacuum.
Thanks to all for the help! That vacuum generator isn't in the air system drawing..

Re: Air exhausting at firewall valve

Reply #6 –
There are also a number of 12 VDC vacuum pumps-- for example on Ford trucks with diesel engines.  Just another option if the air/vacuum generator is $$$ to repair/replace.

Re: Air exhausting at firewall valve

Reply #7 –
Quote from: wolfe10 –
There are also a number of 12 VDC vacuum pumps-- for example on Ford trucks with diesel engines.  Just another option if the air/vacuum generator is $$$ to repair/replace.
My Duramax Express Van uses one for the heater controls...of course GM saw fit to install it directly below the battery so if you have any acid leak it eats it up..  ::)

Re: Air exhausting at firewall valve

Reply #8 –
Speaking of vacuum generator--is that what is under the entry step on my coach and what does it control?  Also, has anyone moved it some other place to better utilize space under step?
Thanks
Chris

Re: Air exhausting at firewall valve

Reply #9 –
It controls the HVAC registers. I moved mine to the back side so I could have the step conversion.
 

Re: Air exhausting at firewall valve

Reply #10 –
Our 91 GV has a vacuum pump up front next to the AC cooler.  Have a great day  ----  Fritz