99 f350 vacuum problems
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99 f350 vacuum problems
Ive got a 99 F350 with a 7.3L and am stumped with this vacuum system
The vacuum pump will not shut off and the HVAC defaults on defrost and after reading I decided to try to isolate to determine if it was coming form the firewall line or the hub line to determine where the leak is.
After pulling each line individually right after the tee on the reservoir and plugging it I still could not get the pump to shut off. I even tried plugging both at the same time and still kept running. I did notice some pressure behind the line going through the firewall but no pressure in the line that feeds the hubs. I'm assuming my problem is either the reservoir, pump, or solenoid.
Has anyone else encountered this problem..
Thanks for any help
The vacuum pump will not shut off and the HVAC defaults on defrost and after reading I decided to try to isolate to determine if it was coming form the firewall line or the hub line to determine where the leak is.
After pulling each line individually right after the tee on the reservoir and plugging it I still could not get the pump to shut off. I even tried plugging both at the same time and still kept running. I did notice some pressure behind the line going through the firewall but no pressure in the line that feeds the hubs. I'm assuming my problem is either the reservoir, pump, or solenoid.
Has anyone else encountered this problem..
Thanks for any help
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Joined: Sep 2013
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From: Edmonton, AB
There isn't a solenoid for the vacuum pump but there is a vacuum switch built into the pump itself that turns it off when the vacuum is pumped down enough.
If your pump runs all the time, the switch is bad. You might be able to fiddle around with it to get it working again but if the switch is bad, then you have to replace the whole pump. Hope that helps, probably not the news you wanna hear thou. If you have checked all your fittings and lines and you do not detect a leak then you can bet your pump is hooped and needs to be replaced
If your pump runs all the time, the switch is bad. You might be able to fiddle around with it to get it working again but if the switch is bad, then you have to replace the whole pump. Hope that helps, probably not the news you wanna hear thou. If you have checked all your fittings and lines and you do not detect a leak then you can bet your pump is hooped and needs to be replaced
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There isn't a solenoid for the vacuum pump but there is a vacuum switch built into the pump itself that turns it off when the vacuum is pumped down enough.
If your pump runs all the time, the switch is bad. You might be able to fiddle around with it to get it working again but if the switch is bad, then you have to replace the whole pump. Hope that helps, probably not the news you wanna hear thou. If you have checked all your fittings and lines and you do not detect a leak then you can bet your pump is hooped and needs to be replaced
If your pump runs all the time, the switch is bad. You might be able to fiddle around with it to get it working again but if the switch is bad, then you have to replace the whole pump. Hope that helps, probably not the news you wanna hear thou. If you have checked all your fittings and lines and you do not detect a leak then you can bet your pump is hooped and needs to be replaced
So there isn't a solenoid? It appears the wires that feed the pump go to a solenoid mounted on the passenger side fender. Wouldn't my vents work and not go to the defrost even if that switch is bad? The way I'm understanding this is the pump wouldn't shut off it would keep pumping but still show be enough pressure to move the vents...
Thanks for the help
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Joined: Oct 2014
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From: NY/Canada border
Posting Guru
Joined: Sep 2013
Posts: 1,348
Likes: 6
From: Edmonton, AB
So there isn't a solenoid? It appears the wires that feed the pump go to a solenoid mounted on the passenger side fender. Wouldn't my vents work and not go to the defrost even if that switch is bad? The way I'm understanding this is the pump wouldn't shut off it would keep pumping but still show be enough pressure to move the vents...
Thanks for the help
Thanks for the help
So if you have checked for leaks in your lines and fittings and have found none , then I would say that the switch in the pump is toast. You could rent a tool that will allow you to hand pump the various lines to see if they hold pressure and try and test it that way to confirm that you have no leaks, but you sound very confident that you have checked those and found no leaks
You could always pull off lines on the vacuum side and plug them off one at a time and double check the various lines and fittings ( you may have done that already though ) There is a vacuum line behind the glove box that can work itself loose? Did you have a look at that one to see if all was good?
There could be a leak in the solenoid itself, but I am not 100% sure on the voltages it needs and what it puts on when it is engaged to test it. Someone else might be able to chime in and tell you though. Lots of smart folks here
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