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Hey folks I have a 2000 f250 with the 7.3, I bought it about a week ago. When I turn the key on engine off this black cylinder device vibrates extremely loudly. It’s on the passenger side next to the fender. I have had a 7.3 before and never heard this noise at least not this loud and aggressive. Thanks in advance
Not quite loud enough to hear once the truck is running. Just when the key is on engine off. However doing some more digging on the internet another post describes how if you lose control of the air flow in the cab it could be a bad vacuum pump. Which my air is flow is stuck on defrost. So I’m thinking that might be the issue.
Yeah, the vacuum pump is responsible for the vacuum supply for the inlet and outlet vacuum motors in the HVAC system. Loss of vacuum = defrost only. Also, vacuum is used for the hubs in 4x4 systems (if equipped).
Those vacuum pumps are not particularly failure prone, sure one fails every now and then, but overall they're pretty dang long lived little vacuum pumps.
If its running constantly and you're stuck on defrost, look for a broken / disconnected vacuum hose somewhere first before dropping money on a replacement pump.
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Yes actually the pump just runs constantly. So that makes sense it must not be building any pressure. Didn’t have a chance to test the auto hubs out when I bought the truck because the oil pan and tranny cooler line were leaking so bad but I’m going to assume they weren’t going to work. I just got the motor back in and running. I will check for vac leaks today.
X2 on the above. You likely have a rotted off hose somewhere that is causing a vacuum leak. Luckily they are easy to find. Follow the lines from that pump and check the lines running down to each hub. You can just cap them off and put on a set of manual locking hubs too.
If you can hear it, check the mounts too, usually you can't hear these running, even if running constantly. It might have a broken mount that is vibrating too.
Ok guys just an update,
I started at the pump it’s self to make sure that was holding vacuum. I pulled the line that went from the pump to tank and plugged the end. The pump just kept running. I also unplugged and capped the line off the pump that loops around to itself just to be sure and it still just kept running. I’m assuming the pump is no good? It’s a Chinese brand so I’m going to replace with motorcraft. Then I can chase the rest of the lines for leaks. I did find that the passenger side hose was unhooked from the hub.
Hey folks just an update.. installed the new pump and it held vacuum. From there I tested the tank which also held vacuum. After that I tested just the lines to the cab vents which held vacuum. Once I got to the 4x4 actuator ( I think that’s what it’s called) vacuum would not hold. Plugging the outlet of the actuator it still would not hold vacuum so that will need to be replaced which I’m not surprised it’s cracked in several places. Once that’s in I can test the rest of the hoses to the 4x4 hubs. Thanks for the help guys!
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