4x4 and defrost
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4x4 and defrost
Hi!
I've year a lot in here trying to fix this issue, but have run into a dead end and hoping you can help.
Here's what I've done so far:
- had power to transfer case motor, but wouldn't engage 4wd, even with hubs locked in manually
- replaced transfer case motor, now I have 4h and 4l, but only when locking in hubs manually. This combined with defrost only I'm thinking vacuum
- line going into one of the hubs is rotted out, so I replace them on both sides, still nothing
- no power to the pump initially, replace blown fuse, still nothing. Whack the pump a few times and it starts spinning, so replace that. Still nothing
- replace the vacuum solenoid (not sure that's the right name? part 600-402) still nothing
So now I'm thinking there must be a leak somewhere? Any tips on how to find that, or something else I'm overlooking?
I've year a lot in here trying to fix this issue, but have run into a dead end and hoping you can help.
Here's what I've done so far:
- had power to transfer case motor, but wouldn't engage 4wd, even with hubs locked in manually
- replaced transfer case motor, now I have 4h and 4l, but only when locking in hubs manually. This combined with defrost only I'm thinking vacuum
- line going into one of the hubs is rotted out, so I replace them on both sides, still nothing
- no power to the pump initially, replace blown fuse, still nothing. Whack the pump a few times and it starts spinning, so replace that. Still nothing
- replace the vacuum solenoid (not sure that's the right name? part 600-402) still nothing
So now I'm thinking there must be a leak somewhere? Any tips on how to find that, or something else I'm overlooking?
Thread Starter
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New User
Joined: Mar 2022
Posts: 7
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Hi!
I've year a lot in here trying to fix this issue, but have run into a dead end and hoping you can help.
Here's what I've done so far:
- had power to transfer case motor, but wouldn't engage 4wd, even with hubs locked in manually
- replaced transfer case motor, now I have 4h and 4l, but only when locking in hubs manually. This combined with defrost only I'm thinking vacuum
- line going into one of the hubs is rotted out, so I replace them on both sides, still nothing
- no power to the pump initially, replace blown fuse, still nothing. Whack the pump a few times and it starts spinning, so replace that. Still nothing
- replace the vacuum solenoid (not sure that's the right name? part 600-402) still nothing
So now I'm thinking there must be a leak somewhere? Any tips on how to find that, or something else I'm overlooking?
I've year a lot in here trying to fix this issue, but have run into a dead end and hoping you can help.
Here's what I've done so far:
- had power to transfer case motor, but wouldn't engage 4wd, even with hubs locked in manually
- replaced transfer case motor, now I have 4h and 4l, but only when locking in hubs manually. This combined with defrost only I'm thinking vacuum
- line going into one of the hubs is rotted out, so I replace them on both sides, still nothing
- no power to the pump initially, replace blown fuse, still nothing. Whack the pump a few times and it starts spinning, so replace that. Still nothing
- replace the vacuum solenoid (not sure that's the right name? part 600-402) still nothing
So now I'm thinking there must be a leak somewhere? Any tips on how to find that, or something else I'm overlooking?
Laughing Gas
Joined: Aug 2006
Posts: 1,002
Likes: 2
From: SW ON, Canada
Had a similar problem on my 2001. Followed a similar path as you. Turned out I had leaking seals behind the hub Auto/Lock switch. Since it was a big job getting in there, I ended up replacing the entire hub assembly ... on both sides of the truck. Lots of work and not cheap. But everything works as it should again. Hope this helps Smellysell.
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Joined: Sep 2000
Posts: 23,174
Likes: 1,678
From: Stephensville WI
Hubs not locking and heating system in defrost mode is a classic vacuum leak flag.
Hub seals are a good bet. You might need to use a smoke machine to pinpoint the source if the seals look OK.
Hub seals are a good bet. You might need to use a smoke machine to pinpoint the source if the seals look OK.
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Hotshot
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From: St Louis
Gas or diesel? If diesel, make sure the electric vacuum pump works and supplying steady vacuum. If gas, check the vacuum supply line and connections coming off the intake manifold.
Cap off the supply to the PVH solenoid and see if your vacuum-powered HVAC functions return or not. This will tell you if the leak is in the 4x4 or the HVAC subsystem.
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Yes, however, there are some things you can check before getting a Mighty-Vac or similar. You have to figure out which section of the vacuum system is at fault. otherwise, you'll run around in circles guessing at what's wrong and wasting time and money.
Gas or diesel? If diesel, make sure the electric vacuum pump works and supplying steady vacuum. If gas, check the vacuum supply line and connections coming off the intake manifold.
Cap off the supply to the PVH solenoid and see if your vacuum-powered HVAC functions return or not. This will tell you if the leak is in the 4x4 or the HVAC subsystem.
Gas or diesel? If diesel, make sure the electric vacuum pump works and supplying steady vacuum. If gas, check the vacuum supply line and connections coming off the intake manifold.
Cap off the supply to the PVH solenoid and see if your vacuum-powered HVAC functions return or not. This will tell you if the leak is in the 4x4 or the HVAC subsystem.
Already replaced the pump and solenoid.
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Hotshot
Joined: Jan 2004
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From: St Louis
Just because you replaced something doesn't mean it is good or the original was not. Perform the recommended tests so you know where to focus your attention. See third sentence in my previous post.
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Never even considered that, I'll cap off the solenoid and see if the HVAC works and report back. Thanks
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Yes, however, there are some things you can check before getting a Mighty-Vac or similar. You have to figure out which section of the vacuum system is at fault. Otherwise, you'll run around in circles guessing at what's wrong and wasting time and money.
Gas or diesel? If diesel, make sure the electric vacuum pump works and supplying steady vacuum. If gas, check the vacuum supply line and connections coming off the intake manifold.
Cap off the supply to the PVH solenoid and see if your vacuum-powered HVAC functions return or not. This will tell you if the leak is in the 4x4 or the HVAC subsystem.
Gas or diesel? If diesel, make sure the electric vacuum pump works and supplying steady vacuum. If gas, check the vacuum supply line and connections coming off the intake manifold.
Cap off the supply to the PVH solenoid and see if your vacuum-powered HVAC functions return or not. This will tell you if the leak is in the 4x4 or the HVAC subsystem.
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