Takes a while to build vacuum
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Elder User
Joined: Dec 2008
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From: North Carolina
Takes a while to build vacuum
When i start the truck air only blows out of the defrost vents... then after about 5-10 seconds it switches to the front vents (or whatever i have selected). It then works fine until i turn off the truck again.
Is this normal or do i have a vacuum leak? (haven't had the truck that long, but it has allways done this for me.) I have searched for a leak several times, but have found nothing...
Also, right when the vacuum builds up enough to switch the vents i get a slurping/farting/grinding noise that lasts for about 1/2 second or so... can't really tell what it is... any ideas?
Is this normal or do i have a vacuum leak? (haven't had the truck that long, but it has allways done this for me.) I have searched for a leak several times, but have found nothing...
Also, right when the vacuum builds up enough to switch the vents i get a slurping/farting/grinding noise that lasts for about 1/2 second or so... can't really tell what it is... any ideas?
FTE Leadership Emeritus
Joined: Aug 2007
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From: Lakewood, Ca.
It's probably the blend door closing.Sounds like you have a very slight vacuum leak that's going to be tough to find.
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Elder User
Joined: Dec 2008
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From: North Carolina
Can the blend door be replaced or somehow adjusted to prevent this? It is quite loud and embarassing when i have others in the cab...
FTE Leadership Emeritus
Joined: Aug 2007
Posts: 42,085
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From: Lakewood, Ca.
Looks like Mr. Chamberlain has what you need.
Thanks for the correction, David.
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Elder User
Joined: Dec 2008
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From: North Carolina
The noise sounds like it is coming from the "panel/floor vacuum control motor" area.
I'll tear into it this weekend.
Thanks guys.
I'll tear into it this weekend.
Thanks guys.
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FTE Leadership Emeritus
Joined: Jul 2002
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From: Long Island USA
Couple of thoughts:
Do you have ESOF? If so, the vacuum solenoid could be leaking, and draining the vacuum reservoir. Then, start the engine, and it takes a few seconds to build vacuum up in the reservoir again which also powers the climate stuff.
Or, there is a one-way valve before the reservoir, so it holds vacuum. That could be leaking, so when the engine is not supplying vacuum, it slowly empties (fills?) the reservoir.
Or, the reservoir itself could be bad - I've heard of them cracking from age.
Do you have ESOF? If so, the vacuum solenoid could be leaking, and draining the vacuum reservoir. Then, start the engine, and it takes a few seconds to build vacuum up in the reservoir again which also powers the climate stuff.
Or, there is a one-way valve before the reservoir, so it holds vacuum. That could be leaking, so when the engine is not supplying vacuum, it slowly empties (fills?) the reservoir.
Or, the reservoir itself could be bad - I've heard of them cracking from age.
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Thread Starter
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Elder User
Joined: Dec 2008
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From: North Carolina
I do have ESOF, and have capped my vac lines (warns). I do not loose vacuum when i switch to 4x4, but if it is a small leak at the solenoid maybe it wouldn't drain the reservoir enough to effect other things... I'll cap the lines going into the solenoid and see if that helps.
Is there a vacuum bleed-down spec? As in how long is should take for the vacuum to go to zero after you turn off the truck based on normal leakage? maybe i can check the 1-way valve and reservoir with a vacuum pump?
Is there a vacuum bleed-down spec? As in how long is should take for the vacuum to go to zero after you turn off the truck based on normal leakage? maybe i can check the 1-way valve and reservoir with a vacuum pump?
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Joined: Jul 2002
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From: Long Island USA
I don't know of any spec - I suspect ANY loss of vacuum in the reservoir is not a good thing. You might just have a kinked/clogged line ... or something else going on.
I haven't spent enough time under the hood playing with vacuum to tell when/how fast the reservoir builds vacuum.
I haven't spent enough time under the hood playing with vacuum to tell when/how fast the reservoir builds vacuum.
