Is it a vac problem?

[Truckin4life]

Driving home from work i have to cross the frontage road of the hiway... traffic is 50mph...
I have to easy on to the road due to the horrible job they did "fixing" the rock road... once i hit the pavement, i have to floor it through second gear to make it, only during rush hour.
Only had to do it twice so far, but both times my heater went from burn your hand hot to cold...
after about 5 min it goes back to hot...
I am wondering if its a vac problem,
In 1st gear i go from idle to 3k before i hit the second lane...

So is it a vac problem due to the very sudden high rev's?
I know 3k isn't hi rev's for the motor, but its all i can think of...

 

[Skandocious]

The blend door for cold/hot is not vac operated-- its the only dial of the 3 that is actually cable operated. So changing from hot to cold is probably not a vac issue. If it changed from dash vents to defrost then yes, vac issue.

 

[countryboytn]

It's cause of that sudden rush of air at WOT, from that big ol' carb/blower set you up got cools the motor down... in turn, cooling the heat down.








In other words, I have no idea what your problem is... I just wanted to add to my post count.

 

[5.0Flareside]

It's cause of that sudden rush of air at WOT, from that big ol' carb/blower set you up got cools the motor down... in turn, cooling the heat down.








In other words, I have no idea what your problem is... I just wanted to add to my post count.

 

[Truckin4life]

hmmmm... anybody got an explanation?
Maybe goin full throttle so quickly the coolant level lowers or possibly creates a vaccum pulling the coolant from the heater lines?


I am talkin out my arse, and thinking out loud here, so bare with me...

But that would mean im low on coolant, which last check i wasn't possibly air in the system?

 

[Skandocious]

Yeah I was kinda thinkin you might have air in the system. Only way you'd be blowing cold is if coolant stops flowing through that element in the dash. I'd try burping the system and checking your coolant level.

 

[Truckin4life]

sounds like a plan then ill hop on it tomorrow... If im not to hung over...

 

[emtzach]

yeah I was gonna say low coolant or air pocket its the most common cause of off and on heat

 

[Truckin4life]

but its not off and on, i can run it pedal down and it still blows lava hot, only when i go from idle to full throttle in first gear....

 

[A_G]

hmmmm... anybody got an explanation?
Maybe goin full throttle so quickly the coolant level lowers or possibly creates a vaccum pulling the coolant from the heater lines?


I am talkin out my arse, and thinking out loud here, so bare with me...

But that would mean im low on coolant, which last check i wasn't possibly air in the system?

Thats exactly whats going on. Check your coolant levels, let it run a bit with cap off and add some coolant.

Eventually it will jsut go through periods of hot and cold as the theremostat opens. if you leave it.

WHen mines gets low i can hear water sounds from the passenger side.

 

[Truckin4life]

It never goes through hot then cold, its warm with in 5 minutes and will burn you out of the truck on the coldest days around here...
Whenever it was, few weeks ago i think it was like 12 degrees before windchill, i still had to cut my heater down to low, so i wouldn't sweat.

 

[countryboytn]

Any luck figuring it out?

 

[Truckin4life]

Low on coolant, not very much though, explains the never losing heat unless the truck revs very quickly.