I have a 1998 Dodge Ram 1500 4x4 and I have a couple questions for you guys. I am new to this forum and have been looking around here for a couple months now and have really enjoyed it. One of my first questions about my truck is about the heater. If I have the heater blowing on the floor or on the front vents and I accelerate all of the air goes on defrost. I think it's because of a break in a vacuum line or to the vacuum Reservoir. I am just not too sure do you guys have any suggestions?
Thanks, Matt

 

Not to sure on the "exacts" of it but search "wild vents". You'll probably find what you need.

 

Wacky vents! And it could be a vacuum leak, does cruise control work?

 

My cruise control does work, but it is a little wacky too. When I set it, it works fine but it won't keep the speed up when going up a hill. In my Chevy Blazer the pedal actually moves and the car will accelerate up the hill and the transmission will downshift. The dodge won't do that at all, if I press the pedal down it will accelerate and will keep that speed up the hill and then when it gets to the top of the hill the pedal will come back out and will go back to the original speed. and maintain that speed till there is another hill. What I usually do is just hit the overdrive button and then it does fine. Sorry if it is a bit wordy.

Matt

 

Looks like a vacuum issue. Check for leaks especially around heater box and around engine and cruise unit.

 

I have seen people talk about Check Valves so that's probably what is wrong and that's what I should check first.

Matt

 

double post

 

Good news. I did have the same problem.
Last week I was replacing the heater blower resistor and finally decided to tackle the vacuum leak so the vents would behave and the cruise control might work.

I replaced the check valve at the manifold, and used a couple new bits of hose to replace the old formed 90° elbows because I felt they were sloppy on the barbed nipple check valve and worse on the new smooth nipple check valve.
Following the two lines from the Y at the check valve, the vent line goes to the reservoir ball and everything looked perfectly usable.
Following the purple line, it went into a sheath and down the side of the radiator to a T at the cruise control module and then to a formed 90° hose that was SUPOSED to be connected to another reservoir ball.

That hose end was sitting right beside the nipple on the ball. I'm sure that was the entire problem, but I kept the new check valve installed.

Two screws for the blinker, two screws for the filler panel below the blinker, and I could reach right in to correct the connection.

Air doors behave perfectly, and the cruise control works excellently.

Wish I’d looked at that before my nearly 3000 mile summer vacation!


1999 Ram Van 1500
5.2 liters, automatic.
140K miles.