Another HVAC / Cruise Control Vacuum Issue

[SFCJCA]

I've read all the threads I can find about vacuum leaks and they've helped me a lot so far with checking my vacuum lines. But I haven't run across this issue in any other threads.

Jeep is a 2006 TJ 6 cylinder. HVAC controls and Cruise Control (CC) work fine for a few days. Then CC stops working and air flow only at the defrosters. I let the Jeep sit over night and check the vacuum lines in the morning. I don't find any apparent leaks. When I disconnect the vacuum line, there's vacuum still in the line and I can feel air rushing into the line. When I reconnect the vacuum line, everything works fine; CC works and HVAC controls work. Works fine for a few days and then back to no CC and defrost only. I then pull the vacuum hose, hear/feel the vacuum, reconnect and everything is good for a few more days.

Any suggestions to fix this issue?

Thanks,
John

 

[NskLJ]

I've read all the threads I can find about vacuum leaks and they've helped me a lot so far with checking my vacuum lines. But I haven't run across this issue in any other threads.

Jeep is a 2006 TJ 6 cylinder. HVAC controls and Cruise Control (CC) work fine for a few days. Then CC stops working and air flow only at the defrosters. I let the Jeep sit over night and check the vacuum lines in the morning. I don't find any apparent leaks. When I disconnect the vacuum line, there's vacuum still in the line and I can feel air rushing into the line. When I reconnect the vacuum line, everything works fine; CC works and HVAC controls work. Works fine for a few days and then back to no CC and defrost only. I then pull the vacuum hose, hear/feel the vacuum, reconnect and everything is good for a few more days.

Any suggestions to fix this issue?

Thanks,
John

Replace the check valves,

 

[TJ Jim]

Check valve is sticking closed

 

[SFCJCA]

Thanks. I ordered a new check valve. I'll update later with results.

 

[SFCJCA]

It seems it was the check valve by the firewall where the vacuum line goes inside behind the dash. Thanks for your help.

 

[hear]

It seems it was the check valve by the firewall where the vacuum line goes inside behind the dash. Thanks for your help.

There's another one near the back corner of the intake. I had one go bad, I assumed the other one was 21 years old so I replaced it too. (they came in packs of 2 so the decision was easy)

 

[SFCJCA]

There's another one near the back corner of the intake. I had one go bad, I assumed the other one was 21 years old so I replaced it too. (they came in packs of 2 so the decision was easy)

thanks. I'll keep that it mind if the HVAC controls go out again.

 

[hear]

I found all my lines to be super brittle, I wouldn't spend a lot of time chasing issues before I just replaced all the underhood lines.

 

[SFCJCA]

I found all my lines to be super brittle, I wouldn't spend a lot of time chasing issues before I just replaced all the underhood lines.

My lines aren't brittle yet. Did you buy a factory vacuum line replacement or run your own lines? The factory option isn't too expensive until you get to shipping costs.

 

[hear]

My lines aren't brittle yet. Did you buy a factory vacuum line replacement or run your own lines? The factory option isn't too expensive until you get to shipping costs.

I just went to autozone to get vacuum hose & some t-fittings or whatever. They didn't have any of that hose, so I now have similar sized fuel-rated hose for my vacuum lines (for the same price since I'm a regular). Slightly overkill, but it required zero effort and it'll outlive me.

 

[NskLJ]

My lines aren't brittle yet. Did you buy a factory vacuum line replacement or run your own lines? The factory option isn't too expensive until you get to shipping costs.

You should be able to find a roll of the plastic line and and assortment of elbows and tees on Amazon for under $20