Cruise control Not what it used to be!

[PHenry]

It is so hard to find a quality vehicle any more. As soon as my truck rolled over 200k I started having problems with the cruise control. It has always worked flawlessly, but now it is operating much more like the older type, when you set the speed, it drops between 10 -15 miles per hour, then very slowly rebuilds the speed.

I have always been greatly impressed with the collective wisdom of this board, and hope that some of you can offer me some guidance on where to go next to fix the problem. Thanks!

 

[100 Proof]

Mine is a 6 speed and the cruise control is completely electronic, but IIRC the automatics do use a diaphragm. If this is the case, I'd check the integrity of the diaphragm and any any other pneumatic components/plumbing and whatever generates the pressure differential for the system.



Good Luck!



100 Proof

 

[Lordsman]

Maybe you have a slight leak on the vacuum line somewhere causing your problem?

 

[Bob4x4]

It is so hard to find a quality vehicle any more. As soon as my truck rolled over 200k I started having problems with the cruise control. Thanks!

I hope you are kidding... ... ..... how many vehicles even make it to 200k :-laf:-laf

 

[PHenry]

I did forget the sarcasm font!

Thanks for the suggestions.

 

[Bill Stockard]

There could be a problem with the electric vacuum pump located on the passenger side fender well near the firewall. The vacuum pump provides vacuum to the cruise control servo located under the driver side battery.



Bill

 

[Axekicker]

There could be a problem with the electric vacuum pump located on the passenger side fender well near the firewall. The vacuum pump provides vacuum to the cruise control servo located under the driver side battery.



Bill

My cruise died a couple of months ago... . put in a new vacuum pump... still didn't work. Ran it over to Jim Marsh Chrysler and Ray (my favorite mechanic over there) had it figured out and fixed in a couple of hours. It was the 'servo'... as Bill mentioned. That's 7 years and 145,000 miles. Not bad in my book.

 

[Bill Stockard]

That's 7 years and 145,000 miles. Not bad in my book.

Yep, not bad... "they don't make 'em like they used to"... :-laf:-laf



Bill

 

[JSooter]

I just found & fixed a small leak in my cruise control vacuum line... right where one of the original zip ties helped route the hose down under the battery. Looks like it was a bit too tight from the beginning. Temp variations eventually caused it to crack.



The parts store didn't have the OEM type vacuum line so I cut the line and spliced with with 2 inches of rubber hose that fit snugly over the OEM line. Works great now.



I first noticed the problem when working on the truck. I had the key in the ON position (w/o engine running) and I could hear the vacuum pump constantly running. The CC still worked at that point, but I didn't want to take a chance on killing the pump.

 

[Axekicker]

I just found & fixed a small leak in my cruise control vacuum line... right where one of the original zip ties helped route the hose down under the battery. Looks like it was a bit too tight from the beginning. Temp variations eventually caused it to crack.

Good catch! :-laf