Folks, my cruise control has developed some issues, which are not addressed in the service manual. So I figured I'll post some information on that.
@BudW has already posted some great information on CC in Mopars and retrofitting.
What happened:
Some days ago, I was able to set the speed on my CC. Then, it lost speed (approx. 8 mph), just to then push the gas to re-gain speed. Then loosing speed, gaining, loosing, you get the idea.
Days later, the CC just hold the throttle at what it was set - but not adjusting to uphill. It just lost speed because the throttle was unchanged. At the same time, I noticed a slightly higher coolant temperature. Might that be related? Thinking while driving keeps you awake
. So I figured, that the membrane inside the servo unit could be broken, allowing unmetered air to the engine, leaning out the mixture and thereby increasing coolant temperature. At the same time, this leak prevents the servo unit to apply sufficient force to increase throttle. In addition, momentarily pushing the set button to increase speed did not work.
I figured, well, there's no parts available at Rockauto and there are hardly any pull-a-part's aroung here in Germany (e.g. none you could stroll around for yourself, anymore), not even thinking of finding any Mopar Parts to pull... So - take it apart.
First, the filter element at the side was pretty much broke. It dis-integrated just by touching lightly (no picture). Cleaned that thing and replaced it with four layers of a filter element for a vacuum motor.
Then, I opened up the vacuum part of the thing. It was pristine inside (see pictures), except that the vacuum inlet "valve" (lower part on first and second picture; second pic has the center cover removed [three screws]) was slightly stained, as well as the conical inlet port. Cleaned that. Other than that, nothing to do - except that I actually found a small leak in the diaphragm (hard to see on the third picture). I put a drop of instant glue (Cyanoacrylate) on it and hope, that it'll hold. If the diaphragm is EPDM (likely), then chance are, that it will not hold very long. Further, risk of breaking at other areas exist, of course...
Fortunately, a good local friend of mine has a servo unit (off a 78 motor home), which has only 27.000 mls on it.
If all this doesn't help, I'll try to get some generic 0.7mm EPDM diaphragm and try that.
Test drive will take place the coming days (hopefully). Not tomorrow, as a friend from South Carolina (another 78 Dodge motor home and 68 Polara owner ) is visiting my house.
Meanwhile, a 7500mls oil+filter change and one of the upper ball joints replaced. I just *love* my impact drill. But, advise: do this whenever you have the brake hose disconnected - it is just completely in the way for this job. (But I hate to bleed the brake system even more and it is possible with the brake hose attached, but you have to be very, very careful if you'll use a (small) puller),
@BudW has already posted some great information on CC in Mopars and retrofitting.
What happened:
Some days ago, I was able to set the speed on my CC. Then, it lost speed (approx. 8 mph), just to then push the gas to re-gain speed. Then loosing speed, gaining, loosing, you get the idea.
Days later, the CC just hold the throttle at what it was set - but not adjusting to uphill. It just lost speed because the throttle was unchanged. At the same time, I noticed a slightly higher coolant temperature. Might that be related? Thinking while driving keeps you awake
. So I figured, that the membrane inside the servo unit could be broken, allowing unmetered air to the engine, leaning out the mixture and thereby increasing coolant temperature. At the same time, this leak prevents the servo unit to apply sufficient force to increase throttle. In addition, momentarily pushing the set button to increase speed did not work.I figured, well, there's no parts available at Rockauto and there are hardly any pull-a-part's aroung here in Germany (e.g. none you could stroll around for yourself, anymore), not even thinking of finding any Mopar Parts to pull... So - take it apart.
First, the filter element at the side was pretty much broke. It dis-integrated just by touching lightly (no picture). Cleaned that thing and replaced it with four layers of a filter element for a vacuum motor.
Then, I opened up the vacuum part of the thing. It was pristine inside (see pictures), except that the vacuum inlet "valve" (lower part on first and second picture; second pic has the center cover removed [three screws]) was slightly stained, as well as the conical inlet port. Cleaned that. Other than that, nothing to do - except that I actually found a small leak in the diaphragm (hard to see on the third picture). I put a drop of instant glue (Cyanoacrylate) on it and hope, that it'll hold. If the diaphragm is EPDM (likely), then chance are, that it will not hold very long. Further, risk of breaking at other areas exist, of course...
Fortunately, a good local friend of mine has a servo unit (off a 78 motor home), which has only 27.000 mls on it.
If all this doesn't help, I'll try to get some generic 0.7mm EPDM diaphragm and try that.
Test drive will take place the coming days (hopefully). Not tomorrow, as a friend from South Carolina (another 78 Dodge motor home and 68 Polara owner
) is visiting my house.Meanwhile, a 7500mls oil+filter change and one of the upper ball joints replaced. I just *love* my impact drill.
But, advise: do this whenever you have the brake hose disconnected - it is just completely in the way for this job. (But I hate to bleed the brake system even more and it is possible with the brake hose attached, but you have to be very, very careful if you'll use a (small) puller), 
