1987 Chevy V10 Suburban 350 V8 4X4 Cruise Control Servo??

[Burb restorer]

Greetings fellow Chevrolet Suburban owners!!!! Well, almost done with my 1987 Suburban 4X4 restoration, now, the cruise control does not work. After prodding, poking and test driving, it seems the cruise control servo is not working. Well, I can NOT find an original GM unit, PT# 25074630 OR a Cardone reman unit, PT# 38-1630. I was wondering if ANYONE out there had a cruise control servo you could sell me OR guide me in the right direction to locate one. I have tried O'Reilly's, NAPA, Advance Auto, CARID, Summit, Rock Auto-don't want to send in a "We MIGHT can fix it and if NOT, we send it back to you" sort of deal. I just want to purchase another working unit. I did find a video of how to disassemble the unit and replace the little foam filter inside. I did that and the factory book has three servo OHM readings to check and they all three check out fine. The module checks out (Using a Fluke DVOM) with the switch when the plug is hooked up. The fuses are good, the vacuum harness is good and working, the brake light switch is all working so I'm am taking a break. The turn signal lever is all new and I checked it again, it's good to go too. I really want to know....when you remove the two solenoids (VERY CAREFULLY) and remove the small spring AND rubber ball on top, there is a small pin on the OTHER side of the servo that is connected to a hidden diaphragm, and it DOES NOT come out. It doesn't separate to gain access to that diaphragm UNLESS you have to remove the light colored plug with the very small hole in it on the opposite side....I THINK. Has anyone ever ventured this far into it? Just looking for a really good answer. Thanks to all for your time and keep those Burb's running!!!

 

[90 suburban]

Hey restorer,
Did you get any where with your question/need?? I have the same situation.
Don

 

[90 suburban]

Here's what I did to fix my cruise control problem.
Symptoms:
Was only occasionally working. Eventually quit working altogether.

Diagnosed all the wiring and everything was correct.

Replaced the cruise brake switch...didn't fix the problem.

Replaced the cruise lever...didn't fix the problem.

Removed the vacuum servo from the firewall. Disassembled and cleaned all contacts with De-Oxit electrical cleaner. Checked the three solenoids for continuity with volt meter. One of the solenoid plungers had some corrosion and the wire wrapping was broken. Peeled off a foot or so of the wire and found the other broken end. Stripped 1/2" of the coating from the loose wire ends, twisted them together, coated the twist with small amount of clear silicon caulk, and verified had continuity with volt meter. Also replaced the circular filter beneath the solenoid with a piece of foam cut to fit. Reassembled the servo and capped the larger of the two vacuum ports on the servo eliminating the brake air dump cruise deactivator. Verified all the vacuum lines were good and reinstalled the servo to firewall.

The cruise system now works like a brand new unit including all resume/deaccelerate functions.

The vacuum servo is not available to purchase from anywhere including Cardone that supplies the parts houses.
So save yourself some time trying to find one and give this a try. Really wasn't that complicated. Just be careful not to loose any of the small parts because they are unavailable anywhere.

Good luck!

 

[90 suburban]

Greetings fellow Chevrolet Suburban owners!!!! Well, almost done with my 1987 Suburban 4X4 restoration, now, the cruise control does not work. After prodding, poking and test driving, it seems the cruise control servo is not working. Well, I can NOT find an original GM unit, PT# 25074630 OR a Cardone reman unit, PT# 38-1630. I was wondering if ANYONE out there had a cruise control servo you could sell me OR guide me in the right direction to locate one. I have tried O'Reilly's, NAPA, Advance Auto, CARID, Summit, Rock Auto-don't want to send in a "We MIGHT can fix it and if NOT, we send it back to you" sort of deal. I just want to purchase another working unit. I did find a video of how to disassemble the unit and replace the little foam filter inside. I did that and the factory book has three servo OHM readings to check and they all three check out fine. The module checks out (Using a Fluke DVOM) with the switch when the plug is hooked up. The fuses are good, the vacuum harness is good and working, the brake light switch is all working so I'm am taking a break. The turn signal lever is all new and I checked it again, it's good to go too. I really want to know....when you remove the two solenoids (VERY CAREFULLY) and remove the small spring AND rubber ball on top, there is a small pin on the OTHER side of the servo that is connected to a hidden diaphragm, and it DOES NOT come out. It doesn't separate to gain access to that diaphragm UNLESS you have to remove the light colored plug with the very small hole in it on the opposite side....I THINK. Has anyone ever ventured this far into it? Just looking for a really good answer. Thanks to all for your time and keep those Burb's running!!!

I did not take that pin apart. Once cleaned and reassembled the smaller of the vacuum ports will not allow air in or out. You can test by blowing or drawing on the port.

 

[mcarlo86]

Might have to try this. The cruise doesn't work in our '90 suburban either and I'm pretty sure the servo is to blame.

 

[Burb restorer]

Well, I fixed the servo a few weeks ago. Took it apart, cleaned it, replaced all of the rubber seal/o rings and made a new little internal filter. All ohm and voltage checks on the brake light switch, connections and module connector-ALL passed with flying colors. Then I sealed the large diaphragm with silicone and it works PERFECT!!