What is this plug for?

Author Topic: What is this plug for?  (Read 1250 times)

Offline kbiggar

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What is this plug for?
« on: December 10, 2018 - 10:19:56 PM »
Found this plug around the master cylinder. Just bought the car (73 Barracuda) and wondering if this was ever plugged in. Oil pressure sending unit?
« Last Edit: December 10, 2018 - 11:07:43 PM by kbiggar »




Offline Beekeeper

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Re: What is this plug for?
« Reply #1 on: December 10, 2018 - 11:13:35 PM »
It’s hard to tell from your photo but taking a wild guess, it reminds me of the plug that goes to the proportioning valve directly below the master cylinder. If there is an imbalance detected in the braking system, it causes a red light on the dash.

Offline 70chall440

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Re: What is this plug for?
« Reply #2 on: December 10, 2018 - 11:46:34 PM »
based on the picture I probably agree, would need to see the inside of the rubber plug; how many connections are in there, if its just one (i.e. a round hole) then it probably is as Beekeeper suggests.
Current Mopar
70 Challenger RT 440-6 EFI, 73 Cuda 416-6 EFI
05 Hemi Durango, 01 Ram 4x4, 14 Ram 2500 4X4, 10 PCP Challenger 6 spd RT, 01 Viper GTS ACR, 52 B3B w/330 Desoto Hemi, 70 Hemi RR (under const)
Past Mopars
9 x Challengers. AAR Cuda, 4 RR, 2 GTX, 4 Chargers, etc... (too many to list)

Offline kbiggar

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Re: What is this plug for?
« Reply #3 on: December 11, 2018 - 03:57:12 PM »
Thanks guys, that seems like the most probable location for this.

Offline Beekeeper

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Re: What is this plug for?
« Reply #4 on: December 11, 2018 - 04:12:13 PM »
Thanks guys, that seems like the most probable location for this.

Easy to verify. It’s directly below the master cylinder. If there is already a wire plugged on then this is probably something different.

Offline jimynick

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Re: What is this plug for?
« Reply #5 on: December 11, 2018 - 10:15:41 PM »
Yeah, that's got to be the warning light plug off the proportioning valve, it's the only plug like that in the car to the best of my recollection. Sometimes, if the car blew a brake line, the valve would get stuck one way and wouldn't reset, thereby keeping the warning light on, necessitating pulling the wire off to make it go away.  :cheers:

Offline kbiggar

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Re: What is this plug for?
« Reply #6 on: December 12, 2018 - 09:39:50 AM »
Yeah, that's got to be the warning light plug off the proportioning valve, it's the only plug like that in the car to the best of my recollection. Sometimes, if the car blew a brake line, the valve would get stuck one way and wouldn't reset, thereby keeping the warning light on, necessitating pulling the wire off to make it go away.  :cheers:

Bingo - talked to the previous owner, it was unplugged to turn off the brake light. Looks like I will have to try resetting the proportioning valve to see if that clears the light.

Offline Beekeeper

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Re: What is this plug for?
« Reply #7 on: December 12, 2018 - 09:48:49 AM »
How do the brakes work? If the old master cylinder is failing, it could create pressure imbalance and the warning light is trying to tell you something.

If it’s the original master, I’d be tempted to replace it along with flushing all the lines with clean fluid. It’s just good insurance and not much cost (though sometimes a sucky job). You would be surprised how a system that seems operational goes from okay to great.

Offline jimynick

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Re: What is this plug for?
« Reply #8 on: December 12, 2018 - 10:21:43 PM »
The valves can be taken apart. There's a thread on here somewhere about that. I've also heard that, contingent on the brake system being up to it, that hammering on the brakes a few times might move the valve back to it's proper position, but it's a Hail Mary deal. Good luck and read up on repro valves which seem to have a lousy reputation.

Offline kbiggar

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Re: What is this plug for?
« Reply #9 on: December 12, 2018 - 10:34:22 PM »
The valves can be taken apart. There's a thread on here somewhere about that. I've also heard that, contingent on the brake system being up to it, that hammering on the brakes a few times might move the valve back to it's proper position, but it's a Hail Mary deal. Good luck and read up on repro valves which seem to have a lousy reputation.
Great advise. I stomped on the brakes a couple times and everything works great now.


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Offline 70chall440

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Re: What is this plug for?
« Reply #10 on: December 12, 2018 - 10:57:03 PM »
 :2thumbs:
Current Mopar
70 Challenger RT 440-6 EFI, 73 Cuda 416-6 EFI
05 Hemi Durango, 01 Ram 4x4, 14 Ram 2500 4X4, 10 PCP Challenger 6 spd RT, 01 Viper GTS ACR, 52 B3B w/330 Desoto Hemi, 70 Hemi RR (under const)
Past Mopars
9 x Challengers. AAR Cuda, 4 RR, 2 GTX, 4 Chargers, etc... (too many to list)

Offline jimynick

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Re: What is this plug for?
« Reply #11 on: December 13, 2018 - 10:39:27 PM »
Hah! Maybe we all should go out and buy a lottery ticket, eh? Good news!  :thumbsup: