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92SCtk
06-08-2017, 08:05 AM
How difficult is it to rebuild the brake actuator assembly/re-do seals? Mine leaks enough while it sits that I have to top it off every few weeks, but that's getting old. Remanfactured or sending it out to SCP to have it done is $600. Is there another option? Probably would end up being a winter project at this point, but I want to get some ideas.

KMT
06-08-2017, 09:46 AM
How difficult is it to rebuild the brake actuator assembly/re-do seals? Mine leaks enough while it sits that I have to top it off every few weeks, but that's getting old. Remanfactured or sending it out to SCP to have it done is $600. Is there another option? Probably would end up being a winter project at this point, but I want to get some ideas.

Can you identify exactly where the leak is originating?

The SC has a pressure switch down on the firewall that is used to trigger the ARC system...auto shocks. These are common leakers when they they get old. They are generally below the master cylinder, and can make it appear the MC is the leak source. They were hard to find for a while, but I think they've come back on the market, recently. The switch itself leaks thru the connector body.

As well, the seal on the hydraulic pump motor can fail over time - it sits on the master cylinder assembly, right below everything else. Replacements aren't common, but some have used a Honda part, as I recall. The MC assembly has to come out of the car to do this.

Another leak source is the o-ring on the accumulator. This seal can be sourced without too much trouble, just be sure to get the right type - info here via search. Accumulator R&R is not hard. Tips here via search.

I haven't seen general leaks from the master cylinder body itself, but I'm sure they can happen.

The difficulty in re-sealing the 'assembly' might be more about finding a proper kit, I think.

92SCtk
06-08-2017, 10:07 AM
Can you identify exactly where the leak is originating?

The SC has a pressure switch down on the firewall that is used to trigger the ARC system...auto shocks. These are common leakers when they they get old. They are generally below the master cylinder, and can make it appear that's the leak source. There were hard to find for a while, but I think they've come back on the market, recently. The switch itself leaks thru the connector body.

As well, the seal on the hydraulic pump motor can fail over time - it sits on the master cylinder assembly, right below everything else. Replacements aren't common, but some have used a Honda part, as I recall.

Another leak source is the o-ring on the accumulator. This seal can be sourced without too much trouble, just be sure to get the right type - info here via search.

I haven't seen general leaks from the master cylinder body itself, but I'm sure they can happen.

The difficulty in re-sealing the 'assembly' might be more about finding a kit, I think.

Thanks for the reply, and the heads up on the ARC pressure switch. That never crossed my mind. Forgive me for ignorance, but does that switch run off the brake fluid? I only ask because I know what's leaking is brake fluid. The accumulator o-ring was one of my initial thoughts as well. I have to find some time to get underneath the car, and try to track where it's coming from. I "think" I've resolved some lingering cooling system issues I've had (whole other story) so my next move is onto this leak. Otherwise the brakes, and ARC system for that matter, work fine.

KMT
06-08-2017, 10:21 AM
Yes, that pressure switch is inline and relies on brake fluid. It serves to signal the ABS controller when a hard stop has occurred, activating the shocks to firm.

92SCtk
06-08-2017, 01:08 PM
Yes, that pressure switch is inline and relies on brake fluid. It serves to signal the ABS controller when a hard stop has occurred, activating the shocks to firm.

Well, that gives me a starting point then. Thank you very much.

KMT
06-08-2017, 01:18 PM
Sorry, I meant the 'ARC controller'. Automatic Ride Control, which works in concert w/the ABS controller/system.

92SCtk
06-08-2017, 01:41 PM
No worries, I knew what you meant.

92SCtk
06-13-2017, 09:59 PM
So I found the pressure switch, and it does seem to be my culprit. Through searching past posts on here, I've came across both the Ford and GM part numbers, but I haven't been able to find a definitive instruction on what the easiest way to swap in a new one is. Any advice? Is it as easy as disconnecting, unscrewing (with what?), and working backwards with a new one?

KMT
06-13-2017, 11:04 PM
Is it as easy as disconnecting, unscrewing (with what?), and working backwards with a new one?

Pretty much, yes.

Once you find a replacement, use it to size a thin open end wrench and have it ready to go in. Confirm there is a good/new o-ring. If you have to source your own, be sure it is brake fluid compatible.

Disconnect the wire harness - the connector may be brittle from age, so be gentle, then use the wrench to loosen - once loose, continue to unscrew by hand, then act quick to swap it for the replacement so as to not lose more brake fluid than necessary.

Screw it in by hand as far as you can, then snug it down w/the wrench. Clean out the connector as best you can, then couple it to the switch.

If you're careful and don't leave the system open, you shouldn't have to bleed it later.

Tidy up, check the level in the master cylinder and watch for leaks after driving.

67314

TbirdSCFan
06-13-2017, 11:27 PM
If you can't find a replacement part, you can just cap off the fitting with a bolt. Its an NPT thread.. not metric nor SAE. I don't have the specs, but if someone REALLY wants to know, I can go out and measure it. :D

RalphP
06-14-2017, 06:42 AM
If you can't find a replacement part, you can just cap off the fitting with a bolt. Its an NPT thread.. not metric nor SAE. I don't have the specs, but if someone REALLY wants to know, I can go out and measure it. :D

That depends on WHICH switch he's talking about.

There's the motor run switch (turns the motor on when pressure drops low enough in the accumulator), and there's the ARC switch.

You're talking about the ARC switch on the proportioning valve; I think the other posters have been thinking about the motor switch.

RwP

92SCtk
06-14-2017, 08:22 AM
.....You're talking about the ARC switch on the proportioning valve; I think the other posters have been thinking about the motor switch.

RwP

I did see that there were a majority of posts that were referencing the motor switch, but this one is the ARC switch on the proportioning valve. Picture is of mine.

I actually found TbirdSCfan's post from 2013 where he plugged it. I may go that route if it ends up being difficult to get. TBSCshop.com has a used one for $95, but I'd prefer it to be new if I can. See what I can find.

Thanks for all the help

sam jones
06-14-2017, 10:19 AM
Good morning


I believe Super Coupe Performance sells the new Proportioning brake pressure switch for $49.99



https://www.supercoupeperformance.com/content/images/thumbs/0001465_pressure-sensor_300.jpeg


New pressure sensor that is located in the brake line of the '89-92 Thunderbirds and Cougars with the Adjustable Ride Control Shocks.



Comes with a new brake fluid compliant rubber O-ring.



These sensors often break and/or leak brake fluid so we have you covered for a stock replacement!



Shipping is free if your order total is over $50. If ordered individually shipping will be approx. $4-7.

Tim Groth
06-14-2017, 10:44 AM
If you plan to just plug it here's a link to the plug .

http://www.mcmaster.com/#50925k337/=13oho6f

-Tim

92SCtk
06-14-2017, 10:51 AM
Good morning


I believe Super Coupe Performance sells the new Proportioning brake pressure switch for $49.99



https://www.supercoupeperformance.com/content/images/thumbs/0001465_pressure-sensor_300.jpeg


New pressure sensor that is located in the brake line of the '89-92 Thunderbirds and Cougars with the Adjustable Ride Control Shocks.



Comes with a new brake fluid compliant rubber O-ring.



These sensors often break and/or leak brake fluid so we have you covered for a stock replacement!



Shipping is free if your order total is over $50. If ordered individually shipping will be approx. $4-7.

Great call on that. I've ordered from Bill before so I'm familiar with the site, but I was looking in the brakes section rather than the suspension. Awesome. Thank you.

92SCtk
06-25-2017, 07:37 AM
So I finally got around to swapping out the old ARC pressure switch yesterday, had it done in 10 minutes. Checked the brake fluid, and took it for a ride. When I turned the car on, "Firm Ride" stayed on, and remained on. Cycled the switch, no change. Did a 60-0 stop, and right as soon as I hit 0, the light went out; comes back on after about a second. I am able to repeat this too. The only thing I can think of is that the switch is backwards internally, and is causing the system to work opposite from what it's supposed to. The connector on the car was clean, and snapped right on. I emailed Bill at SCP to see if he's heard this before, and he was unaware of any switches with problems. Other than this, the car's brakes are working normally. Any thoughts?

TbirdSCFan
06-25-2017, 08:00 AM
Unplug it and drive around normal for a while. Firm ride should stay off. Try switching the console switch back and forth and see it if otherwise does what it should do. If thats all OK, try cleaning the inside of connector with brake cleaner to clear out any brake fluid that may have built up from the old switch. Reconnect and drive around some. Firm solid braking should make the ARC switch to firm. Panic stops are not needed.
Thats about all I can suggest for now.

92SCtk
06-25-2017, 08:23 AM
Unplug it and drive around normal for a while. Firm ride should stay off. Try switching the console switch back and forth and see it if otherwise does what it should do. If thats all OK, try cleaning the inside of connector with brake cleaner to clear out any brake fluid that may have built up from the old switch. Reconnect and drive around some. Firm solid braking should make the ARC switch to firm. Panic stops are not needed.
Thats about all I can suggest for now.

Yeah I'm actually on my wait out now to drive it for today's errands (too nice of a day not to). Unplugging it was one of the thoughts I had last night so I'm gonna try it.

KMT
06-25-2017, 09:56 AM
The only thing I can think of is that the switch is backwards internally, and is causing the system to work opposite from what it's supposed to.

As with any basic switch, testing with an ohm meter will tell you. Remove the connector, set the ohms Ω scale to the lowest number and probe the two metal tangs inside - an open circuit with the switch off/not under pressure will read the same as if your test probes aren't even connected. A closed switch, under pressure that would be 'on' and light the ARC dash light, would read some resistance and be same or close to the reading as when the test probes were touched together.

It should not be closed when the engine isn't running. Check the old one off the car to confirm. They should both test the same.

Might want to remove the connecter, let it hang for a bit, then fire the car up and test - if the new switch is the culprit, the light should stay out. Hit the pedal hard/full to test otherwise.

Does the new switch look the same as the old one?

92SCtk
06-26-2017, 08:29 AM
Yeah, unfortunately an ohm meter isn't something in my toolbox yet. Working on my cars (beyond changing oil) is somewhat brand new to me since I'm out of college and done with football/coaching (for now, i.e. no kids). I've used them in college, but never got one of my own. Rather than make my running car a non-running car, I'm actually going to be using my old 5.0 Mountaineer as a teacher, and get it running again (and possibly to be a donor down the road :eek:). Best way to learn is to do it, and thankfully I have something that I don't need to rely on if it takes me a little bit.

As far as the switch goes, drove it all day yesterday unplugged. ARC worked normally, both in Auto and Firm Ride. Going to try to get a meter by this weekend, and test it.

KMT
06-26-2017, 10:35 AM
As far as the switch goes, drove it all day yesterday unplugged. ARC worked normally, both in Auto and Firm Ride. Going to try to get a meter by this weekend, and test it.

Seems odd a new switch would do that, but there you go. Outside of temporarily installing the old switch, not sure I'd test more ;) Did the old and new parts match up in appearance?

Harbor Freight has a decent cheap digital volt meter they occasionally give away with a purchase, BTW.

92SCtk
06-26-2017, 11:26 AM
Did the old and new parts match up in appearance?

Sorry I forgot to answer you from the first time. Yes, they were identical.