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View Full Version : Vacuum Canister - Needed for vacuum brake swap?



92SCtk
08-23-2017, 05:40 PM
Putting together a parts list and instruction for myself to do the vacuum brake swap on my 91 so I have brakes (pump is shot so I'm just saving money and doing the swap). What I learn from this will eventually lead me to knowing what I need to do when the system on my 92 inevitably starts to fail. I've read every post on this forum about the swap, and I'm using the baseline LX/5.0 parts for the same year because I'm not fond of two proportioning valves on the same line. One thing though that I've really only seen one discussion on is using a Vacuum Canister. Has anyone added one, or felt they should? How did you set it up? Can't think of a time where I'd be on the throttle and gas at the same time during some spirited driving or possible autocross now and then, so I'm thinking it may not be worth it.

Roboplex
08-23-2017, 06:13 PM
Putting together a parts list and instruction for myself to do the vacuum brake swap on my 91 so I have brakes (pump is shot so I'm just saving money and doing the swap). What I learn from this will eventually lead me to knowing what I need to do when the system on my 92 inevitably starts to fail. I've read every post on this forum about the swap, and I'm using the baseline LX/5.0 parts for the same year because I'm not fond of two proportioning valves on the same line. One thing though that I've really only seen one discussion on is using a Vacuum Canister. Has anyone added one, or felt they should? How did you set it up? Can't think of a time where I'd be on the throttle and gas at the same time during some spirited driving or possible autocross now and then, so I'm thinking it may not be worth it.
I don't have one in my system, but I feel like it may help during driving on the highway, abrupt stops, or when I'm using cruise control. I've maybe had a few instances in the past few months where I went to press the brake and there was a delay of a second or two before I got any stopping power. Also note that (at least in my system) the braking power is a little bit less right off the bat than it was with the ABS system. A vacuum canister might help with that too, but I can't say for myself.

Have you looked into the Hydroboost system from Bosch? It's pricier than the Vacuum conversion, but I'm kind of wishing I did that instead of the vacuum conversion, just for the extra stopping power.

Good Luck,
Joseph

MadMikeyL
08-23-2017, 08:30 PM
As long as the check valve on the line going into the vacuum booster is functioning properly, there is no need for a vacuum canister. If that check valve goes bad though, then every time you get into boost, it will pressurize the booster and cause it to take a few seconds of vacuum before you get power assist again.

92SCtk
08-24-2017, 09:37 AM
As long as the check valve on the line going into the vacuum booster is functioning properly, there is no need for a vacuum canister. If that check valve goes bad though, then every time you get into boost, it will pressurize the booster and cause it to take a few seconds of vacuum before you get power assist again.

The more I tried to break down the vacuum system in my head last night, you confirmed what I eventually concluded myself so thank you for your input. Appreciate it.

92SCtk
08-24-2017, 09:52 AM
I don't have one in my system, but I feel like it may help during driving on the highway, abrupt stops, or when I'm using cruise control. I've maybe had a few instances in the past few months where I went to press the brake and there was a delay of a second or two before I got any stopping power. Also note that (at least in my system) the braking power is a little bit less right off the bat than it was with the ABS system. A vacuum canister might help with that too, but I can't say for myself.

Have you looked into the Hydroboost system from Bosch? It's pricier than the Vacuum conversion, but I'm kind of wishing I did that instead of the vacuum conversion, just for the extra stopping power.

Good Luck,
Joseph

Thanks for your input on how your brakes feel. I've seen that same reaction a few times on here, but I think I'll be OK. Honestly, if I hadn't had my 92 as long as I have or bought a non-SC, I wouldn't know the difference.

I have looked at the Hydroboost system, and I really would prefer it, if money wasn't a problem. I'm trying to allocate more of my funds to a paint job on my 92 at this point though.

Thanks again!

DrFishbone
08-24-2017, 10:48 AM
I've done footbrake / gas burnouts at the track with mine without a problem for years.

On the street, you definitely don't need to add a canister.

I'd pull vacuum from a place that never sees boost if I were you though. ;)

92SCtk
08-24-2017, 11:08 AM
I've done footbrake / gas burnouts at the track with mine without a problem for years.

On the street, you definitely don't need to add a canister.

I'd pull vacuum from a place that never sees boost if I were you though. ;)

Great, thank you! I have it planned that I'm going to pull from the main line between the TB and the supercharger so I think I'll be good.

DrFishbone
08-24-2017, 11:59 AM
I don't have any good pictures of it, but I was able to connect to the vacuum tree over in the drivers corner of the engine bay....real short piece of hose....this tree pulls vacuum from inlet plenum, prior to the SC..... 😉

92SCtk
08-24-2017, 01:57 PM
Ah, OK. As many times as I've looked at the vacuum routing, that never even crossed my mind. That makes it cleaner too. Thank you for that.

92SCtk
09-02-2017, 05:40 PM
I don't have any good pictures of it, but I was able to connect to the vacuum tree over in the drivers corner of the engine bay....real short piece of hose....this tree pulls vacuum from inlet plenum, prior to the SC..... 

Would I be guessing correctly that you removed the line for the speed control vacuum, and routed the brake booster to that port on the tree? Having or not having cruise control is not really a concern for me, and that would be really simple/clean.

RalphP
09-03-2017, 11:12 AM
Would I be guessing correctly that you removed the line for the speed control vacuum, and routed the brake booster to that port on the tree? Having or not having cruise control is not really a concern for me, and that would be really simple/clean.

Well, they used the same T for both baseline and SC Thunderbirds; all you have to do is remove the cap, and there's the factory tap for the vacuum brake booster.

The cruise control is a different size hose anyway.

(Pay careful attention: There's actually TWO T's made as one assembly; the very bottom, furthest from the mount, is for the windshield washer, and then there's the vacuum manifold, which isn't quite "T" shaped, closer to the mounting tab for the screw.)

RwP

92SCtk
09-05-2017, 01:36 PM
Well, they used the same T for both baseline and SC Thunderbirds; all you have to do is remove the cap, and there's the factory tap for the vacuum brake booster.

The cruise control is a different size hose anyway.

(Pay careful attention: There's actually TWO T's made as one assembly; the very bottom, furthest from the mount, is for the windshield washer, and then there's the vacuum manifold, which isn't quite "T" shaped, closer to the mounting tab for the screw.)

RwP

So I'm seeing what you're talking about on my 92, but not on my 91. Unless someone can tell me my 91 is routed incorrectly, the vacuum lines after the throttle body aren't the same. On my 91, the capped tap that you're talking about runs to the boost bypass valve because the inlet after the throttle body doesn't have the vacuum ports on the front side like the 92 and later years did. I'm following dthompson's thread, and, his being and 89, is why I'm assuming he ran a line over to the throttle body side. Below is what I'm talking about. The picture to the right of the supercharger is my 92. The picture to the left of the supercharger is my 91. On the later year cars, they routed the bypass to that front port. If it was a non-SC car, that tap wouldn't be going to a boost bypass anyway, but I see why they changed later on. For the time being, I'm going to route the "long" way. I'm not planning on this early year supercharger to remain on this car anyway, but that's a long way from here. I got the car to run and idle smooth, but I can't see what else it does without brakes.

6763467635

DrFishbone
09-05-2017, 04:42 PM
Would I be guessing correctly that you removed the line for the speed control vacuum, and routed the brake booster to that port on the tree? Having or not having cruise control is not really a concern for me, and that would be really simple/clean.

I think I removed the connection off the driver's side tee that was previously used for the boost control solenoid (a useless feature on only '89 SC's)

DrFishbone
09-05-2017, 04:47 PM
Here's a picture...

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KMT
09-05-2017, 04:56 PM
Good place to hide used roach clips...cops will never think to look there ;)

92SCtk
09-05-2017, 06:02 PM
Here's a picture...

So because the picture I took isn't the greatest, I actually found this from one of KMT's (thanks) threads a few years ago. http://www.sccoa.com/forums/showthread.php?131145-boost-control-solenoid If you go to post #7, my lines look identical to this. To me, it looks like you went into the 3/8" line, arrows in the pic, that goes to the bypass valve. I'd be able to route to this tap on my 92, but not my 91.

Sorry if this is frustrating to explain, but I really do appreciate all the input. This hands on work is new to me, and this car sure is doing it's job as a teacher. Plus I can't stand going into something without any understanding of what I'm doing...look out if I start and can't finish for an unknown reason :mad::mad::mad:

RalphP
09-05-2017, 07:04 PM
Umm .. the vacuum tree (miscalled a "T" by me earlier) that I was talking about, was the one that Dr.Fishbone had in his picture.

The pictures from 92SCtk are the OTHER side of the motor ...

RwP

92SCtk
09-06-2017, 08:14 AM
No I know which one you're talking about on the driver's side. With my pictures, I'm trying to point out that the earlier cars didn't have the ports on the front to route the bypass to so that 3/8" tap on the driver's side T is not capped on my 91, it's actually where the bypass vacuum is routed. It is capped on my 92 so eventually when that one gets swapped over to vacuum brakes, I'll be able to go right there. Sorry for the confusion.