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OK, since getting the dash back together a couple months back I haven't had any functioning AC/heater controls. I got the fan going just fine finally, but I only have air coming out the defrost vent. I also have no heat in the car despite the cable controls working fine. My manifold vacuum is good and the headlights and trunk release work well. My question revolves around the two vacuum reservoirs under the driver's side fender that connect to the heater controls, and how I can test them. There are no vacuum leaks that I can hear anywhere, and I don't understand why the vacuum controls inside the car don't work when the car is running. I can see the vacuum hoses are connected properly both behind the dash and under the hood. But would the AC/heat controls not work if the reservoirs were bad? I have a hand vacuum tester I can use to test them, but how do I do that? Do I just hook up suction to the large center port and apply vacuum to it? Do I need to plug the other port? Thanks for any guidance!
Last edited by BSiegPaint; Oct 13, 2025 at 10:53 AM.
In spite of not knowing if there are any differences between '66 and '67, my logic says to procced relative to your last 2 sentences - connect your hand vacuum tester to the large port, with the smaller port blocked off. Pump up the vacuum and observe for any drop to test for leaks, and then I would say remove the blockage on the smaller port to verify pressure drop which would indicate no blockage.
Quite honestly, I doubt that anything changed with these vacuum reservoirs - more than likely something got disconnected or cracked as part of your work.
Good luck. To justify such frustrating obstacles in a project, I try to tell myself that it wouldn't be fun if it was all easy.
In spite of not knowing if there are any differences between '66 and '67, my logic says to procced relative to your last 2 sentences - connect your hand vacuum tester to the large port, with the smaller port blocked off. Pump up the vacuum and observe for any drop to test for leaks, and then I would say remove the blockage on the smaller port to verify pressure drop which would indicate no blockage.
Quite honestly, I doubt that anything changed with these vacuum reservoirs - more than likely something got disconnected or cracked as part of your work.
Good luck. To justify such frustrating obstacles in a project, I try to tell myself that it wouldn't be fun if it was all easy.
Just about everything is frustrating to some degree lol. Thanks for the quick lesson on the reservoirs - I wasn't quite sure how they worked, since the big tanks have a check valve in the line and these don't. I keep listening for some kind of vacuum leak, but don't hear anything. And I would think if there was a leak then the vacuum lines going to the headlights (which share the same trunk line) wouldn't ever evacuate properly either. So I'm hoping I find these reservoirs are broken or plugged in some fashion, rather than finding out they are perfect and the vacuum hoses are the culprits...
So the reservoirs hold vacuum with or without the outlet hose connected, which I guess tells me there is a blockage of some kind behind the dash in some way, whether a bent hose or something else. It's such a mess of wires and hoses under there that I may consider removing the dash again to get to all the connections. Everything is connected properly that I can see, but you never know.
I don’t have a Toro, but have added power vacuum door locks, power trunk lock to my ‘66 Starfire and have worked with the vacuum heater/AC controls for 40 years or so in repair/maintenance mode.
First up, unit test the reservoirs and dash unit with a length of vacuum hose and a hand pump or engine vacuum, a vacuum gauge + a vacuum cap or 3. I can’t recall if the Toro had 1 or 2 inner fender, or firewall mounted vacuum reservoirs. I believe vacuum was used to pop those headlights up. Some owners have installed latter-day electric replacements.
Upshot is luxury Olds of this era used vacuum extensively for remote features: power trunk lock, power door locks, every heater/a/c control variant and, in Toro's, headlights too. There are a few points of failure in these systems: #1) cracked, split or broken vacuum lines - usually in the door rubber boots, if you have power door locks ; 2) cracked, split or leaking vacuum diaphragms at the remote ports; 3) vacuum leaks at the heater a/c control dash unit. Olds (really Trico) used very high quality very thick hoses generally in 5/32"s and 7/32"s sizes in those days. Strong vacuum didn't collapse them. Replacements today, even if the inner diameter is correct, are much thinner. So if you can get away with reusing or repairing your old hoses, that's usually the way to go. But a length of short modern hose to replace a cracked or split old one works fine too.
For Olds in this era, the more vacuum accessories you had, the more reservoirs they added. They had the largest reservoirs on the front end of the inner fenders, as did Caddy. To test these, figure out which vacuum line is the input and connect your known-good (ideally new & correct size) hose to it. Then cap off the output side with a vacuum cap. Then put a “T” on the input line to allow you to connect one leg of the “T” connector to a vacuum gauge and the other to your vacuum source.
For the big cans, I’d use engine (i.e. manifold) vacuum since their volume is huge and doing that with a hand plum would be a pain. For the smaller plastic/bakelite bulb style or even the tin can style reservoirs, use the same process, but a hand pump can do the evacuation job since the volume is smaller.
The procedure is get the inches of vacuum in the tank to around 15-18” of mercury from your source, then see how long they take to leak down. If it’s immediate, the tank is leaking. If it takes a few minutes to leak down to zero, it’s slow-leaky. If it holds vacuum for 20 minute or more, you have a good tank. Some vacuum systems I’ve seen (like my ‘66 Starfire) take _hours_ or overnight to leak down. That’s fantastic, but rare. So, job one is to confirm your tanks don’t leak. If they leak, seal with your favorite silicone caulk, or solder up the joint/holes you find. Or find a repalcement.
Be aware that there is high vacuum grease. This is what I used this morning on an NOS heater control to seal a dried up (but all new!) heater control rotary vacuum valve:
Depending on what’s easiest, you can remove the control unit, cap off all the output lines, then hit the unit with your gauge / hose / vacuum hand pump and see if the unit’s switching rotary dial is leaking. There's no gasket on it, so I've "sealed" the well machined plates with the high vacuum grease to good effect.
Even if you don't remove the heater control, you can test it using several vacuum caps on the hoses to the control unit. You cap off all the output lines with vacuum caps, then connect your vacuum pump/gauge tester and again see how long it hold vacuum, or how quick it leaks down. From the factory these control units generally only worked when the car was running, so don't expect a 60 year old, dry valve with no gasket to hold vacuum for more than a few seconds. Maybe a minute or 2 if you're lucky. But regreasing the mating surfaces of the rotary valve (if the unit is out of the car) is pretty easy - you just need the grease & a 1/4" nut driver.
The now-60-year old hoses are the next point of failure. For the heater control the originals were color coded and those colors matched to a numbered port on the rotary control valve. The colors tell you which port line should be connected to which remote vacuum diaphragm.
You will need a Chassis Service manual to get the "pin out". Here is the pinout diagram for '66 big cars which shows you what to look for, but the pinouts are _very_unlikely_to_be_the_same for your '67 Toro: Not Toronado: '66 88/98/Starfire vacuum line diagram, in case it helps...
Olds represented the PIN numbers in a line, but really they're in a circular arrangement on the big car valves in small font on the left side of the unit. I post this only because generation 1 Toros reused selected big car parts here & there and I've never owned a Toro. So look for a similar diagram for your Toro in you Chassis Service Manual or consider burning time on the chance that this one is wrong for your car...
Over the years the general fix for previous owners facing a split, cracked or broken hose was to snip off 1/4" to 1/2" off the end of the hose since it was usually split by the nipple it was sitting on. Snip it back to fresh (ish) rubber and the system works again. But 60 years later your car may have had more snips than a busy urologist. Or a previous owner may have just replaced a colored line with generic hose leaving you no road map of what goes where. So you trouble shoot each heater control output with your hand pump and gauge to see if the hoses and vacuum diaphragm at the end of the hose hold vacuum. If not, well you found your problem area. Then unit test the diaphragm with your test hose & gauge unit.
On the output side, if the diaphragm holds vacuum, the hose from the controller to your remote diaphragm is your problem. So get some new longer-than-stock hoses. But use a labeler (or blue tape) to put the color and port on both ends of each replacement hose. That way you know what you did 5 years from now. Line color and port labels are a gift to future you. Avoid creating a mess of same-size black hoses and the hope you'll remember which one went where.
If the diaphragm rubber has cracked or split, you'll get no movement from the spring loaded arm when you apply vacuum. Across 2 such cars in 40+ years, maybe I replaced 1 diaphragm over the years. Just remove the suspect one, apply vacuum to it on the bench and if the arm moves, it works.
If the activation arm doesn't move, there may be restoration services, but I haven't had to use them yet. Head for here or eBay for replacements - and consider other GM cars - particularly E-Bodies from 66-70 for replacement parts.
Theoretically you could make your own diaphragms at home if you're really good a cutting rubber in perfect circles, stretching it onto old plungers, spring loading them and perfectly recrimping the outer diameter sealing lip, but I've never done it.
Warm recommendation that if you pull the dash, to _really_ do it up, consider going through the electrical harness while you can get at all those connections too. At least in my big cars, the heater control just drops out of the dash with a couple of 1/4" hex head and a little twisting on my part. Each year that kind of Oldsmobile-twister game gets a little harder....
He's using them in an earlier car, so the lengths can't be expected to work in a 67 Toro. If it were me, I'd get 2 sets to be sure I could make some union joints and get the job done right.
Chris - I thought I had replied here to thank you but somehow I never posted a reply...! GREAT information that I need to sort through. It took so long for me to get the dash off and back on with all the repairs that I've taken a break from the whole car for a bit. BUT I fully realize that the control panel has to come back out for radio repair, cruise control cable routing, and now the heater/AC control panel work. Now that there's some familiarity with the time and effort needed as well as what to expect as I dig into this car, I don't think the second time will be as daunting as the first. I actually have a second control panel for the AC that I'm going to disassemble and test like I should have the first one so I can familiarize myself with what needs to be done and how this unit works. I was pretty convinced that the one in the dash now was sealing and working properly, as it was absolutely stuck in place until some penetrant was able to loosen the mated surfaces at the vacuum port - but I never tested to see if they really were tight enough to keep the vacuum once applied. As the weather is starting to change rapidly, I see this project rapidly approaching again. And I recently found a well cared for '67 98 in a salvage yard and I was able to harvest a load of proper diameter and color-coded vacuum hoses, which are amazingly pliable and in excellent condition. I should probably replace a number of hoses on the Toro, as this car was a barn dweller for a number of years and shows the ravages of time and neglect. Winter is for projects!! I'm more equipped to take this one on than the last. Thank you again!!!
