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Tech Editor's DeskProjects, papers, writings, thoughts, musings of our technical editor Joe Padavano. To begin with, he will be making threads and can approve posts to it if he wishes. This can be changed in the future if it does not work out well.
The "climate controls" (defrost, heat, vents) are operated by vacuum lines connected to a vacuum tank on the firewall, which draws vacuum off the intake manifold. This is clear, but optional accessories like the vacuum operated trunk release, and "power locks" appear to require a 2nd vacuum tank. Am I correct? I've got power locks that don't work, and my vent/heat controls don't work so I'm trying to sort out the vacuum lines. I have one vacuum tank on the firewall and a line that runs to a tee. One hose off the tee goes through the firewall, the other goes to the inner fender under the hood, and is blocked with a screw. I'm thinking there should be another vacuum tank there, and from that tank, a vacuum line to control the door locks.
I can't find a reference to "power locks" in the tech guide, but I do see this about the vacuum trunk lock. Do I need another vacuum tank for the door locks? Sure looks like there's supposed to be 2 vacuum tanks
Dave
Dig around under my user name for more on power door locks. I think somewhere around here I wrote something useful. This was a fairly complex system manufactured by Trico and sold to the big 3 back in the 60’s. In the late 60’s or early ‘70s’, GM went to electric solenoids and vacuum accessories became obsolete.
The short answer your question about multiple vacuum reservoirs (aka tanks…) is Olds usually had 1 reservoir for heat/AC and another for anything else that was on the car: power door locks, power trunk lock for example. It’s a good idea to follow the factory design since it helps isolate any vacuum leaks from other vacuum connected systems and then engine. A good place to start restoring your power door locks is a vacuum tank. Plumb the input line to your other tank with a “T” fitting and your door locks may come back
I’m not saying a new tank will fix your problem. Quite the opposite, but with 2 tanks at least if the power door lock system has 1 (or maybe many more) leaks, it won’t upset your heating system.
Between the engine and your vacuum accessories, you are well advised to put a 1 way check valve in the system so they don’t create a vacuum leak for the engine itself. You may want to add another check valve between your door lock tank and your heater tank, just in case the door lock system has leak(s).
That screw in the vacuum line going up under the inner fender is a dead giveaway. Usually the power door lock extra tank was located there on the inner fender passenger side. Be aware that these “tanks” or reservoirs were really just tin cans with metal tubes stuck (and soldered) in to the ends maybe with a valve inside. You can make your own of arbitrary size without too much effort at home. Or dig one up on EBay. GM made a few different sizes, I like the big ones that fit on the front of the passenger side inner fender. They might hold 32” ounces of “air” or so, as compared to the more standard 12 ounce cans that were standard. As you look, have a look at Cadillac parts, these system were more common in Caddies than Olds since they were usually better optioned.
Be aware that the vacuum switch rubber wears out and can create a leak after 60 years. Also the vacuum diaphragms which actuate the door locks themselves can also deteriorate and leak after 60 years. You can remake the switch rubber with a bit of bike tire inner tube and some minor hand tool skills, but I have yet to figure out how to remake the stem seals or the corrugated seals in the actuators.
Thanks Chris- great post. I chased the vacuum lines down and I had to re-connect a few. They feel soft, but there's signs of cracking at the tight turns. Before I put the whole dash together I'm going to fire her up, check the wiring and lights, I'll operate the ventilation system and I hope I'll find I can open and close all the doors for heat, defrost, and vents. I'm a bit concerned about the blower motor too, and I hope the heater core doesn't leak. I don't think it does, and I think I would know by now, but I'm going to give the system a shake down before I install the speedo cluster, the radio, and the glove box. Having them out just makes access easier.
There's still a lot of unanswered questions... Wish I had pictures to share but it's so clumsy working alone, and my knee is messed up, which makes it hard to crawl around, so I took the path of least annoyance.
If the dash is out, that is _the_ time to get at everything underneath, specifically including the heater core. The aftermarket heater cores ain’t quite GM-original quality, but maybe you can find an NOS part on EBay. I keep a few cores in storage for my 2 big cars because heater cores usually fail without warning. If I had my dash out and didn’t know when the core was last replaced, I’d be tempted to replace it just as a preventative, knowing the difficulty when the car is assembled. If you replace the core, replace the hoses too and look up how GM had a brace to protect soft brass from engine movement/vibrations. Or ask here.
If your vacuum lines are original, replacements are cheap and sold by the foot. The replacements won’t be color coded, so you’ll need to label them or you’ll go crazy with the rubber spaghetti. I use a Dymo Rhino 6000 and label both ends to track that stuff if I don’t have the color coded hoses. Blue tape is cheaper and works just as well if you have enough Sharpies & good penmanship.
Before you head out and replace all the (very good quality, durable) factory vacuum hoses, be aware you can fix some leaks at the nipples the hoses slide onto with just a 1/4” snip sometimes. My method is to shoot silicone lubricant inside the hose, snip 1/4” and see if I see any cracks that might be leaks. GM generally left enough length on these hoses in those days to allow some of this type of repair. Keeping the old stuff, if its sound for vacuum signaling, means you keep the color coding the manuals refer to.
Especially if the dash is out, it’s quick to test all the vacuum diaphragms that control heat and A/C if you have it: left vent, right vent, heat/defrost and so on.
Use either a hand vacuum pump or just use a vacuum hose to mouth-suck test the vacuum diaphragm actuators for the vents, defrost/heater door, etc. I don’t think I’ve ever had one of these go bad across 2 cars in 40+ years. Again this is easier to test with the dash out.
If the dash is on the bench, that’s also a great time to polish all the electrical male spade connectors so you minimize heat and maximize conductivity. On the female side of you electrical connections, look for melted plastic. If you find one or more, that’s an indication of high amperage and heat. The electrical connector system GM used in those days was called Packard 56 and you can still get the male, female connectors in many wire sizes plus the plastic shells. I recommend blue tape to identify melts/corrosion/wire breaks & other potential hazards, then get the stuff to fix the harness. A spare harness or 2 really helps in this process if you can source one from a boneyard or other enthusiast.
And of course while yer at it, you might want to pull, clean and grease your speedo cable… and on & on.
Finally, dash-out, with interior out, is a good time to think about sound deadening the entire interior floor with modern stuff. I slathered my big cars stem to stern - meaning firewall, floors, even trunk floor with Dynamat and Dynaliner to replace the old GM jute for quietness. Expensive, but good fix. 1 warning: when you quiet all the big noises, you hear the little noises.
Yeah- that's in the works... I got this from Speedway, it was about $100 for all of it. I used construction adhesive on the edges to tack it down, and metal tape on the seams. There's new carpets going down next.
Sound deadening looks great. The more layers the better.
Consider Dynaliner in place of water retaining jute on top under the carpet. Not sure of the cost though.
I also like 1/4" thick closed cell foam under my door and rear quarter panels as a double duty sound deadener/water barrier. Way better than the old GM tarpaper. I use the aluminum backed white stuff "Volara" and just spray-glue it down. Kind of a pain to remove, but it's not that often you need to take it off.
If you happen to run a stereo hidden in the glove box, that chase on the passenger side is a great way to run speaker and signal wires to amps in the trunk.
Didn't realize you have a convertible. Nice! If you want to join me in noise-quieting geekdom, Trimlok sells a 3" flap seal with a 1/4" u-channel that you can trim to snug onto the top rails and get the top a little quieter.
