Auto Level System

[SS Haze]

I've been trying to find out some details on my 70 SS level system and just what the heck it does. I assume that when I load up the back seat with gravity-challenged folk it'll compensate. Is that the idea? Also: tube up on the underhood canister leading to the engine vacuum system and air fill nozzle behind the rear license plate. It's all a little confusing.

 

Any Help? Thanks - Mike

 

[Sam (Bones)]

basically, they are auto adjusting air shocks, if you have an air fitting at the back, they were more than likely replaced with air shocks

 

Sam

[gronlit]

Warning, I started writing and wrote more than I planned:

 

The canister under the hood is a pump; it takes the vacuum created by the engine and converts it to a positive pressure used to pressurize air shocks. The back part (towards the firewall) is a diaphragm pump mechanism, the long cylinder in front of that is just a pressure vessel to hold the pressurized air. On top of the pump there is a pressure relief valve (with yellow cap) that prevents the system from over pressurizing. On the pressure relief valve there are two fittings, one with a valve stem similar to that used on tires – this is used to manually charge the system. The other fitting should have a small black plastic airline leading from it to the rear of the car where it connects to a level sensor/valve assembly.

 

This assembly is connected to one of the upper rear control arms. The assembly has a piston / flapper valve system which is filled with somewhat thick clear oil....This system acts as a damper or time delay. When the ride height of the vehicle changes the lever arm on the assembly is rotated against a spring which in turn presses on the piston which pushed the fluid through one of the flapper valves. Since this is a thicker oil it takes some time for it to move through the valve and thus acts as a time delay. This time delay prevents the system from reacting to road bumps and other short duration changes in ride height. If the ride height remains changed for a long enough period of time the piston completes its travel and opens one of two stem valves. Two more black plastic airlines should route from the level sensor to each of the shocks. If the ride height has lowered it opens a valve which ports the pressurized air from the pressure vessel under the hood into the air shocks until the proper ride height returns. If the ride height of the car has increased it ports the pressurized air from the air shocks to the outside through a black rubber hose. When the car is at proper ride height both valves are closed and the air pressure in the shocks is locked.

 

The pressure fitting at the rear of the car is not original, and probably means your autolevel system stopped working and a previous owner disconnected the air shocks from the autolevel system. That fitting at the rear of the car was added and is used to adjust the ride height of the car manually by adding or removing air.

 

I recently finished rebuilding both my vacuum pump and level sensor. (when I got my car the vacuum line to the pump what tied in a knot and i had the air connection added at the back of the car.) I found that nothing inside either of the components was broken, just dirty. There was also a lot of rust dust in the pressure tank (im guessing water tends to build up in the pressure tank over time when its used since air acts like and sponge…it holds water but if its squeezed the water comes out.) I took the pump apart and cleaned all the componets and reassembled it…It wasn’t too bad but there are some small pieces to keep track of ….the relief valve was one of the harder pieces to disassembly but must be done…there are some small ports and a screen in this piece which were all clogged with rust/dirt… if you rebuilt the pump there are probably 4-5 springs in various check and relief valves which like to shoot parts across the room – just a warning.…since my 70SS is still in pieces I connected the pump to the vacuum system of my 97 monte to check it out and it worked much to my pleasure(also went and had all the exterior pieces of the pump replated for a brand new look). The level sensor was also clogged with rust dust/dirt. There are two screens in this assembly which where clogged. Also part of the assembly is filled with the clear (funny smelling) oil used in the damping system…try to catch all of this fluid so you can reuse it. The viscosity of this fluid is important to how the system operates and I imagine a fluid with too low of a viscosity (or if no fluid at) could make for a very uncomfortable (and possibly dangerous) driving condition since the system will start responding to every road bump and possibly reach a resonance.

 

I don’t think I saved enough of this oil from mine and need to find a replacement – anyone else find an oil with roughly the same visocity?

 

Hopefully my rambling made some sense

 

Tim

[SS Haze]

Tim - that was great. I pretty much figured out how/why the system worked but the rear bumper air fill really confused me. Being that I just got the car from my uncle, i think I'll hold off on any rebuild. I'm waiting for classic car insurance, tags, and state inspection. Hopefully I'll have it cruising next week.

Again, thanks for the detailed explanation. I couldn't find the info anywhere.

 

Mike

 

[jstadter]

If the fluid is clear, there's a possibility it's silcone. Lots of cars use silcone in the engine cooling fan clutch. I've heard that Toyota sells small bottles of silicone to use for servicing the fan clutch.

 

Jim