In last month's D.O.C. (See www.southernwheels.com, click archives) I gave a brief history of GM's Hydro-Lectric system beginning with the 1946 cars with the 6-volt, negative ground system, to its final year, 1953, with its 12-volt system. Only the Special and Century retained Hydro-Lectric for 1954; Buicks other cars with power tops, windows and seats were all electric.
In 1953, Hydro-Lectric was available at Buick in its 56R, 56C, 76R, 76C, 76S. Our car is the 53 76R (2 door hardtop) with Hydro-Lectric power windows and front seat. The windows, as covered in last months article, are fairly simple: Fluid moves them up and a spring pulls them down as the fluid voids the cylinder and returns to the pump reservoir. The seat mechanism is a little more complex. The similarities are: The seat has a single switch the same as the windows, and it works the same. On the right back of the switch is marked MOT(motor) and has a tan/green tracer wire attached. The center post is marked BAT(battery) with a tan/red tracer wire, and the left post is marked CYL(cylinder) with a tan/black wire. All are 14 gauge wires. Finding people who know anything about the seat tracks has been next to impossible. Fortunately, I have most every GM manual that covers the Hydro-Lectric system. At the end of this article, I will list and rate them. Some have been very helpful.
Our Cars Hydro-Lectric System: When we got the car over ten years ago, the only thing that worked right on the power system was the pump. The windows would go up but not down, and the seats wouldnt move at all. All of the interior had to be done anyway, so we removed everything from the interior and totally rebuilt the Hydro-Lectric system. That was ten years ago, and everything still works with no leaks. Now it was time to go through the seat tracks and get them to work with the Hydro-Lectric seat mechanism.
The Hydro-Lectric seat unit consists of frame, cylinder, spring and switch. The unit is positioned under the front seat on the drivers side and the unit attaches at the rear by a single bolt through the unit to the floor board. This also grounds the unit (it wont work unless grounded). It attaches in the front from the Hydro-Lectric unit to the seats pivoting Vbracket with one bolt. The seat unit is the same as the window units, except the seat unit is slightly larger (uses same cylinder). The seat is moved forward when the switch is pushed to the UP position, moving 260 PSI of fluid into the cylinder and will move a maximum of 500 pounds of weight in the seat from its furthest rearward to the furthest forward position in five seconds, then back to its furthest rearward position in three seconds. When the seat moves backward, it does so by the large spring on the Hydro-Lectric mechanism and the voiding of the fluid back into the pumps reservoir.
Of course, all parts of the front seat had to work, so we set up a 4x8 table and re-constructed the seats out of the car.
GM's description of their 50 (Super) and 70 (Roadmaster) Series cars is: These cars have Tilt-in Seats(split seat backs) mounted on a bench seat bottom. The seat unit has a diagonal pivoting movement of the seat cushion to provide maximum ingress and egress for rear passengers. When either front seat back is tilted forward (one at a time) as it tilts inward, it also acts as a lever to rotate the entire seat assembly about a pivot point on the opposite side. This allows the seat to move forward beyond its furthest position on the Hydro-Lectric unit.
Seat terms that GM used, which we will use in this article are:
Seat adjusters: are seat tracks
Inertia Locks: are counter-weighted lock arms
Actuating plates: a piece that attaches the outside hinge of the seat back to the seat track.
The seat adjusters are designed to prevent diagonal or lateral movement when the seat backs are in normal position. The seat adjusters (seat tracks) are equipped with inertial locks, which prevent free forward movement of the seat in case of a sudden stop, causing the seat back to be thrown forward. A sudden stop causes a counter-weighted lock arm to swing forward around its hinge pin until the hooked end of the arm engages a lock pin, thus locking the seat in its Hydro-Lectric position. This makes the seat to move forward and back by the Hydro-Lectric unit only.
How to Check Operation of the Inertia Lock:
1. Make sure that inertial lock arm operates freely on its hinge pin.
2. Operate the seat backs by folding inward (one at a time) to check for free operation of the seat adjusters (tracks) and actuating plate assemblies on the outside hinge arm of the seat backs.
3. With seat backs in full rearward position so that the inertial locks are touching the rubber bumpers below them, raise the lock arm into contact with the lock pin above the lock arm. A gap of 1/16should exist between the arm and the pin.
4. If seat tracks and actuating plates on the seat back outer hinges are working correctly and not binding, but the lock arm does not have 1/16clearance in its lock position, filing or grinding the front edge of the lock pin can be done, so long as no more than 1/16" of stock is removed from the lock pin. That is from the 1953 Buick Shop Manual Supplement to the 1952 Buick Manual. The previously mentioned rubber bumper blocks were changed mid-year. Here is the change posted in 1953 Buicks Product Sales Bulletins.
New: INERTIA LOCK RUBBER BUMPER REPLACEMENT. The early '53 rubber bumper that the inertia lock arms rest on were thicker, allowing less arm travel. Later in the year, they were replaced with thinner ones, allowing greater arm travel. The thicker ones may have prevented the arm on occasion from coming down and not letting the seat to move forward when the rear passengers were entering/exiting.
I replaced the thin ones and made thick ones for our '53. Mine are made to keep the arms in the locked position. I found when I repeatedly tested the lock arms, they didnt always work, and when they dont work, the seat can freely move forward and back, possibly resulting in losing control of the car. So for my rear passengers, I move the seat forward, Hydro-Lectrically, and fold the seat back inward and there is plenty of room to get in and out, and its safe! I did find what seems to be a contradiction in the Buick Shop Manual and the '53 Buick Owners Manual. The Owners Manual refers to the rear passenger inertia lock mechanism as slide away seatand is on the passenger side only. Yet the Motors Manual does not mention one side, but both sides as found on our car. I bought another set of tracks from our Buick Buddy Keith, and his tracks were set up the same as mine. Both sides have inertia lock arms that override the Hydro-Lectric travel when the seat backs are folded inward.
The seat track assembly is attached in the front to the Hydro-Lectric unit with a V pivot plate. It is attached to the equalizer bar (that connects left and right seat tracks). The bar connects on each track at two points with Cclips. When the Hydro-Lectric switch is activated, the entire Hydro-Lectric seat unit kicks up at the front (remember its only connected to the floor board at the rear of the unit) and rotates the equalizer bar and moves the seat in the direction of the switch position. When the switch returns to rest, the seat is locked in place by fluid trapped in the line and the relaxed position of the bar. The top track is now locked to the bottom track and will not move unless operated by the switch or overridden by the inertia lock slide awayseat function.
When we checked our seat tracks to find out why they were locked up, we discovered some one had put a large sheet metal screw in each track to lock it up! This probably happened when the Hydro-Lectric unit stopped working and they locked the seat in a position that was right for them. I wish people would keep project books!! A lot of time was spent to find this.
We removed the connector bar, removed the screws and greased the tracks with an air grease gun to get into all the parts of the tracks.
The construction of these tracks is: The lower track is riveted onto the bottom section which bolts to the floor board. The top and lower tracks are separate and ride on ball bearings moving freely when in the neutral position. The seat and connector bar connect to the top track. With the tracks free, we reconnected the connector bar and set the track without the seat cushion back into the car, bolted it down and hooked up the Hydro-Lectric unit. The seat track now moved forward and back correctly. Great news!! Now for the installation. . .
Originally, the seat track bolt holes were round holes in the front and oval holes in the left rear track. This was to keep the front stationary while the rear could be brought into alignment by moving the track rear in or out as needed. This kept the tracks from binding. Our original tracks had all of the holes ovalled and so were the bolt holes on our extra set of tracks. This was probably done for track alignment over the years. As the seats were removed for servicing. With the Hydro-Lectric system working and the seat tracks sliding, we were ready to install the seat. Instead of using the original bolts through the seat tracks to the floor boards, we put in 5/16 f/t stainless steel studs and ran them down so we could just get a star washer and nut, then tested the seat frame movement. We would have to shave a little off of the back ones, as the seat frame scraped in the far rearward position. But we would wait until the final seat installation.
We assembled the seat bottom cushion to tracks outside of the car. In the front, there is only one bolt. However, the rear mounting bracket rotates and is made so that one side is higher than the other, to fit the bottom side of the seat frame. The higherbracket surface is positioned toward the outside of the car and the lower side toward the inside of the car. We bolted the tracks to the seat bottom, put masking tape over our floor studs to protect the threads and lowered the seat to the floor. Everything fit beautifully. The star washers and nuts were tightened down, then we ground a little off of the high stud in the rear, making the track clear and still making it able to remove the hex nuts later if there is a need.
To connect the Hydro-Lectric unit to the seat V plate, we toggled the switch to move the unit until it was directly under the Vplate, dropped in the bolt, star washer and nut, and it was locked down. Now all that was left were the seat backs. Each seat back has a slotted stud on the inner side that fits into a slot in the center hinge of the bench seat. The seat backs are turned inward, pushed into the slot and rotated back, locking them in place on the inner hinge.
To install the seat backs to the tracks, first slide the actuating plate into the groove in the upper seat track (this connects the actuating plate to the track and allows the seat frame hinge pin to slide through the rear hole in the seats outer hinge. A 7/16 spring washer and a cotter pin go here. The front hole of the seat hinge to the left of the above slides over the actuating plate pin, but does not get a cotter pin. The seat is now done. All that's needed are the side cover panels.
The Hydro-Lectrics are finished, and we can continue with the interior installation. There's always a challenge with old cars. Never give up! And keep 'em driving!
Our thanks to Hydro-E-Lectric, who supplies our cylinders.