this is for Jay Friedman and other 49 aficionados. I'm restoring a 49 sedanette with power windows and seat.model 62. came that way. shop manual says that closed cars have 2 hoses off the pump. is that a printing error? I have worked on a lot of hydraulic systems both convertible and closed cars and see no reason for 2. pump is a moraine. it has original hose still screwed in. the other 2 orifices have plugs. and to confuse the issue even more, there was an extra pump hose though much longer in the box of parts. I know GM used dura pumps also. the car is plumbed for a single line only. what gives? Dave
bump
Dave, I apologize but I know very little about the Hydro-Lectric system.
However, I have looked in my copy of the shop manual and found on page 32 under note (23) a it says: "On convertible ..bodies the pump has three ports: The one at the front...is a return port and the other two....are pressure ports. On... ..closed body styles, there is only one pressure line...at the left side of the pump." Is this what you are referring to when you ask "shop manual says that closed cars have 2 hoses off the pump. is that a printing error?" My question to you is isn't there a return line besides the pressure line, making for 2 hoses?
For help with the Hydro-Lectric system I suggest you contact Art Gardner and/or Joe Cutler, whose contact information is in the Georgia and Massachusetts section of the CLC directory, respectively.
The 48 Fisher body manual has an extensive section on the hydraulic system for windows and convertible tops. On the windows it is a single line system. Going up the valve on the cylinder is opened and the pump is started causing the window to go up. On the down cycle only the valve is opened, and the pump does not run allowing the oil to be returned by the force of the spring. The power seat works the same way, but I think the convertible top is a two-pipe system with a multi-port valve.
As Jay and Brad wrote, there is a second and third port (for return) for the convertible top but Dave says the shop manual states closed cars have 2 hoses off the pump and his car is plumbed for a single line. This article on the 49 Cad hydro-lectric system suggests that closed cars use just one port.
1949 Cadillac Hydro-Lectrics (http://www.1949cadillac.com/category/hydro-lectrics/) describing the '49 Hydro-Lectric system (part 2 troubleshooting first and part 1 on how it works at the bottom of the same document).
It leads one to conclude a closed car uses only one port so "2 hoses off the pump" would appear to be incorrect. I assume both closed cars and convertibles would use the same pump, just capping off the extra ports when not used.
Now
1952 Buick Hydro-Lectric Power System (https://www.hometownbuick.com/1952-buick-hydro-lectric-power-system/)
describes the '52 Buick Hydro-Lectric systems which I'm assuming is close if not identical to the Cadillac system: It has an interesting paragraph describing the system that says "One pressure line runs from the power unit pump to the door window hydraulic cylinders and this line serves to return fluid from the cylinders to pump reservoir. Another (2nd) pressure line runs from the pump to the SEAT ADJUSTER, folding top control valve and cylinders, AND REAR QUARTER WINDOW hydraulic cylinders. This line also serves to return fluid from the seat adjuster and quarter window cylinders to pump reservoir. A SEPARATE RETURN LINE is provided for the folding top hydraulic cylinders.
So there's a second line for the convertible top but it also services the seat adjuster and rear windows. The the return line is only for the folding top on convertibles, since on windows the single pressure line also doubles as the return line.
That segment could leave someone to infer that the rear windows and seat adjuster could possibly have a separate pressure line on some closed cars as well - except Dave's '49 is plumbed for only one and Jay's setup agrees. The extra hose Dave mentions is likely for the convertible. Don't know if any of this helps.