Windshield washer system problem

I've searched the archives and haven't found this particular problem. It's a '72. The pump and both check valves are new as are most of the supply lines. The only original lines are from the second tee fitting to each of the nozzles. The lines are routed as per the PET illustration 904-15. I cleaned the pick-up screen and nozzles and they flow easily. At this point I have the reservoir on the workbench with extra tubing connecting it to the car and I'm using another battery to supply power to it (too many times I have smugly reinstalled it thinking I had it fixed, only to pull it out again when it was clear I hadn't) Here's the deal: All I get is a dribble from both nozzles UNLESS I pinch off the return line. That is the short line that "tees" off the pressure line and returns overflow to the reservoir. When I do so the pitch of the pump lowers and the nozzles squirt as they should. What am I missing here? As per the PET illustration and the original lines, there are two sizes of supply lines. I'm using 3/16" ID clear tubing for the pump-to-reservoir lines and as reducers at the check valves and second tee fitting, and 1/8" ID clear tubing for the run from the pump pressure line back to the tee fitting under the cowl. It's as if the overflow is running back to the reservoir too easily. Any ideas?

Here's a shot of the lines at the pump. Thanks

That doesn't make sense, there's no return line in a washer circuit. I think the extra line should be an air intake for the washer bottle so it doesn't implode from the pump pressure.

Rich, it may not make sense, but the pic above illustrates how mine is set up on a '73 and the system works great. "Try it, you'll like it."

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Originally Posted by RickS

Rich, it may not make sense, but the pic above illustrates how mine is set up on a '73 and the system works great. "Try it, you'll like it."

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I still don't understand why you would need that, but I defer to Dr. Porsche and Rick. My '66 doesn't have a bypass tube or a provision for one.

I could see it working if the washer bottle was totally sealed...i.e. pressurized, otherwise you'd just be pumping back into the bottle. Maybe there's a rubber washer/gasket on the filler cap or the inlet cap that's missing or worn out, or a leak in the bottle.

Or...is there a check valve in the bypass tube inlet on top of the bottle? That would make sense to relieve pressure in the bottle, but not let anything back in. Did you try swapping the lines on top of the bottle?

I know, Rich, it doesn't make sense to me, either. When it's running I can see the fluid racing right back into the reservoir from the tee fitting in the pressure line. That's why I eventually tried pinching off the return line. Because I'm convinced I have the line layout correct, the only thing left is to replace the remaining old line and make sure the tee fitting under the cowl is fully clear. I guess it's possible there is a clog just big enough to restrict but not stop the flow to the nozzles and that restriction then makes the fluid flow back to the reservoir more easily than designed. I'll get at it and report back. Thanks

I'm with Rich on this one, that system layout makes no sense. IF there was a restrictor in the return line only THEN would it make sense. Otherwise, the fluid will flow through the path of least restriction, hence the short loop back to the tank . This is exactly what is happening. Therefore there is something missing in the system you have hooked up. Where is the tank vented; there MUST be a vent. What happens if you reverse the tank connections? Is one of those connections a restrictor?

Yes, Rich and Dave, I think the restrictor is the issue. The tee fitting in the pressure side may have been replaced incorrectly with a common full-flow tee. The system hasn't worked since I bought it, and I just assumed (there you go) that the tee is original.
I checked online at Stoddards and have found that the tee is called "Washer hose "T" valve, air bleed. Fits 1968-1989." and is 4.5 times as expensive as the other tee which is called "Washer hose "T" valve, all passages open. Fits 1965-1973" Stoddards parts is closed today, but I'll order the correct part Monday and report back once it's installed. Thanks you guys for pointing out the issue.

Update! The correct "Washer hose "T" valve, air bleed. Fits 1968-1989." made all the difference. The PO had installed a free-flow in all directions tee. The new one flows freely straight through but has an obvious restriction off the "T" part. Washer system now operating as it should. Thanks all for the feedback.

Old thread, but I need a diagram of the clear hose connections from the washer tank to the squirters. The above photo is still confusing based on the last comments. Was the black t-fitting in the photo wronge? Can someone show a close-up of the correct fittings throughout the system, this would help. This photo is my starting point, I don't have a T-fitting as the above? For the below photo...is mine correct or do I need a special t- fitting.

Scott