Good evening. I have a '30 Model A with a Y block. It has a Deuce grill and an unknown aluminum radiator. I have been having a problem with the thermostat housing (awesome design, geniuses) dripping antifreeze but it seems to only happen AFTER shutting it down. I am running a Murray 7616 (16 psi) cap currently, and when it's cold there is a significant bleed off of pressure when I open the radiator. I am wondering if it stays under a lot of pressure and that causes the leak. I was thinking of running a 7 psi cap. 1. Am I wasting my time? 2. Any idea what that part number may be?
16 psi seems too high to me. It keeps it from boiling out when running, but when you shut it off, the radiator isn't 'in play', so all that heat soak in the engine transfers to the bottled-up water in the block. That raises the pressure, but not up to the opening point of your cap, hence, it finds a place to leak. The 16 psi cap raises the boiling point (I don't recall the exact amount, but you can google it) more than a 7 psi cap will, so that might be helpful in your situation, but not necessary. What to do? Add a recovery tank and CAREFULLY match a new 7 psi cap to the dimensions of the radiator fill spout. Make sure the cap is the "recovery tank type"... in other words it allows backflow into the radiator. If it seems to run hot, try the next step up in cap psi (IIRC there are 12 psi caps). There should be very little (or no) residual pressure in a cool radiator. Good luck!
Thanks for the info! I grabbed a 7 PSI cap today and cinched down my thermostat housing again and (knock on wood) it seems to be better. Not sure if it worked, but I also think 16 PSI was unnecessary. Thanks again.
Is it a chrome thermostat housing? They are know to be hard to keep from leaking. You can make sure the mounting surface is flat by sanding it on a piece of glass or flat steel. Some never leak, some you can't seem to keep them from it. If all else fails, find a stock cast iron unit, they seldom leak.
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