Hey guys, I've been looking all over the internet tonight to find out what radiator cap fits my 41 Plymouth...without any success. The cap currently on the radiator is not labeled There's no part number, no PSI rating but I'm reasonably sure it's not the right one anyways. It fits very loosely and it's not sealing well. Anybody have a part number/manufacturer for the proper cap...or simply where did you go to get a new one?...Thanks, Bob
Unless you simply do not like the looks of your cap, it is probably going to be fine for your car. "Sealing" up the original rad's to bring up pressure is tricky. 3-4 pounds pressure MAX is proper. This amount could be done by simply putting the palm of your hand over the neck. To build better pressure would cause leaks and splits...
I have found that making a simply leather gasket to fit the bottom of my cap works like a charm!
If this still does not foot the bill, I'm sure I have some old Stant caps, still in original boxes in storage.
No PSI rating because it is a non-pressurized cooling system. As long as the cap stays on it is probably okay. Mr. McConnell's comment about making a leather gasket would work if it is leaking a bit. My local hardware store carries sheet rubber in various thicknesses. That might work too.
Hello there Lindsay!...Thank you for your reply and also to Tod. I do appreciate it. Here's my story...I'll try to get right to the point. I just finished flushing the cooling system in my 41...The only thing I took apart was the lower radiator hose...but by the end of my process I was just opening the petcocks to drain the system...the one on the lower hose and the one on the driver side of the motor. I did not use anything harsh...I actually used just straight water and a little Dawn dish washing soap. At the very end, just straight water. I flushed the system at least a dozen times to get "near clear" water to come out. There was a lot of sediment in there. Obviously the previous owner really neglected the cooling system in this car. :( Anyways, just a few days ago I added the 50/50 mix of Prestone and Distilled water and I thought I was done. I took a drive in her yesterday and I noticed at my first stop...the gas station...a little steam was coming out from under the hood. The temp was normal...around 160 F. The steam was coming from down low at the radiator and it was wet down low too... :o I quietly freaked out a bit and wondered if I now had a leak! I know I hadn't filled the radiator to the top. I purposely left some air space up there. Now I'm hoping that it spilled over a bit. When I was flushing it, I always filled it to the top and never noticed any spill over? My cap is quite rusty underneath...I cleaned it up last night after I started this thread. Under the rust I found "Stant 7lb". It has a spring and rubber seal at the bottom...and it looks like some of the upper seal is actually missing...some of the brass that seals with the top of the filler neck has actually rotted away!...so I know I need to replace it and start there. By what you guys have said this does appear to be the wrong cap then. I hope this issue disappears when I get the right cap on there! If I can't find a cap locally I'll probably be giving you a call Lindsay! Thanks again
Bob
Until I found a better (non-pressurized) cap for my '36, I made a gasket for the (non-pressurized) cap that I was using from a piece that I cut out of an old inner tube.
Pat O'Connor
Well...I fixed my radiator cap by removing the corroded/1/2 missing round brass plate and replacing it with a 1/8" think piece of rubber. That's the good news...Unforunately there's bad news here too. Since flushing the cooling system I now have a leak...It's coming from up front in between the water pump and the cylinder head. When the engine is hot...it doesn't leak a drop but when it cools down and sits, it leaks and runs straight down and drips off the front of the oil pan. Does anybody have personal experience to know what's leaking here? As I say, it's coming from the crevice in between the water pump and cylinder head...can't say for sure which though....Would the cylinder head leak when cold/not under pressure? Well...I guess when the radiator is full it's a little higher than the top of the cylinder head...
Bob
somefpf the bolts go into the waterjacket. Your flushing may have dislodged the rust and caused a seeping leak. As the engine heats and stuff expands it likely seal it. I might try a half a tuve of the alumaseal type leak stopper rather than tearig into stuff. Check to make sure its not the weephole on the waterpump thats leaking. That is a indicatio of a failig seal in the WP.
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