MTFCA Forum

Folks, this radiator came with my un-assembled model t. I'm trying to locate a radiator cap to fit. Thought a 28-29 model A cap would fit, but this is 16 tpi, and the model A is 18 tpi. Note the diamond pattern cooling fins. Hose connections appear to be in the right spot for a T. Any suggestions on sourcing a cap, besides making one? Thanks for your help.

I would recommend that you put the radiator on a T and put something such as a piece of old innertube and fasten with a wire tie or something. Then take the T out for a drive and try to get it as hot as you can to see how well the radiator performs before you look for a cap. The reason why is that that design radiator cannot be rodded out and can only be boiled out so when it gets plugged, it is beyond usefulness.

If the radiator is good, then search for a cap. They can be found in swap meets, antique stores, especially those who have auto parts. Maybe someone you know who has a radiator with outside threads will have a cap which will fit. Then you can look for a source of that type cap.

Otherwise, the radiator is good for a wall hanging.
Norm

One could always change the filler neck too...

Very interesting after-market radiator. While most after-market radiators were made with a filler neck that would fit a standard T radiator cap, or therefore a standard accessory for a T cap. A few did use any of other neck sizes or threads. Another possibility, is that someone may have changed the neck at some time. You may or may not be able to tell by looking at the base of the neck and top tank closely.
That is what is usually referred to as a "honeycomb" radiator, more properly called a "cellular" design. They can be very good. Or not so good clear to very bad. The cellular design cannot be rodded out, and they resist cleaning by most methods. Some people love them, some hate them.

Got one on my speedster. This one came with a Model A cap and T era wings & Moto-meter.

Ordinary vinegar works pretty good for cleaning this type of radiator. My approach is;
Figure out a way to seal the neck temporarily. Perhaps a piece of bicycle inner tube would fit.
Now lay it carefully face down and pour vinegar into it through the lower connector. You will probably need a couple of gallons. Leave it for 24 hours and then dump the vinegar into a plastic pail. Now flush it good with the garden hose.
I wish you all the best

Excellent advice, I'll try the inner tube/hose clamp advice first, see if its worth going any further - then soldering on a different neck makes sense. Or at the next swap meet I'll start my "radiator cap collection that doesn't fit anything I own". Thanks all.

It would not be that difficult to make a cap to fit
The cheap and easy might be from a piece of aluminum round bar. Yes you need a metal lathe

There are screw on hubcaps that are close to the size of the neck on your radiator. I would highly suggest you try to use a temporary cap of some kind and make sure it will still cool before spending time on the radiator. Old radiators can sometime be OK but most of the time their not.

Looks a lot like a Whippet or Overland neck.

Hank

You can also take some 2x4's builld a box large enough for the radiator to fit in laying down cover the inside of the box with heavy plastic sheeting making a leak proof "bucket" set the radiator in and fill it all up with vinegar.

These work just fine. I keep a set for blocking fuel tank filler holes for cleaning/sealing fuel tanks, and sealing radiators for mild chemical cleaning (like vinager): https://www.petersenproducts.com/143-5- ... s/1901.htm

Additionally, this style is particularly suited to fuel tanks as well, if you're worried about it falling in like above plugs could (which I tie off for safety as necessary): https://www.petersenproducts.com/143-9- ... s/1904.htm

when used with fuel tank sealer, a layer of Saran or generic cling wrap keeps the thing free of the sealing goop