Hi Gang,

One of the many items I'm inspecting this winter is the cooling system on my car.  I already found a non-stock thermostat and restrictor plate, and the caps on the system tanks may be another possible deviation from stock...

But first and foremost, how can I tell if the filler necks on my tanks are US spec or European spec?  There must be a measurement I can make, no?

Meanwhile, here's a photo of my leaky main tank:

IMG_7029

It has a older Stant 13 PSI cap on it now, it's obviously not sealing well.  Before I try a new 16 PSI cap, I'd like to be sure I've got the US filler neck installed.  I do believe these are aftermarket tanks in my car, as they are not in the OEM locations, and the main tank does not have a temperature sending unit bung.

Regardless of the pressure rating I end up choosing, should the cap on the smaller tank be 'vented', or 'non-vented'?

https://www.coolcatcorp.com/Ra...ps/Radiatorcaps.html

Looking at the larger tank in the background, I noticed that it also has a pressure rated cap.  It's got a 14 PSI lever vent cap installed now, but from what I've read, this should be a non-pressure rated cap from NAPA or equivalent.  That will allow the large tank to function as a recovery tank, correct?

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Hi Larry,

Thanks for the link, I hadn't found that thread in my previous search....very enlightening.

I read it, and re-read it again, and now I'm VERY seriously considering George's auto-bleed conversion for the two tanks.  It sure would be a lot easier to do with complete access to the entire system.

It may be a moot point if I do the conversion, but I'd still like to know how to tell the difference between US spec or European spec filler necks.  Anyone know?

The difference between European and US filler necks is, a European neck is deeper, from the top of the neck to the sealing surface. Accordingly, a US spec rad cap is shorter than a European rad cap. If you put a US cap on a European neck, it doesn't seat with the pressure the cap was designed for. That reduces the "release" pressure (or temperature) by a significant amount.

To answer your previous question, in an OEM cooling system, the shorter (pressure) tank requires a pressure rated rad cap and the taller (coolant recovery) tank uses an un-pressurized, vented cap.  

davidnunn posted:

The difference between European and US filler necks is, a European neck is deeper, from the top of the neck to the sealing surface. Accordingly, a US spec rad cap is shorter than a European rad cap. If you put a US cap on a European neck, it doesn't seat with the pressure the cap was designed for. That reduces the "release" pressure (or temperature) by a significant amount.

To answer your previous question, in an OEM cooling system, the shorter (pressure) tank requires a pressure rated rad cap and the taller (coolant recovery) tank uses an un-pressurized, vented cap.  

Or maybe just get a European Cap?

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