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I'm going to interrupt this program which hasn't been sent yet to give you an update: I'll be taking the new radiator back, since I don't think it has any more, or possibly less cooling capacity than the stock Alfa one. However, will continue since I still want info on expansion tanks.

This sort of a turning point in the '116 heat extraction thread' since I just bought a radiator, but for starters, I need advice/information regarding radiator expansion tanks.

I'm having overheating problems on evenly warmish days when I'm in stop-and-go traffic. The LA area's freeways are all too often stop-and-go.

First photo is as is.

2nd, the 'new' radiator with which you will notice has no radiator filler - thus the expansion tank questions. It is 26" wide and same height as the original tank. As mentioned I will be returning it but hope to find another one 26" long since I can then get/mount another fan like the one in the photo. One turns the fan blade around depending on whether it is used as a push or a pull fan. (I've just plugged in the specs to Cool Craft for a custom radiator).

Then an assortment of expansion tanks under consideration.

The specs for the custom radiator didn't include anything about a radiator cap, so that remains to be seen (or not seen).

Let's say the radiator has a cap. It seems to me all that is then needed on an expansion tank is a place for radiator cap and an outlet roughly in the middle of the tank, 3/8" in diameter which would go to the tube at the neck of the radiator filler. I don't see why the radiator has to go through the expansion tank.

I am confused as to how the bleeder tube on the radiator works. Also how can the expansion tank be pressurized (though suspect that is where the bleeder tube comes in) since it can't be filled - or else no where to expand.

Paul/sidewaysalfa has a good point regarding directing the air flow, but boy is that tough to do if for no other reason than because of the water pump's snout. In the case of Spiders, it's worked out pretty well with a truly analog fan along with the stock shroud. Also, I've found that Alfa Spiders are much more immune from overheating.

Not sure if I've mentioned it in the heat extraction conversation but I have 10:1 pistons and the 'good' Euro Alfa cams. Hardly highly modified.

I'm sure open to suggestions here.


40 Posts
Biba -

I think you are asking about how cooling systems works. My understanding is:

The tube from the filler cap on the radiator goes to the over-flow tank. With a FULL cooling system, as the coolant heats, it expands, and needs somewhere to go. That 'somewhere' is the over-flow tank. When the coolant cools down, and contracts, it sucks coolant back into the radiator/motor through that same tube. If the over-flow tank weren't there, it would spill on the ground, which it did in the "old days".

If you have an expansion tank, there is a "free" flow of coolant between the radiator and tank. The cap on the expansion tank would provide the pressure needed to keep things from boiling over too early, as in atmospheric pressure. I think that the expansion tank would not be full to the brim, so as coolant expands with heat, there is room for the coolant to expand, albeit under pressure.

PS - see my post regarding the cooling capacity of Alfettas under the original thread. I think there's enough if all is OK with the radiator and/or motor...
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