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Another Sen-Dure question

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actthree

Member
I didn't want to hijack Mike33egg's post below.

I'm having the Sen-Dure heat exchangers on my Chrysler 360's boiled out and pressure tested at a local radiator shop. As part of this cooling system project, I'm adding Sen-Dure coolant recovery tanks. I finally found a Sen-Dure dealer in Alabama who had them. I asked him if I needed new caps for the surge tank and he said that the new recovery bottles came with caps. Turns out, they didn't but the instructions say to add a fairly thick gasket (supplied with the recovery tank) to the old 7 lb. surge tank caps.

Does anyone know if the old surge tank cap with the new gasket added will work or do I really need a completely different cap that is designed to work with the recovery tank?

I understand how the recovery system works but from looking at the caps, I can't see how the antifreeze will be able to be drawn back into the surge tank when cool.

Not much info around on this obscure subject so I'm hoping that someone here will know.

Bill
 
It's basically very simple.
The correct pressure cap for a recovery system performs two functions.

The inner most portion seals against the inner seat, and releasese as pressure dictates.
It is also capble of reverse coolant flow (i.e., the recovery)

The outer most portion seals against the locking area.

The recovery hose makes it's connection between these two areas.

As pressure builds, the expanding coolant is directed to the reservoir.
As pressure decreases (as in an engine that cools back down), the negative pressure can now create a siphon from the reservoir.

It can do this only if both areas of the cap provide the proper seal.
The recovery hose connections must be sealed tightly.
Also helps if the reservoir coolant level is at the correct elevation. Not too high, but definitely not too low.
IOW, you'll want to be able to remove the pressure cap without having coolant back-flow out the H/E neck.

Here's an example of an automotive coolant recovery system pressure cap and radiator neck.
The principle is the same for a Marine Heat Exchanger.

NOTE: What's not shown, is that the inner most "cap seal" also serves as a one-way valve..... or we'd not get any reverse flow during recovery mode.
 

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Thanks, Rick. I think I know how that recovery system looks and works. My only question is "if the old surge tank cap with the new gasket added will work or do I really need a completely different cap that is designed to work with the recovery tank?"

That's really all I'm trying to learn.

Bill
 
Bill, if the systems did not have the recovery reservoir prior to this, then the caps may not be correct.
It may have been a "release" only style cap.

The little "snout" may have been there simply for over-flow.
With the correct cap, it should work as a recovery system. However, the neck surfaces must be fairly pristine.

Bill, do you own a Pressure/Vacuum tester? If you do, you could probably set up a test for this.
Or ask the shop for advice as to which caps you need.

.
 
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