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Surge tank vs overflow tank


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I'm not Guru by any means - but I'm surprised you did not get any replies (especially from this unruly crowd) ;)

I'll guess that the "holy grail" of a near maintenance-free system requires a tightly sealed system with pressure cap, etc. Perhaps the overflow tank allows some evaporation since it is vented and all. A sealed system also eliminates oxidation and contamination, etc from breaking down or screwing up the coolant.

Well, maybe the old system of puking out and sucking back (a nice picture) was difficult to regulate if the pressure cap or seating surface got flakey.

One more, albiet a bit out there... If the Dexcool is indeed acid, then some fumes could vent and condense/collect - where they should not be outside the tank.

Aside from the above, I can't think of another fundemental reason to switch. <_<

A good question - in any case! :(

Add power to leave problems behind. Most braking is just - poor planning.
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A whole lot better than my feeble attempt.


I remain confused by the statement that the surge tank is better because the pump inlet is at a higher system pressure - compared to a reservoir style.

Isn't the pump suction at system pressure in either case?

I could not find a Caddy coolant system to compare plumbing to, so I stole, cut pasted a conventional system with the res tank blanked out and a surge tank added (I think correctly - from Guru's explanation).

I'm not doubting the statement and all (not that stupid just yet anyway...but the night is young). I'm just having a hard time visualizing the differences. :huh:

Oh, and while seaching - I found out that the LT-1 engines use reverse flow cooling pattern, such that the heads get the coolest coolant first (to preclude detonation from the high comp ratios). Any trick stuff like that on the NorthStar?

Thanks in advance

Add power to leave problems behind. Most braking is just - poor planning.
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Regarding coolant flow and why the water pump is at system pressure with a surge tank - as opposed to an overflow tank:

I still don't understand the improvement - because it appears in both systems - the water pump suctions have to be at "system pressure" and the major parts seem to be lined up about the same. Granted, one system may have better routing and all to reduce pressure drop across fittings etc.

Maybe I misunderstood or perhaps a "mistpye" occurred in the explanation.

I actually opened the hood tonight and began to trace coolant hoses a bit until "she who must be obeyed" yelled at me to quit climbing in and under that dirty car engine in my good clothes... again...<_<

OK, shes gone for now...sheesh! :unsure:

It looked like the bottom of the surge tank tee's into one of the hoses to/from the heater - probably the outlet?

The raditor to/from is relatively straight-forward enough.

The water pump (or is that bulge the thermostat?) is in an odd location.

I had to quit tracing then as I was caught.

Anybody have a coolant flow diagram for the NorthStar? :(

Add power to leave problems behind. Most braking is just - poor planning.
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This one Guru?


Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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Guru and Scotty...What a "Technical Tag Tem" ! :)

Thanks for bringing enlightment to the ignorant. :blink:

My head hurts... :P

From all the sage advice this forum has offered - I feel like the Prof's will give a test tomorrow and the thesis is due soon after. :(

Thanks again

ps, gonna take the BRD on a quick road trip of about a 1,000 low-flying miles. It'll just be run hard, put up wet - and then be happy to go it again.

The dealership replaced the door latch assembly on the same passenger door that "she" had somehow damaged the power lock module (my story anyway).

Add power to leave problems behind. Most braking is just - poor planning.
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Diggetty dog! The older I get, the less I know..(where else have I heard that..)..

I actually just learned me somthin.

You guys are too cool.. ;)

'93 STS.. opened, dropped, wide...fast.

user posted image

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