School me surge tanks, swirl pots, etc...

[Wookie384]

Okay so I know how most cooling systems work, radiators, thermostats, rad. caps etc... but I lack knowledge on surge tanks, swirl pots etc...

The back story is I have a friend who turbo'ed his Honda Fit, and lately he's noticed that he will randomly loose coolant, I've let the car warm up and messed around with it trying to figure out where the leak is and try to see it for myself, but I can't, I always find the traces of the coolant all around/over the area that the overflow tank is, so it's safe to assume it's overflowing from the overflow tank while he drives it. He has a stock radiator and all fittings, hoses, and etc are proper. I'm at the point where he might need to add a surge tank/swirl pot but I'm only guessing since I don't really know for sure the purpose of either one. So please help me out and school me on this? Thanks in advance.

[Bigsyke]

Its to extract air bubbles, not stop leaks.

He needs to truly isolate the leak and repair it. If its overflowing while hes driving, and he didn't over fill the coolant, then he needs to check to cap

[Wookie384]

Originally Posted by Bigsyke

Its to extract air bubbles, not stop leaks.

He needs to truly isolate the leak and repair it. If its overflowing while hes driving, and he didn't over fill the coolant, then he needs to check to cap

The cap is a new J's racing one, so I'm sure that can't be the culprit, but I'll double check.

So why do people install surge tanks if it's only to remove air bubbles? Once you refill the system and properly bleed the air out, it should be done and over with correct? Why have an additional component that should technically be considered redundant? Is it's purpose to only make peoples lives easier when it comes to bleeding out the cooling system?

[Def]

Nobody with a Japanese car seems to understand how a cooling system works... Does air just magically appear in a cooling system that's in proper working condition? No...

I'll break it down, coolant is incompressible. Coolant expands when heated. If you're running really hard and generating lots more heat than stock, it HAS to expand somewhere. Doesn't matter what your radiator cap is rated to, if you don't have sufficient volume in the system to allow the coolant to expand, it will pop the cap and go out in the overflow tank. Coolant tends to slosh out of these since they're not 100% sealed.

A "surge tank/swirl tank" does create a self bleeding system which is good, but its MAIN PURPOSE is to provide plenty of airspace to compress and give the coolant room to expand.


Note that all nicer European cars have a surge tank/swirl tank integrated into their cooling system stock. Japanese manufacturers tend to be cheap and use the very top of the radiator as the expansion volume. Works fine for stock power and driving on the street, but run the car hard with more power and it needs more expansion volume.

[Wookie384]

Originally Posted by Def

Nobody with a Japanese car seems to understand how a cooling system works... Does air just magically appear in a cooling system that's in proper working condition? No...

I'll break it down, coolant is incompressible. Coolant expands when heated. If you're running really hard and generating lots more heat than stock, it HAS to expand somewhere. Doesn't matter what your radiator cap is rated to, if you don't have sufficient volume in the system to allow the coolant to expand, it will pop the cap and go out in the overflow tank. Coolant tends to slosh out of these since they're not 100% sealed.

A "surge tank/swirl tank" does create a self bleeding system which is good, but its MAIN PURPOSE is to provide plenty of airspace to compress and give the coolant room to expand.


Note that all nicer European cars have a surge tank/swirl tank integrated into their cooling system stock. Japanese manufacturers tend to be cheap and use the very top of the radiator as the expansion volume. Works fine for stock power and driving on the street, but run the car hard with more power and it needs more expansion volume.

Okay, that's actually what I was thinking, I just didn't know for sure. My guess was the additional load on the cooling system is overloading the OEM cooling system on my buddy's Fit, So in theory he should look into a surge tank. Thanks for clarifying that for me Def! One more question, are there any differences between a surge tank and a swirl pot, or are they basically the same?

[Def]

Same thing. Domestic/NASCAR guys call them surge tanks, swirl pot is a Japanese/import term.