Hi Guys,
I'm about to make the expansion tank for the sealed sytem cooling for the Toyota V8.
Any opinions on how large it needs to be? Or is it a case of the bigger the better?
My instinct says about 4 litres should be pretty good. After all the top tank on the radiator of my val works out at only about 1.5 litres....
Cheers!
Neil
Expansion tank - How big???
Re: Expansion tank - How big???
Neil,
1 litre would be enough, but it's the "overflow" that needs to be big enough to cope with the expansion and contraction. You should run an overflow bottle at least twice the volume of the amount of expansion in the system from cold to hot, start with it at 1/4 cold and it should be at 3/4 hot so that you have some room if it gets over normal max temp, and doesn't make a mess in the bottom of the boat. The easiest way to get the sizes is probably to look at the car the engine came from and use that as a starting point.
I would use at least 2 litres, my experience with closed systems on ski boats has been that they have trouble holding the temp down after you go for a run then stop quickly to pick up the wounded (skier). Without positive water flow they can spike and fill the overflow bottle real easy, so, if you can fit a 4 litre tank, then that should give you heaps of room.
Are you running a separate pump to the heat exchanger ?
Alan.
1 litre would be enough, but it's the "overflow" that needs to be big enough to cope with the expansion and contraction. You should run an overflow bottle at least twice the volume of the amount of expansion in the system from cold to hot, start with it at 1/4 cold and it should be at 3/4 hot so that you have some room if it gets over normal max temp, and doesn't make a mess in the bottom of the boat. The easiest way to get the sizes is probably to look at the car the engine came from and use that as a starting point.
I would use at least 2 litres, my experience with closed systems on ski boats has been that they have trouble holding the temp down after you go for a run then stop quickly to pick up the wounded (skier). Without positive water flow they can spike and fill the overflow bottle real easy, so, if you can fit a 4 litre tank, then that should give you heaps of room.
Are you running a separate pump to the heat exchanger ?
Alan.
Re: Expansion tank - How big???
Hey Alan,
Thanks for the detailed response. From what little experience I have with coolant systems, there seems to be two approaches to it. Old school and new school. I had my last motor setup the way you are referring to and it was only moderately successful. The other method (old school) is like my valiant which doesn't have an overflow bottle, but has a large radiator top tank which holds some air. This air compresses to allow for the expansion of the coolant without the need to go into a seperate bottle.
I was hoping to replicate this last scenario.
I am hoping to avoid any overheating problems by running the engine a bit cooler than the normal thermostat would allow. I am running a Fynspray 3/4 inch belt driven pump for the heat exchanger / manifolds.
Is it possible to run either type of system in a boat?
Cheers!
Neil
Thanks for the detailed response. From what little experience I have with coolant systems, there seems to be two approaches to it. Old school and new school. I had my last motor setup the way you are referring to and it was only moderately successful. The other method (old school) is like my valiant which doesn't have an overflow bottle, but has a large radiator top tank which holds some air. This air compresses to allow for the expansion of the coolant without the need to go into a seperate bottle.
I was hoping to replicate this last scenario.
I am hoping to avoid any overheating problems by running the engine a bit cooler than the normal thermostat would allow. I am running a Fynspray 3/4 inch belt driven pump for the heat exchanger / manifolds.
Is it possible to run either type of system in a boat?
Cheers!
Neil
Re: Expansion tank - How big???
Neil,
apart from the sizes of the bottles the only difference between the two systems is the length of the tube into the overflow bottle. I would always run an overflow bottle even on an old school setup just to catch the odd dribble, your boats to nice to get coolant stains through it. Where did your last setup have problems ?
Alan.
apart from the sizes of the bottles the only difference between the two systems is the length of the tube into the overflow bottle. I would always run an overflow bottle even on an old school setup just to catch the odd dribble, your boats to nice to get coolant stains through it. Where did your last setup have problems ?
Alan.
Re: Expansion tank - How big???
The last setup I was losing coolant somewhere and I could never work out where. The expansion / overflow bottle was about 2 litres in size.
Hmmmm..... Thinking about it logically though I'll need to make sure that in the tank I make there is a proportionately large enough air space in the tank relative to the amount of coolant in the sytem. So in reality I don't want to have too much extra coolant in the tank as that will just mean there is more coolant expanding that I will need an air space for. Damn. There's more science in a cooling system than I realised.
Cheers!
Neil
Hmmmm..... Thinking about it logically though I'll need to make sure that in the tank I make there is a proportionately large enough air space in the tank relative to the amount of coolant in the sytem. So in reality I don't want to have too much extra coolant in the tank as that will just mean there is more coolant expanding that I will need an air space for. Damn. There's more science in a cooling system than I realised.
Cheers!
Neil
-
Batesy
Re: Expansion tank - How big???
Find a radiator shop and ask some questions.
I may be wrong, but I believe that the old setups where there is air in the radiator header tank suffer from increased corrosion, due to oxygenation of the coolant.
I'm pretty sure the modern way where the header tank is always full and overflows into an expansion bottle when the engine heats up then draws coolant back into the radiator when the engine cools down is a lot better in terms of engine corrosion.
Let me know how you get on.
To work out your coolant tank sizes, work out the ratio of coolant volume (it's in the owners manual) to overflow bottle of the car that your engine came out of.
Then measure how much coolant your heat exchanger setup holds and then scale the overflow bottle to match the ratio of the original car.
ie donor car held 10 litres in radiator and 2 litre overflow bottle - your boat cooling system holds 5 litres of coolant therefore you only need a 1 litre overflow bottle.
Cheers,
Andrew
I may be wrong, but I believe that the old setups where there is air in the radiator header tank suffer from increased corrosion, due to oxygenation of the coolant.
I'm pretty sure the modern way where the header tank is always full and overflows into an expansion bottle when the engine heats up then draws coolant back into the radiator when the engine cools down is a lot better in terms of engine corrosion.
Let me know how you get on.
To work out your coolant tank sizes, work out the ratio of coolant volume (it's in the owners manual) to overflow bottle of the car that your engine came out of.
Then measure how much coolant your heat exchanger setup holds and then scale the overflow bottle to match the ratio of the original car.
ie donor car held 10 litres in radiator and 2 litre overflow bottle - your boat cooling system holds 5 litres of coolant therefore you only need a 1 litre overflow bottle.
Cheers,
Andrew
Re: Expansion tank - How big???
Hey Andrew,
I haven't heard of that corrosion issue before but you could be right. Somehow I think being in a boat that if I get even half as much corrosion on the inside as I do on the outside I'll be ahead. Anythings going to be better than running sea water through the engine too....
Unfortunately I don't have access to any cars with that engine in it. I bought the engine as an import. I talked to a couple of different people and I think I'm going to go with about 2 litre expansion tank and a 2 litre catch / recovery can. I recon that should cover all my bases....
Cheers!
I haven't heard of that corrosion issue before but you could be right. Somehow I think being in a boat that if I get even half as much corrosion on the inside as I do on the outside I'll be ahead. Anythings going to be better than running sea water through the engine too....
Unfortunately I don't have access to any cars with that engine in it. I bought the engine as an import. I talked to a couple of different people and I think I'm going to go with about 2 litre expansion tank and a 2 litre catch / recovery can. I recon that should cover all my bases....
Cheers!
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