Why do some engines have coolant expansion tanks and others don't

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Deleted User YDKXO

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My last boat had Cat engines fitted with coolant expansion tanks fitted. My present boat also has Cat engines, albeit a different model, but don't have coolant expansion tanks.
Anybody know why this should be?
 
I think that boat engines have developed in a similar manner to car engines.

Older cars had large header tanks on their radiators with an air space to allow for expansion. Later, designs became more compact with small header tanks and separate expansion bottles became necessary. These could be located away from the radiator, allowing the bonnet line to be lower.

On boats the heat exchanger replaces the air-cooled radiator of the car. Space is still needed to allow the coolant to expand, either by an air space in the heat exchanger itself or in a remote expansion tank. Since boat engines are often squeezed into small spaces a smaller heat exchanger can be advantageous.
 
macnorton said:
Indirect cooling has a header tank and heat exchanger to cool the engine.

Direct cooling sends sea water through the block.
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??? Mike's big fine caterpillars are indirect

Mike I dunno. My current Cats have the tank; my prev D12s didn't. My prev smaller gensets did; my current gensets don't. I have no idea
 
jfm said:
??? Mike's big fine caterpillars are indirect

Mike I dunno. My current Cats have the tank; my prev D12s didn't. My prev smaller gensets did; my current gensets don't. I have no idea
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Do you mean D12 or C12?
 
The CAT C12 engines have header tanks.

Header tanks are a very good idea in terms of quick visual checks, you can see there is water without having to remove any caps (and risk cross threading when replacing! ).

Henry :)
 
henryf said:
The CAT C12 engines have header tanks.

Header tanks are a very good idea in terms of quick visual checks, you can see there is water without having to remove any caps (and risk cross threading when replacing! ).
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Mmm, thats odd 'coz the C12 is the current version of the 3196 which I have on my boat so you'd expect them both to have expansion tanks. Yes I agree much better with expansion tanks, especially on my boat, as the filler caps are very tight up against the underside of the saloon floor and you need to be very dexterous to get them off.
Anyone know whether the boat builder has the option not to fit expansion tanks on some engines?
 
Deleted User said:
My last boat had Cat engines fitted with coolant expansion tanks fitted. My present boat also has Cat engines, albeit a different model, but don't have coolant expansion tanks.
Anybody know why this should be?
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Depends on header tank draw down capacity.

There are times when designing an engine that it is expedient to reduce the capacity of the header tank to improve overall engine package. Engine draw down capacity is cast is tablets of stone as part of base engine application criteria, however one can work around the rules by having separate coolant expansion/make up tank.

Hope this makes sense, not sure after I re-read it!
 
My two engines are one with and one without expansion.

The engine with expansion tank supplies hot coolant to the domestic water heater. With the amount of air that can be trapped after winterizing (draining), it is a good idea to have the extra capacity and it works well.
The expansion tank is accessible from under a seat in the cabin, ie. the highest point in the coolant circuit.
 
Spi D said:
My two engines are one with and one without expansion.

The engine with expansion tank supplies hot coolant to the domestic water heater. With the amount of air that can be trapped after winterizing (draining), it is a good idea to have the extra capacity and it works well.
The expansion tank is accessible from under a seat in the cabin, ie. the highest point in the coolant circuit.
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As latestarter said +1 and another use:-
we have one with , one without, on ford sabres, & as above the one plumbed to the domestic water heater tank has it fitted to aid filling the heating coil, as itis higher than the engine.


the bottom of the expansion tank is plumbed to the engine coolant system, unlike the onan genny on board , where the bottle is only plumbed to the rad cap and open to atmosphere. to catch & retain expanded water and return it on cooldown. (only reallycoes into play when there hasnt been a long enough light load period on shut down after high load running
 
jfm said:
??? Mike's big fine caterpillars are indirect

Mike I dunno. My current Cats have the tank; my prev D12s didn't. My prev smaller gensets did; my current gensets don't. I have no idea
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With Onan generators, It is a coolant recovery tank.

It is designed to catch and refill any additional coolant not required in the header tank within the generator during the expansion and contaction of the coolant during heating and cooling.

This stop's the leakage of coolant into the bilge after refilling.

It is up to each boatbuilder wheather they use this recovery bottles or not. On all Fairlines you normally see the bottles fitted with the exception of SQ78

Regards Anthony
 
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