Overheating

[jimfin]

Having just reconed the engine I want to fit an over heating alarm buzzer.

 

Would like to get one where I can set it to buzz at about 90c

 

Where would I find one or something that would suit?

[mross]

What engine do you have?

 

Does it have a temperature switch or sender fitted in the water circuit? Most do.

[Slim]

ASAP Supplies used do one

 

. Can't remember the details other than I've still not fitted mine after 19 years. Has anyone got a roundtoit.

 

 

Frank

[jimfin]

Yes I have the temp sender off the head and a guage. Just thinking a buzzer alarm would give a audible warning.

[Tony Brooks]

You may find ASAP supplies will do a combined sender and switch but it would have to match the gauge for the sender part.

 

An electric fan switch from a car may do the job but you would ave to find a suitable mounting point. You can get what are referred to as "Outboard overheat alarm switches" that just bolt to a suitable bolt or nut on the cylinder head.

 

The original 1.5 head had (I think) two heater take off plugs, one at each end of the head. One of these might provide a mounting point.

[Jellybelly]

Have a chat with Edmond or his son at:

 

Murphy Loughman Guages
Address: Kilkenny Rd Athy Co. Kildare
City of Kildare
Phone: (059)8640991

[David Schweizer]

Why do you need an alarm? Surely a temperature gauge would be sufficient, that is waht we have on our boat and in 19 years it has never registered more than 82 degrees (BMC 1.5)

[ditchcrawler]

Why do you need an alarm? Surely a temperature gauge would be sufficient, that is waht we have on our boat and in 19 years it has never registered more than 82 degrees (BMC 1.5)

But if it did can you guarantee you would see it straight away.

[jimfin]

Why do you need an alarm? Surely a temperature gauge would be sufficient, that is waht we have on our boat and in 19 years it has never registered more than 82 degrees (BMC 1.5)

I loose some water from the pipe that sticks out just under the water filler cap. Have to top up, about 1/2 pint or so, after about 10 hours.

[David Schweizer]

I loose some water from the pipe that sticks out just under the water filler cap. Have to top up, about 1/2 pint or so, after about 10 hours.

 

That is simply an expansion overflow. There is no need to fill the heat exchanger to the top, as long as there is water visible, it will be ok. It is also very wasteful of coolant additive, and if you are topping up each morning with plain water, you are diluting the additive which contains a rust inhibitor. On our boat if I fill the heat exchanger to the top, I will collect about 500ml of water in the overflow bottle (something I fitted myself) after a days cruising.

 

May I suggest that next time you do not top up in the morning, but instead measure the distance between the top of the filler and the water level when the engine is cold, and check again the next morning after a days cruising, I would be very surprised if you discover any significant difference in the water level, you would only need to top up if there was a significant visible drop in the coolant level.

 

P.S. I am probably teaching you to suck eggs, but always top up with a percentage mix of water and additive, not plain water.

Edited July 16, 2016 by David Schweizer

[MtB]

There is a slight problem with temperature alarms.

 

If the engine is overheating due to loss of coolant,neither a temperature gauge nor alarm can be relied upon to tell you as their sensors might be hanging in air not water.

 

If all the coolant has gone you can;t even rely on that more traditional indicator, steam billowing out of the engine room!

[Iain_S]

There is a slight problem with temperature alarms.

 

If the engine is overheating due to loss of coolant,neither a temperature gauge nor alarm can be relied upon to tell you as their sensors might be hanging in air not water.

 

If all the coolant has gone you can;t even rely on that more traditional indicator, steam billowing out of the engine room!

Not my experience. Even if the temp sender bulb is in air, it has a good thermal connection to the block.

[MtB]

Not my experience. Even if the temp sender bulb is in air, it has a good thermal connection to the block.

 

 

You'd think so, but I had a car once with a coolant leak. I knew I had to add more water when the temperature gauge stopped working, as fierce boiling followed on soon after!

[jimfin]

I never use coolant or antifreeze as we lay the boat up for the winter and I always drain everything. Engine and domestic.

[Higgs]

I loose some water from the pipe that sticks out just under the water filler cap. Have to top up, about 1/2 pint or so, after about 10 hours.

 

 

Fit an expansion tank.

[David Schweizer]

I never use coolant or antifreeze as we lay the boat up for the winter and I always drain everything. Engine and domestic

 

Does your engine and keel tank have a drain tap? many marinized BMC engines do not have one. The only way I can completely drain our BMC 1.5 is to remove the bottom hose, and that still leaves a small amount of water in the water jacket.

 

To be honest no one (well hardly anyone) drains their engine down over the winter, unless it is raw water cooled. Far better to make sure you have the correct mix of Antifreeze/anti corrosion coolant and leave it in over the winter. It only then needs changing every few years,

 

I would also be unhappy about running an engine all summer without some form of anti-corrosion in the coolant. OK it will eventually become inert but if you are constantly topping it up you are introducing more oxygen which will enhance corrosion

Edited July 16, 2016 by David Schweizer

[David Schweizer]

 

 

Fit an expansion tank.

 

If the engine has a standard marinization, it will have a Bowman or similar heat exchanger, this also serves as a header/expansion tank.

[jimfin]

 

If the engine has a standard marinization, it will have a Bowman or similar heat exchanger, this also serves as a header/expansion tank.

Think I'll just keep an eye on it

[Iain_S]

You'd think so, but I had a car once with a coolant leak. I knew I had to add more water when the temperature gauge stopped working, as fierce boiling followed on soon after!

Interesting. What sort of car was it? Was the temp sender in the radiator, or in the head? I've had coolant loss on a Ford Anglia, Landrover td5 and a Vetus 4.15, and in each case the temp gauge redlined before the steam came out.

[Higgs]

 

If the engine has a standard marinization, it will have a Bowman or similar heat exchanger, this also serves as a header/expansion tank.

 

 

Mine's pretty standard Thornycroft with a Bowman (BL 180) The point at which Jimfin is getting the water loss, on mine it is nipped and soldered. My calorifier is upright and the coils are higher than the engine. With this arrangement, I need the expansion tank and can't fill the engine using the cap on top of the Bowman.

 

If Jimfin is not finding the Bowman adequate, an expansion tank would offer a degree of expansion and flow-back on cooling. It might not mean that the filler cap pressure outlet needs to be sealed. The expansion tank could be fitted just above the level of the Bowman with the coolant level able to rise higher than the Bowman.

 

The cap on top of the Bowman would have to be in tip-top condition.

Edited July 16, 2016 by Higgs

[Tony Brooks]

I never use coolant or antifreeze as we lay the boat up for the winter and I always drain everything. Engine and domestic.

 

To emphasize what others have said. By far the most important job of antifreeze is the corrosion inhibitors. Run without antifreeze (the easiest to get) or corrosion inhibitors and you are asking for trouble. You have a cast iron engine block and head, cast aluminium exhaust manifold jacket, brass and/or copper heat exchangers tubes and thermostat. In other words a perfect recipe for galvanic corrosion. If will be fine if the manifold outer case corrodes through but if its a exhaust tube then you may well bend a connection rod or worse.

 

If you have a very old BMC with a separate heat exchanger across the engine front then it might have a cast iron manifold and heat exchanger body, but they are very old now.