Tips for unlocking air in water cooling system?

[Dan Simon]

Hi - sorry if this is an oft repeated question, couldn't find an answer relating specifically to my problem.

 

I have a steel narrowboat with a BMC 1.5 raw water cooled system. I think the thing on the side of the sump is a heat exchanger.

 

My engine has been overheating - rising quickly to 80 degrees celc and hovering around that mark while cruising.

 

The water appears to be pumping around the system fine, I can't detect any issue with the head gasket, so am assuming that there's air in the system.

 

I've heard popping the lid off the heat exchanger and running the engine is one solution - do any of you knowledgeable people have any tips?

 

Thanks!

[Scholar Gypsy]

Do you mean an indirect system, ie with raw rater pumped (by water pump 1) through the end caps on the heat exchanger) and clean water pumped (by water pump 2) through the heat exchanger?

 

Also, why do you say this is overheating? My engine has an 82 deg thermostat, for example.

[Tony Brooks]

Doesn't sound like overheating to me. More like an 82C stat that is working well. If there is an air lock it is likely to be in the calorifier circuit otherwise the calorifier would slow the warm up.

 

Photos, a better description of your system (how many water pumps and of what type, where all water sources flow etc.)

 

If it really is a direct raw water cooled engine I would expect it to have a 60C or no thermostat in it so that might indicate overheating (direct raw water = a single BRASS water pump.) However nowadays very few boast have direct raw water cooling so if the boat is post (say) 1980 it is not likely to be direct raw water cooled.

 

The thing on the side of the sump might be an engine oil cooler, some 1.8s had them I believe, not many 1.5s but I doubt it on a direct raw water cooled engine. Oil coolers are much more common for hydraulic gearboxes.

 

Better info and photos gets you better advice.

[pete.i]

Yep I agree Although I have now got rid of my narrow boat that had a BMC 1.5 the temperature guage hovered around the 80 degree mark always without any problems. I had an 82 degree thermostat fitted.

[Dan Simon]

Thanks guys

 

I'll get some pix up tomorrow. The water comes in, passes through a filter to impeller, is circulated around the engine and then expelled - I'm not exactly sure what water system this is called, but will provide images.

 

The thermostat thing is bothering me because since owning the boat, the thermostat rarely budges above 50 degrees, unless really worked. The gauge is 50-150 degrees. If I continue cruising, it gradually gets hotter past 90 degrees until I have to turn the engine off to cool.

 

More tomorrow, cheers again

[Alan Saunders]

Thanks guys

 

I'll get some pix up tomorrow. The water comes in, passes through a filter to impeller, is circulated around the engine and then expelled - I'm not exactly sure what water system this is called, but will provide images.

 

The thermostat thing is bothering me because since owning the boat, the thermostat rarely budges above 50 degrees, unless really worked. The gauge is 50-150 degrees. If I continue cruising, it gradually gets hotter past 90 degrees until I have to turn the engine off to cool.

 

More tomorrow, cheers again

Dan, best that I can guess from your description is that your engine is cooled by river/canal water.

 

If it is indirectly cooled a running temperature of 90C+ would be ideal. If it is directly cooled (the river/canal water passes directly through the engine, not via a heat exchanger) 90C is still ideal but more difficult to maintain.

 

If there is no steam emitting from your cooling system you probably do not have a problem.

 

Alan

[Tony Brooks]

Where does the cooling water exit the boat? It could be via the exhaust or out of a skin fitting in the side/stern. I will assume the former.

 

This is based on what you say and assumes a direct raw water cooled system , NOT an indirect raw water cooled one where you have another water pump like a car's and a water filler for a separate engine cooling circuit. Often with a "radiator" cap to fill through.

 

It is very unlikely to be an air lock because the raw water pump can produce a degree of pressure to force any air out of the system. It is far more likely to be a lack of raw water flow.

 

Check things in this order:-

 

If its an official 1.5 marinisation check the belt driving the raw water pump is in good order and tight enough (say 1/2" of play in the middle of the run between pulleys).

 

1. Check the inlet filter is clean, there is nothing stuck in/over it under the boat, the cap is actually airtight when in place, make sure the seacock (tap/valve) that should be below the filter is turned fully on.

 

2. Check the rubber impeller in the raw water pump. If it has lost any wings you need to find them. They or their predecessors may be stuck in an elbow or bend in the pipework partially blocking it.

 

3. Make sure the face plate of the pump is not heavily scored and also the opposite face down inside the pump. Make sure there is minimal play between the shaft and pump body. It should be all but nothing.

 

4. Check all pipe/hose joints between the filter and pump are airtight.

 

5. If the raw water passes through the "heat exchanger/oil cooler" you mention make sure there is no build up of muck in the voids/under the rubber caps at each end. Make sure the tubes are clear.

 

6. If water exits via the exhaust take the mixing elbow off and make sure the area where the raw water mixes with the exhaust gasses is not furred up like a kettle.

 

7. Take off each hose and pipe to make sure nothing is blocking them.

 

8. If the water is exiting the exhaust make sure the exhaust hose is not partially blocked or de-laminating.

 

The thing that gives you the temperature is the temperature gauge not the thermostat so the gauge or its sender may be faulty, much depends upon how much water is exiting the boat.

 

9. If you have as much water as you ever did exiting the boat remove and test the thermostat in a pot of water on the stove plus a thermometer. It should start to open at the temperature marked on it. Probably about 50C by your info. If faulty ON NO ACCOUNT put a hotter one in. If you do you are likely to fur up and crack the cylinder head.

 

Now the gauge circuit if electric.

 

10. Make sure the negative (earth) to the temperature gauge is in good condition with no loose/dirty connections.

 

11. Make sure the wire between gauge and sender on the engine is not chaffing against metal or trapped under metal.

 

12. Test the sender in a pot of hot water at a known temperature. It must be connected to the gauge wire AND its body wired to the engine block. use a length of wire with a croc. clip on each end.

 

If it turns out not to be direct raw water cooled the above may not all be applicable, but it will be as far as the raw water circuit is concerned.

[Dan Simon]

Thanks all so much - such helpful advice.

 

Here are some pix and Tony I'll run through the list. When the engine reaches 80+ degrees it might be worth mentioning that it start to smoke a bit and I've taken off cover panels when cruising to vent.

 

https://drive.google.com/file/d/0B-Rsew-HkVo4a3BRN2VRcHQxV0k/view?usp=sharing

https://drive.google.com/file/d/0B-Rsew-HkVo4VVdnWXdyU3dUSGs/view?usp=sharing

https://drive.google.com/file/d/0B-Rsew-HkVo4NmJrNVhZQnhOT0E/view?usp=sharing

 

...and the gauge is 50 to 110c not to 150.

Edited July 12, 2015 by Dan Simon

[Tony Brooks]

I can not see the front of the exhaust manifold but from what I can see of the run of the alternator belt this looks like an INDIRECT (heat exchanger) raw water cooling system.

 

I think there will be a "radiator" cap on the front of the exhaust manifold. Make sure the header tank under this is filled to about 1" from the filler neck with coolant.

 

80 degrees is a perfectly acceptable running temperature for this type of system but we have to find out why it was running at 50 so you need to check everything I wrote except the exhaust mixing elbow (you do not have one).

 

You have a gearbox oil cooler. This needs checking for blockages as well.

 

This type of system is unlikely to suffer an airlock. That is far more likely on tank cooled boats.

[Dan Simon]

On it. Thanks so much.

[Scholar Gypsy]

A detective story is fun.

 

My hunch is that

• the sea cock is visible in the second photo) ...
• feeds the sieve/filter (you can see it just in front of the battery box) and then ..
• goes to the water pump that is visible under the alternator, on its own belt. Take the screws off to have a look.
• and then through the oil cooler
• and then into manifold via the end cap on the front (not visible) and then
• out to the canal via the pipe that comes out of the aft end cap

And then the primary cooling circuit is as Tony says. The thermostat housing is visible next to the oil filler.

Edited July 12, 2015 by Scholar Gypsy

[Dan Simon]

just to be clear - this device left of the sump is where the coolant goes right? it's dry which might be the issue...

 

https://drive.google.com/file/d/0B-Rsew-HkVo4bjB4a0hhUWlPZU0/view?usp=sharing

[Scholar Gypsy]

Yes - use an antifreeze mixture.

 

As Tony said, don't fill it right to the top else when the water heats up and expands it will just come out of the little expansion pipe and dribble down into the bilges. As Tony says an inch from the top is about right.

 

I have a pipe connected to mine, which then drains into a bottle/container to collect any overflow.

 

What do you do with your raw water circuit in the winter?

[Dan Simon]

THanks Simon, the engine has been performing well in winter - I can't honestly believe I've been overlooking the coolant the last two years. Got to do a BMC course

[Tony Brooks]

just to be clear - this device left of the sump is where the coolant goes right? it's dry which might be the issue...

 

https://drive.google.com/file/d/0B-Rsew-HkVo4bjB4a0hhUWlPZU0/view?usp=sharing

 

OK, so that photo shows the filler cap so it is a heat exchanger engine.

 

I can't see anything beside the sump, in fact I can hardly see the sump. What I can see is the air cleaner that is mounted on the inlet manifold and is beside the engine block - not the sump. Of course an air cleaner is not wet although you are supposed to dip the metal mesh or foam in oil and let it drain or wring it out before refitting (after cleaning) but as BMCs are good at self oiling I would leave it dry.

Edited July 12, 2015 by Tony Brooks

[Scholar Gypsy]

THanks Simon, the engine has been performing well in winter - I can't honestly believe I've been overlooking the coolant the last two years. Got to do a BMC course

 

Ah, I was asking (out of interest) what you do when leaving the boat in winter, given the risk of freezing in the raw water circuit.

[Tony Brooks]

As we have confirmed it has an engine water pump you had better make sure the alternator belt is in good condition and correctly tensioned.

[Dan Simon]

I'm a liveaboard cc'er year-round in London. Winters have been pretty mild!

 

Checked the alternator belt tension Tony - can confirm it is in good nick and does seems well tensioned.

[Alan Saunders]

... make sure the seacock (tap/valve) that should be below the filter is turned fully on. ...

... the sea cock is visible in the second photo ...

Well spotted, top right. There does not seem to be a 'mud box', just a through-hull fitting (¾", 20mm diameter?) a few inches below water level that could easily be blocked by weed, leaves, silt etc. Also, I cannot see a water filter.

 

I once.had a problem with overheating on my indirect cooled Vetus (exhaust temperature alarm). I thought I had fully opened the sea-cock but the gate valve was faulty, maybe a burr. With a little more force I was able to fully open it.

 

Alan

[Scholar Gypsy]

Well spotted, top right. There does not seem to be a 'mud box', just a through-hull fitting (¾", 20mm diameter?) a few inches below water level that could easily be blocked by weed, leaves, silt etc. Also, I cannot see a water filter.

 

...

 

I think the filter can just be seen here?

 

[Tony Brooks]

Agreed, it certainly looks like one of the horrible plastic strainers. Make sure the seal the lid sits on is in good order and also that there is a nylon or other "soft" soft washer under the wing nut or lid retaining nut.

[Dan Simon]

Hey - yes it is one of those horrible strainers. Has to be on right tight otherwise it doesn't work properly - any recommendations for a replacement gratefully received. Just topped up the heat exchanger with an antifreeze solution - hopefully that's the fix. Cheers.

[Bee]

Not a lot to add really, Tony and others have covered the lot but if it still does it I would turn the sea cock off, remove the hose, stuff the end in a bucket full of water and run the engine, the bucket should empty quite quickly, Is there a good suction? then stop the engine and have a think. Is the sea cock bunged up? does the hose collapse through suction when running? Top of the water filter needs the correct washer/ seal in it or it will suck air. try not to mangle the sea cock and sink the boat.

Edited July 15, 2015 by Bee