BMC 1.5 trapped air after coolant change

[ATO]

Ok. The MT cock washer is not stuck and is operating as it should, however there nothing coming out when opened with the engine running. No movement of air, no coolant, nowt. I've uploaded pics of the in/out pipes and the MT valve on the top pipe. The pipe from the cylinder head is attached to the bottom of the calorifier. Is this the correct orientation? Owner says it was running fine and not too hot before I changed the coolant.

[Tracy D'arth]

I connect them that way. its easier to bleed when the air is going up rather than down!

 

Question.  Did you add neat antifreeze or did you dilute it first?

[TheBiscuits]

Just now, Tracy D'arth said:

Question.  Did you add neat antifreeze or did you dilute it first?

 

I was just about to ask the same thing.

 

 

[Tony Brooks]

I think the last photo may give a clue but I don't understand why the head of the coolant into the engine did not allow coolant to come from that valve UNLESS it is  a vertical calorifier with the coil connection higher than the engine.

 

I can't tell much from the jumble of pipes and photos but what I do know is that on a tank cooled boat the rubber boot at the back of the manifold should be a plain one. It looks to me as if the calorifier return is piped into it rather than T'd into the tank to engine water pump pipe. Once the thermostat opens you are likely to have the same pressure on the calorifier feed and return so much flow is unlikely.

 

If that connection is a connection to the skin tank it is too small.

[ATO]

11 minutes ago, Tony Brooks said:

 

The top pipe from the calorifier is tee'd into the water pump pipe (middle pic)

 

I did dump neat coolant in there yes. The engine has run for well over an hour since, surely that would have mixed it up? 

 

The cal tank is higher than the engine.

Edited June 27, 2022 by ATO

[Tony Brooks]

5 minutes ago, ATO said:

The top pipe from the calorifier is tee'd into the water pump pipe (middle pic)

 

I did dump neat coolant in there yes. The engine has run for well over an hour since, surely that would have mixed it up? 

 

The cal tank is higher than the engine.

 

5 minutes ago, ATO said:

The top pipe from the calorifier is tee'd into the water pump pipe (middle pic)

 

 

So what is that pipe connected to the rubber on the back of the manifold and how are we supposed to know what a photo shows unless you label it?

 

5 minutes ago, ATO said:

The cal tank is higher than the engine

 

If the COIL is higher than the engine then try a lash up higher level expansion tank to see if it helps the bleeding.

Edited June 27, 2022 by Tony Brooks

[ATO]

The only pipe connected to the boot is going to the skin tank. Sorry if I didn't make it clear enough. 

[ATO]

I see what you are saying about the neat coolant, however I did manage to bleed the calorifier on one occasion after trying for ages. That time nothing would come out at all like now, however after running the engine for a while I noticed the pipe from the cylinder head has partially warm for about 30cm from the head, so I tried bleeding again and suddenly coolant spurted out and both in/out pipes were hot. I thought the job was done at that point, however the next time the owner ran the engine a few weeks later, she called me concerned as it seemed to be running very hot after 20mins of idling. The coolant level in the heat exchanger tank had dropped and the calorifier loop just had air in it again. Owner says it idled at around 85c before.

Edited June 27, 2022 by ATO

[Tony Brooks]

15 minutes ago, ATO said:

The only pipe connected to the boot is going to the skin tank. Sorry if I didn't make it clear enough. 

 

Well, in my view it is too small. The pipe and hose ID needs to be at least 1" or larger. The more bends and the longer the tank pipe runs the larger the pipe bore should be. Usually the outlet to the tank is under the manifold. The connection in use on your boat usually feeds RAW water into the exhaust stream.

 

I would not expect this to affect the calorifier circuit but might be the cause of running hot.

Edited June 27, 2022 by Tony Brooks

[ATO]

1 minute ago, Tony Brooks said:

 

Well, in my view it is too small. The pipe and hose ID needs to be at least 1" or larger. The more bends and the longer the tank pipe runs the larger the pipe bore should be. Usually the outlet to the tank is under the manifold. The connection in use on your boat usually feeds RAW water into the exhaust stream.

It may well be, however it has been like that for years without issue. The problem I'm having has been brought about by me changing the coolant. The engine hadn't been serviced for many years, she only asked me to service it as it was stalling when idling. Change of filters sorted that.  However when it did run properly it did so at 85c. I wish I hadn't agreed to help now!

[Tony Brooks]

Can't remember if I have already mentioned this, and it has nothing to do with the calorifier circulation. When wax type thermostats (modern ones) are overheated they can vent wax. If they do this they start to open at a higher temperature than they should. That makes the engine run hotter but if anything it would help calorifier circulation until it did start to open.

[Troyboy]

I'm not as expert as many on this forum but I have had a similar problem with air trapped in the calorifier in the past . I disconnected the return hose from the calorifier at the engine end put something [ thumb] over the pipe to stop water coming out of the engine  and then run the engine with the filler cap off until water emerged from the pipe leading from the calorifier and then quickly reattach the pipe to the engine. Do this with the engine cold obviously and keep clear of belts and pulleys . Best of luck .

[Tony Brooks]

24 minutes ago, Troyboy said:

I'm not as expert as many on this forum but I have had a similar problem with air trapped in the calorifier in the past . I disconnected the return hose from the calorifier at the engine end put something [ thumb] over the pipe to stop water coming out of the engine  and then run the engine with the filler cap off until water emerged from the pipe leading from the calorifier and then quickly reattach the pipe to the engine. Do this with the engine cold obviously and keep clear of belts and pulleys . Best of luck .

 

That is how we did it on the fleet, but often it is a two-person job. One to deal with the hose and put thumb over the engine side of the hose connection and the other to top up the header tank. We did it with the engine revving.

 

I can't help feeling there are two problems here. The running hot and the no water passing through the calorifier. Once  a calorifier is up to temperature it takes no more heat from the coolant so it can only affect the warm-up stage. With no calorifier circulation the warm-up would just be faster than with circulation.

[Tony Brooks]

On 23/04/2022 at 15:25, ATO said:

So I've got the top calorifier hose Tee'd into a pipe between water pump and gearbox oil cooler, that then goes into bottom skin tank outlet.

 

I have been reviewing this topic because it seems a very odd one and noticed this quote.

 

I think the OP may have the water flow model in his head going backwards. The flow should be the cold return from the skin tank into the gearbox oil cooler and from there to the engine water pump inlet.

 

Hot coolant from the thermostat into the manifold header and from there to the skin tank (hot) inlet.

 

The calorifier flow is totally separate apart from where it is returned into the engine water pump inlet. From cylinder head to calorifier coil and then from the coil to where it joins the water pump inlet.

 

However, the jumble of hoses, trunking and cables makes working much out from photos difficult. It might help if the OP put wraps of coloured tape around the four pipes/hoses we are interested in so they are easy to identify.

 

They are for the actual engine cooling circuit manifold to skin tank in, skin tank out to gearbox oil cooler, gearbox oil cooler to engine water pump inlet. For the calorifier cylinder head to one coil connection, other coil connection to the engine water pump inlet.

[Mikexx]

Photo 3 suggests the water out of the back of the Bowman is entering the top of the skin tank.

 

While the density of ethylene glycol is high I would have thought it would have diffused and mixed by now. If propylene glycol based then this has a density comparable with water so shouldn't present an issue.

 

Has anyone mentioned removing the thermostat and checking function?

 

Another failure I have had is a water pump where all the blades had rotted away. If it was marginal before then ...................

 

As Tony has said regarding photos. We need more information. I think I am right in saying that only one photo has been posted regarding the engine coolant pipework. Calorifier issues can be addressed after.

 

 

[Tracy D'arth]

I have read back to the beginning of the post.

 

Neat antifreeze added, but by now it should have mixed.

The engine was previously running OK, not overheating.

There is signs of oil in the water, possibly past problem.

No circulation to calorifier.

Engine overheats, not getting cooled.

 

The problem has only arisen since the coolant was drained and refilled, taking less than came out.

Therefore there is air still in the system, likely in the skin tank, which is preventing circulation.

 

The skin tank needs venting.

 

Does the skin tank have a top connection going to the heat exchanger/header tank and a bottom connection going to the water pump inlet?

Or are both skin tank connections somewhere else? Could the circulation through the skin tank be the wrong way, hot into the bottom, cold into the top? This would stop it venting.

[ATO]

1 hour ago, Tony Brooks said:

 

I think the OP may have the water flow model in his head going backwards. 

 

This isn't my boat or my engine, it's been running well for years. The owner (a neighbour) asked me to service the engine as it has not been serviced for some time. What ever the set up that exists now, it's as it has always been without any input from me. I've just approached it, serviced it and attempted to change the coolant. Whatever the issue is, it's not the existing pipe work, as it'd been bled in the past. I'm just attempting to understand why the calorifier circuit won't bleed. 

 

The stat is opening as I've monitored it warming up with an infra red temp gun. It opens around a bit late around 85c.

 

There are three photos in one of the posts above however I'm not sure you can see them from the comments. There's one pic of the pipe coming from the cylinder head, it goes to the lower union of the calorifier. There's a pic of the pipe from the top union where it is Tee'd into the waterpump pipe & there  is a pic of the MT cock on the calorifer.

 

I'm starting to think there is some sort of partial blockage in the coolant system within the engine.

[ATO]

2 minutes ago, Tracy D'arth said:

I have read back to the beginning of the post.

 

Neat antifreeze added, but by now it should have mixed.

The engine was previously running OK, not overheating.

There is signs of oil in the water, possibly past problem.

No circulation to calorifier.

Engine overheats, not getting cooled.

 

The problem has only arisen since the coolant was drained and refilled, taking less than came out.

Therefore there is air still in the system, likely in the skin tank, which is preventing circulation.

 

The skin tank needs venting.

 

Does the skin tank have a top connection going to the heat exchanger/header tank and a bottom connection going to the water pump inlet?

Or are both skin tank connections somewhere else? Could the circulation through the skin tank be the wrong way, hot into the bottom, cold into the top? This would stop it venting.

 

Top connection for skin tank comes from heat exchanger, bottom to water pump. I have no concerns over the piping orientation - it ran fine before. skin tank is lower than the heat exchanger. I think I may have to drain down again totally, flush through/back flush. 

Thanks all for your continued suggestions.

[Tracy D'arth]

20 minutes ago, ATO said:

 

Top connection for skin tank comes from heat exchanger, bottom to water pump. I have no concerns over the piping orientation - it ran fine before. skin tank is lower than the heat exchanger. I think I may have to drain down again totally, flush through/back flush. 

Thanks all for your continued suggestions.

I was just trying to establish whether the difficulty venting was because the skin tank was not venting into the heat exchanger, not saying its the piping that is wrong.

It could be a load of muck/rust in the skin tank has settled in the bottom outlet if its an old boat.

We all seemed to be clutching at straws, when it all started when you drained down. Previously it was working.

 

Have you a wet vac? That will suck the muck and air from the skin tank.

[Tony Brooks]

56 minutes ago, ATO said:

This isn't my boat or my engine, it's been running well for years. The owner (a neighbour) asked me to service the engine as it has not been serviced for some time. What ever the set up that exists now, it's as it has always been without any input from me. I've just approached it, serviced it and attempted to change the coolant. Whatever the issue is, it's not the existing pipe work, as it'd been bled in the past. I'm just attempting to understand why the calorifier circuit won't bleed. 

 

The stat is opening as I've monitored it warming up with an infra red temp gun. It opens around a bit late around 85c.

 

There are three photos in one of the posts above however I'm not sure you can see them from the comments. There's one pic of the pipe coming from the cylinder head, it goes to the lower union of the calorifier. There's a pic of the pipe from the top union where it is Tee'd into the waterpump pipe & there  is a pic of the MT cock on the calorifer.

 

I'm starting to think there is some sort of partial blockage in the coolant system within the engine.

 

I only pointed out that your word order did not match the correct water flow in an attempt to ensure you have got the correct flows clear in your head.

 

the calorifier circuit seems fine as you described it and should work but it obviously is not. Are you absolutely sure there is not a non-return valve somewhere in the calorifier circuit. They are sometimes fitted to stop thermosyphoning into the engine a night but the way that one is connected means that is less likely to happen.

 

I think we all are trying to work out why it won't bleed. I think you need to understand that the calorifier circuit and cooling circuit are really two independent systems with only the engine water pump being common to both. Hence, the suggestion that you look at the pump impeller.

 

It may well be a blockage in the calorifier circuit. Those hoses look old to me and as they age the inside wall tends to harden. If this cracked and fell off it could easily block a bend or where a hose goes onto a metal fitting. if you give all the hoses a good squeeze at varying places along their length and you feel them crunch then it is a fair indication that the inner wall has hardened. Any hose debris circulating could well partially or fully block the gearbox heat exchanger core. That could explain the running hot. Debris from a calorifier hose could get carried into the main cooling system and then into the oil cooler.

[ATO]

1 hour ago, Tracy D'arth said:

Have you a wet vac? That will suck the muck and air from the skin tank.

 

I think the owner has - we'll deffo try that.

[ATO]

1 hour ago, Tony Brooks said:

 

I only pointed out that your word order did not match the correct water flow in an attempt to ensure you have got the correct flows clear in your head.

 

the calorifier circuit seems fine as you described it and should work but it obviously is not. Are you absolutely sure there is not a non-return valve somewhere in the calorifier circuit. They are sometimes fitted to stop thermosyphoning into the engine a night but the way that one is connected means that is less likely to happen.

 

I think we all are trying to work out why it won't bleed. I think you need to understand that the calorifier circuit and cooling circuit are really two independent systems with only the engine water pump being common to both. Hence, the suggestion that you look at the pump impeller.

 

It may well be a blockage in the calorifier circuit. Those hoses look old to me and as they age the inside wall tends to harden. If this cracked and fell off it could easily block a bend or where a hose goes onto a metal fitting. if you give all the hoses a good squeeze at varying places along their length and you feel them crunch then it is a fair indication that the inner wall has hardened. Any hose debris circulating could well partially or fully block the gearbox heat exchanger core. That could explain the running hot. Debris from a calorifier hose could get carried into the main cooling system and then into the oil cooler.

 

Definitely no non return valve on the calorifier. Pump impeller is on the list if there are still issues after a hosepipe flush/back flush - however again no problems prior to me draining down it's unlikely to be that. Good point on possible blockage in the gearbox heat exchanger, if there is a blockage that's a prime spot. I'll replace the hoses too. I'm definitely leaning toward a blockage somewhere now. It'll be a while before I'll find the time to flush the engine unfortunately. 

Edited June 28, 2022 by ATO

[Tony Brooks]

1 minute ago, ATO said:

 

Definitely no non return valve on the calorifier. Pump impeller is on the list if there are still issues after a hosepipe flush/back flush - however again no problems prior to me draining down it's unlikely to be that. Good point on possible blockage in the gearbox heat exchanger, if there is a blockage that's a prime spot. I'll replace the hoses too. I'm definitely leaning toward a blockage somewhere now. It'll be a while before I'll find the time to flush the engine unfortunately. 

 

As well as flushing the engine and skin tank I would connect the hose to calorifier hose on the head and take the return connection off that copper pipe as well. That should give you a good idea if there is a partial  blockage in the coil circuit.

 

When back flushing the engine we usually remove the thermostat to allow the full hose flow. It may be a good idea to test it in a pan of water to see if it has lost any wax.

[ATO]

I've been over to the boat and done a bit today. Flushed the engine and skin tank separately. I've mentioned before oil in the coolant but I'm amazed by the amount of oil that has come out of the skin tank. I flushed for an hour and it's still coming out in drips and drabs. Have a look at this photo of the skin tank contents drained into the bilge. I can only think that someone has poured engine oil in the heat exchanger instead or the rocker cover at some point, owner denies any knowledge! Didn't have time to fill up and run it. Do these skin tanks have an internal baffle? 

Edited July 2, 2022 by ATO

[Tony Brooks]

36 minutes ago, ATO said:

Do these skin tanks have an internal baffle? 

 

Should do but there is no way to be sure. Who built the hull?

 

You may have to flush it several times with a strong hot soda solution.