BMC overheating

[eddysaddington]

Hi all, any help and advice would be so much appreciated.

 I've been running my BMC 1.5 narrow-boat engine for six months now and I've serviced and replaced quite a few parts...Glow plugs/lift pump/water pump/ thermostat 82 degree Celsius  ect.

It has been starting and running well for the most part but the calorifier the cooling system it is linked to has never produced any hot water. During my last cruse the engine stated to overheat  running over 100 degrees which has not been a problem in cooler weather before now. 

My first thought was there must be a blocked pipe in the calorifier loop system but having just taken it all apart it all seems to be free flowing.

 

First off can someone tell me what temperature the engine should run at during  say a steady 1500 rpm?

Is the calorifier essentially the engines radiator?

Is the engine water pump (brand new) powerful enough to circulate the coolant through the whole system...or do I need an additional pump for the calorifier?

Is the thermostat supposed to kick in at 82 degrees and then allow circulation of the coolant?

Any advice or answers to these questions would be really great

Thank you

Eddy

[Tony Brooks]

My initial thought is air in the system. Air trapped in the calorifier pipework stopping circulation and probably air in the skin tank unless you bled it after changing the water pump and thermostat. Air expands far more than water when heated so trapped air and gas in the skin tank tends to blow coolant out of the overflow as the engine heats up.

 

Assuming the skin tan is adequate for the job I would expect an 82 degree stat to give a running temperature of maybe 88 degrees but much depends upon the load.

 

I have yet to meet a 1.5 where the water pump is not powerful enough to circulate around the calorifier.

 

More info please. Horizontal or vertical calorifier? Is there a bleed point at the highest point in the calorifier pipework? Where are the calorifier feed and return pipe connected to the engine?

 

 

 

 

[Tony Brooks]

PS have you verified the temperature reading with an infra-red thermometer? Electric gauge senders are not the most reliable.

[eddysaddington]

Thank you for the quick reply Tony. I will have another look in the engine room first thing and try to answer some of those questions.

 

Edited July 12, 2022 by eddysaddington

[eddysaddington]

I have a the original gauge which i managed to get working but also rigged up a Digital prob thermometer. I take it it shouldn't run above 90 degrees??

[eddysaddington]

I'm keen to get it the engine all back together so just had a look. It is a vertical calorifier and there is a small header tank above for topping up the coolant. The Flow and return come from the engine head and below the skin tank.

 

How would bleed air out of the system?

[Tony Brooks]

27 minutes ago, eddysaddington said:

I'm keen to get it the engine all back together so just had a look. It is a vertical calorifier and there is a small header tank above for topping up the coolant. The Flow and return come from the engine head and below the skin tank.

 

How would bleed air out of the system?

 

Thanks.

 

The flow out to the calorifier should come from the head, but the return should T into the pipe going into the water pump. With both from the head both are subject to the same pressure so you are unlikely to get any circulation.

 

If the small header tank pipes into the highest point in the calorifier circuit then the calorifier should bleed itself into the tank. The main cooling circuit is usually bled from the bleed screws/plugs on the top of the skin tank.

Edited July 12, 2022 by Tony Brooks

[eddysaddington]

Yes the return pipe comes from the pump, then T's off to the calorifier and up to the skin tank. 

 

I thought that the air would just bubble out of the top tank as well!

 

My main concern is whether the calorifier system is necessary to keep the engine cool??

Edited July 12, 2022 by eddysaddington

[Tony Brooks]

1 minute ago, eddysaddington said:

Yes the return pipe comes from the pump, then T's off to the calorifier and up to the skin tank. 

 

I thought that the air would just bubble out of the top tank as well!

 

My main concern is whether the calorifier system is necessary to keep the engine cool??

 

Not being picky but the return pipe from the calorifier goes into the return pipe from the skin tan, both pipe's liquids then flow into the pump.

 

A calorifier will only aid cooling while it is heating up, once it is up to temperature it contributes very little, if anything at all, to the cooling.

 

I think your small header tank feeds into a calorifier pipe on  a vertical calorifier. If so then the calorifier circuit should self bleed into that tank. With that setup I feel it unlikely that air/gas trapped in the skin tank can vent into the small header tank. I can't be 100% sure without assessing all the pipe/hose runs and levels.

[Tony Brooks]

Further thought. Are you absolutely sure that small tank is not a header tank for wet central heating. The cooling system, including the calorifier coil circuit, is typically filled via a radiator pressure cam on the exhaust manifold cum header tank.

[eddysaddington]

I think you might be right about it not bleeding correctly,The 15mm copper flow pipe from the engine head gets hot up to about 1 foot then cold the other side(I thought it was a blockage but probably an air bubble)

 

I'm fairly certain the header tank is purely for the calorifier loop, It's an old setup and I don't think it has pressure cams or manifold/ exhaust header tank(I'm A bit out of my depth with those terms)

 

Thanks very much for all your help and info Tony..... I wish I could buy you a pint or two!

[Tony Brooks]

25 minutes ago, eddysaddington said:

I think you might be right about it not bleeding correctly,The 15mm copper flow pipe from the engine head gets hot up to about 1 foot then cold the other side(I thought it was a blockage but probably an air bubble)

 

I'm fairly certain the header tank is purely for the calorifier loop, It's an old setup and I don't think it has pressure cams or manifold/ exhaust header tank(I'm A bit out of my depth with those terms)

 

Thanks very much for all your help and info Tony..... I wish I could buy you a pint or two!

 

Sorry, too late at night. That should read "pressure cap on the manifold/header tank".

 

If you do not have a pressure cap on the exhaust manifold either it still has the automotive exhaust manifold (that should be wrapped in insulating material, or, more likely, an old direct raw cooling marine manifold from the 1960s. If it is that then your water pump might be a brass Jabsco type raw water pump.

 

 

This is a 1.5D with an unusual oil filler, so ignore that. Look at the red X and you can see the coolant pressure/filler cap on the other side of the engine on top of the exhaust manifold. If yours is not like this then please post a photo looking down on the engine.

 

If the boat has wet central heating please be aware that typically the calorifier has two coils and the central heating coil may have the central heating header tank piped into the top of that calorifier coil.

[eddysaddington]

Yes there is a sprung cap for coolant on the exhaust manifold      (is that called the skin tank can you tell me?)

 

There is also the same sprung cap on the header tank above the calorifier.

 

The boat is from 1973 and has had many owners ripping out and changing things. There is evident of a stove back boiler being installed once upon a time. Quite possible that this tank powered radiators also but not sure. I shall post a few pics... if you don't mind?

[eddysaddington]

I don't suppose you'll be able to tell much from this picture but the tank is quite sizable!

[Tony Brooks]

The skin tank should be a large area but shallow depth tank welded to the side of the swim. Sometimes they are welded onto the bottom of the boat below the engine, and in a very few cases it is a metal pipe or pipes fixed to the outside of the hull.

 

Normally the spring cap on the manifold is where you fill the coolant, typically the one above the calorifier will be used as an expansion tank to accept the extra volume of coolant as the engine heats up and then put it back into the system as it cools.

 

Re your photo.

 

First if the lever valve runs up to the small header tank it is turned off so it can't vent any air. The pipe it is fitted to runs downhill from the calorifier to the T where the upward pipe joins it. Air will collect in the downward slope. The best way to vent it at present is to fill the engine and the small tank, turn the lever valve on and then carefully loosen the connection to the calorifier coil and move it a little to allow any air to exit. Then tighten.

 

Assuming the small tank is for engine coolant the pressure cap on that needs to be a lower pressure one to the one on the manifold. Without seeing this tank and if it is the one I suspect it is, once the system is bled and working the normal COLD level in the small tank is probably all but empty. I suspect the small tank is  a bit larger than a clenched fist.

[eddysaddington]

Hi Tony, Thanks again for the reply I only just noticed!!

 

I can say for sure there is no skin tank fitted to the system! There is A bowman type heat exchange with raw water/exhaust and a jacket of coolant setup.

 

The red lever you see is on the fresh water circuit.... There are no valves on the calorifier circuit.

 

The header tank is about the size of a rugby ball.

 

I am about to have another go at trying to squeeze any air from the system.

 

Thank you again for your reply!

[Tony Brooks]

54 minutes ago, eddysaddington said:

The header tank is about the size of a rugby ball.

 

 

That sounds far more like an accumulator or expansion vessel for the domestic water system that a simple header tank to me, but you do say it has a pressure cap on it and accumulators/expansion vessel (same item, different air pressure inside) have a car type car valve on top.

 

Now you explain it is an indirect raw water/ heat exchanger cooling system, it would have helped if you did that in your first post. Your initial overheat was probably caused by a loss of raw water and that may have damaged the impeller in the raw water pump.

 

Where does the raw water exit the boat, it is often via the exhaust pipe so how much water is coming from the exhaust?

 

To reiterate: that calorifier should not have any part if engine cooling, although it will help while it is cold. The cooling system has to be designed to cope when the calorifier is hot so not helping with the cooling.

 

The engine speed should have nothing to do with the running temperature because the thermostat will control the cooling water flow and thus the running temperature. I would suggest that with an 82 degree stat it would run at  maybe 86 at full power.

 

There is much about this boat that seems odd or not typical so where does the hot calorifier feed leave the engine and where does it return? CLEAR photos helpful but not ones that do not show what is needed because it ism hidden by insulating material.  etc.

[eddysaddington]

 

 

Sorry about the confusion of the systems and terminology  .... I am totally new to both engines and narrowboats.

 

Yes The header tank is linked to the calorifier and has a sprung cap... for the first time in 6 months the said tank was overflowing ad rejects about a pint of coolant. clearly something has changed!

 

The raw water pump does work and is expelled through the exhaust pipe ALTHOUGH I'm not sure how effectively it is working....Some water comes out but not a great deal and I have nothing to compare it to!   Would you say that this is the most likely cause of the engine overheating?

 

I shall try and post more pics

 

[eddysaddington]

[Tony Brooks]

Thanks

 

A in the image below seems to be the raw water supply to the heat exchanger. I think B must be the return from the calorifier, but I can't see where it connects to the engine circuit. It should T into a large pipe running between the heat exchanger and the ENGINE water pump (not the brass raw water pump). Can you confirm this is the case. See * below.

 

The top photo shows the hot supply to the calorifier running from the back top of the cylinder head. That is correct but the way it rises so high and then falls seems to be a sure fire way of creating an airlock. I would want an elbow or bend close to the head so the pipe/hose running to the calorifier is below the level of the coolant in the manifold, or as close as possible.

 

 

47 minutes ago, eddysaddington said:

Would you say that this is the most likely cause of the engine overheating?

 

A partial or total loss of raw water is by far the most likely cause of overheating with your type of cooling system. This could be cause by any of the following  or even a  combination.

 

Blocked raw water strainer

Wear or damage to the raw water pump or its impeller

Air leak anywhere between the raw water inlet and the raw water pump

Blockage in the raw water pipework, usually in elbows or bends.

Blockage at the inlet raw water side of the heat exchanger core or any oil cooler core.

Any form of full or partial blockage of the exhaust system - this is rarer on inland boats unless there has been a lot of running with no raw water flow.

 

When an engine fitted with a wax type thermostat overheats the stat can vent wax. This means it opens at a higher tempertaure that it should so is worth thinking about.

 

A bad overheat can damage the cylinder head & gasket, especially if refilled when hot with cold water, but if you have it running now and it does not overheat this is less likely.

 

* BELOW. Once you locate that T into the main cooling circuit back to the engine water pump try the following

 

 

Get a watering can filled with coolant mixture plus and assistant.

On a cold engine (so the engine stat is preventing flow to the heat exchanger) loosen the connection where the calorifier loop returns to the engine, do not yet remove.

Set engine to about 1500 RPM +

Pull off the connection and put your thumb over the engine side of the broken connection.

While the assistant tops up the header tank watch the flow back from the calorifier. With a bit of luck you will see a slug of air come out. Then  quickly remove your thumb and refit & tighten the connection.

 

[Tracy D'arth]

On 12/07/2022 at 20:11, eddysaddington said:

Hi all, any help and advice would be so much appreciated.

 I've been running my BMC 1.5 narrow-boat engine for six months now and I've serviced and replaced quite a few parts...Glow plugs/lift pump/water pump/ thermostat 82 degree Celsius  ect.

It has been starting and running well for the most part but the calorifier the cooling system it is linked to has never produced any hot water. During my last cruse the engine stated to overheat  running over 100 degrees which has not been a problem in cooler weather before now. 

My first thought was there must be a blocked pipe in the calorifier loop system but having just taken it all apart it all seems to be free flowing.

 

First off can someone tell me what temperature the engine should run at during  say a steady 1500 rpm?

Is the calorifier essentially the engines radiator?

Is the engine water pump (brand new) powerful enough to circulate the coolant through the whole system...or do I need an additional pump for the calorifier?

Is the thermostat supposed to kick in at 82 degrees and then allow circulation of the coolant?

Any advice or answers to these questions would be really great

Thank you

Eddy

You should spend the next 6  months  sorting out the terrible plumbing and wiring.

[eddysaddington]

Hi Tony, that's correct..... pipe B is the return from the calorifier (and exactly as you say) T's into the water pump below and the heat exchange above. 

 

Last week I identified a leak in the raw water system (very inaccessable right under the engine) lt looks like it could be a compression fitting on a 24mm copper pipe... This I Shall look into fixing first... 

 

 The calorifier producing hot water is further down on the list but it would be nice to have it working at some stage. 

 

Thanks again Tony, can I make a donation to your cold beverage fund some how? Bank transfer perhaps? 

 

 

[Tony Brooks]

2 minutes ago, eddysaddington said:

Hi Tony, that's correct..... pipe B is the return from the calorifier (and exactly as you say) T's into the water pump below and the heat exchange above. 

 

Last week I identified a leak in the raw water system (very inaccessable right under the engine) lt looks like it could be a compression fitting on a 24mm copper pipe... This I Shall look into fixing first... 

 

 The calorifier producing hot water is further down on the list but it would be nice to have it working at some stage. 

 

Thanks again Tony, can I make a donation to your cold beverage fund some how? Bank transfer perhaps? 

 

 

 

Thank you but absolutely no need. I have found that what you give out in some way you get it back. I help you, you help someone else and eventually someone will help me. If my knowledge has helped I am pleased. Have you found my website where you may find the free to print our course notes helpful.

[Tracy D'arth]

10 minutes ago, eddysaddington said:

Hi Tony, that's correct..... pipe B is the return from the calorifier (and exactly as you say) T's into the water pump below and the heat exchange above. 

 

Last week I identified a leak in the raw water system (very inaccessable right under the engine) lt looks like it could be a compression fitting on a 24mm copper pipe... This I Shall look into fixing first... 

 

 The calorifier producing hot water is further down on the list but it would be nice to have it working at some stage. 

 

Thanks again Tony, can I make a donation to your cold beverage fund some how? Bank transfer perhaps? 

 

 

copper pipe will be either 22 or 28mm  or if ancient 3/4" or1"

[eddysaddington]

Yes sorry 22mm copper pipe. I am a great believer in that philosophy also it always comes back! Thanks once again!