BMC 1.5 trapped air after coolant change

[ATO]

Hi - first time poster, hope you can help. I'm not a boater but I'm helping out a friend with their BMC 1.5 - I usually work on old Land Rovers so am not used to marinised systems.

 

The engine hasn't been serviced for a long time, I've changed oil and replaced the two diesel filters. The air filter which is a basic thing was soaked in oil which suggests heavy breathing, but then it hasn't been changed in years and the oil level was just over max so may have been the reason. Engine starts and runs fine. 

 

There is however mayo in the coolant, though no sign of water in the oil. In a car this could mean the engine is not getting up to temperature enough to burn it off, does this happen on boat engines with skin tanks too?

 

Also I've tried to change the coolant. the engine is above the skin tank so I dropped the bottom hose from the skin tank and let it run out under the engine, from where I pumped it out into a container. I then refilled from the tank next to the rocker cover (sorry don't know the terminology/names), this goes into the top connector for the skin tank. I would've thought that as the engine is above the skin tank it would fill the tank without air getting trapped but definately more coolant came out than has gone back in again. Is there a typical spot that air gets trapped as I'm struggling to find it. I can't see anyway of bleeding the skin tank. Also there is no expansion tank fitted to this engine, so when it gets warm coolants flows out of the small pipe by the cap.  What would be the reason for no expansion tank? This engine has been running like this for years.

 

Would appreciate any advice! Thanks.

Edited April 21, 2022 by ATO

[Tracy D'arth]

Vent the tank by loosening the top hose at the highest point.

 

Often there is no expansion tank, the exhaust manifold cum heat exchange where you filled it is not completely full, it takes the expansion.

 

Is there  a calorifier in a circuit from the back of the cylinder head to the water pump? If so that has probably drained too and you will have to vent it at a high point, usually on the top coil connection on the calorifier.

 

If you run the engine on a fast tick over up to working temperature with the cap off, topping up as you go, it will likely bleed itself and start circulating.

 

If you put antifreeze in I hope that you diluted it first as if put in neat it sinks to the bottom and it is a devil to get circulation.

Edited April 21, 2022 by Tracy D'arth

[cuthound]

Some skin tanks have a bleed bolt on the top to aid blending air out.

[ATO]

Thanks for your reply, that's definitely a help. I did pour the coolant straight in, thinking it would slowly mix, so that's something I'll have to sort. I'll try loosening the top tank hose, though it is lower than the manifold/heat exchanger (I'm learning!) so don't expect that there would be any air there as I would expect it to vent through the manifold/heat exchanger? 

 

What should the coolant level be in the heat exchanger? I filled it up to the top, too much now I realise.

 

It does have a calorifier in the circuit, didn't think of that, I'll check it out.

[Tracy D'arth]

6 minutes ago, ATO said:

Thanks for your reply, that's definitely a help. I did pour the coolant straight in, thinking it would slowly mix, so that's something I'll have to sort. I'll try loosening the top tank hose, though it is lower than the manifold/heat exchanger (I'm learning!) so don't expect that there would be any air there as I would expect it to vent through the manifold/heat exchanger? 

 

What should the coolant level be in the heat exchanger? I filled it up to the top, too much now I realise.

 

It does have a calorifier in the circuit, didn't think of that, I'll check it out.

If its cold, the stat is still closed, may prevent bleeding.

Heat exchanger will find its own level by blowing out excess but usually they are about half full cold.

 

You will struggle getting circulation if there is neat antifreeze in there...............................................

[Tony Brooks]

Mayonnaise in the coolant?

If so how did the oil get into the coolant?

 

Mayo in the rocker cover etc. may well mean the engine is running cold but not in the coolant.

 

I would expect mayo in the coolant to indicate:

 

If he is lucky the system was not properly cleaned after a previous oil leak into the coolant  or an idiot topped the oil up in the wrong filler..

 

If he is unlucky one of:

failed head gasket

Cracked cylinder

Possibly but very rare a cracked head

[Tracy D'arth]

Just now, Tony Brooks said:

Mayonnaise in the coolant?

If so how did the oil get into the coolant?

 

Mayo in the rocker cover etc. may well mean the engine is running cold but not in the coolant.

 

I would expect mayo in the coolant to indicate:

 

If he is lucky the system was not properly cleaned after a previous oil leak into the coolant  or an idiot topped the oil up in the wrong filler..

 

If he is unlucky one of:

failed head gasket

Cracked cylinder

Possibly but very rare a cracked head

I could add, gearbox oil cooler leak if it has one.

 

Lets be charitable and assume oil added by mistake, he will have enough trouble getting the antifreeze to mix!

[Tony Brooks]

Just now, Tracy D'arth said:

I could add, gearbox oil cooler leak if it has one.

 

Lets be charitable and assume oil added by mistake, he will have enough trouble getting the antifreeze to mix!

 

Yes, that as well. However I have never had problems getting antifreeze to circulate and mix in the engine cooling system. Definitely a problem in central heating systems,  especially gravity ones.

[ATO]

6 minutes ago, Tony Brooks said:

Mayonnaise in the coolant?

If so how did the oil get into the coolant?

 

That's whats bothering me. I've got a diesel compression testing kit so I'll see if that gives anything.

Edited April 21, 2022 by ATO

[Tracy D'arth]

Just now, ATO said:

That's whats bothering me. I've got a diesel compression testing so I'll see if that gives anything.

Ream the carbon out of the heater plug holes whilst you are testing, a long 11/64" drill, by hand, carefully.

 

I would doubt you will find much if the engine runs well.

[Mikexx]

2 minutes ago, ATO said:

That's whats bothering me. I've got a diesel compression testing kit so I'll see if that gives anything.

 

Can you check the gearbox oil, level and cleanliness, to remove any possibility there is a leak in the heat exchanger?

[ATO]

9 minutes ago, Mikexx said:

 

Can you check the gearbox oil, level and cleanliness, to remove any possibility there is a leak in the heat exchanger?

 

I can have a look, is there a dipstick on the gearboxes? If not how do I check? Do they have an independent oil tank or is fed from the engine?

 

It hadn't dawned on me that they were water cooled!

Edited April 21, 2022 by ATO

[Slim]

10 minutes ago, Tracy D'arth said:

I could add, gearbox oil cooler leak if it has one.

 

Lets be charitable and assume oil added by mistake, he will have enough trouble getting the antifreeze to mix!

That's what happened to me. The design of my skin tank has both the flow and return exiting at the top. To flush the tank, engine throughly I first used a strong mix of washing soda (twice) then flushed with water 4 times. To empty the skin tank l sucked the çontents out with a Pela. A long job.

[Tracy D'arth]

3 minutes ago, ATO said:

 

I can have a look, is there a dipstick on the gearboxes? If not how do I check? Do they have an independent oil tank or is fed from the engine?

 

It hadn't dawned on me that they were water cooled!

It will only have a cooler if its a hydraulic box. What make model is it ? or a photo would solve it.

No independent tank or oil feed from engine, just oil in like a car gearbox.

[Slim]

2 minutes ago, ATO said:

 

I can have a look, is there a dipstick on the gearboxes? If not how do I check? Do they have an independent oil tank or is fed from the engine?

 

It hadn't dawned on me that they were water cooled!

Weirdly when my gearbox cooler leaked it was under an end cap and there was no trace of water or mayo in the box.

[ATO]

12 minutes ago, Tracy D'arth said:

It will only have a cooler if its a hydraulic box. What make model is it ? or a photo would solve it.

No independent tank or oil feed from engine, just oil in like a car gearbox.

No idea on make and model, I'm having a look again on saturday afternoon so I'll take some pics if I don't get anywhere. The more I think about it I did follow a coolant pipe round to the gearbox.

[Tony Brooks]

2 hours ago, ATO said:

That's whats bothering me. I've got a diesel compression testing kit so I'll see if that gives anything.

 

Unfortunately, in my view, there are far too many "experts" and other un or semi-qualified people working as engineers on the canals so there is every chance that mayo is the remains of a past poorly completed head gasket job.

[ATO]

4 minutes ago, Tony Brooks said:

 

Unfortunately, in my view, there are far too many "experts" and other un or semi-qualified people working as engineers on the canals so there is every chance that mayo is the remains of a past poorly completed head gasket job.

haha like me! It seems there could be a few sources for the mayo so I'll investigate further. Gut feeling is it's not the head gasket.

[Tony Brooks]

1 minute ago, ATO said:

haha like me! It seems there could be a few sources for the mayo so I'll investigate further. Gut feeling is it's not the head gasket.

 

Nah, you have the sense and interest to admit the level of your knowledge and ask.

[ATO]

Is the large brass nut likely to be a bleeder? Both in and out of the calorifier are at the bottom.

[ATO]

Actually the inlet is halfway up and has a drain tap, I'll try that first.

[Tracy D'arth]

Brass blanking nut is for an electric immersion heater -- not fitted.

Bleed air from on high not low.  You are trying to bleed air from the coil, not the hot water store side. Follow the pipes from the engine.

Plumbing & wiring is a mess, you are welcome to sort that one out. I hate horizontal calorifiers.

Edited April 23, 2022 by Tracy D'arth

[ATO]

Sorry It's not horizontal, photo has just uploaded that way. 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. Bottom calorifier hose goes into the cylinder head. I've tried opening the valve on the top inlet and get nothing at all. Will the engine thermostat need to be open?

Edited April 23, 2022 by ATO

[ATO]

Having no joy at all.  Is the inlet into the calorifier the lower hose that goes from the cylinder head? Therefore bleed the hose that connects to the water pump?

[Tracy D'arth]

Are the calorifier coil connections  higher than the engine? If so bleed the top coil connection with the engine running fast,  topping up as you go. I plumb them in that way as it makes the heat transfer more efficient.