Yanmar 3GM30F cooling problem - urgent advice needed please

[sebastiannr]

Hi there,

Whilst in the marina I thought I'd change the coolant in the motor as I'd been meaning to do it for a very long time. I did it, brought the engine up to operating temperature and all seemed fine. Today I finally got the weather to make the passage across Biscay to Falmouth and 10 minutes out the harbour the engine starts over heating. I've sailed back in and am on the anchor.

I assume there must be a air lock in the cooling system, but I don't know how to bleed the system.

The motor is a Yanmar 3GM30F with a remote reservoir and a SureCal calorifier.

There are 2 drain points for the coolant, 1 near the oil filter and 1 under the heat exchanger. There is also a drain point for the sea water on the heat exchanger.

When I drained the coolant, no coolant came out of the drain point under the heat exchanger. I should've realized that was probably a problem, but stupidly chose to ignore it as plenty of coolant came out of the other drain point.

When filling the coolant, I removed the hose entering the exhaust manifold and topped up the coolant until it was full, replaced the hose and put coolant in the remote reservoir. That's all the book say to do. It says to check the level in the remote reservoir after running the engine and to top up as necessary, but the level didn't go down at all in the remote reservoir.

If anyone could offer any advice as to where I've gone wrong I'd much appreciate it - I've been stuck here waiting for the weather for 10 days and really don't want to miss this window!

Many thanks,

Seb.

 

[sebastiannr]

Note:

The book says to remove the fill cap on the exhaust manifold to fill it. I can so no such cap, hence why I took the hose off. There is a pressure cap next to the remote reservoir, but this would only take 1/2 litre before overflowing.

 

[sebastiannr]

Also, on another similar thread, someone answered that there should be a square section bolt on top of the heat exchanger, which when removed acts as an air vent. There is no such bolt on the heat exchanger, only a square plate bolted onto the heat exchanger with four bolts. I assume that's where the filler cap would be.

 

[Cloven]

I have the 2GM20F which is to the same as yours but one cylinder less. I have drained and refilled regularly. All I do is remove the filler cap/thermostat on the top of heat exchanger and then open the the two drain "taps" which are on the starboard side of the engine - near to the fuel lift pump. One drains very little if any, the other drains a lot. Once drained I remove the reservoir and drain that.

Refilling is simply a matter of topping up through the heat exchanger filler cap/thermostat until full, remembering of course to refill the reservoir tank. Once running, there is very little if any draw down from the reservoir, I'm sure it acts as much as an expansion tank. Never had a problem using this method and I can't remember ever having to top up the reservoir between changes.

Not sure if this helps as it does not exactly answer you question but maybe it will point to something different you have dome which could solve your problem.

Good luck.

Dave

 

[sebastiannr]

I have the 2GM20F which is to the same as yours but one cylinder less. I have drained and refilled regularly. All I do is remove the filler cap/thermostat on the top of heat exchanger and then open the the two drain "taps" which are on the starboard side of the engine - near to the fuel lift pump. One drains very little if any, the other drains a lot. Once drained I remove the reservoir and drain that.

Refilling is simply a matter of topping up through the heat exchanger filler cap/thermostat until full, remembering of course to refill the reservoir tank. Once running, there is very little if any draw down from the reservoir, I'm sure it acts as much as an expansion tank. Never had a problem using this method and I can't remember ever having to top up the reservoir between changes.

Not sure if this helps as it does not exactly answer you question but maybe it will point to something different you have dome which could solve your problem.

Good luck.

Dave

Thanks so much for the advice Dave. It seems that the only difference is that there is no filler cap on the heat exchanger on my engine, the filler cap is up between the reservior and the calorifyer.

I've drained the coolant again now, but the reservoir has not drained. What does this mean????!!!!!

 

[sebastiannr]

Ok sorry for all this drama,

I may have found the problem. When I refilled coolant through the filler cap, I think what I thought was full was actually just air pushing coolant back up the pipe. I'll try again.

Sorry again, had a bit of a pannick there engine failure at the beginning of a 450NM trip is not good for the nerves!!!

 

[Cloven]

Found a pic of a 2GM20F showing the cooling water filler/thermostat cap top left of the pic referred to in my earlier reply which is used for refilling after draining.

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[Cloven]

Ok sorry for all this drama,

I may have found the problem. When I refilled coolant through the filler cap, I think what I thought was full was actually just air pushing coolant back up the pipe. I'll try again.

Sorry again, had a bit of a pannick there engine failure at the beginning of a 450NM trip is not good for the nerves!!!

Hoped you have solved the problem, yes you are correct in saying that the reservoir will not drain when you drain the rest of the system. I remove mine from its mounting and empty it separately.

 

[Gordonmc]

I had an air-lock on a car engine (Essex 6 cyl) which was cured by "burping" each large bore hose in turn, ie water pump to manifold, rad to pump etc.
I squeezed each hose in turn while keeping the level topped up at the coolant filler until air stopped bubbling out.
That might help.

 

[viva]

Found a pic of a 2GM20F showing the cooling water filler/thermostat cap top left of the pic referred to in my earlier reply which is used for refilling after draining.

[/URL]

What is that reservoir with the green top and black hoses at the fron of the engine and to the right of the crank pulley? I have the same engine but I don't think have one of those !

 

[sebastiannr]

Thanks for the responses.

So I double checked the drain plug that wasn't draining, and it turns out it was blocked with gunk and when unblocked alot more (filthy) coolant came out. I've now flushed through many times with fresh water by keeping the valve open and pouring in water.

The problem with refilling is that there really doesn't seem to be any bleed points in the system, so when I pour water into the filler cap I can only get about 1/5 litre in.

I'll try 'burping' the hoses, but there must be a correct way to do it.

 

[sebastiannr]

Found a pic of a 2GM20F showing the cooling water filler/thermostat cap top left of the pic referred to in my earlier reply which is used for refilling after draining.

[/URL]

Thanks for the pic. No, on my engine the filler cap is way up along side the reservior and the place where the cap was on the exchanger has a plate bolted over it. I assume it has a different arrangement because of the calorifier - the filler cap has to be above it.

 

[Cloven]

What is that reservoir with the green top and black hoses at the fron of the engine and to the right of the crank pulley? I have the same engine but I don't think have one of those !

It's the raw water strainer. Very similar to on my boat, not surprising as it's the same type of boat. Pipe going off to the left (starboard) is the raw water feed to the raw water pump. The other pipe is nothing to do with the strainer, it's just that you can't see the open end as it's behind the strainer. It's the end of the pipe leading to a manual bilge pump.

 

[Cloven]

Thanks for the pic. No, on my engine the filler cap is way up along side the reservior and the place where the cap was on the exchanger has a plate bolted over it. I assume it has a different arrangement because of the calorifier - the filler cap has to be above it.

You may well be right for your setup. This pic is not my boat, mine has a calorifier but I still use the cap as per the pic for fresh water changes.

 

[sebastiannr]

Thanks again for all the help. I've managed to get the coolant in by removing a hose from the calorifier. Bringing it to temp now, fingers crossed!

 

[sebastiannr]

Very disturbing.

Everything seemed fine after bringing the engine to temp, I checked the hoses at the calorifier and they were warm/hot, a good sign. Then left the motor running for 45 minutes, no alarms, but checked the temp of the hoses at the calorifier again and they were cold.

Does this mean that the coolant isn't circulating? If so, does that mean a knackered pump?

 

[vyv_cox]

It does sound as if the calorifier may be airlocked, not unusual. I suggest you run the engine and add coolant while it is running. When you cannot get any more in, put the pressure cap on and squezze one of the main hoses to the heat exchanger, using a mole wrench if necessary. This will divert the flow from the pump to the calorifier and usually clears airlocks. If this does not happen you will need to backfill the hoses from the calorifier, leave the pressure cap off and fill each hose in turn until everything overflows.

 

[sebastiannr]

It does sound as if the calorifier may be airlocked, not unusual. I suggest you run the engine and add coolant while it is running. When you cannot get any more in, put the pressure cap on and squezze one of the main hoses to the heat exchanger, using a mole wrench if necessary. This will divert the flow from the pump to the calorifier and usually clears airlocks. If this does not happen you will need to backfill the hoses from the calorifier, leave the pressure cap off and fill each hose in turn until everything overflows.

Thank you.

I started the motor again, did as you recommended and the hoses at the calorifier are now hot. I suppose one way of ensuring that water is running through it is if I get hot water out of the tap. I'll check in 30!