More waterworks

[robp]

Has anybody got any idea what would cause water to be ejected from the overflow pipe out of the fresh water header? It's a Volvo 2040. Not too keen on tasting much, as there are still traces of anti freeze but it doesn't seem to be salt water. I was advised by an engineer not to re-fill it if all else seems OK, as it does do. But it's still coming out. I tied a lemonade bottle to the pipe to prove it and motoring for four hours seems to produce about 2 litres. It could also be that motoring faster than normal (2,750 to 3,000), accelerates the problem.

Any ideas?

 

[ccscott49]

You should not be chucking two litres of water out of your fresh water cooling, no matter how much expasion you get, due to temperature, it should not be 2 litres worth! You do have a problem, that is obvious, it could be an airlock, it could be a leak on the raw water side, allowing sea water to enter your fresh system, it could be a head gasket, but by now you would or should be seeing a drop inpower. The fastest way of checking a fresh water cooliling system, is to put a pressure tester on it, they use them for cars aswell, any good boat mechanic should have one. If it's a airlock, you should be able to bleed the system and get rid of it, but unless the systemm has been drained lately, I doubt it's an airlock. It's maybe time to call in an expert, before damage is caused by overheating or spot overheating. IMHO

 

[charles_reed]

My guess is a leak in the heat-exchanger - salt water replacing the coolant.
Not much you can do but replace the heat-exchanger core.

You'll not be likely to blow the engine up, but raw water cooling without anodes will soon result in cylinder-head problems, so I'd not leave it too long.

 

[vyv_cox]

I don't see how it can possibly be salt water replacing fresh coolant, as the fresh side has far greater pressure than the salt. Check your pressure cap for precise figure but it will be at least 4 p.s.i. and could be up to 13 p.s.i. Salt water from the pump will be only a few inches water gauge as it is open ended.

I've had lots of cylinder head gasket failures that caused water to expand out of the expansion tank but there is obviously a limit to how long this can continue.

Without knowing what you have, the most likely cause is a leak in a calorifier coil. The pressure, at least in mine, is higher than the coolant pressure and there is an unlimited supply of water.

 

[ccscott49]

Never considered the calorifier, mainly because I don't have one! But you may well be right! It would be an unusual failure though wouldn't it, or is it quite common?

 

[robp]

Thanks for these replies all. Vyv, sounds like you might have something. Yes I do have a calorifier and it would explain why the antifreeze has diluted and pretty well gone but with what is now quite clear water.

I know nothing about these systems although I can learn but I guess Colin is right and I'll have to get it sorted. I did get an engineer to check it a week or so back cos it happened just before my holiday. He was puzzled and mentioned heat exchanger but felt it was OK to use as it wasn't overheating in any way.

Presumably the coil is within the fresh water system?

 

[pvb]

Easy check...

Vyv's suggestion of the calorifier coil is good. You could check this easily by switching off your pressure pump and seeing whether the overflow still produces the same amount of water.

 

[ccscott49]

Re: Easy check...

You should be able to turn off your calorifier, there is normally cocks in the lines to do it, or should be, you could just disconnect it and loop the pipe.

 

[ccscott49]

Re: Easy check...

You should be able to turn off your calorifier, there is normally cocks in the lines to do it, or should be, you could just disconnect it and loop the pipe. If it is a fault there, you should be able to take off the filler cap, with the pressure pump on and the water level should rise and water come out of the header tank, with the engine stationary. But I would have thought you would have noticed that already, it must be a very small leak.

 

[robp]

Re: Easy check...

I will check it like that. This has only happened in the past couple of weeks or so. I've twice cleared water from the moulding under the engine. (cursing the fact that they don't run it into the bilge - but then it wouldn't have been so easy to find). I had assumed that it happened only whilst the engine was running so didn't check anything whilst stationary. Why though, wouldn't I keep hearing the pressure pump operating with no tap on?

 

[vyv_cox]

Re: Easy check...

Be careful. The pressure of your domestic water supply is what is stopping your engine from boiling. If you shut your pump down the pressure in the coolant will drive it into your domestic water, poisoning you and wrecking the engine! Easiest short-term solution is to by-pass the calorifier altogether with a jumper of hose between the inlet and outlet on the engine. You won't lose any antifreeze because there's none left but you will have to do without hot water until you fix it. You might need to clamp the hose if the coolant system plays up a bit. The open ends will leak, so plug them.

Unfortunately I doubt if your calorifier is fixable. The coil is probably pitted so you need a new unit.

I assume your pump is running periodically but you are on deck driving the boat, so you don't hear it.

 

[ccscott49]

Re: Easy check...

Thats my point, if the water were being pumped in, if you take the filler cap off, it would come out of the header tank.

 

[ccscott49]

Re: Easy check...

I said do it with the engine switched off, I also suggested the "loop", sorry you must have not read the other post.

 

[robp]

Re: Easy check...

Yes sorry, I was forgetting about the pressure in the cooling system. Doh!

 

[robp]

Re: Easy check...

Looks like a job before sailing this weekend! I need to see what it all looks like now. Assuming that it is the calorifier, which seems to be the most likely answer, it hasn't lasted long - 4 years. Or is that normal?

Again, thanks for your help Vyv.

 

[vyv_cox]

Re: Easy check...

No, I would have expected much better than this, especially from a modern calorifier. My old one was all copper and running on a raw-water cooled system. It was still OK after 15 years when I replaced it. Reason for replacement was that the insulation was in a bad way and I couldn't get an immersion heater to fit it. The new one is all stainless steel.

Running in a closed coolant circuit I would not have expected any problems with a stainless steel for many years, assuming that you always use antifreeze. Some new units have ceramic coated carbon steel reservoirs but all the tubes I have seen are stainless. One possible is that you have had some aggressive water on the domestic side - have you been cleaning the reservoir with bleach or something?

Before chucking out the old unit, run a few tests to make sure that is the problem. If it wasn't for the fact that you are dealing with a domestic water supply I think Radweld in the coolant might do the job.

 

[ccscott49]

Re: Easy check...

We seem to be locked into the calorifier! The test I suggested would prove it one way or another, but I am sceptical that it is the problem. Also why would the overflow increase with RPM, If that is what he said?

 

[vyv_cox]

Re: Easy check...

I agree, don't jump to conclusions. Difficult to imagine how else 2 litres of fresh water can come out of the coolant overflow without boiling the engine, though. My total coolant capacity, Yanmar 3GM, is only 4 litres so this situation could not go on for very long. I agree with your tests and said so up above. I checked my pressures, as far as possible, last night and it looks feasible. My domestic water pressure switch is set at 2 bar, coolant pressure is 4 psi and raw water I guess will be a few inches water gauge.

How's this for a scenario. There is a split in the coolant heat exchanger inside the calorifier. See my last posting, I doubt very much that corrosion pitting is the problem. The split is normally almost closed but opens when the coolant pressure/temperature increases. Domestic water can then go through into the coolant. Engine stops - split closes. Not revs related, but certainly engine-operation related. How accurate is the revs observation?

 

[ccscott49]

Re: Easy check...

Yes. good diagnosis, could well be a split which opens with temperature. I would still isolate the thing and then check the engine. A coolant system pressure test should also help to prove things.

 

[robp]

Re: Easy check...

The rev's observation is not at all substantiated. I simply wondered in the first instance whether by using more rev's than I normally do, I had induced or exaccerbated the problem.

It's hard for me to provide any more intelligence until I can get to the boat. I don't know even how the calorifier works in practice. (Meaning how/where the coil is fitted and where water is run etc). I've asked for info on the setup and am waiting a call back.