Why does the water level in my header tank increase?

[whiteoaks7]

Volvo 2003T, indirect cooling.

Symptoms: First noticed when checking the water level the day after a five hour hard slog on engine. The header tank level had increased from min to overflowing.

Tests: Next day measured engine temperatures at the thermostat housing which indicated a reasonable time to reach temperature and then remained static at 70C ish for the three hours of that voyage. Removing the pressure cap while running indicated that there was no pressure being maintained. There were no leaks (just a check for thoroughness) and there didn’t seem to be oil in the coolant nor coolant in the oil. Drying out a sample of coolant to check for salt was inclonclusive; the coolant was pretty dirty despite being fresh 25hrs ago.

Diagnoses: (1) Pinhole in the heat exchanger. This would allow coolant out or seawater in depending on the local pressure difference. Assuming the coolant was initially under pressure it would flow out until the pressure difference was zero and then stop. This wouldn’t result in an increase of volume in the header. The other way – seawater into the coolant – would result in an increase of volume and but the coolant would have to be at a lower pressure than the seawater in the exchanger. Is that likely? There would also have to be enough seawater pressure to overcome the coolant pressure which should be induced by the pressure cap.

(2) Pinhole in the calorifier: This would allow domestic water into the coolant if the pump was set at a higher value than the pressure cap. If this were the case then there would be nothing to stop the entire contents of the domestic water tank emptying through the pressure cap. The domestic pump does run at odd moments but I’ve always assumed this was just a pressure ‘weep’. Besides the engine bilge would fill up with the overflow. [Update: overnight there was no increase in header tank volume] If coolant was pushed into the domestic hot water I hope we would notice before we were poisoned – and again this would not account for the increase in volume.

(3) Faulty cap: The symptom of no pressure can be explained by a faulty cap but how could this result in an increase in coolant level. We need to know if this is a repeating phenomenon, in which case it has to be an inward leak, or a one off that could be caused by something like the cap failing.

David Berry

 

[ksutton]

Could well be the very first signals of a failing cylinder head gasket, putting a small amount of combustion chamber air into the coolant. Coolant going dirty over a short period of time would support this also.

 

[lw395]

The other possibility is that you now have a volume of air in the cylinder head or elsewhere in the circuit?

 

[vyv_cox]

Your 1. Coolant pressure is normally higher than raw water pressure, 10 psi against nominally atmospheric, open ended system. However, there have been cases recently where salt accumulations in the manifold have pressured the raw water sufficiently for it to go the other way. I understand that it is easy to displace the seals and end cover on the heat exchanger on that engine, although no direct experience.

Your 2. I worked on one like this two weeks ago, but that coolant system 'made' water all the time. Domestic water pressure is normally a good deal higher than coolant pressure, so it makes sense. Watch upcoming PBO!

Your 3. I don't think so. I have run road vehicles for years with no pressure cap at all.

 

[Martin_J]

Unless you're going to take out the heat exchanger and have it cleaned and pressure tested (by someone with a good test rig)... the I'd initially go with Vyv's option 1.

With a slightly blocked exhaust elbow and a good impellor, the seawater would be under more pressure than the coolant (especially when first started).

If the heat exchanger cap was put back on with the o-ring seal slightly displaced or if it has moved since then, then you have a possible leak between sea water and coolant water at that point.

No direct experience of the 2003 but on the 2030 type engines with the rubber boots - that's where a common leak tends to be especially when put back together slighty skewy.

Seal 6 I guess in this diagram
2003 heat exchanger

It's worth a try - re-seating at this point before pressure testing and cylinder head checks.

 

[VicS]

Unless you're going to take out the heat exchanger and have it cleaned and pressure tested (by someone with a good test rig)... the I'd initially go with Vyv's option 1.

With a slightly blocked exhaust elbow and a good impellor, the seawater would be under more pressure than the coolant (especially when first started).

If the heat exchanger cap was put back on with the o-ring seal slightly displaced or if it has moved since then, then you have a possible leak between sea water and coolant water at that point.

No direct experience of the 2003 but on the 2030 type engines with the rubber boots - that's where a common leak tends to be especially when put back together slighty skewy.

Seal 6 I guess in this diagram
2003 heat exchanger

It's worth a try - re-seating at this point before pressure testing and cylinder head checks.

The OP said a 2003T engine so the inner of the two seals #3 in THIS DIaGRAM


But I would also check for obstructions in the seawater circuit downstream of the heat exchanger resulting in increased pressure, as Vyv suggests.

In view of the deterioration of the coolant in a relatively short time I would favour the idea of salt water entering the coolant circuit rather than water from the calorifier.
However that must not be lost sight of as a cause. Isolate the calorifier/ domestic water pump perhaps

 

[Martin_J]

I missed reading the T...

The 2003T looks like it even finer seals (o-rings) then..

 

[pvb]

As already pointed out, the 2003T has a unique heat exchanger. If it's partially clogged with deposits, it might be possible for raw water pressure to force water into the coolant system if there's a pinhole leak.

Next step in diagnosis would presumably be to isolate the calorifier - maybe disconnect the hoses and connect them together with a short section of copper pipe. That will then confirm whether or not there's a calorifier problem.

If it isn't the calorifier, removing and testing the heat exchanger should be the next step. I've just had my 2003T heat exchanger cleaned and checked, it's relatively easy to do (although getting all those stupid little O-ring seals to actually seal afterwards is a nightmare!)

PS Whilst the heat exchanger is off, check the oil cooler very carefully for corrosion. The aluminium body can corrode, leading to a hole, which then dumps oil into the bilge and (ultimately) stops the engine in a catastrophic manner!

PPS Also check the external steel oil pipe which supplies high pressure oil to the turbocharger. This can corrode and develop a pinhole leak which then dumps oil into the bilge and... well, you know the rest.

 

[Sans Bateau]

Whilst its not the 2003T that I have, it is the 2003, I have exactly the same problem and have carried out extensive tests in an effort to isolate the problem. I removed the heat exchanger several times, each time trying new ideas in an effort to test it. What you will find is small hole/s in the pipework of the exchanger allowing seawater to enter the fresh side. It is beyond me how the sea water pump can create enough pressure to do this, but is does. I have checked and ensured that the outlet in the exhaust elbow is clear.

The tests I carried out were at first to isolate the calorifier, it is only a couple of years old, but still I wanted to be sure. Next I took the heat exchanger home and mounted it so I could blank off one of the water ports, allowing me to fill that side of the unit with water, it matters not which side. I then applied compressed air to the other side with that exit port sealed too, this was to look for air bubbles. This test proved negative and I was left scratching my head even more!

These tests ran over a period of a couple of seasons. Finally I repeated the test above, realising that a small hole may only appear when the water is hot, then the copper pipe may well expand enough to allow the small hole to become troublesome. I mounted the exchanger once again as before, but this time I set up a blow lamp playing on the side of the exchanger, I then applied the air pressure once I could see the water was steaming hot. Eureka! This time when air pressure was applied small bubbles appeared in the water. Whats more I could see the holes, it was the joint between the pipes and the end plate.

The only cure is a new heat exchanger. It has been suggested that I convert to raw water cooling, but I will eventually see if it possible to fit an exchanger from ASAP. The VP replacement is stupid money.

What is odd, since I identified the source of problem, touch wood, I have not had water rising in the header tank, curious that.

 

[pvb]

The only cure is a new heat exchanger.

I think I'd try a repair first!

 

[Sans Bateau]

I think I'd try a repair first!

Can I send you mine?

 

[pvb]

Can I send you mine?

Errr... no, thanks!

But, seriously, with a new heat exchanger costing around £800, it surely makes sense to try a repair. If there's a leaking pipe, it can be isolated by filling it with epoxy, for example.

 

[whiteoaks7]

Leaky head gasket

Could well be the very first signals of a failing cylinder head gasket, putting a small amount of combustion chamber air into the coolant. Coolant going dirty over a short period of time would support this also.

Can I have opinions on whether this is a possible candidate? I'm guessing that if the head gasket leaked cylinder pressure into the coolant it would pretty much be a fountain out of the filler cap (which is not the case) but I'm absolutely not a diesel mechanic so educate me please.

David Berry

 

[Bobc]

Before you start taking the engine apart, just change things like the tank cap and seal, the thermostat, etc.

I had a similar problem and the "so-called experts" telling me that the head was cracked, the head gasket was blown, the heat exchanger was knackered, and one even suggested that I might be best-off re-engining the boat!

Well, as it turned-out, after a complete strip-down and re-build (nothing wrong with the head gasket, head and heat exchanger were tested and found fine, etc.), it turned-out to be a £4 rubber seal that goes inside the header tank cap.

3 months and well over £1,000 wasted (if I'd listened to the idiot who suggested a new motor, it would have been £2k wasted!).

PS. By "so-called experts" I don't mean forumites, I mean Volvo engineers.

 

[VicS]

Can I have opinions on whether this is a possible candidate? I'm guessing that if the head gasket leaked cylinder pressure into the coolant it would pretty much be a fountain out of the filler cap (which is not the case) but I'm absolutely not a diesel mechanic so educate me please.

David Berry

A leaking head gasket ( between cylinder and water ways) would tend to lead to an overall loss of coolant.
The level would rise as though it was gaining water and some would be ejected but when the engine cools it would be apparent that overall coolant has been lost.

If you are actually gaining water, either from the raw water circuit via the heat exchanger or from the domestic water system via the calorifier, there will be no apparent water loss when the engine cools.

 

[Sans Bateau]

Can I have opinions on whether this is a possible candidate? I'm guessing that if the head gasket leaked cylinder pressure into the coolant it would pretty much be a fountain out of the filler cap (which is not the case) but I'm absolutely not a diesel mechanic so educate me please.

David Berry

No it is not the head gasket. You say that the water level in the header tank rises, if it were the head gasket, where is this additional water coming from? The water in the engine, is the same as that in the header tank, so it cant be from there can it?

I know this is a puzzle, it puzzled me! But you will, I'm sure, find the problem where I describe.

 

[vyv_cox]

My experience with automotive engines is that one of the first signs of a failed head gasket is that the heater stops working due to air locks. I assume the same would happen to the calorifier on a boat.

 

[Sans Bateau]

My experience with automotive engines is that one of the first signs of a failed head gasket is that the heater stops working due to air locks. I assume the same would happen to the calorifier on a boat.

I doubt that, the reason this happens in a car is that the heater is usually higher than the head of the radiator or engine. The header tank on a boat engine is more likely to be the highest point.

 

[penfold]

Errr... no, thanks!

But, seriously, with a new heat exchanger costing around £800, it surely makes sense to try a repair. If there's a leaking pipe, it can be isolated by filling it with epoxy, for example.

Or soft solder coaxed by baker's fluid; the VP matrix that I've seen was a crappy thing with the tubes crimped into the endplate but not fully swaged, it's no surprise they leak. For £800 I expect a brazed assembly, not this halfbuilt nonsense.

 

[vyv_cox]

I doubt that, the reason this happens in a car is that the heater is usually higher than the head of the radiator or engine. The header tank on a boat engine is more likely to be the highest point.

Depends entirely on the installation. Many calorifiers are higher than the engine. On my motor sailer by a couple of feet. Conversely, on my VW van the top of the radiator, in the front of the vehicle, was higher than both the header tank and the heater matrix.