VW trident 1991 coolant level dropping

We have had our trident for six years now and have travelled in the UK and on the continent, lots of weekends and a couple of longer breaks up to two weeks. Sometimes we stay on site for two or three nights but often we move on after one night.

We have an intermittent problem with the cooling system that has been looked at by the AA man and several garages over the years. The temperature light comes on within ten minutes of driving the van, and the coolant reservoir is full of air. After leaving it to cool off and taking the cap off (Very carefully), the coolant level comes up again. On one occasion I took it off and got a two ft column of hot coolant.

It doesn't happen all the time. For example. We drove from Cheshire to Hull, stayed on the ferry overnight, drove around Holland for two weeks, parked on the overnight ferry and drove away in the morning. It was only on the return trip from the ferry that the light came on. The same happened on our trip to the mountains of the Auvergne last year. It also occurs on our weekend trips (sometimes). The coolant reservoir, water pump, thermostat and radiator have been replaced at intervals in an attempt to resolve the issue.

Just been told off by himself for giving all this detail. I should have only told you about the ferry trip and not the other details!

Any comments appreciated :-)

Hi Wandering.

Wondering. When coolant gets hot the coolant expands in volume. The vehicle radiator system pressurises as the coolant heats up. This pressure allows the coolant to attain a higher temperature without boiling. Hence when you released the pressure when it was still hot the coolant boiled up and shot out of the coolant tank. Taking into account both of these factors the coolant level in the coolant tank will or should rise and fall marginally. I wonder if the radiator or the heater hoses have gone a bit soft and are swelling up as the temperature/pressure rises. Thinking if it was the heater hoses it might be possible that when it dosn't do it you are not using the heater and when it does do it you are.
As I am not a mechanic this is only theoretical, but the heater and its hoses seem to be the only thing left that you have not changed.

Just a thought Best of luck sorting it out.

Whisky.

Hi there,

Are you actually "losing" coolant or is it that the coolant level drops under certain conditions?

If you are losing coolant from the system then you have a leak and it should be easy to find as there are only four ways it can escape from the engine:

1. Out of the exhaust via the cylinders. This is usually caused by a broken head-gasket.

2. Out of the engine itself. This can be caused by anything from a cracked hose to a damaged radiator to a cracked head gasket. It has many causes but it is easy to see.

3. Out of the pressure-cap on the radiator or coolant reservoir. This can be caused by a cracked head gasket where the burned gas in the cylinders get into the coolant system and "blow" the coolant our of the pressure-cap or it can be caused by the coolant getting so hot that it boils and the resulting steam "blows" the coolant out of the pressure-cap (due to faulty thermostat, inadequate circulation or problem with the cooling fan).

4. Into the engine sump. This is usually caused by a cracked engine block and is very rare. The coolant shows up as an emulsion on the dip-stick which indicates a "High" oil level.

If you are not actually losing coolant from the system and you don't need to re-fill the coolant reservoir on a regular basis then I go with Whisky and suggest that the pipes need replacing as they are perished and are expanding when they get hot. THIS CAN BE A PRELUDE TO BURSTING!

Hope that this helps.

Best regards,