1980 Scirocco Storm over heating

[Jack Storm]

Hi,
I am new on here but my Scirocco Storm isn't. My dad has taken 'SAG' to a few meets over the years and has spoken highly of the expertise and assistance of the 'Scirocco Register'. My dad kindly drove our MK1 storm from the deep south to my home in south west Scotland last year. I have been enjoying having our very special family Scirocco in my garage and taken the family out on various road trips. I don't believe there can be many MK1 Storms to have been within one family. As such I need to up my knowledge and skills in keeping the Scirocco in the best of health!

Unfortunately I have run into a couple of minor technical issues this year. One being an alternator issue I am still trying my best to diagnose and the other being over heating. I will stick to the over heating issue here!

After very short journeys my car boils its coolant. This is without sitting in traffic and in cold conditions.

I have made the following observations. The top radiator hose gets very hot. The bottom hose is cool. The fan does not cut in. This lead me to remove the thermostat. This kept everything cool with the fan activating when at temperature.

After fitting a new thermostat the overheating issue returned. I also tested the old one and confirmed it was opening correctly.

Any help would be really appreciated!

Thanks, Jack

[GT_II]

A couple of things worth checking. Is the radiator cap or expansion cap allowing the system to pressurise? The hoses should become very firm as the engine warms up. Lack of pressure would reduce the boiling point. Secondly, the water pump. Is the auxiliary drive belt turning the pump as it should (likely if the alternator is working, though I notice you have issues with that as well, so both faults could in principal be due to a failed or very slack auxiliary belt). Alternatively, could the water pump have failed?

[Jack Storm]

Thanks for your help GT_II. I do have an over voltage alternator issue which I have put down to the regulator. I want to get a second voltmeter before I confirm that incase mine is reading strange. The belt is new and tight. It is certainly turning the water pump pulley.

If the water pump has failed or I have a pressure issue would this not still cause over heating with the thermostat removed?
Thanks

[GT_II]

If the water pump has failed or I have a pressure issue would this not still cause over heating with the thermostat removed?
Thanks

Ultimately yes, but perhaps only under load and in hot weather, as there will hopefully be some circulation through the radiator through convection with the thermostat removed to keep the temperature down. I'd definitely check for pressurisation first - squeeze those hoses as it warms up! Pressure should be somewhere between 1.0 Bar and 1.5 Bar, so you could use a bicycle tyre pumped to this pressure for comparison.

[Jack Storm]

Thanks GT_II. I can confirm top hose is far firmer than the bottom hose. I think I may look for a new water pump.

[mr.brown]

It could also be a build up of crap in the radiator preventing flow. Worthwhile removing rad and flushing + reverse flushing. Also, whilst rad is off run a hose through the top pipe (with heater levers wide open) so you flush the heater matrix and engine too.

[mark1gls]

I had a newish genuine VW water pump fail which had a plastic propeller, the propeller had a hair line crack in it so it was was not spinning fast enough to move the coolant.
If you remove the thermostat and drive belt you should be able to see the propeller from where the thermostat normally sits moving when turning the pulley, stick your finger on the propeller and if you can still turn the pulley and the propeller stays still then it’s failed.