1999 Golf GTI, the car over heats and looses coolant. There are no visable signs of a leak anywhere.
Need to check your radiator flow, and thermostat, start the engine cold, with radiator cap off, watch for the water in the radiator, when it starts to bubble over let it, keep water hose close, radiator should blow back till the thermostat opens, the water will go down, and add more water if needed, and put the cap back on,,,, if your thermostat is stick closed it will cause over heating......and you may have to have it replaced.
are your cooling fans running, it is possible that its the water pump? I also think there is a over heat sensor that could be bad, are you sure the engine is really over heating, I would not just go on a over heating light, hope you have a temp. gauge, Check to see if you are getting moisture out the exhaust, blown engine gasket can burn out through the exhaust.
I don't know what State your in and if its cold or hot there, once the engine gets hot the sensor should kick the fan on, also if the sensor if not working propery it may be shutting the fan off too soon, when you shut the car off when engine is hot, the fan may still run for a bit...check that sensor operating the fan,, good Luck, John
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I assume that there are no leaks anywhere and the radiator cap is in good condition. A bad radiator cap wil be indicated by the coolant being heard to boil just after the engine is stopped because of the retained heat in the engine when there is no coolant circulation. Ensure all the hoses and clamps where they connect to the various pipes in the engine bay and fix/replace any that are suspect. The heater hoses and those pesky little bypass hoses in the cooling system tend to go hard and split if they are over 10 years old, allowing coolant loss. Those spring type hose clamps tend to be less effective in clamping as the hoses become hard. Worm drive ones are the best to use.
If there are no leaks and water pump and thermostat are working correctly, but undetected loss of coolant once the engine heats up, then it could indicate a problem with the head gasket (Usually caused by allowing engine to become excessively overheated when cooling system has run dry and warping the head) allowing very hot high pressure combustion gases into the engine water jacket, which super heats the coolant in the engine block, which then boils off, and is released via the cap. If the head gasket leak is bad enough it will allow coolant into the combustion chambers which will produce white steamy smoke in the exhaust and allow coolant to get into the sump while the engine is stopped. This is indicated by a white oil and water emulsion on the dipstick.
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I have replaced the thermostat and still over heats. The radiator doesn't have a cap. Will I do the same to the coolant bottle? Do you think it could be the water pump?
Thanks
Steve
Yeah it is defo over heating, 130 oC+ and the coolant bottle fills up (expansion) and is really hot as are the hoses then when it cools it nearly empties. I dont think the radiator fan is working. I will check for moisture out the exhaust.
Thanks John, you been a great help. I'm in Scotland by the way sio it is cold.
Thanks again
Steve
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