Why, after about 100 miles, does my car engine start to overheat, Get back into traffic and it cools down?
Answers:
headgasket could be at fault, although im not trying to scare you! it could well be airlocked causing the needle to fluctuate and blow water out. are all the water pipes getting hot?
first thing to do, empty and flush out the system including the radiator. re-fill slowly, running the engine after the first couple of litres are in to ensure no air entrapment. then run it stationary up to temperature to make sure your fan works. thirdly do a compression test which will show you any defects with the headgasket. having said all that, if those engines have a viscous fan coupling, that could well be the cause of your troubles.
Anyway, try the above and if its still the same, ask again!
driving fast will not bring your fan into play- the flow of air through the radiator provides enough cooling, and as it cools in traffic, you'd think the fan was fine.
Sounds like the thermostat is going out slowly. Have your thermostat checked and get your cooling system pressure tested. Good luck.
Your electric fan may not be working. Just driving slow may not heat up the motor enough for the fan to need to be on. Driving fast it will need to be. Also check your water pump and thermostat. Your water pump could be failing which can happen when it is strained(i.e higher speeds).
put some engin coolent stuff thats all i can think of
sorry
As a guess, Possible leaking head gasket letting combustion gases into the cooling system and blowing the water out, if the radiator is not full of water, when it gets hot it wont trigger the electric cooling fan but as you are travelling at speed the air blasted through the radiator would keep the engine cool.
Try smelling the water header tank to see if it smells of diesel.
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