Technical Using coolant...

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Technical Using coolant...

py0tr

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About two years ago I had the cambelt changed on my 2006 Punto sporting. The job suspiciously took the dealers in Auckland three days to complete. Their explaination was that the special sparkplugs needed hadn't arrived from Italy???

Anyway about 3 weeks later the cover which fits under the timing end of the engine broke loose. Investigating this I found that the plastic bracket holding the aircleaner down was broken too and the #1 sparkplug cap looked different to the rest. As the car had covered 2000km in the intervening three weeks and taking it back to the dealer meant a 200km round trip during working hours which I couldn't do for nearly a month.

Wind on another 10 000 km and one evening coming home in the rain and cold the heater stopped working. Noise, blowing air, air conditioning, but no heat.
I blamed Italian electrics looked for blown fuses without any luck. Acouple of days later as we neared the end of a 60km drive the dashboard lit up with flashing lights, the temp gauge went into the red and warning beepers sounded.

I stopped the car immediately and dived under the bonnet, exoecting blown gaskets, steam excessive heat... something. There was nothing just a normally warm engine. Then I looked at the radiator expansion tank. It was empty. Totally.

I refilled the tank gradually and except for a couple of small top ups every 1000 km it seems to be fine.

The question.. eventually.. When I check the level when the engine is cold there is always pressure in the system. even when it is stone cold and has stood for up to a week.

Is this right? I can understand where it comes from? Hot systems become pressurised as the water expands, but surely as it cools the pressure drops and the resultant suction or negative pressure, draws necessary water back into the system.

I'd love any suggestions.
Thanks
 
That's exactly the goal of the expansion tank: compensate for coolant volume change due to temperature variation.
JFYI: pure water gets its minimal volume at 4°c and expand from this point, either colder or warmer... An ice cube floats on water at room temp, remarquabely it would dive in hot water !

BRs, Bernie
 
About two years ago I had the cambelt changed on my 2006 Punto sporting. The job suspiciously took the dealers in Auckland three days to complete. Their explaination was that the special sparkplugs needed hadn't arrived from Italy???

Anyway about 3 weeks later the cover which fits under the timing end of the engine broke loose. Investigating this I found that the plastic bracket holding the aircleaner down was broken too and the #1 sparkplug cap looked different to the rest. As the car had covered 2000km in the intervening three weeks and taking it back to the dealer meant a 200km round trip during working hours which I couldn't do for nearly a month.

Wind on another 10 000 km and one evening coming home in the rain and cold the heater stopped working. Noise, blowing air, air conditioning, but no heat.
I blamed Italian electrics looked for blown fuses without any luck. Acouple of days later as we neared the end of a 60km drive the dashboard lit up with flashing lights, the temp gauge went into the red and warning beepers sounded.

I stopped the car immediately and dived under the bonnet, exoecting blown gaskets, steam excessive heat... something. There was nothing just a normally warm engine. Then I looked at the radiator expansion tank. It was empty. Totally.

I refilled the tank gradually and except for a couple of small top ups every 1000 km it seems to be fine.

The question.. eventually.. When I check the level when the engine is cold there is always pressure in the system. even when it is stone cold and has stood for up to a week.

Is this right? I can understand where it comes from? Hot systems become pressurised as the water expands, but surely as it cools the pressure drops and the resultant suction or negative pressure, draws necessary water back into the system.

I'd love any suggestions.
Thanks

This could be a very small cylinder to coolant head gasket leak The failed part of the gasket can act like a flap valve stopping the excess pressure bleeding away. The expansion bottle pressure relief will vent the highest pressure (and some coolant) overboard. Get a small plastic bottle and run the overflow hose into a hole drilled in the cap. Fasten it in the engine bay. See how much coolant it collects over a few runs.


Robert G8RPI.
 
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