Peugeot 206 TU3 runs hot, head gasket?

[Berridale]

Peugeot 206 TU3 runs hot, head gasket?


Alloy TU3 engine, runs hot in hot weather has large GTI radiator in it , thermostat taken out and fan works.

Runs perfectly, slight pressurisation in cooling system.
Cooling water clean and has a new pump.
No water in the oil.

Is this the first stage of head gasket failure?

Seems these engines have their own type of symptoms?

[CitroJim]

Running with no thermostat is not a good idea as this may be leaving the bypass passage wide open and thus short-circuiting coolant with only an inadequate proportion flowing through the radiator...

This can result in all the symptoms you have...

Firstly, reinstate the thermostat and if the problem still shows and you know the rad and water pump are in good nick then suspect the head gasket.

Do check the water pump first as it's not unknown for their impellers to wok loose on their shafts and thus seriously reduce pumping efficiency...

Have you confirmed it is really running hot and not just appearing to due to a duff temperature sensor or over-enthusiastic gauge?

[CitroJim]

When replacing the thermostat, ensure it's exactly the right type for your engine... Not all TU thermostats are the same And treat it to a new one of reputable make.

[Berridale]

Jim,
new pump was fitted.
Also new Temp Sensor.
The telling thing is the temp rises going up hills but on the flat runs 70' or a little below.
Seems as the temp gets between 80'-90' the system struggles to get rid of the heat, open country road.

Might try another Temp Sensor to rule out a fault.

[MattBLancs]

Might try another Temp Sensor to rule out a fault.

New thermostat first, for the reasons Jim has explained?

70°C on the flat - a bit cool really and 80-90°C when working a bit harder doesn't sound excessive to me

[CitroJim]

70°C on the flat - a bit cool really and 80-90°C when working a bit harder doesn't sound excessive to me

Agreed...

[Berridale]

but the slight pressurisation in the cooling system is a concern when the temp rises.

We are in summer here in Australia.

[ozvtr]

but the slight pressurisation in the cooling system is a concern when the temp rises.

Nope. System runs pressurized, increases boiling point. You should never open the cooling system when the engine is hot. The drop in pressure will cause the coolant to instantly boil all at once and explode out the expansion tank! And that's normal!
90°C is the approximate operating temperature. I have a Citroen C3 with TU3JP (KFV) engine and Lexia reports engine temp runs at about 90°C (plus or minus a few degrees).
I live in Brisbane!
70°C without the thermostat in? With a thermostat in the temp shouldn't get that cold.

Any bubbling in the expansion tank?
Any mysterious loss of coolant?

[CitroJim]

but the slight pressurisation in the cooling system is a concern when the temp rises.

Nope. System runs pressurized, increases boiling point. You should never open the cooling system when the engine is hot. The drop in pressure will cause the coolant to instantly boil all at once and explode out the expansion tank! And that's normal!
90°C is the approximate operating temperature. I have a Citroen C3 with TU3JP (KFV) engine and Lexia reports engine temp runs at about 90°C (plus or minus a few degrees).
I live in Brisbane!
70°C without the thermostat in? With a thermostat in the temp shouldn't get that cold.

Any bubbling in the expansion tank?
Any mysterious loss of coolant?

Yep, agreed on all counts. The 70 degrees is fully expected with no thermostat fitted. If you were in the UK you'd really be moaning about a rubbish heater with coolant temps like that!

And yes, 90 degrees fine in such a climate. Trust me, I know as I've lived just up the track in Darwin...

If there's no bubbling and no loss of coolant you have nothing to worry about in my opinion...

And pressurisation will make the rubber hoses appear to go quite rigid. Again, perfectly normal.

I'd get a proper thermostat back in as some engines run sub-optimally at lower temperatures and can take a long while to reach full operating temperature which can hurt fuel consumption and drivability...