Temp question

[HVGRIFF430]

Hello guys,

Recently the temp of my 430 goes to 120° only the first time by warmup ,then even after a long drive everything stays normal just below 90°.
i changed the stat last year (lower temp example). It was cold and my temp stayed long around 70° ,then suddenly it went to 120° for about a minute or two, then went to normal and stayed that way. Some problems with the stat?

Thank you for your advice

[phillpot]

Might help show what's going on?

[Belle427]

Maybe an air lock?

[HVGRIFF430]

Yes i ame gone take a look with temp laser. I guess that the temp raise is due to the steam in the circuit which give this readings at the temp sensor.
A soon as the stat opens ,everything goes to normal. Does this sounds like anything, or is there is something wrong

[blaze_away]

That sounds like air lock.

To fix it........

Unsrew cap on swirl pot.
Screw a large funnel into the swirl pot.
Fill funnel 3/4 full with antifreeze water mix (blue glycol Not OAT Based)
Start engine with heater set to hot.
Continue running engine until air burping out the funnels stops.
If level in funnel drops top it up.
Once burpi g stops remo e the funnel and put the cap back on.

[HVGRIFF430]

Hello again,

I ame gone try this. Same method for preserpentine engine with only swirl pot and no expansion tank?

[Panamax]

This may sound very basic but don't forget the thermostat doesn't control engine temperature, it controls water temperature.

When the water in the block warms up the stat will open, letting cold water into the engine from the radiator. The stat is now in cold water and will close. The temperature sender will see the changing water temp and the needle will fluctuate until the stat stops opening and closing.

Once you're out on the open road there's good airflow through the radiator and the water cools very effectively, which can cause the temperature gauge to drop even though the stat isn't doing anything.

In modern cars manufacturers make the temp gauge non-linear so too cold shows as too cold, too hot shows as too hot but there's a wide range of temperatures in between where the needle will stay around dead centre on the gauge. This suppresses the effect you are seeing and prevents customers fretting unduly.

[HVGRIFF430]

I understand ,but when the temp gauge showed near 120° , i felt on the hoses and the temp of the water wasn't hot hot , i opened the blue cap on the swirl pot( i have a preserp) and pressure (light steam) was comming out the pot ,and i saw no water circulating in the swirl pot at that moment. So i assumed that the stat wasn't open. After some minutes the water was comming in the swirl pot ( so stat open?) and the temp came to his right level.
Then took a ride for for about 100 miles ,with some stop overs to check, everyting was fine. Perfect temperature below 90% and no pressure in the swirl pot.

so what causes the 120°(the steam at the temp sensor i guess), it happened 2 times now. last summer with the new stat allready in never had this.

i want to search the solution. Air lock? can this happens suddenly ? i changed nothing since the last time i drove it in autumn.

[Panamax]

I haven't got many bright ideas other than the rudimentary,

• You could see what happens if you remove the stat completely (and you could test the stat while it's out - saucepan and thermometer)

and/or

• You could see what happens if you blank off part of the radiator with some cardboard.

At the end of the day the suggestion made above of using an IR thermometer will tell you whether the engine's happy or not. It doesn't much matter what's going on in the radiator.