Rising Temp at Idle and strange fan behaviour

[Oohsam]

hey guys,
Yesterday I was at the lights for a while. Looked at the temp gauge and noticed it was a touch higher than normal.
When the lights went green, my fan was SO LOUD. And then the temps started rising, got to the top (not red) and then came back down to normal, as we were driving.

I'm thinking 2 things could be wrong.

1. Sticky Thermostat
2. Clutch fan needs replacing.

Any ideas ?
Its the 4.4 v8.

Cheers

[DiscoJeffster]

Think leak. What’s the level like in the overflow bottle when it cools? Has it dropped?

[Oohsam]

Think leak. What’s the level like in the overflow bottle when it cools? Has it dropped?

Overflow bottle hasn't changed level.
I did a pressure test as I have the kit, the its good, didn't lose any pressure.

Overflow bottle is low, but it's been low for about a month !

[shanegtr]

I would guess a coolant flow issue. So could be a faulty thermostat or could possibly be an issue with the water pump not moving enough coolant at idle speeds

[Oohsam]

Anyway to diagnose these ? I dont want to just start replacing parts without ensuring I've foudn the right part!

DOes the water pump, pump more water as the car moves ?

Reason I thought it was the fan was due to the movement of the car cooling the temps down.

[DiscoJeffster]

My final advice? Take it somewhere and get it seen to before you cook it and ruin it.

[shanegtr]

Anyway to diagnose these ? I dont want to just start replacing parts without ensuring I've foudn the right part!

DOes the water pump, pump more water as the car moves ?

Reason I thought it was the fan was due to the movement of the car cooling the temps down.

Water pumps are normally engine driven, so faster pump speed with more engine revs. Best bet would be to get someone to have a look at it as there are multiple things that could be causing your issue

[scarry]

Or get a GAP tool for the vehicle,particularly if you will be keeping the vehicle for a while,and doing some repairs yourself.
Without one you are going in blind.It will read coolant temps,fan speeds,etc,etc.

[Discodicky]

Overflow bottle hasn't changed level.
I did a pressure test as I have the kit, the its good, didn't lose any pressure.

Overflow bottle is low, but it's been low for about a month !

The basic principle behind the o/flow bottle is that as the coolant depletes (or leaks) the vacuum created causes the water to be sucked from the bottle to replenish. Similarly, as the coolant heats it expands and goes into the bottle, and as it cools it contracts which causes said vacuum, so it gets sucked from bottle back into radiator. All very well and ok, however if the coolant leak is fairly rapid or even not noticed over a long period and is significant it doesn't create a vacuum therefore no water gets sucked from the o/flow bottle. Therefore, by looking at the bottle and seeing/thinking the level is ok however the radiator could be seriously low of water.
Might pay to check the rad level but when cold of course. Pressure test system for potential leak.

[DiscoJeffster]

The basic principle behind the o/flow bottle is that as the coolant depletes (or leaks) the vacuum created causes the water to be sucked from the bottle to replenish. Similarly, as the coolant heats it expands and goes into the bottle, and as it cools it contracts which causes said vacuum, so it gets sucked from bottle back into radiator. All very well and ok, however if the coolant leak is fairly rapid or even not noticed over a long period and is significant it doesn't create a vacuum therefore no water gets sucked from the o/flow bottle. Therefore, by looking at the bottle and seeing/thinking the level is ok however the radiator could be seriously low of water.
Might pay to check the rad level but when cold of course. Pressure test system for potential leak.

He did pressure test it as per the thread you quoted