Hi, I've had a problem with overheating coolant. I don't drive the car as I haven't got my licence yet but i let it sit for 20 minutes idling. My coolant starts spitting out gas at the top  of my coolant reservoir (someone said it was overpressurised due to heat). Is this because my radiator fan is not working? It doesn't start spinning when the engine is on and up to temp. When the engine is switched off it turns on and goes full power. This would tell me that the engine is too hot and that the radiator fan should be working while the engine is running.

Any ideas on how to fix this?

Do you have aircon, does the fan work with aircon on?

How hot is it getting on the temperature gauge?

I wonder if the resistor has failed so it can't work at half speed.  Does seem odd that it works when you switch the engine off though!

The caps and reservoirs are both known to fail over time, so it's worth checking those too.  Though if it's obviously very hot without the fan coming on, that's the first thing to sort.

2 minutes ago, TomsFocus said:

How hot is it getting on the temperature gauge?

I assume the temp gauge on the dash is oil temp (correct me if im wrong). It only gets to halfway and stops. I'm guessing thats around about operating temp. But the coolant just continues to overheat and expand well above the max mark on the tank...

4 minutes ago, CollumPlz said:

I assume the temp gauge on the dash is oil temp (correct me if im wrong). It only gets to halfway and stops. I'm guessing thats around about operating temp. But the coolant just continues to overheat and expand well above the max mark on the tank...

It is coolant temp.  Very few cars show oil temp nowadays.

Half way is about right, the high speed fan won't come on until it's leaving towards the red.

If the coolant level is going well above the max mark, that may mean the cap isn't holding enough pressure on it.

45 minutes ago, Dan62 said:

Do you have aircon, does the fan work with aircon on?

I just tried it but the fan didn't come on.

6 minutes ago, TomsFocus said:

It is coolant temp.  Very few cars show oil temp nowadays.

Half way is about right, the high speed fan won't come on until it's leaving towards the red.

If the coolant level is going well above the max mark, that may mean the cap isn't holding enough pressure on it.

Oh okay. I'm currently waiting for a new coolant cap but just wanted to make sure why the fan was coming on at high speed without any overheating once the car is turned off.. Thanks for your help

If you look down behind the radiator fan, you'll see the resistor on the lower left corner.  Unplug it and bridge across the plug with a peice of wire or an unbent paperclip.

Then start the engine and try the air con.  Chances are the AC gas has leaked so that's a poor test but might work lol! 

Assuming that doesn't work, leave the engine running for a while and see if the fan comes on this time.  If it does, it needs a new resistor.

Image below is the clearest I could find on a quick search, but this is upside down lol.

18 hours ago, CollumPlz said:

I assume the temp gauge on the dash is oil temp (correct me if im wrong). It only gets to halfway and stops. I'm guessing thats around about operating temp. But the coolant just continues to overheat and expand well above the max mark on the tank...

Its difficult to see but the MAX mark on the tank is just below the seam, the visible mark below the MAX is the minimum line. Easy mistake to make jic you have too.
 

On 2/28/2021 at 9:58 AM, Dan62 said:

Its difficult to see but the MAX mark on the tank is just below the seam, the visible mark below the MAX is the minimum line. Easy mistake to make jic you have too.
 

Yes I'm looking at the max mark not the min. The coolant expands about 1.5 inch over the seam of the tank.

EDIT: you can actually see it above the max mark in this video I took a few days ago..

13 hours ago, CollumPlz said:

Yes I'm looking at the max mark not the min. The coolant expands about 1.5 inch over the seam of the tank.

EDIT: you can actually see it above the max mark in this video I took a few days ago..

With the state of that reservoir I'd be changing that as well as the cap myself.  They get tiny 'crazing' cracks in them as they age.  You may even find those bubbles are coming from the tank rather than the cap, that's what was happening on the one I bought.  Bought cheap due to 'suspected headgasket'...cost me about £20 for a new bottle, cap and coolant.  

Tom, 

I have the same problem as Callum in that temp gauge all seems normal but i get a hissing sound from the coolent tank after a drive (rad fan does not switch on).  I was suspecting the water pump may not be doing its job fast enough but your suggestion of replacing the coolent tank seems far easier and cheaper to try as a first hit.  I am definatly loosing coolent as can see a brownish trail on engine mount under container. 

have seen an ebay ad for a cheap replacement will see if that will do the trick. 

2 minutes ago, wilkinm3 said:

Tom, 

I have the same problem as Callum in that temp gauge all seems normal but i get a hissing sound from the coolent tank after a drive (rad fan does not switch on).  I was suspecting the water pump may not be doing its job fast enough but your suggestion of replacing the coolent tank seems far easier and cheaper to try as a first hit.  I am definatly loosing coolent as can see a brownish trail on engine mount under container. 

have seen an ebay ad for a cheap replacement will see if that will do the trick. 

Yeah, I'd be replacing both the tank and cap there.  

The genuine tanks are only about £15 from Ford so I wouldn't risk aftermarket quality myself.  

23 hours ago, wilkinm3 said:

Tom, 

I have the same problem as Callum in that temp gauge all seems normal but i get a hissing sound from the coolent tank after a drive (rad fan does not switch on).  I was suspecting the water pump may not be doing its job fast enough but your suggestion of replacing the coolent tank seems far easier and cheaper to try as a first hit.  I am definatly loosing coolent as can see a brownish trail on engine mount under container. 

have seen an ebay ad for a cheap replacement will see if that will do the trick. 

I replaced the tank with a genuine ford one and it is fine now. The fan also comes on about 2 minutes after the AC is turned on so it is working fine I think.

tom,

Thanks for your help have now replaced the coolant tank.  I did go for the ebay one rather than the dealers also took the opportunity to go over the marking with a black marker so they will be easier to see when in situ.  I did  find this youtube video a great guide to the replacement. 

Looks different again with new tank.  Also I can see the fractures on the old one once it was removed.  Much easier job than replacing the water pump so am over the moon.  With it all done for about £15 my wallet was happy too. 

thanks again