Hot weather and high temp gauge

[sierra3dr 51]

A couple weeks ago I left the MK5 running whilst I jet washed it,and it started to overheat even though I had fitted an electric fan 6 years ago. Turns out that the fan   12v and ground connectors to the relay loom had oxidised. I renewed them and it started kicking as it should. The other day,I was in slow moving school run traffic on the way to work and the temp gauge was nudging into red. I just got into works yard and  looked to see the fan was not turning and then switched it off before it started to overheat. Yesterday,I put an inline fused permanent live feed to the fan so that it will work continually....and this was the result 

Edited May 17 by sierra3dr

[John Mack 315]

It's not a nice feeling, having a hot engine...been there!

 

Check there's enough water in the radiator !

I'd check that the radiator fins are attached and haven't corroded and fallen out....... no fins and the rad will toil under pressure.(so to speak!)

Assuming the alternator belt is in good nic and tensioned as it should be, I'd be for changing the thermostat ?

 

The above is assuming the electric side of things is ok, was the fan actually running this time ?  Is gauge reading correctly?

 

 

[sierra3dr 51]

On 5/17/2025 at 8:04 AM, John Mack said:

It's not a nice feeling, having a hot engine...been there!

 

Check there's enough water in the radiator !

I'd check that the radiator fins are attached and haven't corroded and fallen out....... no fins and the rad will toil under pressure.(so to speak!)

Assuming the alternator belt is in good nic and tensioned as it should be, I'd be for changing the thermostat ?

 

The above is assuming the electric side of things is ok, was the fan actually running this time ?  Is gauge reading correctly?

 

 

ah yes,that would good advise,considering I am convinced it is topped up,but should check it.....I had fitted a new radiator in 2018.....alty belt seems fine.......the fan was working  on this occasion,because I put a permanent live feed on the fan when I started the engine from cold.... I might take the thermostat out 

[norton 96]

On 5/18/2025 at 5:52 PM, sierra3dr said:

ah yes,that would good advise,considering I am convinced it is topped up,but should check it.....I had fitted a new radiator in 2018.....alty belt seems fine.......the fan was working  on this occasion,because I put a permanent live feed on the fan when I started the engine from cold.... I might take the thermostat out 

Taking the thermostat out is to ignore the problem, I wouldn’t recommend it.  Check all the pipes are hot. If you haven’t checked the level for ages, it might be that, air locked or it might be the pump… is your timing correct? There’s so many things that are easy to check

if you take out the thermostat you can get what I think is called cavitation, where the water isn’t circulating through the rad at all, but just going round in the engine and getting hotter and hotter.

Take out the rad and flush it through.

Edited May 21 by norton

[sierra3dr 51]

Right chaps....casting back a week ago the dipped headlights started to not work....couldn't be mithered after work at 2am  going with just the sidelights. The following night after to work I tried to see what is causing the problem in the yard pitched black and using the light off my phone,taking the wiring block connectors off the fusebox looking  at the condition of the spades.I put the wiring block back,but unbeknown to me,I put the block connector back at an angle,and missed out 6 and 7,which I realised the next  day. Explains why the electric fan was not working,as I have  tapped into wire on fuse 6 for switched live. So all is tickety-boo,and having poured in the radiator what was in the overflow tank. And the dipped beam saga was down to an aging fuse

 

 

[sierra3dr 51]

 

On 5/21/2025 at 4:34 PM, norton said:

Taking the thermostat out is to ignore the problem

Thermostats in general are just for cold conditions. Most warm climate countries leave them out

[John Mack 315]

6 hours ago, sierra3dr said:

 

Thermostats in general are just for cold conditions. Most warm climate countries leave them out

 

Not sure where you got that info from ??!!

Warm climates might have a thermostat that opens earlier but they shouldn't be left out, it also acts as a restrictor (of flow) in the system, if left out it will cause hot spots in the system as mentioned by Mr @norton,  if you want to bypass it then jam it open as opposed to taking it out 

 

Just reread your fuse box plug issue.....fan is working as it should yes?......is everything good again?