Overheating

[Crhome]

Hi guys, I know that there are many threads about fans resistors etc but my problem is different now so thats why I created a new thread. Since I got my Cupra R my slow resistors in the fans were fried and I did the slow resistor mod. So b4 I did the slow resistor mod only my fast speed was kicking in. I recently had my thermostat replaced with a brand new 1 and a brand new radiator has been put in. Am getting the car ready for big turbo conversion so I am sorting out all the little bits that are wrong with the car. I dunno if its worth mentioning but I also have a semi forged engine work done recently. Now my fans seem to kick in whenever they want. Car is fine when driving normal but when I boot it and stop and park up for few mins to let the turbo cool down it starts to overheat. Needle goes over 90 slightly to begin with and slow fans kick in sometimes not all the time. Since I done the slow fan resistor mod my fast speed never kicked in. I thought this is because slows kick in lower temp than fast speed so they never let the car get to the temp where fast fans are needed. What do you guys think could be the problem? B4 I got my engine forged and replaced rad and thermostat car was fine and fans worked how they supposed to. Btw when I switch the air con on my slow speeds on my fans work so I sort of know its not the resistors that are playing up. Could it be the coolant temp sensor reading things wrong? If thats the case why aren't fans coming on? or they come on when they feel like it?

Thx in advance.

 

[Crhome]

Oh yea forgot to mention when I read the coolant temp from the climate control screen mode it doesn't match what it is on the gauge in my clocks. I left the car running to see if fast speed fans are gonna kick in when needle goes above 90 but not even slow speed kicked in. Only way fans seem to work is when I switch the climate control on. Rarely slow speed seems to kick in when it feels like it. So Confused

 

[Applemobile]

Have you changed the rad temp/fan switch? the Temp guage on the dash has no relation to when the slow fan kicks in, it's switched from the sensor in the rad. If you disconnect that switch with the ignotion off, and short between pis 1 and 3 (?), the slow fans should kick in.

 

[Crhome]

Have you changed the rad temp/fan switch? the Temp guage on the dash has no relation to when the slow fan kicks in, it's switched from the sensor in the rad. If you disconnect that switch with the ignotion off, and short between pis 1 and 3 (?), the slow fans should kick in.

As far as I know its not been changed. I got the work done at a reputable garage. I knew that I had a small leak under the rad sometimes my temp on the clocks would read less than 90 when driving on motorways. So I thought the thermostat was playing up maybe stuck open. When new rad is installed does it come with a new rad/fan switch?

 

[Dave_c85]

Water pump might be on its way out, worth checking

 

[Crhome]

Water pump might be on its way out, worth checking

Impossible, all work done at the same time of forging the engine. So water pump, head gasket, timing belt and pullys all new. Same as rad and thermostat. I somehow think its something to do with wiring of resistors that I carried out (not sure whether they been moved or played around with during replacing the rad cause it was working perfect b4) or rad/fan switch like applemobile mentioned. I don't know whether rad/fan switch have been replaced while installing new rad. I shall find out 2morw. Thx tho guys for the input.

 

[Crhome]

Rite, since my last post I have replaced the engine coolant temp sensor. It seemed to be all good until I had a spirited drive and when I stopped to cool it down, needle went a little bit over 90 again on the gauge. Fans are kicking in fine, well at least I know the slow speed is working. Whats the next step, rad fan switch??

 

[Crhome]

Problem still exists guys. I have plans of replacing radiator fan switch 2morw. Does anyone know if I need to replace coolant/bleed the coolant system after replacing the switch?

 

[Crhome]

Anyone guys?

 

[Mark One]

What thermostat have you got in it? Cheap one or OEM quality?

050121113C is the PN

What water pump did you get, plastic, ally or brass rotor?

Is the problem that you drive it hard, stop and idle, the gauge goes slightly right of centre, it recovers ?? When do the stage 1 fans kick in during this? It's quite a tough test your doing, you may find this is the intended behaviour. Bare in mind that a more modern car just wouldnt register the overtemp on the gauge before it became more serious. They'll sit dead centre between ~70 and ~105 degrees

 

[Crhome]

I got a metal impeller water pump fitted and its only 2 weeks old. If I boot the car and park up idling to cool the turbo it goes above 90. Even when I dont boot it and park up and let it idle it goes over 90 again. Slow fans kick in and cool it down to 90 where it sits in the middle after that but since I done the slow fan resistor mod, I never had my fast speed fans kick in. I have so far replaced the engine coolant temp sensor and oem thermastat. When it goes above 90 and fast fans dont kick in, this leads me to believe that radiator fan switch is playing up. 2morw I'll be replacing that too see what happens then. Do you know if coolant will be coming out when I pull the current one thats on there Mark One? Do I need to replace coolant after replacing the rad fan switch? I also checked the wiring by sticking little piece of wire in the electrical connections to see if fast speed works and fast speed fans do come on when I short it.

 

[Mark One]

If you're quick with the switch replacement, you won't loose much water. I think there's a bleed at the top of the rad to get rid of any air that you let in. The 'metal' impeller pumps can be a brass or cast aluminium part. The aluminium one I've seen was terrible, i took it back. There's no way it was going to flow like the OEM plastic one. The brass one was better. Low(er) flow is not necessarily that bad until the engine speed drops to idle (even lower flow) and you have a lot of residual heat to cool.
Id be surprised if your rad fan switch switching temp has changed, but you should try that next as it's a cheap easy one to do

 

[Crhome]

Ok cheers mate thx for your input.

 

[Crhome]

Is it normal for the temp gauge to raise above 90 b4 fast fan speed kicks in?

 

[Mark One]

Yes, that's how mine behaved. Normally the low speed fan should stop it getting that far, but it's not serious if it does

 

[Crhome]

Ok I been trying to eliminate the problem for a while now. Just recently replaced thermostat, engine coolant temp sensor and radiator fan temp switch. I just can't seem to understand why my fast fans never kicks in.