1.4 overheating...

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Vanilla cup
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1.4 overheating...

Post by Vanilla cup » Tue Dec 04, 2018 8:43 pm

A family members car is overheating, so I said I'd have a look. Took it for a drive, temp. went up to red/warning light. Fan didn't kick in? Stopped car, loosing coolant from under expansion tank, (hoses+clips look OK, so assume its tank that needs replacing).
I'll change expansion tank tomorrow, I've read that I need to bleed from coolant temp. sensor, anywhere else?
Also need to look into why fan didn't kick in when temp. kept going up. Any suggestions?
Cheers

RUM4MO
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Re: 1.4 overheating...

Post by RUM4MO » Wed Dec 05, 2018 10:45 am

I'm guessing that that car has a 1.4 16V petrol engine with maybe about 86PS power output?

Years ago I seem to remember that some of these expansion tanks did start to leak at the seam, if there is still coolant in it and you keep it high up while replacing the tank, you might get away without bleeding it via the engine coolant temperature sensor. What I discovered when I caused an airlock while replacing an engine coolant temperature sensor - things got out of control and I let all the coolant "above" this sensor drain out as I had trouble making sure that the sealing O-ring really had dropped out - was that the heater would hand out some heat, then go cold, which was annoying as we were heading into winter at the time, easing out the temperature sensor while continuing to keep the expansion tank filled up with enough coolant did the job as air bubbles initially came out.

It could be that either the fan temperature sensor is u/s or the fan(s) control unit is u/s or the fan(s) low speed, if it/they are 2 speed, dropper resistor is u/s - or you have a wiring problem. Best plan would be to start at the fan(s) themselves, check internet for which wires are used for what - same on most VW Group cars cooling fan circuits, if that is all okay then check the fan thermal switch on the radiator, again internet should give guidance, then on to the cooling fan control module. On some VW Group cars I think that a jammed shut thermostat can force the engine overtemp warning on, I've not noticed that being an issue with this engine, but just another suggestion if all else is okay.

Good Luck!

Edit:- ah, you have said that the temperature indication AND the red warning came on, so probably not a thermostat issue, and hopefully not a coolant pump issue, when was the last time the coolant pump and cam belt were replaced?

Vanilla cup
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Re: 1.4 overheating...

Post by Vanilla cup » Wed Dec 05, 2018 12:37 pm

Thanks for the reply.
I don't know when the belt+pump was replaced.
Just picked up new expansion tank, if weather permits, I'll make a start this afternoon and try bleeding system through. Fan is free moving, so would indicate problem with power to..... I've taken on board your suggestions, will plough through.
Thanks again

Ev996sps
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Re: 1.4 overheating...

Post by Ev996sps » Fri Dec 07, 2018 5:45 am

Vanilla cup wrote:Thanks for the reply.
I don't know when the belt+pump was replaced.
Just picked up new expansion tank, if weather permits, I'll make a start this afternoon and try bleeding system through. Fan is free moving, so would indicate problem with power to..... I've taken on board your suggestions, will plough through.
Thanks again
I've never bled on via the temp sender switch,after fitting pistons to the same engined polo top it up let it run..refill that's it..I've never had a expansion tank go either. You need to see if the water is circulating in the tank..and I'd change the temp sender unit could be sending message that it's cold..hence fan not needed..feel your hoses..ie what's hot and maybe what's not..then check that area...maybe thermostat stuck shut. Best of luck..

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CarbonChaos
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Re: 1.4 overheating...

Post by CarbonChaos » Fri Dec 07, 2018 11:49 pm

Could be as simple as the radiator fan switch is bad,you can bridge the two wires and the rad fan should run constantly

Vanilla cup
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Re: 1.4 overheating...

Post by Vanilla cup » Tue Dec 11, 2018 5:43 pm

OK, thanks for the replies, sorry for the delay in replying, I've been busy with work. So, managed a couple of hours on the car today. The fan temp. sensor /rad join are stained so there is a leak there at least. Bumper and cross member off, trying to get the fan switch plug off to check fan, but didn't want to force it, so left for another day. Couple of questions :
Is the fan temp. sensor 27 or 29mm? May try and nip it up, see if that cures it.
If I get a new rad, is a pattern one from ECP ok, or genuine only? If I do fit new rad, what else is needed? Think I've read new temp. sensor o ring, anything else?
Thanks again for your help.
Cheers

RUM4MO
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Re: 1.4 overheating...

Post by RUM4MO » Tue Dec 11, 2018 7:00 pm

I'd be leaving the radiator well alone for the time being and concentrate on finding out why the fan is not being switched on.

Typically the fan thermal switch does end up leaking, but if it is only leaking at the O-ring area then that is normal, if it is leaking through the thermal switch body, then that needs replacing.

Vanilla cup
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Re: 1.4 overheating...

Post by Vanilla cup » Tue Dec 11, 2018 7:23 pm

OK, thanks for the reply.
I'll look into the fan not working and replacing o ring on the sensor. Probably won't be for a few days because of work. Thanks again

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