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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Re: 1.4 overheating...

Post by Vanilla cup » Tue Jan 15, 2019 6:19 pm

So, finally got time to look at the car.
Put power directly to fan- fan works.
Bridged fan switch plug- fan works.
Therefore, appears I need a new thermostatic fan switch.
Bought that, fitted all okay, no leaks.
Tried bleeding the system, squeezed hoses, removed/refitted coolant sensor a couple of times etc...
Still appears to be air in the system - incar heating inconsistent, sometimes warm, sometimes cold.
Temperature dial goes to hot, but still no fan.
So.... I Bridged fan switch plug again and fan works, possibly faulty fan switch? Am I missing something with bleeding the system?

Vanilla cup
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Re: 1.4 overheating...

Post by Vanilla cup » Tue Jan 22, 2019 12:21 pm

OK, spent a couple of hours on the car.
Flushed system through - plenty of particles came out.
Bled system again, run for 10 mins at tick over with expansion tank lid off. All good, temp. up to middle, all hoses hot, heater working fine. Then increased revs and temp goes up, heater goes cold and coolant starts to boil. Fan does not cut in at any point.
I could try another new thermostatic fan switch or fan control unit? Also, fan does not come on when a/c is switched on.
Any ideas???

RUM4MO
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Re: 1.4 overheating...

Post by RUM4MO » Tue Jan 22, 2019 9:43 pm

Fan not coming on when AC is switched on, as long as there is enough gas in the system for it to chill the air, this sounds like your car is only fitted with one electric cooling fan and that that fan has two sets of windings. First set, slow speed, should get switched on when you switch the AC chilling on, this slow speed should also switch on when the engine coolant rises above a certain temperature. Now, if that "normally the only set of windings used on that fan motor" goes O/C because the series resistance has failed, then that electric cooling fan will never switch on when you demand the AC chiller to work, or when the engine temperature starts to get hot enough for it to need that fan to switch on. If you continue to run that engine and the second set of windings, high speed are still okay, then at a certain temperature, the electric cooling fan will finally switch on at high speed, hopefully cool the engine back down then switch off, engine starts to overheat again, fan back on at high speed - etc etc.

By now you should have read up some back ground info and have worked out how to determine is your car has a single cooling fan with two sets of windings, then moved on to check that each of the sets of windings still work, if you have not done that yet, you need to do tha now so that you can move this repair work on.

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Re: 1.4 overheating...

Post by Vanilla cup » Thu Jan 24, 2019 6:10 pm

Thanks for the reply.
Car has single fan with 2 speeds. I've replaced thermo fan switch, but fan still not working as it should, ie. low speed for a/c and temp., and high speed for increased temperature.
I have disconnected new thermo. fan switch, and bridged plug and high speed and low speed work. Indicates possible faulty fan switch, even though it's new. This would not explain low speed not coming on with a/c.
I've finally managed to bleed the system, so temp. stays at 90 at tick over for 20mins,(with fan plug Bridged), so fan at high speed.
I thought that if high+low speed fan worked by bridging thermo fan plug, that indicates that wiring, fuses etc.. was fine.
Any suggestions?

RUM4MO
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Re: 1.4 overheating...

Post by RUM4MO » Fri Jan 25, 2019 10:54 pm

I agree that if you can run the fan at high and low speed by applying a shorting link to the thermal switch car side connector that it does point to the old and new thermal switch. The AC not running the fan might be due to the R134A charge being too low to switch the fan on.

So probably needs another thermal switch, unlikely but no other idea at the moment.

Vanilla cup
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Re: 1.4 overheating...

Post by Vanilla cup » Sat Jan 26, 2019 8:17 am

Thanks for the reply.
I'll get another thermal switch and try again.

RUM4MO
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Re: 1.4 overheating...

Post by RUM4MO » Sat Jan 26, 2019 10:30 am

Just a thought before you buy/fit another fan thermal switch, is the coolant being discharged back into the reservoir via the small pipe okay, if not maybe the water pump impeller has come free and is not circulating the water well enough which is in turn not getting the radiator top end hot enough to switch on the fan.

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