Overheating or not

Tango One

I bought a car a couple of weeks ago. Driving grand but I was putting it through the nct. It ended up being an abandoned test. They said its overheating 116 degrees. I got in the car after and it appears to be fine goes up to 90 and sticks there. I left it idling for about 5 minutes and it seems OK. Not sure what to do

Atlantic Dawn

Any temperature issues when driving it on the road? What was temperature like before the test?

Tango One

Atlantic Dawn wrote: »

Any temperature issues when driving it on the road? What was temperature like before the test?

No none when driving. It was fine before and after the test too

jmreire

What make of car is it? Petrol or Diesel? Do you know if the cooling fan is cutting in ? Have you seen it show a rise on the temp guage on the dash, for example when in heavy traffic, driving uphill or pulling a trailer ( if you have one ) ?

Tango One

jmreire wrote: »

What make of car is it? Petrol or Diesel? Do you know if the cooling fan is cutting in ? Have you seen it show a rise on the temp guage on the dash, for example when in heavy traffic, driving uphill or pulling a trailer ( if you have one ) ?

It's seat ibiza 1.2 petrol. I've never seen it rise past 90. Haven't really been in heavy traffic. Not so sure about the cooling fan have to check that

John.G

Tango One wrote: »

It's seat ibiza 1.2 petrol. I've never seen it rise past 90. Haven't really been in heavy traffic. Not so sure about the cooling fan have to check that

You will never see the temperature changing from 90C in all VAG cars for the past 20 years or so because they have designed their system so that between real coolant temps of 75C and 107C the temp indication will read exactly 90C. This is not of much use when trouble shooting so yes check your cooling fan, this is controlled by a thermo switch in the side of the radiator with two settings, low fan speed cut in: 92C/97c, cut out 91C/84C. high fan speed cut in: 99C/105C, cut out: 98C/91C. (these were the settings in a 2000 Golf 1.4) and for more info the thermostat begins to open at 86C and is fully open at 98C.

I just wonder how the NCT monitored the coolant temp short of plugging in to the vehicle diagnostics, they do display the oil temperature on the NCT cert, but again I don't know how they obtain this.

jmreire

John.G wrote: »

You will never see the temperature changing from 90C in all VAG cars for the past 20 years or so because they have designed their system so that between real coolant temps of 75C and 107C the temp indication will read exactly 90C. This is not of much use when trouble shooting so yes check your cooling fan, this is controlled by a thermo switch in the side of the radiator with two settings, low fan speed cut in: 92C/97c, cut out 91C/84C. high fan speed cut in: 99C/105C, cut out: 98C/91C. (these were the settings in a 2000 Golf 1.4) and for more info the thermostat begins to open at 86C and is fully open at 98C.

I just wonder how the NCT monitored the coolant temp short of plugging in to the vehicle diagnostics, they do display the oil temperature on the NCT cert, but again I don't know how they obtain this.

Strange one all right, just had a look at my last NCT from Jan 2020, and no mention of water temp anywhere just the oil temp. I wonder if the OP could scan the fail sheet, and post it?

jimgoose

John.G wrote: »

...they do display the oil temperature on the NCT cert, but again I don't know how they obtain this.

Probe in the dipstick channel. I believe they do something similar with the coolant.

jmreire

Yes, they check the engine oil temp, and it's noted on the test sheet..So if they test the coolant temp. why is it not noted on the same sheet??

John.G

I have two or three certs showing a oil temp of 2C, a bit surprising as the ambient in all cases was ~ 8/12C. I have quite a number in the range 85/105C which does make sense.

Tango One

John.G wrote: »

You will never see the temperature changing from 90C in all VAG cars for the past 20 years or so because they have designed their system so that between real coolant temps of 75C and 107C the temp indication will read exactly 90C. This is not of much use when trouble shooting so yes check your cooling fan, this is controlled by a thermo switch in the side of the radiator with two settings, low fan speed cut in: 92C/97c, cut out 91C/84C. high fan speed cut in: 99C/105C, cut out: 98C/91C. (these were the settings in a 2000 Golf 1.4) and for more info the thermostat begins to open at 86C and is fully open at 98C.

I just wonder how the NCT monitored the coolant temp short of plugging in to the vehicle diagnostics, they do display the oil temperature on the NCT cert, but again I don't know how they obtain this.

Thats mad I never knew that they had it gear to always read 90c even if its higher. I won't get a chance to look at it again till the weekend. Is it a tough job to replace the fan if that's the issue.

The only detail the nct fail show was engine oil temperature was 116c. The rest of test where not done

To add insult to injury water is some how underneath the rear seat. The door seal looks. OK but there was water in with the spare wheel

John.G

It appears that it failed on high oil temperature, the wife's 2005 1.2 (3 cyl) polo has two certs (both pass) with 107C oil temp. When idling, one would expect the oil temperature to be very close to the coolant temperature so maybe a cooling fan problem, if the fan has failed then you will see the temp shoot up on the temperature gauge eventually but probably not if only the low speed fan contacts are faulty, if the high speed (contacts) fan is cutting in then you may or may not see an indication of high temperature.

I wasn't aware that high oil temperature was/is a NCT failure even though it is in the "Emission Box" in the NCT cert.

Tango One

John.G wrote: »

It appears that it failed on high oil temperature, the wife's 2005 1.2 (3 cyl) polo has two certs (both pass) with 107C oil temp. When idling, one would expect the oil temperature to be very close to the coolant temperature so maybe a cooling fan problem, if the fan has failed then you will see the temp shoot up on the temperature gauge eventually but probably not if only the low speed fan contacts are faulty, if the high speed (contacts) fan is cutting in then you may or may not see an indication of high temperature.

I wasn't aware that high oil temperature was/is a NCT failure even though it is in the "Emission Box" in the NCT cert.

Cheers
Yeah it's the emission box at the bottom of the results.

I might not get a chance to look at till the weekend. I take it easy enough to hear the fan coming on.

Del2005

Tango One wrote: »

I might not get a chance to look at till the weekend. I take it easy enough to hear the fan coming on.

Leave the car ticking over, or give it some juice when warm, and look to see if the fan comes on listening is not how to check. It should only be a few minutes before the fan kicks in, when driving the low ambient temperature will keep the car cool if you aren't pushing it. Keep an eye on the temperature gauge to make sure it doesn't overheat.

Is your heater working?

Tango One

Del2005 wrote: »

Leave the car ticking over, or give it some juice when warm, and look to see if the fan comes on listening is not how to check. It should only be a few minutes before the fan kicks in, when driving the low ambient temperature will keep the car cool if you aren't pushing it. Keep an eye on the temperature gauge to make sure it doesn't overheat.

Is your heater working?

The heater is working grand.

John.G

The fan is quite silent in operation so ensure heater switched off, open the bonnet, and observe the fan cutting in, there is quite a noticeable difference in sound between the low and high speeds but if it is operating on its low speed then in this weather it will never require the high speed mode.

Tango One

Fan looks like it's dead. I had it running for about 10 minutes and no sign of life.

John.G

Temperature gauge "stayed" at 90C?

Tango One

John.G wrote: »

Temperature gauge "stayed" at 90C?

Yeah no movement beyond that

John.G

I'm surprised the temperature didn't exceed 107C, in which case the temp gauge should have risen (when fan didn't cut in), maybe 10 mins was too little time for it to rise especially if you hadn't taken it for a run first.

Tango One

John.G wrote: »

I'm surprised the temperature didn't exceed 107C, in which case the temp gauge should have risen (when fan didn't cut in), maybe 10 mins was too little time for it to rise especially if you hadn't taken it for a run first.

I had drove it for around 10 minutes before hand.

John.G

Wife will be back in a hour or so with that 05 Plol and I will monitor the coolant temp and the oil temp if available with a VCDS and jot down a few readings

John.G

After 12/15 min drive from shops, VCDS temp showed 88C, after another 8 minutes the fan (low speed) cut in at 95c and cut out at 91C, based on that it might be prudent to run it at idling for up to 20 minutes after heat up to rule out any fan problems because if the fan is defective/not cutting in then the temperature gauge should certainly move after 107C, both systems are hardly at fault, I wonder were they getting a correct temperature reading at the NCT because if they were then the coolant temp would certainly IMO be practically the same (116C) temperature and if so then the temperature gauge would have registered this and moved up the scale.

I couldn't monitor the oil temp.

Tango One

Thanks John for the detailed post

John.G

Thinking again re above, my oil temp registered 107C on a number of occasions in the NCT and because the highest coolant temp is 95C before the fan cuts in then the oil temp seems to have been ~ 12C higher (107-95) so if yours is similar then the coolant temp could have been ~ 104C (116-12) so the first stage fan should have cut in before this?....anyway I have another 1 year old Polo in the family which does display the oil temperature so tomorrow sometime when it comes back home I will take a few readings off this.

Having said all this. I am still surprised that yours failed on high oil temperature because all the emission limits are stated in that "emission box" so why not the oil temperature limit?, also any oil vapours do not go to atmosphere but are re ingested into the engine.

John.G

New Polo tests.: max coolant temp: 94C max oil temp 98C (car driving at legal speed limit) both measured with VCDS+ oil temp car display showing exactly same oil temp.
Idling for 18 mins with ambient of 5C,. Coolant temp stayed steady at 93/94C, oil temp fell to 85/86c and remained there.
I suppose the combination of a new engine combined with a relatively low ambient resulted in those steady idling temps and the fan would have never cut in.

Tango One

Let it idling for about 30 minutes no fan but the temperature didn't move beyond 90

John.G

Well, it can only point to the actual temperature not reaching either the cut in point for either the low or high speed fan, if the fan was/is defective and the temperature became > 107C then the temp gauge should have risen?. both fan and temperature gauge are hardly defective.
Of course it doesn't explain the 116C NCT test.

Tango One

Finally got a chance to have another look at this
I removed the connector from the radiator fan switch
. I shorted the 12v on the socket to the other two ports one at a time and no movement out of the fan. I'm guessing the fan is faulty or could it be something else.

John.G

It does look like you have a fan (motor) problem alright (but in case its not the fan motor itself) if you have a multitester I would suggest baring back the insulation on the shorting wire so you can get one of the probes on it and put the other to earth and see if you still have 12V while shorting out, the only other thing I can think of is that you have a poor fan motor to earth connection.
Still doesn't explain though why the temperature indication is not increasing once it exceeds that 107C.

Tango One

John.G wrote: »

It does look like you have a fan (motor) problem alright (but in case its not the fan motor itself) if you have a multitester I would suggest baring back the insulation on the shorting wire so you can get one of the probes on it and put the other to earth and see if you still have 12V while shorting out, the only other thing I can think of is that you have a poor fan motor to earth connection.
Still doesn't explain though why the temperature indication is not increasing once it exceeds that 107C.

I read elsewhere it could be the fan relay, which looks to be in between the fan and the 12v three pin socket

John.G

There could be but I would be a little surprised, anyway if you are shorting that 12V (or any 12V supply) to either of the other ports AND if that 12v is still present the fan should start, have you tried what I suggested above?.

Tango One

Haven't got a chance today to take another look. There is a large amount of space in this engine bay but of course where I need to get to is tight.

It might be easier to remove the fan and test it looks like only 3 screws holding it the the radiator.

Cheers John

landmarkjohn

I would replace the thermostat as a matter of course. €15 part and easy to do on a lot of cars. Certainly before I got into sensors and suchlike.

TheBoyConor

Drop it into the test centre well early so it is cold when they go to test it. Should be still relatively cool by the time they get it into the test lane and should pass.

Tango One

Injected 12v on to the fan and its working but also managed to skin my hands off the fan I'm an idiot. Only thing left is the relay

John.G

If there was 12V present at one of the fan plug ports (which I thought you indicated) then the thermo switch should have brought the fan in.
Still strange though why the engine doesn't show any signs of overheat if that fan never comes in,

Tango One

John.G wrote: »

If there was 12V present at one of the fan plug ports (which I thought you indicated) then the thermo switch should have brought the fan in.
Still strange though why the engine doesn't show any signs of overheat if that fan never comes in,

The 12v was present at the thermo switch I shorted this out to try get the fan on and no life at all out of it. I used a second 12v battery to test the fan. I suppose it could be a bad link from the shorted 12v. I didn't get a chance to check that due to the fan skinning my hand.

Tango One

Not that anyone is too concerned but finally got to the bottom of this. It was an earth cable had become disconnect, easy fix but took me awhile, probably would of given up sooner if it hadn't been to covid and not actually needing the car thanks to all who help.

Cheers

John.G

Thanks for the update and good luck with the NCT if not already done.