Hit a bit of a brick wall with my overheating VTS, so to avoid confusion I thought I'd get a list up of what I have and haven't ruled out so far, so I can hopefully get to the bottom of this.
Basically in short, the problem is that the coolant guage stays right down on cold for 1-2 minutes (whether the car is being driven or just sitting stationary) and then will go from cold all the way into the red (from one extreme to the other, with no gradual warming or anything) and the coolant light will come on, along with the fan.
During this time, the radiator doesn't feel either cold or overly hot - just very slightly warm and then gradually getting warmer along similar lines to how you'd usually expect. I'm thinking this therefore means the fan is basically being tricked into thinking it should be coming on by something, when it actually doesn't need to be. Is it possible for the fan-switch to be backwardly affecting the temperature guage? Seems unlikely?
I've done a compression test to check the headgasket, and it came back as a healthy 220-225psi across all 4 cylinders, fairly sure that a blown headgasket would put at least one of the cylinders out is that correct?
The car is also running poorly on and off and has a bit of trouble starting, although this is quite likely to be an unrelated problem and due to a faulty coilpack according the diagnostics check I did before the MOT, but as far as I'm aware the coilpack can't affect the cooling system, so is unlikely to be having a knock-on effect?
I've also fully flushed, bled and changed the coolant at least 3 times. As I'm using a 2L bottle and tape as a header tank though, I'm slightly concerned that air is being sucked into the cooling system through the seal of tape between the radiator filler and the bottle, how likely do people think this is? My Citroen dealer look at me like I'm an idiot when I asked for the official header tank to fill the radiator with the proper seals and things.
If you ignore the running poorly as a seperate fault, then almost all things point towards the Dash Temperature sensor. For those unaware the VTS has one temperature sensor for the ECU which could easily cause poor running but doesn't affect the guage, and another sensor for the dash which would affect the guage, but can't make the car run poorly?
Since it's very unlikely both sensors have gone at the same time, if the poor running is down to the first sensor, then it's very unlikely that it could also affect the guage. And if the faulty guage is down to the second sensor, then it's very unlikely the first sensor is causing the car to run poorly, unless it happens that air is getting into the system via the tape/bottle when I fill it and they're both reading an airlock?
Although saying that, I would have thought had it been that there was an airlock or that the waterpump wasn't pressurizing/circulating the water properly that it would still warm in a linear fashion on the temperature guage (but obviously much faster than usual) whereas this goes straight from cold to boiling in a click of the fingers and after almost 2 minutes.
Anyway to be thorough and because they're cheap, I've got a new thermostat and both new coolant temperature sensors ready to put in, as well as a waterpump waiting in the wings should that not work, so we'll be able to see what happens then.
Should I be looking into electrical earths and connections? - battery, alternator, ECU plugs, dash plugs etc? Is there anything that could be affecting any of the electrical bits in the cooling system and not anything else (all the other guages are fine).
Basically in short, the problem is that the coolant guage stays right down on cold for 1-2 minutes (whether the car is being driven or just sitting stationary) and then will go from cold all the way into the red (from one extreme to the other, with no gradual warming or anything) and the coolant light will come on, along with the fan.
During this time, the radiator doesn't feel either cold or overly hot - just very slightly warm and then gradually getting warmer along similar lines to how you'd usually expect. I'm thinking this therefore means the fan is basically being tricked into thinking it should be coming on by something, when it actually doesn't need to be. Is it possible for the fan-switch to be backwardly affecting the temperature guage? Seems unlikely?
I've done a compression test to check the headgasket, and it came back as a healthy 220-225psi across all 4 cylinders, fairly sure that a blown headgasket would put at least one of the cylinders out is that correct?
The car is also running poorly on and off and has a bit of trouble starting, although this is quite likely to be an unrelated problem and due to a faulty coilpack according the diagnostics check I did before the MOT, but as far as I'm aware the coilpack can't affect the cooling system, so is unlikely to be having a knock-on effect?
I've also fully flushed, bled and changed the coolant at least 3 times. As I'm using a 2L bottle and tape as a header tank though, I'm slightly concerned that air is being sucked into the cooling system through the seal of tape between the radiator filler and the bottle, how likely do people think this is? My Citroen dealer look at me like I'm an idiot when I asked for the official header tank to fill the radiator with the proper seals and things.
If you ignore the running poorly as a seperate fault, then almost all things point towards the Dash Temperature sensor. For those unaware the VTS has one temperature sensor for the ECU which could easily cause poor running but doesn't affect the guage, and another sensor for the dash which would affect the guage, but can't make the car run poorly?
Since it's very unlikely both sensors have gone at the same time, if the poor running is down to the first sensor, then it's very unlikely that it could also affect the guage. And if the faulty guage is down to the second sensor, then it's very unlikely the first sensor is causing the car to run poorly, unless it happens that air is getting into the system via the tape/bottle when I fill it and they're both reading an airlock?
Although saying that, I would have thought had it been that there was an airlock or that the waterpump wasn't pressurizing/circulating the water properly that it would still warm in a linear fashion on the temperature guage (but obviously much faster than usual) whereas this goes straight from cold to boiling in a click of the fingers and after almost 2 minutes.
Anyway to be thorough and because they're cheap, I've got a new thermostat and both new coolant temperature sensors ready to put in, as well as a waterpump waiting in the wings should that not work, so we'll be able to see what happens then.
Should I be looking into electrical earths and connections? - battery, alternator, ECU plugs, dash plugs etc? Is there anything that could be affecting any of the electrical bits in the cooling system and not anything else (all the other guages are fine).
