Temperature gauge

[seatleon87]

Hi, I've got a MK1 seat Leon 1.4 with temperature gauge playing silly buggers, stationery it's at 90 but when driving it drops all the way to 60?!
My worse feel is head gasket
Anyone else had this or can share some advice I would be much appreciated!

Thanks

 

[bruceR]

I would check/change the coolant and possible sticky thermostat


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[Alexis27]

Yep, coolant sensor or thermostat

 

[mty12345]

Hi, I've got a MK1 seat Leon 1.4 with temperature gauge playing silly buggers, stationery it's at 90 but when driving it drops all the way to 60?!
My worse feel is head gasket
Anyone else had this or can share some advice I would be much appreciated!

Thanks

99.9% chance it's the thermostat. Classic symptoms of temp falling when driving.

 

[iammooks]

My new coolant temperature sensor fluctuates pretty wildly. I can be crawling in traffic and it'll drop in the same way you describe. It never quite gets to 90 either.

The main reason I don't change it again is because I lost half my coolant doing the job the last time, but then I'm guessing it affects engine management, so it might be best to change it.

Just make sure you're prepared to fill the coolant again.


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[andylong]

A thermostat is a fairly crude device, but reliable and the difference in temperature between the coolant in the engine circuit Vs the radiator circuit can be alot so when the thermostat starts to open the cold coolant will drop the temperature fast.
It only really gets stable when the coolants in the 2 circuits get close, which is dependant on so many factors.
Unless you have a really good thermometer, don't get hung up on actual temperature but more how the system operates, or is the thermostat doing anything.

 

[mty12345]

My new coolant temperature sensor fluctuates pretty wildly. I can be crawling in traffic and it'll drop in the same way you describe. It never quite gets to 90 either.

The main reason I don't change it again is because I lost half my coolant doing the job the last time, but then I'm guessing it affects engine management, so it might be best to change it.

Just make sure you're prepared to fill the coolant again.


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1.8t should get to 90C in 5 mins and then stay there, any downward movement is almost certainly the thermostat stuck open. There is a drain tap on the bottom of the radiator, you can use that to drain part or all of the coolant with relitive ease. Engine not reaching operating temp causes reduced mpg and long term can cause engine wear due to excess fuel washing the bores.

 

[seatleon87]

Changed the thermostat sorted the problem, cheers guys! A great forum

 

[mty12345]

Changed the thermostat sorted the problem, cheers guys! A great forum

No problem mate. Glad to hear you got it sorted.

 

[seatleon87]

So the saga continues, it's back to 60 not 90 at all now
Changed the thermostat and the thermostat sensor, any ideas?! At my Witt's end with it

 

[andylong]

Measure the temps with something else, a food thermometer for example.
It's possible your guage it not reading correctly

 

[mty12345]

So the saga continues, it's back to 60 not 90 at all now
Changed the thermostat and the thermostat sensor, any ideas?! At my Witt's end with it

If the gauge is just stuck at 60 and never rises at all, then it's a 99% chance that the fault lies with the temp sensor or the wiring, or possibly but unlikely the dash cluster

If the new thermostat was faulty then you would almost certainly see it get hot when in traffic or going uphill, but then cooling down again when coasting down a hill etc.

 

[Alexis27]

https://www.amazon.co.uk/febi-bilstein-32510-Temperature-retaining/dp/B006DHZ1HG/ref=asc_df_B006DHZ1HG/?tag=googshopuk-21&linkCode=df0&hvadid=310764720204&hvpos=&hvnetw=g&hvrand=18175261606289687629&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9046605&hvtargid=pla-565254663261&psc=1&th=1&psc=1

Stick one of these in (works absolutely fine despite the cheap as chips price)

 

[mty12345]

https://www.amazon.co.uk/febi-bilstein-32510-Temperature-retaining/dp/B006DHZ1HG/ref=asc_df_B006DHZ1HG/?tag=googshopuk-21&linkCode=df0&hvadid=310764720204&hvpos=&hvnetw=g&hvrand=18175261606289687629&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9046605&hvtargid=pla-565254663261&psc=1&th=1&psc=1

Stick one of these in (works absolutely fine despite the cheap as chips price)

I agree, for that price probably the best course of action.

 

[iammooks]

I always tend to get Febi if there's not a Bosch part available, but a Febi one is what I've got in my car at the moment. I guess whatever the brand, sometimes they just go wrong.


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[seatleon87]

Changed that sensor and it made no difference, I've since done a live data drive and the below is showing up, it's rinsing fuel as well

 

[mty12345]

I'm guessing that code is for one of the lambda sensors, but it's in a weird format. I can't see how that would effect the temp though.

Here are the pin outs for the CTS. 2 pins feed the ECU, 2 pins feed the dash. If you put a 300ohm resistor across the gauge pins in the plug, that shoukl give you roughly 90C on the gauge for testing your wiring