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Discussion Starter #1
Good Morning everyone!

From the sublime to the ridiculous...I'm taking thursday off, to rip the seats and the carpet out

However today, I was sat at the traffic lights for 5 minutes and the temperature went from 90-80...also at the weekend it never warmed up sat on the drive way with the heaters on full blast!

Dave says it's worth checking it's not the fan control unit kicking in, so I'll check that, but otherwise it's a warranty job :)

However here's the useful info...for those of you who are OUT of warranty, and it needs changing, first off search for the 159 elearn cd thats on here.

It gives you instructions on how to change pretty much everything, and it all seems REALLY quite simple if you've ever done any mechanical stuff before in your life.

Secondly i've found a supplier of 2.4 diesel 159 thermostats....

Toyota Car Parts UK apparently

So hope this helps anyone with a stuck thermostat in future, as the one thing i have noticed on this forum is that whilst the bant and intentions are epicly awesome it could do with more answers than questions :)
 

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A diesel produces very little heat while idling. Especially when its cold outside. Whats even stranger is that if your aircon is turned on the radiator fan will kick in every minute making it even colder !
 

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...Whats even stranger is that if your aircon is turned on the radiator fan will kick in every minute making it even colder !
It won't make the engine colder if the thermostat is working.
 

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Discussion Starter #4
It won't make the engine colder if the thermostat is working.
This :thumbs:

The whole point of the thermostat is to keep the engine at 90 degree (88 if you want to be finickity) therefore if the coolant in the rad is at say 70 degrees, it won't matter because, until the thermostat reaches 90 degrees it should stay closed. Its only when it reaches above that that it opens to allow the water to pass into the radiator where it can be cooled and so on and so forth. This constantly repeats whilst the engine is at operating temperature!

But thanks for the input Steve, i was surprised at how little heat an idling diesel engine produces!
 

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This :thumbs:

The whole point of the thermostat is to keep the engine at 90 degree (88 if you want to be finickity) therefore if the coolant in the rad is at say 70 degrees, it won't matter because, until the thermostat reaches 90 degrees it should stay closed. Its only when it reaches above that that it opens to allow the water to pass into the radiator where it can be cooled and so on and so forth. This constantly repeats whilst the engine is at operating temperature!

But thanks for the input Steve, i was surprised at how little heat an idling diesel engine produces!
I think the opening of the thermostat is a little more gradual. It will start opening before 90 degrees.

I'm assuming you've verified it's the thermostat, as opposed to:
1) an airlock / lack of coolant
2) the damper in the gauge failing (modern gauges are HEAVILY damped)
3) faulty sender
4) electrical issues
 

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Discussion Starter #6
It's not a lack of coolant, been under the bonnet a lot in the last few days, theres definitely coolant (which was a pleasant surprise to see ;)

I can check with Fiat ECU scan, on the damper in the gauge (although you are right, the gauge would always read a good 5 degrees above actual engine temp...until it came up to operating temp.

But the fact that the heater wouldn't get hot, and you can feel it getting cooler as it's sitting in traffic..unable to maintain a temperature.

It also takes 5ish miles to get to temp, or a 10-14 minute drive.
 

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I think the opening of the thermostat is a little more gradual. It will start opening before 90 degrees.
I think they usually start opening at 83degC and are fully open at 88degC.

83degC is still quite warm so fine for the heater.
 

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It's not a lack of coolant, been under the bonnet a lot in the last few days, theres definitely coolant (which was a pleasant surprise to see ;)

I can check with Fiat ECU scan, on the damper in the gauge (although you are right, the gauge would always read a good 5 degrees above actual engine temp...until it came up to operating temp.

But the fact that the heater wouldn't get hot, and you can feel it getting cooler as it's sitting in traffic..unable to maintain a temperature.

It also takes 5ish miles to get to temp, or a 10-14 minute drive.
OK, on my other car, it's possible to remove the thermostat and check it to make sure it's faulty by putting it in boiling water and seeing it open. Not sure how easy it is to remove or check operation on the 159.

My only concern is that you have two threads open, one for a lack of coolant/heater temperature and one for wet footwells. This suggests to me a possible heater matrix leak. Hopefully you've ruled this out.

Ian A.
 

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Discussion Starter #11
Fear Not Ian, we've had plenty of rain since the weekend and it turned out to be a blocked drivers drain hole at the bottom of the windscreen.
 

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Fear Not Ian, we've had plenty of rain since the weekend and it turned out to be a blocked drivers drain hole at the bottom of the windscreen.
Ok, glad to hear the solution was simple, even if the drying out process will take a while in the current weather! :thumbs:
 
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