2.0 tdi coolant temp issues, cause?

[arron1995]

Since I’ve had my car I have noticed that the coolant temp takes ages to get to 90, and when I say ages I mean it can take 30+ miles, once It’s up to temp it will then fluctuate between 90-75 ish, I have noticed the temp will fluctuate faster if I have the heating on and the heater temp will fluctuate with it, I have had the water pump changed but not the thermostat, could this be the issue? Thanks

[Stevey Y]

Hi most likely the thermostat is stuck slightly open which is a better prospect than stuck shut with tat you would get plenty of heat at two miles and at twenty a lot of steam.

Steve.

[Magnet]

Hello Arron, 

Just one point to add to Steve’s response - don’t take it to the same garage to renew the thermostat, as the ones who suggested your symptoms were as a result of a faulty water pump - rather than a faulty thermostat! 
Kind regards,

Gareth. 

[arron1995]

15 minutes ago, Magnet said:

Hello Arron, 

Just one point to add to Steve’s response - don’t take it to the same garage to renew the thermostat, as the ones who suggested your symptoms were as a result of a faulty water pump - rather than a faulty thermostat! 
Kind regards,

Gareth. 

I had my water pump done as I was having my timing belt done mate, i didn’t get my stat done as I forgot about it at that time, my mechanic didn’t know about the issue 🙂

[arron1995]

1 hour ago, Stevey Y said:

Hi most likely the thermostat is stuck slightly open which is a better prospect than stuck shut with tat you would get plenty of heat at two miles and at twenty a lot of steam.

Steve.

Do you not get any other symptoms with a stuck open stat steve? I’ve seen people mention poor mpg etc but mine has been spot on

Edited October 31, 2021 by arron1995

[Magnet]

Hello Arron,

You didn’t ‘self diagnose’ the need to fit a new water pump did you??  Am I being unfair to the garage which fitted it, because they didn’t diagnose it? 
The symptoms you describe are typical thermostat associated issues. 
Kind regards,

Gareth. 

[arron1995]

1 hour ago, Magnet said:

Hello Arron,

You didn’t ‘self diagnose’ the need to fit a new water pump did you??  Am I being unfair to the garage which fitted it, because they didn’t diagnose it? 
The symptoms you describe are typical thermostat associated issues. 
Kind regards,

Gareth. 

Car had done 150k miles mate so I thought while the belt was off I may aswell put a new water pump on just incase it did fail later down the line, so I could save on labour costs :).

[Magnet]

Thanks Arron, obviously a good call then.

Detail is king. 
Kind regards,

Gareth, 

[cliffcoggin]

The slow warm up and wide temperature flictuations suggest to me that the thermostat is stuck wide open. When you renew it make sure to be thorough in getting rid of airlocks. They can be a devil to eliminate.

[Stevey Y]

21 hours ago, arron1995 said:

Do you not get any other symptoms with a stuck open stat steve? I’ve seen people mention poor mpg etc but mine has been spot on

Hi poor MPG would be a factor that would manifest itself when the ambient temperature is very low and the enrichment strategy on the injection system runs for longer to try and get the engine up to temperature, its been quite mild so at around 9-12 degrees you won't really notice any difference, in view of the cost of a new thermostat its better to just replace it rather than limp along with a problem that in the long run may cost a whole lot more to fix.

Steve. 

[arron1995]

all sorted guys, found out that my battery health is 54% though so thats going to cost me even more money, anyone know where i can get the stop/start battery cheap as possible.

[Magnet]

Do not buy cheap batteries Arron. This will be bad news for you in the long run. Buy once and wisely - Bosch/Varta with a 5 year warranty - from on line suppliers (look on EBay) at most competitive prices.

Kind regards,

Gareth. 

[cliffcoggin]

I am a little surprised at the diagnosis. I realise that a poor battery can give rise to electrical problems, in fact I have frequently suggested as much elsewhere on this forum, but if Aaron's battery was so bad I would have expected all sorts of other faults ranging from door locks to limp made to false dash warning lights etc.

The proof of the pudding will be in the eating, so Aaron do please let us know the effect of the new battery on your problem.

[Magnet]

I’m confused with this as well Cliff.

My interpretation had to be that Arron had had the thermostat replaced - or indeeds intends to get it replaced ?- but now has a further (unrelated) issue with a sub standard battery. 

If my interpretation isn’t correct, then Arron will need to correct us. 
Kind regards,

Gareth. 

[arron1995]

On 10/31/2021 at 9:16 PM, Magnet said:

Thanks Arron, obviously a good call then.

Detail is king. 
Kind regards,

Gareth, 

I have had a new stat fit and the coolant temp issue is fixed, but I asked my mechanic to check my battery as I believe it’s the original one and my car was registered in 2012, turns out the battery health is only 54% and the machine told me to replace it, my stop/start stopped working recently and this is why I had my battery checked too.

[cliffcoggin]

42 minutes ago, arron1995 said:

I have had a new stat fit and the coolant temp issue is fixed, but I asked my mechanic to check my battery as I believe it’s the original one and my car was registered in 2012, turns out the battery health is only 54% and the machine told me to replace it, my stop/start stopped working recently and this is why I had my battery checked too.

I am glad to hear both faults are fixed Arron. In summary, the temperature problem you asked about was solved by a new thermostat. The faulty battery had nothing to with it. As Gareth pointed out earlier detail is king.

[Magnet]

Thanks for clearing that up Arron. 
You may need to get your new battery coded to the car. 
Hopefully Stevey will let us know whether this is likely to be the case or not. 
Kind regards,

Gareth. 

[Stevey Y]

On 11/3/2021 at 7:08 PM, Magnet said:

Thanks for clearing that up Arron. 
You may need to get your new battery coded to the car. 
Hopefully Stevey will let us know whether this is likely to be the case or not. 
Kind regards,

Gareth. 

Hi all models from 2004 need a BEM recode but almost any of the diagnostic platforms can do this using the original BEM Code and changing one digit it thinks its getting a new O.E. battery and as long as the BEM is happy life is good.

Steve.

[arron1995]

2 hours ago, Stevey Y said:

Hi all models from 2004 need a BEM recode but almost any of the diagnostic platforms can do this using the original BEM Code and changing one digit it thinks its getting a new O.E. battery and as long as the BEM is happy life is good.

Steve.

Spot on steve, my mate is a coder and has vcds,Odis etc