Thermostat query

[Cragh]

Hi Guys and Gals. Newbie here, so be gentle. Very little time on my hands as outside work I’m having to be a a carer for an elderly parent.

If I had a sticky thermostat, how would it exceed the engine. 
I had a run out today (38  miles either way) and all was well, but when I started up to head for home, idling was a bit ropey. I should have looked at the rev counter as it felt as if it was idling lower than it should. A  quick blast on the accelerator pedal seemed to sort it.

Whilst driving home didn’t seem as smooth as normal. I have been putting it down to regen of the DPF getting noisier with age, but noticed the temperature gauge had hardly moved. 
Admittedly it was 3’C outside and I had the heater on 21’C

audi a4 Avant 2.0tdi Technik 2011

Edited January 14 by Cragh

[alpha omega]

hi and welcome.....would you think having a diagnostic check for codes may help.....good luck if you need to change the thermostat.i had a right job getting the thermostat out in such a tight space.(thermostat sealed in a plastic casing)....i ended up taking the alternator off to get to it.then you try getting the pipe back on that runs to the right of the thermostat for the coolant to run through.check for leaks in that area once its all back together best wishes stephen

[Magnet]

Welcome Cragh, and thanks for joining. 
If the temperature doesn’t reach normal, leave alone hardly moving, the you can put your money on a failed (open) thermostat. 
I would take note of Stephen’s comments, and probably entrust the job to an independent -unless you are very good with the spanners.

Kind regards,

Gareth. 

[Cragh]

Thank you for the replies. My local garage found no error codes but maybe I should get him to plug it in again now this has happened. 
There’s been a couple of times in the last year it’s kind of sounded a bit rough, but put that down to the times it’s gone into re-gen mode.

i kind of got it in my head today that a sensor may have picked up the thermostat wasn’t working properly, which then was sending out the wrong instructions to something else, which was creating a fault. Maybe time to replace it.

Had the air con regassed the end of last summer, but had to take it back the day after as it failed to cool. The fella that did it then found the pump had stopped working, but it started up whilst he was still underneath the bonnet, and it seemed ok thereafter.

I didnt seem to be using more fuel today

 

 

 

[Magnet]

Hello Cragh,

I think it’s one thing at a time, and I’m not sure why you want to plug it into diagnostics. If the coolant temperature shows near enough to cold after a reasonable run, then the chances are it’s a classic case of a failed-open thermostat - pretty simple. Of course it maybe a case of a faulty gauge sender, but….
From the book of simple logic - take the car on an at least 10mile run, switch off and open bonnet and have a feel of the radiator hoses - if the gauge reads low, the hoses should feel warm rather than hot. If they only feel warm, and the gauge reads low, then you have carried out your own diagnostics! 
If you want to go down the diagnostic route, then the garage should be able to give you an operating temperature during a road test. 
Just forget about any potential noise/performance issues until you have a vehicle which operates at a correct temperature. One thing at a time! 
Let us know how you get on Cragh. 
Kind regards,

Gareth. 

[Cragh]

Thanks Gareth. I mentioned the other bits in case they may be linked in some way.
I don’t think I’ve ever had the temperature up to 90 during the colder days, but yesterday seemed exceedingly low. Heating in the car itself was fine, and car has been faultless this morning going to work. (Not any distance that I can check hoses)

[Magnet]

Thanks Crag,

‘…don’t think I’ve ever had the temperature up to 90 during the colder days..’ - something is wrong then. It could be the gauge if the heater is fully efficient, but whatever, you will need to investigate this, by the methods suggested. 
‘Not any distance I can check hoses’. You will have to extend your journey then Crag. 
Kind regards,

Gareth. 

[BenKenobi]

For the record too it won't regenerate (clean out the DPF) if the car doesn't think it is warm - a lot of stars must align for that to happen and engine temperature is one of them at least according to VW bulletins which have above either 50°C (stationary forced regen) or 70°C driven with the particulate load below 40 grams above 40mph and 2000 rpm in top gear. There are measurement blocks visible in a diagnostic tool that will indicate what the car thinks the temperature is vs the instrument cluster display.

You need to get a number of measurables checked - water temperature is one, the current DPF ash level, particulate load and differential pressure are others - though if clogged it should set a check light your mechanic hopefully knew enough to look for this stuff. The diesels need at least an hour I believe above 2000rpm or a forced regen, a 38 mile trip around town won't cut it for sure - I really don't know what the star alignment needs to be for Audi but I doubt it is massively different to the 2013 2.0 Passat we have. If the regeneration cycles are occuring then the DPF should be fine, but if they aren't then for sure it is when not if that DPF chokes and a DPF can make a diesel run really poorly.

You may want to ask your mechanic to check the intake also, our Passat needs all the crud from the EGR cleaning out at least every two years, first sign of this is usually an intake air flap intermittent fault.

Diesels for short around town stuff are a liability but they never tell people this when they sell them, if all that you do is short around town stuff do yourself a favour and get out of the diesel into a petrol.