Issue with my FSI coolant temps (Long post)

Pummy

Member
Hi

I have been searching around for some information on how to resolve a temp issue I have been having.

The Symptoms...
1) Car starts up and after a few seconds the red low coolant light turns on. Check the tank and coolant is at the correct level, so to that effect I am changing the tank and sensor this weekend. Question is whether to use G12+ or what I believe is G40

2) The engine takes a long time to warm up, without the climate running, in either auto or econ mode. It sometimes reachs 90 however when the climate is turned on at the "HI" setting the temp drops down to a little over the 60 mark. We worked around this by setting the control temp to 25 - 27 and this resolves the issue a little and keeps the temp up a little more than the previous scenario.

The car had it's cambelt changed around 18 months ago and presumed that the water pump had been changed. I will check this with West London Audi to see if it was or not. If not, whilst I will not be impressed, I will look to get it changed for the recent metal impellor version at the earliest opportunity.

My initial attempts to resolve this have led me to attempt the following this weekend.

1) drain the coolant system
2) replace the expansion tank (Cosmetic decision)
3) replace the low coolant level sensor in the tank
4) replace the thermostat
4) replace the coolant with the current specified coolant
5) replace the temp sender whilst the coolant is drained.

I really want to keep the car tip top as I have been bowled over on the car's practicality and fuel economy after going for fast, thirsty cars for the last 10 years or so. I figure that whilst I replace the coolant (not one to believe that the coolant will last the life of the car) I can change all those pieces cleanly and hopefully resolve the issue.

I know that a failed thermostat and sender can have interchangeable symptoms so this is really a double check I am doing the correct things, if nothing else.

The car was scanned for error codes and was not able to fnd any errors. This was done with a code reader and VAG COM also.

I realise that changing all the components may not be the best way to try and resolve the issue, however I figure that a complete drain and refill with all the sensors will at least give me some peace of mind.

Any input would be greatly appreciated as I have a long trip planned soon and the temp issue is something I would like to resolve before I faced with being stranded on a motorway somewhere with a non functioning car.

Thanks in advance
 
From your description of the cab heater performance it sounds more like a thermostat problem than the temp gauge.
I'd agree with your work plan but if you want to save a bit of cash don't change the temp sensor. It can be done later if needed and you don't need to drain the coolant again if your quick.

Cheers Spike
 
Thanks Spike. So what I will do in that case is...

1) Drain coolant
2) Replace Thermostat
3) Replace Expansion Tank
4) Refill Coolant
5) Run system and do a check

If the issue still remains, I will change the temp sensor and then refill the coolant lost in the tank and bleed off the air as per Elsawin.

Thanks for the tip about changing the temp sensor.

Interestingly, I was PM'ing dan_b about coming round to see if he had ideas and he floated the idea about the water pump not being changed when the cambelt was done. I called up West London Audi and they claimed that the car had never been at their showroom for a service when the cambelt was done. Further digging by them provides no other information about the car being at that location. Seems odd that the car has the stamp but they have no record. Cause to be concerned? Or the dealer fishing for more work?
 
I wouldn't trust the stealer either way to be honest - maybe worth visually inspecting the cambelt when you're digging about changing the thermostat just for peace of mind?

I'm also wondering if maybe my stat and/or pump is starting to get tired as even though I've changed my temp sender my car still never gets above the line before 90. Interestingly with my car the cambelt was changed before I bought it (receipts to prove) but not the stat and water pump...
 
hi pummy last year i had a new thermostat fitted to my fsi due to it putting the e.m.l light on the dash.when scanned the car would say thermostat implausible signal--or something like that. well for your info the thermostat on the fsi is electronic and comes as quite a large assembly made of plastic complete with new sender unit---should be as you wont get much change from £75 if i remember correctly. if you are not yet getting the eml light coming on i suspect it is malfunctioning.
please be aware that the fsi engine in cold weather does take a long time to warm up unless you start to drive it properly IE not just letting it idle.
my independent mechanic that looks after my a2 says that the changing of the thermostat is one of the most frustrating jobs on the engine due to silly location of pipe work and access to the clips--so its no quick job!

good luck in sorting this out mike
 
An update

So we got the pipes off the expansion tank, removed expansion tank, checked the sender cable on the thermostat and found it to be corroded :(

In trying to remove the gearbox linkages, we got a little stuck as I thought they were the new ones so I was looking for a clip to remove before compressing the spring. Turns out it require simple brute force so once that was done, got a replacement thermostat and one of three torx bolts that hold it in place was turned.

The bolt is bathing in WD40 and I have some other rust releaser stuff coming in an hour to apply and leave overnight so hopefully it releases and the head remains on the bolt.

Lesson of the day for 1.6FSI owners is to get the bolts checked on the thermostat. Take one out at a time and check they have not seized up anywhere.

I have tried...

Molegrips - Grabs the washer so trying to make up a washer depth face so they grip the bolt head instead of the washer. Also the space in that area of the engine is a little small for the mole grips.

Slightly oversized Torx bit - Still not able to open up the bolt, and this was attempted by a mechanic of many decades experience

Oversized Hex Bit Jammed in - This I am going to try in a few mins, but do not hold out much hope.

In retrospect, I would have liked this to have been done by a mechanic, however at least if I do it, I know it will be done properly and hopefully not require the head to come off to be able to extract the stud.

Update later on tonight or tomorrow. Wish me luck.
 
SUCCESS!

In the end I needed to chop the thermostat up leaving only the plastic around the seized bolt, and a smaller pair of mole grips than the ones I was using to get at the bolt with the restricted access. The bolts holding them in were round head torx bolts. If you can replace the bolts with hex head ones, I highly recommend that you do so in the event you need to change it.

Took a while to cut up the plastic with a cut piece of hacksaw blade and my hands in the bay moving it back and forth. However half way through with a screwdriver and hammer and a bit of force, helped split up the plastic easily enough to give me full view of the bolt.

Then got the mole grips on the bolt and it started to give. Upon examination it was corroded from base to tip.

Now the guage warms up to 90 and stays there despite however high I keep the temps on the climate or how fast I drive to get the airflow going. I have yet to see how it works when the day is much colder, but given it opens up at 106C, I would think it would be ok.

If you have an FSI and the guage is wavering, definately look to replace the thermostat. I got the part for £47 from German and Swedish as this part is dentical to the 1.6FSI A3 engine version, and given Audi were out of stock and the tech told me I should go there if I wanted one that day. Upon examination of the stat, the OE one has the Audi stamps, the German and Swedish one had some burring where the OE one had stamps ;). One thing I had to do was to rotate a clip around a pipe to the expansion tank as the edge was blocking me from being able to plug in the connector to the stat connector cleanly at the correct angle.

The one sensor I did not change was the 4 pin temp sender as I could not figure out where this was located. For the life of me I was looking all over the top of the engine but could not determine where it was. If anyone has some pictures they could show me, I would be grateful.

So after...

£14 for G12++
£47 for 'stat
£27 for the tank

The car is now able to keep us warm and toasty :)

I would say that if you have small hands then you should be OK to do the work yourself. Be prepared for awkward locations for the clips and the gearbox linkage to be in the way with sockets and your hands.

Also if you are going to remove the stat, attempt the bottom bolt first so that if it comes out cleanly, you have no issues, otherwise you can start to get ready for some time over the bonnet operated a hacksaw blade with your fingers.

Thanks all for your input.
 
Hi Pummy
Good to hear you got the thermostat sorted
The 1.6 fsi temp sender is on the same housing the thermostat fixes to - Item 11 on the attached diagram

Cheers Spike
 
Nice one -I'm wondering therefore if my 'stat is similarly on the way out as even though I've changed my 4pin temp sender I still never get temps above the line before 90.
 
I am on shaky ground here as I read in a manual that the stat on the 1.4 opens up at 86 degrees. How that relates to the temperature in your engine's case, I could not comment on. If you draining the coolant anyway, might be worth changing it regardless, assuming you can get to the unit and remove the bolts.

If I were in your shoes, I would change it, IF you are planning on keeping the car for at least a year.
 
I think the 1.4TDi stat opens at the same temperature. It's been bugging me for a while that I can't get up to 90C even after a2hour motorway drive - of course I've been thinking the exceptional cold weather has played a part, but after changing the temp sender to no real effect and seeing the impact you changing your stat has had, I think mine might be not operating correctly either. Could also help explain my car's stubborn refusal to return economy figures above 48MPG in spite of aero mods and altering my driving style!

Where is the 'stat on the TDi engine does anyone have pictures?

Sorry for the slight thread-jack!
 
stat issues

Pleased to hear that the stat solved the problem- having the same symptoms and decided to remove my thermostat at the weekend - only to find I didn't have the right part and nowhere open to get one.

The screws holding the stat in place were a complete PITA to get out- access is awful and I would agree about replacing with hex heads if poss.

Currently running car with No stat (having dismantled the unit to try it in a pan of water an see if it opened) = No heat.

Looking forward to receiving new stat tomorrow to fix the prob. finally. Had replaced the temp sender already which corrected the problem of a guage which sometimes registered and other times didn't - another job for the hands of a gynaecologist.

Thanks for your post - it gives me hope of solving long running woes... If this doesn't work I fear for my water pump impeller (genuine audi ?quality part).
 
Would changing the water pump be a physically easier thing to do if I am changing the stat at the same time or are they in different parts of the engine bay?
 
Water pump is normally driven off the cambelt. If I were you, I would do the stat first before worrying about the pump as it will be much easier. If you have to do the water pump, in my humble opinion, you are better off paying a professional to do the work instead due to the space that you have to work with on that side of the bay.
 
Well I've ordered both parts, so yes I'll do the stat first and see where we go. The water pump is more of a precaution as it's not been changed and they don't last for ever.
 
fixed

bonus!

new stat solved probs also and only took 1hour to drain / fit as I'd had a practice run. V. pleased I don't have to change water pump

I now have a spare stat for a 1.4 petrol and O-ring... free to a good home.
 
I am sure that it will be available in ElsaWin if anyone has one. I can print something off for tonight if you do not have much luck. I will need some info on the car to get at the diagrams but give me a shout if nothing turns up Dan.
 
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