Poor MPG on A4 2.5 TDI 180 Quattro

sammi

sammi

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verwood, Dorset
Hi All

In the past few weeks I have noticed that the average mpg of our car has dropped from 39 mpg to between 26 & 29 mpg..... surely there is something wrong.

The temp gauge in the car does not work or get up to temperature fully so am guessing I need a temp sender ( This has been like this since I bought the car in January, have never got round to replacing it)

And the heater in the car only gets warm and not hot

Could any of the above contribute to the mpg issues or should I be looking for something else.

Any help would be greatly appreciated

:confused::confused: :sos: :sos: :sos:
 
Is that an average mpg over a fill up or daily driving? How far you driving as if it's only short distances then the extra cold weather could be doing it as the car keeps it in choke mode for longer, could be a sensor tricking the ecu into thinking your car is cold all the time

I'm sure a diesel specialist will be along shortly to help you out
 
Thats the thermostat blocked open most likely ! It will be an expensive job as its right under the cambelt and everything needs taking off and its good practice to renew all the parts while they are off...Parts cost nearly £350 (full cambelt kit, water pump,tensioners/rollers,thermostat,etc.) Not a job for the faint hearted ! Expect 600+ for a decent job from an independent or more from dealer.
 
26-29mpg is what you'll be getting as an avg on a 15mins trip... as it does take about 10mins to get the TDI's up to warm-ish, so lots of short trips could explain it.... but I'm assuming this is on longer journey's too?

any chance of getting it on vagcom and checking for error codes?

note them down, clear them off and then take it for a drive and check again....
 
I do know someone with a Vagcom so will look at the error codes.

In terms of trips some are short 15-30mins locally (School run etc) but others are more 30-60 mins.

£20 worth of fuel is only doing about 90-100 miles now where before it was doing 140 + depending on how it was driven
 
adamss24 said:
Thats the thermostat blocked open most likely ! It will be an expensive job as its right under the cambelt and everything needs taking off and its good practice to renew all the parts while they are off...Parts cost nearly £350 (full cambelt kit, water pump,tensioners/rollers,thermostat,etc.) Not a job for the faint hearted ! Expect 600+ for a decent job from an independent or more from dealer.
Click to expand...

Could this not be the temp sensor? I was really hoping it was,! I had the cam belt done 3 years ago and the water pump done 18 months ago! Would be a b!tch if need to pay for labour for it all again!:banghead:
 
VagCom.... error codes... then answers....

Anything else will just be people guessing and no matter how educated, they will still be guesses.
 
I will get the Vagcom on it in the morning if I can and feedback my findings.
 
sammi said:
I was hoping it would be the temp sensor..... any other ideas?
Click to expand...
Coolant temp. sensor does have 4 pins: 2 for the ECU wich when duff will overfuel, ****** timing and keep the glow plugs active for a long time and the other 2 wich send the signal to the gauge in the dash. If you have poor heat output in the cabin and the fuel consumption is high, the thermostat is stuck open...as a failsafe measure. I'm afraid there is no other option and they really should be done toghether: cambelts, thermostat, water pump + relay rollers and aux. belts + pulleys. You could check the sensor too, its under the engine cover next to the oil filter housing. If the sensor is green, then its fairly recent/revised part. Funny thing is i have worked on many v6 Tdi and seems to me only thermostats fitted after T reg(1999) have problems, none before that !
 
trying to speak to GSF about the parts, what a nightmare cant make any sense of what i need and what I dont!!!
 
i was getting similiar consumption i.e. a bit on the low side

it turned out to be a cracked drivers side intercooler

is the boot of your car black, from unburnt fuel?
 
sammi said:
GSF Arent sure what additional pulleys I will need can anyone help?
Click to expand...
I would make shure GSF wont supply you with a DAYCO cambelt kit ! Reason is they break at the joint line so, even the dealer kits come with Contitech cambelt and Dayco pump belt. In the kit you should get the relay roller and the tensioner. There is also a hydraulic tensioner (not supplied in the kit!) wich on its own cost about 100 quid from dealer. They are made by INA and Euro Car Parts do them for about 60 quid. Rest ofthe rollers are made by Littens (canada) or NTN (japan) and they are the only OEM suppliers. I would get an genuine thermostat though just for peace of mind ! I use Contitech full kits wich have everything in the box. They are not cheap though !
 
Sammi - I've just put two and two together .....

Try TPS on Stanley Green Road in Poole. They are very helpful and knowledgable, good prices too.
 
Thanks James I will have a look at them. What a nightmare this is turning out to be. We are in Wimborne by the way so not far from you
 
Yes I remember now from Audifans ;)

Did you ever get the codes scanned for yours?

You're asking about cambelt parts as it's the thermostat needs replacing is that right?

Off the top of my head:

Timing belt
Idler pulley and bolt
Tensioner pulley and bolt
Fuel pump belt (optional)
Water pump (optional but recommended)
Thermostat (if needed)

I can recommend Autotechnics in Gillingham - maybe not the cheapest, but certainly (one of) the best in my experience.
 
Yeah we sorted the alarm in the end thanks, now we are looking at the poor mpg and finger is pointing to the thermostat, cant believe such a small part is so hard to fit!! I have been calling around for prices which vary quite a lot GSF are the best at present with everything I think I need for £210 plus then fitting... We love the car but since we have owned it had nothing but problems with it in one way or another!!! hopefully soon we will be able to enjoy it
 
Quick update on the never ending mileage and cold issues....

The car does get warm inside but not super hot like my 08 A3, so I decided to try my luck and change the temp sensor next to the oil filter to see if I could get a reading on the gauge.... It hasnt worked. Is there another temp sensor somewhere that I should change? Are fingers still pointing at the thermostat? The only thing I did notice that when the temp sensor was disconnected the revs in the car dropped to normal warm idle rather than cold start idle.

We have also checked vagcom and there was a temp sensor fault code that we have now erased after changing the green temp sensor on the top of the engine.

Any Help much appreciated

Many Thanks
 
Nope mate, that is the only one you need to change. You can check with vag com what temp the engine see. If it does not go above 70 celsius, then the thermostat is faulty...
 
Excellent I will try that, will get the car back on the Vagcom over the weekend.
 
I had a similiar problem with my 1.9 tdi, where the car would not fully warm up and had a dodgy idle. The temp would take ages to reach 90 and then drop down to 70. Heating was not hot when set to HI, it was only chucking hot air when travelling on the motorway.

The temp sensor was changed 4 months ago - error flagged on vagcom.

I had the thermostat replaced by Audi Leicester - £138 (done this week). This was for labour, thermostat and new coolant. I had it fitted by Audi because it covers me for two years. Temp reaches 90 and the idle is perfect again.

Lion Garage quoted me £90 if its a normal thermostat and £150 if its an electric thermostat. Mine is a normal thermostat.

I hope that helps.
 
Thats good to know, I am going to be looking at quotes this weekend for a thermo replacement on the car.
 
The thermostat on the v6 IS behind the cambelt so its wise to replace the belt and rollers just for piece of mind ! On the 1.9 its easy to change the thermostat and its accesible from underneath the car or from the top but its a bit fiddly ! 90 quid is a bit expensive for a normal thermostat as its just a fiver at ECP and all you need is some antifreeze to bleed and top up the system. On v6 engines its a bit more involved than that...
 
I seem to have a similar problem - both water and oil temperature gauges go no higher than 70 degrees and the heater is a bit anaemic. Fuel consumtion is very disappointing around town and on a run I get maybe mid 30s at a push. Not impressive for a diesel (2.5TDI tiptronic quattro). I had the cam belt changed last April and the water pump was relaced at the same time. I hope I don't have to have the whole shebang taken apart again for the sake of a fecking thermostat! What a stupid piece of design to have a thermostat buried in the depths of the workings. In the old days it was fitted at the top of the cylider head or even on the radiator where it was easy to get at. Not impressed at all. I really like my Audi but some of the costs caused not by poor quality but by design that precludes simple repairs is unbelievable.
 
Alibi said:
I seem to have a similar problem - both water and oil temperature gauges go no higher than 70 degrees and the heater is a bit anaemic. Fuel consumtion is very disappointing around town and on a run I get maybe mid 30s at a push. Not impressive for a diesel (2.5TDI tiptronic quattro). I had the cam belt changed last April and the water pump was relaced at the same time. I hope I don't have to have the whole shebang taken apart again for the sake of a fecking thermostat! What a stupid piece of design to have a thermostat buried in the depths of the workings. In the old days it was fitted at the top of the cylider head or even on the radiator where it was easy to get at. Not impressed at all. I really like my Audi but some of the costs caused not by poor quality but by design that precludes simple repairs is unbelievable.
Click to expand...
You lucky it fails open and doesn't let the engine boil ! I agree with you that the v6 is a bit overengineered compared with the older 1.9 tdi engines but its a decent engine in my opinion. It should be really replaced at cambelt time as its easy then. The stat can be replaced without the need to change the cambelt but, when is soo much work involved just to get to it, then why risk-it ? On a different note, you only likely to change the cambelt 2 or 3 times troughout the life of a car...so 4-500 quid at a independent isn't that much !
 
got the same problem on my c5 the heating will only ever get warm not hot and in this weather it's a pain in the backside! Thing is my belts were changed not that long ago and stat at same time so how long till they stop working or could it be something else?
 
Sorry to tell you,

i had the very same issue with my 2.5TDI mate, bad news, it was all down to the thermostat, stuck in the open position, i tried to find out what it could be just like your doing, but there is no escaping it, look at it this way, after all has been fixed, you wont need to worry about the watr pump cam belt pullys of the thermostat again, also think of the cash you will save on the fuel, it will pay for itself in the end and have a great heating system!
 
HerefordQuattro said:
got the same problem on my c5 the heating will only ever get warm not hot and in this weather it's a pain in the backside! Thing is my belts were changed not that long ago and stat at same time so how long till they stop working or could it be something else?
Click to expand...
That's strange because Marius (previous owner) supplied the parts himself and they were genuine audi parts. Are you shure the thermostat is duff ? I did not had a new one fail this soon... Is your water gauge reaching 90 because if it stays smack in the middle then the temp. control flap might be stuck. If you have vcds then you can see the temp. in Celsius wich the ECU sees from the CTS...
 
I also fitted 2 cheappo thermostats on my 98 a4 quattro and a mate's a6 from ECP. 2 years on and they still work propperly... on customer's cars i dont chance-it and allways get genuine ones !
 
adamss24 said:
That's strange because Marius (previous owner) supplied the parts himself and they were genuine audi parts. Are you shure the thermostat is duff ? I did not had a new one fail this soon... Is your water gauge reaching 90 because if it stays smack in the middle then the temp. control flap might be stuck. If you have vcds then you can see the temp. in Celsius wich the ECU sees from the CTS...
Click to expand...


cheers for the reply mate, i was sure you'd said you'd changed the stat with the belts for Marius - yet another reason for me to get hold of VCDS (but cash is tight right now-kids chrimbo presents more important than vcds unfortunately)

what's the temp control flap then?:detective2:

ps i have Elsawin open now looking
 
Last edited:
HerefordQuattro said:
cheers for the reply mate, i was sure you'd said you'd changed the stat with the belts for Marius - yet another reason for me to get hold of VCDS (but cash is tight right now-kids chrimbo presents more important than vcds unfortunately)

what's the temp control flap then?:detective2:

ps i have Elsawin open now looking
Click to expand...

The temp. control flap is the one that mixes cold and hot air to regulate the temp. inside the car hence called "climate control". Sometimes it gets stuck and gives poor heat output. If the gauge temp. stays in the middle at 90 Celsius then suspect the flap's motor. It can be reset with VCDS and sometimes they start working again but i've seen them staying stuck as well wich means replacement is needed. Thing is they not expensive but a right pain to do- one in particular requires dash removal !
 
I'd feared it might be a dash out job!!!!

Gauge sits in the middle at a constant "audi 90 deg" so hope the stat is ok - I wonder if reseting the motor has anything to do with the AC temps not syncronising? i.e. drivers control doesn't alter passengers temp (thought you could reset this by holding down 'auto' but doesn't seem to work)?
yet another reason to buy vcds
 
If the gauge temp sits smack in the middle then the thermostat is working fine so its the temp. flap at fault. If the stat was faulty it would not have got higher than 60-70 Celsius. I have done a thermostat on my allroad last night + the aux. belt tensioner bracket (PITA as the oil cooler needs disconecting and the AC compressor+brackets are in the way) and the power steering pump. The aux. belt tensioner was worn out really bad that the belt would have came off the pulley in the next few days ! It dammaged the casting so it needed a new bracket, pulley and bushes/washers/bolts at about 150 quid in parts ! I towed a passat a few days ago and even with the heavy load the temp did not go to 90 !
 
I know this is a bit of a thread hijack sorry but thought i'd update on my heating issues.

As adamss24 confirmed thermostat problem being unlikely for me and vcds (lite) showed temps of high 80's i started chasing the possibility of heater temp flap problems,
Next problem VCDS won't communicate properly with the HVAC controller so I couldn't analyze fault codes (pressumed this coms issue might be the fault or part of it)

Anyway next line of attack was a coolant change and flush as it didn't look the best (rusty brown), 3 litres of G12+ from the dealer (£14) and some Holts 2 part coolant flush from Halfrauds.
Removed undertray and found the very handy drain tap which fits a garden hose perfectly, and emptied the old crap, and flushed through a few times then used Holts flush part 1 which requires a half hour drive, then flush again while warm before using Holts flush part 2 which neutralizes part 1 and then flush and flush and backflush (took me all afternoon on and off and would cost a fortune in garage labour rates!)
Also removed the coolant reservoir and used bleach and rice to clean the crap out of this before refilling the system with fresh G12+.
Run up to temp and then bled through the hole in heater matrix top hose (in scuttle)

Long long job but finally low and behold I have decent heating so worth the effort
 
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