low water temp

[rox]

hi just got my oct vrs mk1 and the temp never goes above 70 on the guage even when it traffic would people say stuck thermostat or temp sender unit?

anyone had the same problem getting quite bad fuel consumtion aswell no matter how i drive cant seam to get it about 30 over a journey it tends to be around 25-28 average

thanks

[SideshowBob]

Hiya mate

Almost certain that this will be a sticky thermostat. I replaced mine a few weeks ago because it took an eternity to warm up and it wouldn't get above 80deg unless caning it. Fuel consumption was poor-ish too. After replacing the stat and o-ring seal it now hits 90deg much quicker than before and stays there regardless of the type of driving I'm doing.

A how-to guide can be found HERE

I didn't bother removing the dipstick cover, it didn't get in the way at all. However I did remove the connections to the alternator and cable-tie them out of the way. If you're half decent with tools and take your time, you should be fine. Mine needed about 250ml of G12 coolant afterwards to top up.

If you get the job done at a main dealer I believe it's quite expensive because they remove the aux belt, alternator and possibly drain all the coolant too.

[David 8]

This is the forth one too my knowledge in recent weeks :wonder:

Mines in monday for a swap

CBA doing it myself as I ain't got time and the weather is too cold lol

What mileages have you fellas got and what year cars out of interest ???

[mbames]

Funny, I would go for the reverse and say a faulty temperature sender was the issue. With a faulty thermostat the car should eventually get up to temperature. If the car thinks it is operating at a colder temperature than it really is that would cause a lower fuel consumption.

I changer my sender unit on my 110TDi a couple of years ago and managed to do it without needing to top up the coolant. Removed the clip holding it in, pulled it out, along with the o-ring, and popped in a replacement (green) unit. I was changing mine due to turbo issues, rather than the guage reading low. Note these senders have 4 contacts - one set feed the ECU and the other the guage on the dash.

[SideshowBob]

I think with either of these problems (stat or sender) the good bit is that both parts are cheap if you can do it yourself, and quite easy jobs to carry out. I did the stat and fully expected to have to do the sender too, in fact I have a brand new sender in my garage unused but I'll keep hold of it because sooner or later it will need going in...

When I had a failed sender in my Golf it would wander wildly from 70-100deg within a couple of seconds, it was obvious that the coolant temp could not change so much in such a short space of time.

At this time of year if the stat is knackered and stuck open it really will struggle to get up to temp even in traffic imho, I still put my money on it being the stat But I can see where you're coming from. On my Octy in 10-15deg ambient temps it would take 15-20 minutes of gridlock traffic before it got up to 90deg. As soon as I was clear or in any other kind of driving it would stick between 70-80deg.

[David 8]

My sender went mental and did the rev counter impression.

I'm with Bob on this one :yes:

[eltax90]

Folks. I posted about this a couple of weeks ago, my Wife's A3 100 TDi has done the same thing. Temp gauge up and down between cold and 90, temp sender changed recently whilst diagnosing another fault. I'm going to change the Thermostat, and probably all the coolant, since the A3 is a recent purchase, i've no idea of the age of the current coolant, so in for a penny etc.

My question is around the G12 coolant (thought i'd reply in here as the OP might be interested). Do i have to buy G12 coolant from a dealer, or will GSF/ Halfords RED do the job? Also, once drained from the bottom of the radiator, is there a procedure to re-fill and bleed the cooling system?

[David 8]

I'm not entirly sure but I know you shouldn't mix the coolants, not sure about using fresh though, you may be ok doing that but don't quote me on that :wonder:

[SideshowBob]

For what it is, and the potential problems of mixing G12 with anything else (can turn to gel) I would stick with G12. It only costs about £6 a litre so no big deal really...

[Fodenman]

Not sure about the gel aspect,but if you've got G12 in there now,then replace with same.

It's cheaper in the long run as it's long life and should last 5 years or so,plus it's kinder to hoses and O rings.If checked at service time with a refractometer,it could go even longer.

The real no no is mixing OAT (G12) red/pink,with IAT (G11) blue/green.

The IAT will degrade the OAT so depending on how much contamination there is,you could have a life of 2,3,4,or maybe five years,pick a number.

As to flushing to change from one to the other,you don't want to be doing it at this time of year.

Using hose pipe,remove rad hoses and flush rad,top to bottom.Flush out engine block.

Still not cold enough for you?There's more. :'(

Remove (water) coolant hoses from oil cooler and flush.

If using what's in there,just drain and refill.

When refilling,fill slowly at expansion tank while squeezing bottom hose to expell air.

When bubles have stoped at tank,fill to max mark,and replace cap.

Start engine and run until fan cuts in.Watch temp gauge to see that temp doesn't go too high (if it does,you've got air lock).

When fan stops,stop engine and allow to cool.

When cold,top up if required.