csh1234 Posted November 21, 2007 Report Share Posted November 21, 2007 Hi all, just bought a 4.2Q Sport, 1998, full Audi SH, 113k miles. Driving around today I noticed that the temp guage reading varies between approx 70 degrees when traveling at 60 plus and increases to 90 (but no higher) when stationary or moving slowly. I am guessing this is not normal and probably sounds like a dodgy thermostat? Does this sound likely? Is there only one thermostat? How difficult is it to change? Any advice on getting a workshop manual? Cheers Chris Link to comment Share on other sites More sharing options...
grdunn123 Posted November 21, 2007 Report Share Posted November 21, 2007 Normally sits at 90 degrees when warmed up regardless of speed. Could be a number of things. Link to comment Share on other sites More sharing options...
Joylove Posted November 21, 2007 Report Share Posted November 21, 2007 If you read your manual you will find that's normal. Link to comment Share on other sites More sharing options...
grdunn123 Posted November 21, 2007 Report Share Posted November 21, 2007 Welcome to the forum by the way! You'll be asking loads of questions because you've bought a wonderful piece of German engineering! It's like no other car! Link to comment Share on other sites More sharing options...
csh1234 Posted November 21, 2007 Author Report Share Posted November 21, 2007 Many thanks! I certainly love the car (at the moment!) - amazingly different to our previous car - a 540i, which (on paper) should be reasonably similar. The A8 is more relaxing to drive, but also feels more sporty! Thanks for the replies - I did see the bit in the manual, but thought that it ment that the temp 'could' rise into the right hand side of the guage (above 90) under significant load, I expected the temp to get to 90 then stay there under normal driving conditions.....the A8 also takes much longer to warm up than the 540... Cheers Chris Link to comment Share on other sites More sharing options...
grdunn123 Posted November 21, 2007 Report Share Posted November 21, 2007 Yeah it takes a few miles to reach temp. Mine (2002 4.2QS) sits bang on 90 degrees when warmed up. Link to comment Share on other sites More sharing options...
Joylove Posted November 21, 2007 Report Share Posted November 21, 2007 Mine drops to 60 on the motorway. But then I don't speed and it's minus eleventy degrees out there. Soon goes back to 90 after I exit the m'way. Link to comment Share on other sites More sharing options...
LostKiwi Posted November 22, 2007 Report Share Posted November 22, 2007 Mine sits very low at motorway speeds too... to the point where I was going to replace the thermostat this weekend (but not sure if there is any point now!). I've also noticed that while the rngine has no heat (ie on the the motorway) the car suffers badly from misting up. Stop and let the car warm up and misting goes away...? Seems to me the A8 is overcooled - I may try blanking part of teh radiator off to see if it has a benefit... Link to comment Share on other sites More sharing options...
Atomic Posted November 22, 2007 Report Share Posted November 22, 2007 Well if you insist in living in a cool climate Kiwi!!! Link to comment Share on other sites More sharing options...
csh1234 Posted November 22, 2007 Author Report Share Posted November 22, 2007 Seems to be a split in how different cars are behaving. I expected the car to get to 90 quie quickly and stay there regardless of ouside temp (within reason!) and driving conditions. I would have thought the thermostat 'should' prevent overcooling. Assuming the thermostat closes when the temp falls much below 90, which would seem reasonable, the remaing cooling would be due to oil cooling, using the interior heating, and airflow over the engine. I would not expect the effect of these to be suficient to significantly affect the temp of the engine.... Link to comment Share on other sites More sharing options...
thenamesross Posted November 22, 2007 Report Share Posted November 22, 2007 Mine gets up to 90 pretty quick and stays there regardless of driving conditions. If its dropping to 60 on motorways etc it does sound like the thermostat might be playing up - but thats just my opinion... Link to comment Share on other sites More sharing options...
cheet22 Posted November 22, 2007 Report Share Posted November 22, 2007 I absolutely don't want to alarm you here - just that mine did this for a bit, then after a while started rising above 90 when I was at speed (ie the opposite to you are seeing now) I replaced the viscous fan, which kinda helped, but did not resolve the problem. In the end I got the whole front end done (cambelt, pump, thermo) for a 'scary cost' to find it was indeed a dodgy thermostat. I'm no mechanic, but changing the thermostat itself I believe is no easy job, and needs lots of stuff removed, hence I had to go the 'replace the lot' route. Since it was fixed, it now rises to 90 and sits dead on regardless of speed, motorway or otherwise. Sound though, that other folk are seeing various things, so maybe it is indeed normal, and I mine was 'normal' then went 'bad' Link to comment Share on other sites More sharing options...
Malairt Posted November 22, 2007 Report Share Posted November 22, 2007 My 133k mile 4.2 1997 stays at 90 whether in town or on the regular journey from Cheshire to West Lothian Link to comment Share on other sites More sharing options...
csh1234 Posted November 22, 2007 Author Report Share Posted November 22, 2007 Thanks for all the comments, I am thinking that the evidence suggests that the thermostat is not working correctly albeit has not (yet) failed completly. May I ask TheYeti roughly how much a 'scary cost' would be? The annoying thing is that the service history shows a cambelt change at Audi at 90k (now 113k) at a huge cost (cambelt bit approx £700, total bill approx £1700, with new brake bits and goodness knows what else..!) but no mention of a waterpump or thermostat, which I am beginnng to understand would have been sensible to replace at the same time... Link to comment Share on other sites More sharing options...
cheet22 Posted November 23, 2007 Report Share Posted November 23, 2007 To replace the water pump, cambelt, tensioners etc, thermo and viscous fan (all original parts) cost me just shy of £800 all in. The viscous fan was £150 tho from Audi. This was of course a good independant I now have in Glasgow, whom I've now spent some £3000 with over past 4/5 months - so he was kind to me! Be choosy tho, I took it to another guy and he wanted £1400 for same job. Lord knows what Audi themselves would want. This is for a 3.7 QS facelift (2000) - not sure if its all exact same but think its very much so. One thing - I asked him to replace water pump as he was doing all this, even though he suggested it had metal impellers on these - but I thought otherwise - turned out he was right and it was metal, so water pump was actually fine. If yours is a slightly older 4.2, I think I read on here that those were plastic blades, so if thats true, I would replace the pump for sure, just in case. As I said before, don't jump to this conclusion, but it deffo sounds like the way mine was behaving. One thought, if temp drops at speed, does that not signal that the viscous fan might be duff, as its spinning too much when it dont need to? Search on here for viscous, loads of posts - thats much easier to replace on its own. Use the "carrot" test, worked for me! I really hope you dont need to go this route. Good luck. Link to comment Share on other sites More sharing options...
10bellys Posted November 23, 2007 Report Share Posted November 23, 2007 My 160k miler S8 gets quickly to 90 then sits there all day.( Read that as MPH or degrees c) Link to comment Share on other sites More sharing options...
topgolfer1 Posted November 23, 2007 Report Share Posted November 23, 2007 My 1998 2.8 sport with 118k gets up to 90 degrees and then stays there,regardless of speed etc Best of british with yours Link to comment Share on other sites More sharing options...
LostKiwi Posted November 23, 2007 Report Share Posted November 23, 2007 Bought a thermostat today... weather permitting guess what I'll be doing tomorrow...... Link to comment Share on other sites More sharing options...
csh1234 Posted November 24, 2007 Author Report Share Posted November 24, 2007 Good luck with the replacement - hope its not too cold - I really hate that sort of job when you can't feel your fingers! I would be very interested to know how much has to be dismantled to get to the thermostat, and any tips - I am pretty sure I will be doing the same job in the near future.. Link to comment Share on other sites More sharing options...
Ska Posted November 24, 2007 Report Share Posted November 24, 2007 [ QUOTE ] My 1998 2.8 sport with 118k gets up to 90 degrees and then stays there,regardless of speed etc [/ QUOTE ] Same here but 140k on the clock Link to comment Share on other sites More sharing options...
LostKiwi Posted November 24, 2007 Report Share Posted November 24, 2007 Right... looked at this and it would seem very straight forward. Remove all the plastic covers from the top of the engine. Remove the hoses at the front of the engine (one doesn't need to be removed but do it just to gain a bit more access, the other goes onto the thermostat housing). There are 2 T27 head bolts at around the 2 and 8 position on a clock face. Remove these and it loosk like the whole lot comes out. I've had to abandon mine for the moment as my t27 torrx snapped so its off to Hellfrauds for a new one. But since its also started to chuck it down not sure if I'll get back under the bonnet today.... One thing though. With the thermostat hose off (and a whole lot of water everywhere) you can put your finger onto the thermostat top. Feels like mine was closed (as expected since the engine was stone cold).... More later! Link to comment Share on other sites More sharing options...
csh1234 Posted November 24, 2007 Author Report Share Posted November 24, 2007 Sounds not too bad - did you remove the cambelt? Link to comment Share on other sites More sharing options...
LostKiwi Posted November 24, 2007 Report Share Posted November 24, 2007 Nope... never even removed the cam belt covers... Link to comment Share on other sites More sharing options...
csh1234 Posted November 24, 2007 Author Report Share Posted November 24, 2007 Thats very good news! Link to comment Share on other sites More sharing options...
LostKiwi Posted November 24, 2007 Report Share Posted November 24, 2007 Hopefully tomorrow I can put together a quick how to with pics.... Link to comment Share on other sites More sharing options...
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