Audi A8 This full sized Audi A8 sedan offers interior luxury and spaciousness comparable to any car in the full sized luxury sedan class

Thermostat Change A8 BFM

Old 12-04-2010, 01:22 AM
1st Gear
Thread Starter
Join Date: Nov 2010
Location: Orange County
Posts: 59
Default Thermostat Change A8 BFM

How long does it take change the thermostat on the A8 2004 BFM engine. Any special equipment needed?

Reading the forums sounds like have a thermostat issue. Here are some pictures of the temp. It goes up and down like a yo-yo. No coolant loss at all, once very nearly hit the red zone, but backed off. Strange?

I have had the car overheat 6 months ago when I had a hole in the expansion tank. So I have seen the steam and pouring out the red overheating sign flashing in the dash.

But the needle going from 1/2 to 3/4 back to 1/2 way, has me going crazy, any idea where it's supposed to stay under normal operating conditions? (the flash did not fire in one the pics)
Attached Thumbnails Thermostat Change A8 BFM-heat1.jpg   Thermostat Change A8 BFM-heat2.jpg   Thermostat Change A8 BFM-heat3.jpg   Thermostat Change A8 BFM-heat4.jpg  
Old 12-04-2010, 01:22 PM
1st Gear
Join Date: Oct 2008
Location: north nj
Posts: 23

Thermos are notorious on the A8s for failing and R/R a thermo is 3/4 the way to a new timing belt - if you are close to belt change time, bite the bullet and do the entire job.

But, if you had a coolant leak in the past and have had the bouncing temp since, I would suspect a pocket of air in your coolant system, reference your Bentley manual to bleed the air out of the system (you do have one, dont you? )
Old 12-04-2010, 05:26 PM
2nd Gear
Join Date: Jun 2010
Posts: 624

Yep , the thermo is buried on the front of the engine, behind the timing belt on earlier engines and I assume similar on yours. Changing does generally require all the special tools used for the belt change, since it has to come out of the way to get to it.

A really inconsistent needle can also be a bad coolant temp sensor.
If you have a bad thermostat and temp goes back down, it should do it for a logical reason...higher rpms and/or heavy heater use will temporarily send the temp down some (high heat, high fan speed is agreat emergency cooldown method...common used used by racers as an extra radiator). But if the temp needle drops back for no apparent reason, it may be the sensor...or, in rare cases, an intermittently sticking thermostat... possible but not likely...they usually stay stuck open or closed.

And yes, A8's are notorious for thermostat failures...mine was on it's 3rd before 100K miles.

Last edited by silverd2; 12-04-2010 at 05:30 PM.
Old 12-05-2010, 11:21 PM
1st Gear
Thread Starter
Join Date: Nov 2010
Location: Orange County
Posts: 59

I checked the Bentley manual, and bleed the air out of the cooling system, not a huge amount, but made a big difference on temp needle, staying around the half way mark now. Easy fix I hope. I shall monitor for the next week.

I have ordered the TB and thermostat, any idea where I can buy the special tools for this change, at least I will have all the bits to do the TB job, in the future.
Old 12-06-2010, 11:40 AM
2nd Gear
Join Date: Jun 2010
Posts: 624

First, rents the tools BUT with a have to buy the entire belt kit from them first and another catch to that: their kits tend to be "overkill", include a lot of parts that many people don't change (myself included): cam seals, crank seal, all rollers, tensioners, water pump, etc ( I DO recommend water pump, while you're in there).

I buy most special tools from Ebay...actually discount tool companies that use Ebay for sales (like Zdmark, El Paso Tools, etc) with very good results at great prices. Take the tool numbers out of Bentley and punch those into Ebay, Google or whatever and you'll find suppliers. Full price for exact factory tool is outrageous and unnecessary.

Last edited by silverd2; 12-07-2010 at 06:05 PM.
Related Topics
Thread Starter
Last Post
B7 Models
09-11-2014 05:02 PM
Audi A6
09-23-2012 04:03 PM
DIY - Do It Yourself
03-07-2009 10:22 PM
Audi A4
01-21-2008 03:26 AM
Audi A4
02-08-2006 08:25 PM

Thread Tools
Search this Thread
Quick Reply: Thermostat Change A8 BFM

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to and affiliated sites.