Hi all,

my temperature gauge sits on minimum all the time if the ambient is below about 12-14 deg C.

I did have an intermittent cold start problem which was cured by fitting a new temperature sensor (coolant) about 6 months ago.

So I am thinking that either this new CTS is a dud, or I have a thermostat issue.

Thinking of isolating the problem by dipping the CTS into a kettle that boiled 2 minutes ago and see what the car reads 

 - should be 90-95 degrees, i.e. normal operating range.

But if the CTS is found to be OK, how bad a job is it to change the thermostat on the V6??

Edited 21 October, 201312 yr by oh_superb

Checked the resistance across the pins: A-B is 1.6 kOhm and C-D is 3.7 kOhms at approx 30 deg C coolant.  So clearly C-D broken.  That's the one read by the dash gauge.  On my old sensor that failed 6 months ago (ECU seeing wrong temp causing cold start problems) pins A-B were at 800 Ohms at 30 deg C and C-D at 1.6 kOhms.  So last time A-B thermistor failed and this time C-D.  

Glad it's not the "stat", see a video of it being changed, not something I'd fancy doing!!

Something makes me think it's not two 10mm bolts and about 5 minutes?  :think:

 

Gaz

I think it is the thermostat after all!!  Apparently, according to info I have found on the web, the two pairs of pins on the CTS are not meant to have the same resistance anyway!

Will check with VCDS what temperature the ECU sees after a few miles of driving and cross check against the dashboard (constantly at 50!), but I reckon I have a stuck stat issue thats progressively been getting worse over the last year.

Having seen what many people say on Audi forums, the V6 is renowned for this, and it is also a proper b@stard of a job, t/belt off, water pump out, major job it is, and with winter coming in I will either have to wrap the front of the car in thick cardboard to try and keep some heat in the engine (and cabin!) or just bite the bullet and do it.

With the age of the car, there is no way I am paying someone around 7 hours labour for this job.

Can I get away with minimal / makeshift cam locking tools, or do I need to invest?

I was thinking of marking up the belt and cams and crank with paint dots and re-assembling it all in the same position, but as I don't want the cams to rotate, what is the best way of locking?

I have access to a machine shop who could turn out on a lathe any diameter tool.  On some cars I know you can just use a standard 6 mm drill bit, is that applicable on the V6 or is it a special case.

Cn you get away with not locking the crank or is that a bad idea?  Is it locked on the rear end or the front?

Any info is welcome.  I am thinking of tackling this this weekend!

I don't suppose it's worth considering if you could fit an in-line thermostat on the top or bottom hoses as a potentially simpler solution?

 

Nearest example of what I mean:

http://www.the75andztclub.co.uk/forum/showthread.php?t=68468&page=12

 

Good luck anyway with what doesn't sound like a lot of fun to me  :wonder:

 

Gaz

Thanks V6TDI!

It was actually today that a colleague (quite switched on, into kit cars and racing) suggested this course of action, and now you have suggested something along those lines too.

Well worth considering, as a "temporary" fix until I have completed another 30k miles and the timing belt/water pump is due to be replaced anyway at which point I could tackle the t/stat!

 

Just not sure if 1"1/4 is the right size for the hose we have?

Also, they have 85 and 91 deg C stats (Chevy spec), not sure which one would be better TBH, I thought the V6 was meant to run at around 88?

Alternatively I could design one around a standard thermostat for our engine and get a local machine shop to machine on a lathe.  That way it will have exactly the flow rate required and open and close at the right temperature.

Edited 25 October, 201312 yr by oh_superb

It won't work.

 

A thermostat has to have a circulation of coolant around the sensing element in order to be able to react to coolant temperature - which is its job. In the engine, the thermostat is fitted so that the bypass coolant flows around the sensing element when the main valve controlling the flow to the radiator is closed. When the engine gets very hot, the second valve on the thermostat closes off the bypass so that all coolant flows through the radiator.

 

Bodging these engines doesn't work - they're not Ford or GM designs.

 

rotodiesel.

Roto

 

Could he tee a smaller bore pipe off elsewhere (maybe tap into the heater matrix pipework?) for the circulation required?

 

I've certainly seen external thermostats with three outlets.

 

I wasn't thinking about bodging, merely that it's an awful lot of work just to get the coolant flow thermostatically controlled.

 

Gaz

It might work, but designing cooling systems is not straightforward. Water flows and vapour/airlock venting are critical if you want to avoid a BL K series disaster - they just had no idea. If you start a major redesign, you might end up with unintended coolant flow paths through what would effectively be 2 bypasses. Water has a tendency to operate as a fluidic bistable when faced with 2 path choices. Flow through each is unpredictable and variable.

 

Usual VAG advice - choose your engine carefully and don't bodge.

 

rotodiesel.

Edited 26 October, 201312 yr by rotodiesel

Thanks to both of you for the advice offered.

I think I might be going down the route of a replacing the original stat, but don't have the torque settings for the bolts that will need to be coming out.

In particular, crank pulley damper bolts, etc.  Is there a reference document someone has available for these?  Does ETKA have torque specs?

Once the components that contain coolant are removed, and re-used, what sealing material is recommended for these engines?  I might I might get away with not having to remove the water pump, but the thermostat outlet manifold will need to come off of course and be re-fitted.

Finally, to whip the timing belt off, and ancillary belt, is there a special procedure to avoid damaging the tensioners, or is it just a matter of pull one way to release tension and then reverse to re-assemble?  Do I need to insert a pin into them to be able to "fire" them out again on re-assembly?

Basically any info/advice will be appreciated.

I think based on some 2.5 tdi guides I have seen on the net (very incomplete though, hence so many questions), ancillary belt comes off, (I will use the opportunity to change the alternator pulley which I believe is still the original at 120k miles, and was noisy once), then a big plate comes off behind which the t/belt sits.  It looks like the t/belt might actually not have to come off if I can access the two screws holding the thermostat outlet manifold, but I want to be prepared in case it does with tippex, torque settings and all the tools I might need, as the car is a daily driver and cannot afford to keep it off road for a week as the other half might not appreciate me borrowing her Honda!

I understand I need a 32 mm spanner for the fan? 

Have found a good guide (in German) on how to do the t/belt change.

All makes sense.

It's just the tensioner and damper pre-tensioning that I don't quite get.  I guess it must be quite important to do that step right.

Is it absolutely necessary to remove the right hand camshaft sprocket?  Or can the belt be wiggled off both sprockets just by loosening the tensioner?  Is that possible?