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VAG TDi Coolant temp needle moving
Kriss - 4/1/11 at 12:59 PM

2003 1.9 TDi audi A4 B6 Chassis

Following my last thread, I have replaced the thermostat as the car was only getting about halfway to its peak operating temprature on the guage. (I ruled the temp sender out on the basis it was replaced 8 months ago)

The car now is taking a few miles (5-6) I would say and needs to reach a half decent speed for a while to reach 90 degrees. Before it was not moving past 70 degrees after 30 miles of motorway use.

My concern is with light town driving, its still taking an age to warm up on the guage, and ten miles across south west london at the weekend still didnt reach 90 degrees.

My suspision lies with an airlock somewhere.

When I replaced the stat I lost no more than 2 litres which was replaced with nice new pink audi approved mobil 1 coolant mixed 50/50

There is a bleed hole on the top heater hose into the cabin (a small pin sized one which you have to wiggle the hole away from the mount enough to uncover the hose but still flow the majority of its contents. Can I do this when hot, or when is best to play with it.

Also, on my 10 mile drive the header tank was cold to touch after the drive.

britishtrident - 4/1/11 at 02:15 PM

What temperature was the thermostat you fitted ?

nick205 - 4/1/11 at 02:29 PM

Just a thought (and I suspect not) but is the car fitted with an aux heater?

See recent threads on the subject...

http://www.locostbuilders.co.uk/viewthread.php?tid=147782

http://www.locostbuilders.co.uk/viewthread.php?tid=147566

I'm about to replace the glow plug in the aux heater in my Alhambra which should hopefully resolve my issue with engine warm up.

By coincidence I spoke to the independant VAG specialist garage next to work earlier today on this subject (they smoke outside our back door). He agreed with my diagnosis on the Alhambra and also commented that with such low ambient temps many diesels will struggle to reach 90, particularly at low speed/light load. He cited his own 02 plate A4 as not shifting from 50 on his 5 mile route to work.

Chippy - 4/1/11 at 02:58 PM

I run a Citroen HDI and that has the same problem, takes miles to get of the stop, and it just runs around 65-70 all the time, the only time it actually gets up to 90 + is stationary in traffic. Once on the move again it promptly goes back to the 65-70 mark. I would add that it has always done this, my local garage guy just said "well it's a diesel mate, thats what they do", :-) Cheers Ray

Kriss - 4/1/11 at 03:03 PM

nick - does the aux heater have anything to do with water temp in the engine? I always thought the engine warmed the water that runs these heaters in the cabin?

stupid question so sorry.

New stat is 87 deg, same as the last one.

The stat change has deffinately improved the situation massively as far as I now reach 90 degrees

auroan - 4/1/11 at 03:10 PM

VAG diesels do take a while to warm up. How clean was the coolant when you took it out ? Also VAG water pumps are prone to failing (the pump vains are plastic and eventually break up).

Kriss - 4/1/11 at 03:13 PM

what would the key sign of a broken pump be though? I would expect high water temps?

also want to know what blasting the heaters reduces/slows water temp increase on the guage?

Stott - 4/1/11 at 03:15 PM

Drove my car with the same engine to cardiff the other day (16 miles) and it didn't warm up. When the gauge got to 1/3 hot I put the heaters on and it cooled it back down. When I drive to work in the morning it doesn't warm up until I get there which is 9 mile, however it's better on the way home as it's uphill.

Anyway, mine is ok in the summer but much worse in the winter, yours might be the same. 10 mile to warm up a VAG 1.9tdi is not a lot when it's cold outside.

ATB
Stott

Stott - 4/1/11 at 03:16 PM

quote:
Originally posted by Kriss
what would the key sign of a broken pump be though? I would expect high water temps?

also want to know what blasting the heaters reduces/slows water temp increase on the guage?


because you are moving air past a small rad inside the car full of coolant thereby cooling the engine down.

auroan - 4/1/11 at 03:17 PM

quote:
Originally posted by Kriss
what would the key sign of a broken pump be though? I would expect high water temps?



Initially the symptons are what you're seeing. Then all of a sudden the car will overheat.

britishtrident - 4/1/11 at 03:25 PM

I may help to blank off roughly 50% of the radiator intake --- just remember to take it off when ambient goes above about 8c.

britishtrident - 4/1/11 at 05:51 PM

quote:
Originally posted by Chippy
I run a Citroen HDI and that has the same problem, takes miles to get of the stop, and it just runs around 65-70 all the time, the only time it actually gets up to 90 + is stationary in traffic. Once on the move again it promptly goes back to the 65-70 mark. I would add that it has always done this, my local garage guy just said "well it's a diesel mate, thats what they do", :-) Cheers Ray



No matter what your local garage tells you classic thermostat problem symptoms ---- by and large these days most people in the spanner end of the motor trade aren't much brighter than tyre fitters.