A4 AFN very slow to warm up

[Mikkijayne]

Hi all,

Background: I have two A4s and an A6 all with AFN engines. The two A4s are identical - same year, same spec, same ecu, standard 110hp engine. The A6 is tuned to >200hp with bigger everything. EGR is disconnected on all of them. They are all timed in-spec with VCDS.

The A6 and one of the A4s are blowing hot air within 2 miles of my house, and up to temperature a few miles after that. The problem A4 doesn't blow hot air until 10-12 miles, and needs properly thrashing to get up to temperature.

The only difference between the three is that the problem car still has its viscous fan whereas the good ones have electric instead, but I don't see how that should affect the warm-up when its driving so have mostly ruled it out.

The problem car has a good water pump, new thermostat, new rad, new sensors, good flow through the heater core, fresh coolant. VCDS and a hand on the hoses match what the gauge shows. The coolant glow plugs are working fine, although with air temp at 14C none of the three cars are using them.


I'm stumped now. Anyone got any ideas please?

 

[JB05]

I'm not sure what you mean by viscous fan. Viscous- having relatively high resistance to flow according to an on-line dictionary. Is this a belt driven fan? 10 minutes or more is normal for my A4 to put out any kind of heat in urban, stop-n-go driving.

 

[frosz]

Your Audi's is probably equipped with extra heater. It looks like a glowplugs in to the coolant. That could malfunction and result in longer warm up.

My AFN engine is not equipped with a extra heater and it can take 5-15km on the highway to get get it up to 92c (I have a higher temp thermostat).

It looks like this:

 

[Mikkijayne]

Yeah it has that. Its all working fine, but doesn't operate when the intake air is over 5*C. Its currently at 14, so that system isn't switching on, although output tests confirm it is working fine. All three cars have that though, and none of them are using it at the moment.

JB05 - yes, belt driven fan with a viscous coupler. The spiky thing under the alternator:

Thanks for the ideas! Keep 'em coming

 

[frosz]

Is the EGR working? It helps to speed up the heating of the engine.

 

[Mikkijayne]

Disconnected on all of them. I'm going to reconnect it on the problem one tomorrow and see if it helps

 

[DPM]

I'd query the fan clutch regardless of logic, tbh. I replaced the V-fan with an E-fan setup in an old Toyota I once had and warmup timmes did shorten. Remember that even when a viscous is "unlocked" it's still pushing a fair bit of (cold) air...