A4 engine slow to heat up.

[boz the dog]

Hi All,
Checked thermostat and everything else OK, back flushed and all that. I drive 5 miles and it heats to 70deg and another 5 and it eventually reaches 90deg. Feet are freezing. Any ideas please.

 

[Siena]

Could be the control flap's jammed in the "cold" position?

 

[boz the dog]

Thanks Siena, I'll have a look.

 

[marms]

The heater actually has its own matrix. When you back flushed did you get much junk out of the radiator? If so then the heater matrix may be blocked.

Having said that, it is more likely to be the control flap.

Good luck, hope you get it fixed as it's getting cold out there.

 

[boz the dog]

Hi guys, the back flush was clean and the heater controls are all Ok! I am now looking at engine management and thinking it could be the exhaust gas recirculation valve has gone wafu. This might explain the temp guage rising slowly. Thanks and yes its getting parky out there.

 

[mwstewart]

Check the simple things first..Thermostat stuck open?

 

[boz the dog]

Hiya, I've checked the thermostat which opens at the right time and the temp guage agrees. The heater unit and matrix are both A1. As the engine is slow to warm me thinks it has to be something to do with the air intake which has a vacuum controlled bypass from the turbo manifold. There are two sensors and a switch for the vacuum on off. If it continued to draw cold air from starting, instead of hot, would it take longer to heat up? Thanks guys.

 

[AndyMac]

I'd replace the temp sensor before doing anything else - this is a common fault and can cause all sorts of strange behaviour - cold running, stalling, running like a dog etc. For £20 I'd rule that one out before going any further.