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RS2'd 93 UrS4 5 spd sedan
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After-run Auxiliary (additional) Coolant Pump and Switch Info
Originally posted by Biggss2
hmmm, Johne, maybe im not reaching temp enough to see fan/hear the afterrun activate, however i do hear it upon turning on the ignition!
The after-run pump (and the related rad-fan) should not come on unless triggered by a temp switch. Here is some after-run pump info (updated with Thuppu's photo and Bosch PN)
The Audi Enthusiast website. Forums for all Audis including A4, S4, A5, S5, A6, S6, allroad, A8, S8, TT, R8, Q5, Q7, 4000, 100, 200, v6, v8, vintage, local forums
RS2'd 93 UrS4 5 spd sedan
94 UrS4 V8 6 spd manual avant
reading that again, 110degrees, dont think iv let my car get that warm, the heaters come on before then! maybe why ive never experienced the afterrun!
A properly operating thermostat will keep the coolant at just under 90 C while the engine is running. However, if you have run the car hard and the turbo, etc. are well and truly heated, when you turn the ignition off, the heat stored in the metal of the head, manifolds, etc, will quickly warm the water in the water manifold and trigger the 110 C switch on the water manifold. This typically occurs in the summer. You have driven the car and didn't get a chance to drive slowly for a bit before you shut the engine off. You lock the car and start to walk away. You don't get 3 steps before you hear the after-run rad fan (and pump but the sound is drowned out) come on. With a properly functioning 324 (etc) relay, these stay on for no longer than 10 minutes. If the relay fails closed, it will run the fan and the pump until the battery is completely flat.
RS2'd 93 UrS4 5 spd sedan
94 UrS4 V8 6 spd manual avant
As above it needs to be very hot for the the system to kick in, there is a thread somewhere on the forum with part numbers for sensors with lower temp values to make the system come on sooner. Think they switched at 100c instead of 110c.
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