Porsche 993, Advice please. Troubleshoot, calibrate, diagnose.

[BigBleBill]

Advice please. Troubleshoot, calibrate, diagnose.
Loud humming sound like a fan behind dashboard. Much louder under bonnet than inside the cab. Only when engine running. New Fuel Pump fitted 1800 miles ago.
Is this an easy fix ?

 

[sday12]

It’s the fan in the air conditioning control unit. It gets dirty, if you clean it it will stop.

 

[ToreB]

Climate Control Unit fan. The motor bearings wear out and it starts to rattle, and the motor magnets weaken and the motor stops.
It is time for changing the fan. Be seated if you call a Porsche service centre and hear the price. An alternative is found here:
https://www.bergvillfx.com/products/ccu-fan-964993
The fan is important for the CCU to measure and regulate the cabin temperature. Please be aware that the CCU with fan is supposed to stay on for up to 20 minutes after ignition off to ensure correct cabin temperature control after short stops.
Cheers,
Tore

 

[BigBleBill]

See video attachment.

 

[BigBleBill]

Climate Control Unit fan. The motor bearings wear out and it starts to rattle, and the motor magnets weaken and the motor stops.
It is time for changing the fan. Be seated if you call a Porsche service centre and hear the price. An alternative is found here:
https://www.bergvillfx.com/products/ccu-fan-964993
The fan is important for the CCU to measure and regulate the cabin temperature. Please be aware that the CCU with fan is supposed to stay on for up to 20 minutes after ignition off to ensure correct cabin temperature control after short stops.
Cheers,
Tore

Thanks Tore. It's much more noisy from inside the bonnet however. Much more than inside the cab. I was thinking it was something to do with the fuel pump. Can I send you a video ?

 

[Gwsinc]

Consistent loud humming may well be the fuel pump. With the standard DME relay the pump only comes on with engine start, there is no priming, so aligns with what you've said.

As in the comments above, the internal CCU fan can continue for up to 20 mins, so if the noise stops every time the engine is turned off then I don't think its the internal CCU fan.

When the pump was done did any of the fuel filters get replaced? There are two, a 'normal' one in the engine bay and another at the base of the tank, this one is rarely replaced, certainly not routinely.

To test the pump you can use a jumper wire to activate the fuel pump when the car is off, see the first part of this: https://www.pelicanparts.com/techar...elivery_Tests/20-FUEL-Fuel_Delivery_Tests.htm

If the noise is indeed the pump, I would replace both filters alongside the pump to be sure. The state of the in-tank filter will dictate wether or not you need to 'flush' the tank to remove any varnish or debris.

Hope this helps.

 

[BigBleBill]

Consistent loud humming may well be the fuel pump. With the standard DME relay the pump only comes on with engine start, there is no priming, so aligns with what you've said.

As in the comments above, the internal CCU fan can continue for up to 20 mins, so if the noise stops every time the engine is turned off then I don't think its the internal CCU fan.

When the pump was done did any of the fuel filters get replaced? There are two, a 'normal' one in the engine bay and another at the base of the tank, this one is rarely replaced, certainly not routinely.

To test the pump you can use a jumper wire to activate the fuel pump when the car is off, see the first part of this: https://www.pelicanparts.com/techar...elivery_Tests/20-FUEL-Fuel_Delivery_Tests.htm

If the noise is indeed the pump, I would replace both filters alongside the pump to be sure. The state of the in-tank filter will dictate wether or not you need to 'flush' the tank to remove any varnish or debris.

Hope this helps.

Thank you, very helpful.

 

[stewart rix]

Could be the brake booster pump if your 993 is a 4WD variant. You would hear a low (loud) hum/buzz on start up for maybe 20 secs or so if it's operating normally. If it keeps going, you've possibly got a faulty pump.