Electric axiliary coolant pump

[Nigel1959]

I have a 2018 2L.eco blue custom. A previous owner has bypassed the auxiliary coolant pump, all seems to run well enough, doesn't over heat etc. But why might they of done that, what's it's purpose, does it matter and should I get it fixed ?

[metalworker0]

Not knowing anything, i just did some research ..on what its for.:

The cabin heater coolant pump is available on vehicles equipped with Auto Start - Stop feature only. The cabin heater coolant pump provides coolant to the heater core whenever the HVAC system requests heat and the vehicle is in auto start-stop mode. Refer to the Owner's Literature, Unique Driving Characteristics for full auto start-stop enabling/disabling information.

The PCM sends a PWM signal to the cabin heater coolant pump based upon the:

Auto Start-Stop mode enabled
HVAC system temperature control setting (requesting heat)
Ambient air temperature
Engine coolant temperature
Engine Revolutions Per Minute (RPM)
Vehicle speed

......................................................................................

So in other words; keeps heat flowing into your heater matrix when it's in stop start mode and stopped.. otherwise it would be sometimes blowing cold air when stopped at junctions traffic lights for any length of time.


Is this a good thing or bad thing
It's good, if you value comfort, and demisting ability... but this is at the detriment of engine longevity and reliability .
It's bad if you are one that does lots of short trips, is it will over cool engine and could prevent things like DPF regen happening.

I personally value engine longevity and reliability over comfort ....i put more clothes on and never use the heater except on long trips of over 10 miles.

A diesel engine is slow to warm up in the winter, (im talking about my 2006 transit connect) using the heater can prevent it ever reaching running temperature on trips below say 6 miles , the coolant also warms the engine oil too via the oil cooler / heat exchanger...

What these short over cooled trips can do to the motor.
1. Prevent regen of DPF ..as it is only activated when coolant reaches the right temperature.
2. Prevent engine reaching the right temperature, which is harmful as most wear happens when engine is cold as oil is slow to move to places when not warmed up.
3 . May be introduce cycles of it warming and cooling ....you don't want cycles of warm and cool in an engine ...you want it at a constant temperature.
4. make it use more fuel.

As said, it can be disabled or enabled ..you make that choice based on the info ive just given you.

Perhaps the last owner was a short tripper and shelled out lots of money on getting his blocked DPF problem sorted and this was part of the cure.

all the best.mark

[Nigel1959]

Thanks, I've googled it several times and got nowhere, even tried ChatGPT and all I could get was a vague description of coolant systems and pumps.
I've only had this van a month or so and didn't realise it had stop and start which I probably wouldn't want anyway.
When I stop after after a long and/or warm journey, there is something electrical running for a minute or so on the right hand side of the engine, only other oddity is a message on first start up saying "Hill Start Assist unavailable" again not really an issue, I've been doing unassisted hill starts for nearly 50 years

[Altransit]

If the batteries are a few years old, stop-start is unlikely to work, except after a long drive, but it could also be down to a faulty clutch switch, which may also be the cause of HLA not working?
HLA also uses the ABS sensors etc. in order to work