Electric in-line water pump & HG Failure

[Angarak]

Hi all,

A couple of questions for you, any help greatly appreciated:


Question 1:
Can anyone tell me what the default behavior is for the electric in-line water pump situated near the bulkhead to the left of the header tank when:

1> ignition on (prior to engine start)
2> whilst engine is running
3> after ignition off (cold engine + warm engine)


Question 2:
Can anyone also tell me what fuse this pump is on?


Question 3:
What are the repercussions of this unit failing?


Background Info:
I have a 2001 1.9TDI (AUY) Alhambra, I love the car but seem to have no luck with head gaskets on this supposedly bullet proof VW engine

I've replaced the original engine after it suffered 2 failed HG's and eventually a cracked block with another 1.9TDI (AUY) from an 04 Alhambra that had done 64k (I couldn't afford replacing the car at the time).

I do quite a bit of motorway driving and the water/oil temps have always been at normal readings, nothing to suggest the engine was running too hot that it would cause the head to swell and crush the gasket causing HG failure.

I don't drive the car like its stolen as its important for my work. Before each long journey I check the oil/coolant levels to make sure they're fine and the car has been serviced when required.

I now have HG failure again on this 2nd engine which has only done approx 10k since fitting it (loss of coolant, no heat, chemical HG test to confirm failure).

I know there are many things that can cause HG failure:

• Thermostat - checked (radiator pipes are hot)
• Water Pump - checked (updated with metal impeller)
• Heater Matrix - checked (no leaks)
• Blocked coolant pipe - checked (coolant circulating in header tank)
• Split coolant pipe - checked (no visible stains suggesting leak)

Thanks for reading

 

[Jon Olds]

cooling system pressure test needed maybe

 

[Angarak]

That's something I'm going to do once the HG has been done Jon.

For now, my suspicions are that the electric water pump is not 'running on' after the engine is switched off after a long motorway journey - resulting in the head remaining hot and maybe swelling a little crushing the HG causing failure.

 

[Jon Olds]

think the leccy pump is to make the heater more efficient, not primarily for engine cooling

 

[Angarak]

I know its not the main coolant pump but if its default behaviour on the AUY engine is supposedly to 'run on' for a couple minutes after the engine is turned off, it makes me think it plays a part in cooling the engine once the ignition is off as it would continue to circulate the coolant.

 

[Jon Olds]

you have a point, but gut feel is that is not the route cause of your problem. but heh, what do i know?

 

[A-spot]

I'm loooking at this pump myself at the moment, and as I understand it the pump is only really designed to circulate water around all of the heating systems as the Alhambra has a rear matrix for the rear cabin as well as the dashboard heater. Also the primary use of the pump is to circulate water thrught the Auxilary heater under the rear floor to provide faster warm up during colder weather, I'm not aware of any requirement for it to run on. My pump was not running at at all thoughout last summer and we had no overheating issues at all.

 

[Angarak]

Having looked further in to it I don't think this pump would be responsible for my problem (HG failure), looks like I just have bad luck.

As you say, I think its on the cabin heating side of the coolant system as opposed to the engine side.

On the AUY engine I believe it is meant to run on, on later engines I don't think it does.

I'm still not sure of what conditions it should run on for - whether its default behavior is to always run on or to only run on if the auxillary heater has been operating, or if the engine temp and external temp are XY values.