2000 B5 1.9tdi ATJ cooling issue.

Hi guys, new to this so please bear with me!

I have a 2000 B5 1.9 tdi which I use to commute to work and back daily (80 mile round trip).

Last week, roughly 25 miles into the journey the car suddenly felt 'lumpy' on the throttle for a couple of seconds and I noticed the temp gauge started to creep up until I pulled over and knocked the engine off. Lifted the bonnet and released the pressure from expansion tank and it started to bubble over violently and dumped a load of coolant out of the overflow. Replaced cap and started engine, temp returned to 90 and stayed there for remainder of journey.

Return journey all was good too until next morning same this happened around the same distance into drive. Bottom hose to radiator was cold to touch so so assumed thermostat was sticking or broken. Replaced with vw part and fine for a couple of days.

Had the same issue again today but this time after realising the pressure and continuing on journey I released the expansion tank cap and no water returning to the tank. Am I right in thinking this is a water pump failure/failing?

Cheers, Keir.

The bottom radiator hose should be cool as this is the radiator outlet back to the engine, If your pump had failed, as in the impeller spinning loose on the shaft I think the temperature would be high all the time on every journey. It sounds to me like you have the beginnings of a head gasket failure.

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Originally Posted by Rob69

The bottom radiator hose should be cool as this is the radiator outlet back to the engine, If your pump had failed, as in the impeller spinning loose on the shaft I think the temperature would be high all the time on every journey. It sounds to me like you have the beginnings of a head gasket failure.

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Thanks for the reply, compression test to diagnose then I guess?

A compression test would be unlikely to show anything as the engine would be cold, if it is the head gasket then the leak will likely be occurring while it is hot or being driven hard for a period of time, it might develop until it is leaking all the time. Could be something less serious though, The dashboard temp gauge is very inaccurate, actual temperature varies a lot more than you'd think, if you hook up a decent OBDII scanner / diagnostic tool you should be able to see actual temperature while driving and get an idea when the temp starts to increase beyond normal.
I had a 1.9 passat until recently and mine was running cool, fortunately it turned out to be just the stat being lazy, but live temperature data helped pin point it.

Try reving a warm engine whilst looking at expansion tank for air bubbles. This would indicate a hg failure.