E39 528i overheating - run out of ideas - suggestions needed

[fat80b]

My dad's 528 (P 97') with about 100K on the clock has had a recent problem of overheating every time it is used, he has taken it to a local garage who have replaced several bits. Some of which seemed to make the problem go away for a short time until the problem re-occurs. Both my Dad and the garage are out of ideas.

They have replaced:
head gasket
Radiator
Water pump

but the car still overheats even on a very short journey.

One possibly related fact is that the interior heater system does not work at all. Could this be related? or a cause or a symptom.

Any ideas gratefully received,

Cheers Bob

[fat80b]

Cheers for the suggestions.
I am not sure if the thermostat ahs been replaced, I will get them to check that first thing.
And look into the airlock.

oOTomOo said:

How long does it take to overheat? from stone cold in steady driving.
If the temp gauge keeps going up and up and up and up it's probs thermostat.

Yep – it heats up almost straight away – and is hot within a few miles.

oOTomOo said:

Although the fact that the heater doesn't work also points to an Airlock.
The system needs to be bled with the heaters on blowing full hot. I suspect this wasn't done?

I am guessing not.

Paoloh/essayer - I don’t think it is a head issue or a Nikasil issue – as they have looked into the head and the bottom end was done under recall years ago.

eliot said:

The thermostat is usually on the return (lower) hose, so the easiest way to diagnose is the fact that the return hose will be cool and the top hose will be hot and probably rock-hard.

This sounds like the first thing to try

Cheers everyone, I will get my dad to look into these and report back on the findings

Bob