Coolant Temperature

[cayod5]

Hi There. I am new to the forum. I own a Volkswagen Passat 1.8 20V Sports and recently the head gasket blew. I also found some murky brown stuff in the coolant containter which could have been the cause.

The gasket was replaced and for a few weeks, my mechanic had to keep replacing the coolant (G12) as oil was mixing with it. He told me this was the residue oil from the radiator and not from the engine. Since the last time he changed it, I have been keeping an eye on the coolant and the amount of oil in it is so little so it looks like he is telling the truth.

Anyway, my main concern is to do with the coolant temperature guage:

1. It now takes longer (between 18 and 20 mins.) for the temperature to reach 90 degrees. This used to take about 7 mins.

2. When I drive in the city where there is traffic, the temperature remains on 90 degrees but as soon as I drive for a long period without stopping (especially on the motorway), the temperature goes below 90 degrees.

Does anyone know what could be causing this.

Thanks

Cayod5

[Mike McKinstry]

I am having exactly same prob if you look at thread "temp guage"however am coming to the conclusion it may be a sticky thermostat so am going to change this first.
Regards,
Mike

[martin1810]

Sounds like thermostat is jammed open. Replace that and see what happens.

[cayod5]

Thanks guys

I will get the coolant thermostat changed and see if it works

Cayod5