This may be normal. It takes longer than you might think for the
thermostat to open to the point where hot coolant is flowing through the
radiator. What is the temp gauge reading? The 87 degree thermostat does
not open until the gauge needle is up near the LED. If the needle goes
above the LED and the radiator is still not hot, something is wrong.
With everything working normally it may take ten minutes or more of
idling before the radiator gets warm and if the heaters are on the
thermostat may not open at all, depending on air temp.

Mark

Javier Zavala wrote:

> I need some help on finding out what happened to my engine (blown heads and
> gaskets 4 weeks ago).
> Now everything is fixed, welded heads, new gaskets, new thermostat; the
> radiator flushed, system is w/coolant and bleeded, but.....
> Temp of water tank in engine compartment....... very HOT
> Temp of water in rear tank (reservoir?)...... Tepid
> Temp of water in Radiator................................COOL
>
> Can anybody help me understand this and tell if this caused my heads to
> blow in the first place and what to do?
>
> MANY Thanks in Advance
> Javier Zavala
> 85 1,9L Westy Joker