On 14/6/20 12:33 am, Scott Dorsey wrote:
> > wrote:
>> A friend put in stop leak and now the heater core is blocked. Unfortunately
>> it is much harder to replace than radiator or thermostat (which seem to be
>> okay anyway). He put some detergent in the coolant and reversed the hoses,
>> which achieved nothing.
>
> It does that. Replace the heater core. Don't just remove it and try to clean
> it either. Likely there is enough stop leak in the radiator that if it comes
> out, it will clog the heater core up again, so it may be worth replacing
> the radiator pre-emptively as well. At the very least try to do a reverse
> flush on the radiator.

Any radiator that is 10+ years old should be replaced pre-emptively
because the plastic top and bottom tanks, which get brittle with age and
heat cycling, are likely to crack and develop a massive leak.
>
> The first question: where was the leak that he was trying to stop? If it
> was in the radiator, the radiator has to go anyway. Worry first about
> fixing that leak because fixing it may free up more stop leak to clog the
> heater up.
>
> Also.... make sure it is the heater that is clogged and not the valve.
> The valve may be comparatively easy to replace, rebuild or clean. Either
> way, it's something to clean before touching the heater core.
> --scott
>
Most modern cars I've seen no longer have a heater valve as such. They
were always a point of failure - sticking, blocking, leaking, etc. The
trend now is to run hot water through the heater core all the time and
use *air flow control* to regulate the car's internal temperature. For
this purpose they use a *blend door/flap* in the heater/AC to achieve a
much more rapid temperature change - necessary with climate control.

--

Xeno


Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)