On 13/6/20 12:06 pm, 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. Look through other forums, I see various ideas:
> 1) put vinegar or tartaric acid into radiator, warm up engine then rev it to
> 4000 RPM. Then quickly flush system with water and refill with correct coolant.
> 2) disconnect heater hoses, and pump gasoline into it. Then flush heater with
> water.

That's pretty much a standard event with some forms of stop leak. It is
also why I *fix* the problem properly by repairing the leak at its
source in the time honoured manner. The problem is that the flow through
the heater core slows allowing the lumpy bits to sediment out.
>
> I gather that trying to blow it out with compressed air is bad, as this may
> dry out the stop leak, making it worse.

Any form of cleaning, including flushing, will likely bring about the
return of the leak that you originally tried to fix. It may also
discover *more leaks* for you.
>
> Has anybody succeeded with clearing a clogged heater?
>
Remove, properly flush, refit. That stuff sticks like baby**** to a blanket.

--

Xeno


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