Re: 84 spider heater (intermittent)

[bgiller@xxxxxxxxx (Bruce Giller)]

 Rodney,
	I've had the heater in my '86 Spider melt sleet off the back window
when stuck in DC rush hour traffic one year.  And this is after I replaced
the heater valve.  So I know that these heater systems can put out some
serious hot air (just like Congress!).

	First off, make sure that your thermostat is keeping the water
temp. at around 175-180F degrees.  You'll definitively feel a reduction in
heat output if the temps are below these figures.  I had a leaky thermostat
and the temp. never got to normal operating temps in the winter time.

	My guess is that your heater valve is shot.  The internal rubber
bits tend to swell over time and reduce the flow of water thru the heater
core.  Yours might be letting water thru when cold but closes up as it
warms up.  One way to test the flow thru of the heater valve is to drain
the coolant from the system.  Disconnect the supply heater line and the
return heater line from the engine.  Take the business end of your garden
hose and apply it to the supply heater line and see how much water flow you
get out of the return line.  It should flow easily thru the system - if you
see anything less than almost full flow, then the heater valve is clogged
and needs to be replaced.

	If you had air in the coolant system, it usually ends up in the
thermostat housing not in the heater core; symptoms are apparent
overheating since the thermostat isn't opening because it isn't contacting
the heated water just air.  When filling the radiator, open the heater
control to allow coolant into the heater core.  Remove the 10mm bleeder
bolt atop the water pump housing to release any trapped air - replace when
coolant gushes out.  Then crack open the bleeder bolt (brass) on the FI
heater circuit on the FI intake plenum and pour in more coolant until
coolant gushes out there.  When you do this, make sure that your car is on
level ground otherwise you might trap air in unknown locations.

	The heater valve and gasket can be replaced without removing much
interior bits if you don't have A/C.  The valve is located on the drivers
side of the center console.  But if you have A/C, the heater valve is
behind too much A/C plumbing to allow you access and this means at least 4
hours of removing interior parts to gain access.  I've done it far too many
times....

	Bruce

> I bought my spider in April.  Last weekend was the first time I've had
> an opportunity to use the heater.  I was driving at night.  It was
> chilly with the top down.  I turned the heater on.  It seemed to work
> okay, for awhile.  I stopped at a convenience store.  I left.  A few
> miles down the road, the heater seemed not to be working to well.  By
> the time I reached my destination, there was no heat (a 40 mile trip).
> I'm referring, of course, to hot air from the heater core, not the
> blower motor.
> I assume my problem is one of the following:
> 1)Heater core and/or heater valve is mostly clogged (my #1 choice)
> 2)Heater valve is broken (seems unlikely since heat works sometimes)
> 3)Something is affecting the linkage between the heat lever and the
> valve (also seems unlikely)
> or,
> What about air in the system?
>
> I plan to flush (the stuff in the little prestone bottle) the entire
> cooling system this weekend.  I also thought about forcing some of the
> "flush" chemical through the heater core by way of  the hose between the
> firewall and the air bleed valve with the aid of compressed air, if
> necessary.  If the latter is advisable, what is the max psi I should set
> my compressor regulator at?

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