car no heat/overheating; normal temp and heat under heavy acceleration


Asked by Mar 28, 2016 at 06:46 PM about the 1994 Ford Mustang STD Coupe

Question type: Maintenance & Repair

I have a 94 v6 mustang and it drives fine for a little
bit sometimes (heat works) but inevitably I lose
heat and shortly after that, temp starts to rise. But,
if I put it to the floor,  about 75% of the time, it
cools down to normal and heat will work. It's very
short lived because in about a min or 2 it will
happen again. It happened 4 times when I tried
getting to work in a 7 mile span from my house. It
won't overheat at idle even though most of the
time it has no heat at idle ( it was checked in below
freezing temps after a drive cause that's the only
way of getting it up to temp). All that being said I
am just finishing up school for automotive
technician and I know it can't be thermostat due to
no heat issue. I have flushed the system twice and
bled air out at least 5 times. I don't think the heater
core being clogged would cause an overheating
I'm leaving toward water pump and guess some or
all fins are worn/erroded. Has radiator and
thermostat replaced about 15k miles ago due to
overheating. No coolant in oil and vice versa. I do
have a lean code for bank 1 but only bank 1. I'm
lost and don't have a lot of money so all help would
be appreciated. Sorry such long description

1 Answer


Sounds like you know the bases...usually it is low coolant or air pockets in the system. And if you have good flow threw the radiator, watching with the cap off you can tell, all that is left would be the water pump, the fan clutch if there is not an electric fan, and thermostat. Possible the thermostat is not good.

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