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bad heater core?

1102 Views 3 Replies 3 Participants Last post by  diver9000
91 corolla, 145,000 miles.

my thermostat has been stuck open for some time but i havent had the time/tools to find and replace it, so i've just been dealing with the car not heating up. today my windshield was covered with ice and i started the car and defrosted the front window. then i drove to work (about 2 miles at 35 mph) and i just went out to the parking lot for my lunch break, and all over the passenger side of the windshield and the front passenger window was a dewy condensation. as i entered the car i also noticed a faint warm coolant smell and wiped the condensation with my fingers and tried to smell it but the moisture itself had no strong color or odor. i looked under the car and there did not appear to be any sign of leaks.

is my heater core bad? how will i know for sure? is it the kind of thing that can leak slowly and then one day my coolant will all be gone and the temp gauge will go up to Hot even with an open thermostat (if i lose all my coolant?)? is this hard to replace myself?

thanks, bill
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its not the easiest job to do yourself but condensation on windshield around passenger side with coolant smell is a good hint that your heater core is going on the fritz. as for the thermostat its two 10mm nuts that hold it in place under the distributer, less than a 5 minute job to change the thermostat. yes, some day your car could overheat from the lack of coolant being leaked out of the heater core. look at your carpet around the passanger and driver floor and see if there is any dampness. you do need to replace it if the heater core is bad, i would monitor coolant level, and the coolant smell along with condensation on the window for a week before i decide to go change the heater core. keep us updated. and i sent you a link in your pm to download the FSM for the corolla
I don't think the job is all that hard, it's more just a pain, I'd say if you're comfortable with dismantling your dash and connecting two heater hoses on the firewall, shoot for it.
Actually if he goes in behind the glove box he can access most of what he needs to get to without taking the rest of the dash apart. I agree though, its pretty straight forward on how it comes apart but it is more of a pain than anything else.
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