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Q: heating and cooling system

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I am having an issue with my Corolla overheating. Recently installed a new thermostat, water pump and head gasket sealant (blue devil). I am leaking coolant but I cannot pinpoint where. Heater in the car blows hot air only when accelerating and braking. (heater core?) I snapped a bolt on the water pump just today however, I see no leakage from that area. Please help I cannot think of any other possibilities. No leaks in hoses either.

Thank you, Jen

My car has 300000 miles.
My car has an automatic transmission.

Hello. I can help you with your 2006 Corolla. It sounds like you have four issues:

1) Overheating

2) Leaking coolant

3) Water Pump installation problem

4) Heater core problem

The water pump bolts, which ensure a good seal between the pump and the block, are not particularly redundant. That is, if one is missing, the pump flange either already leaks under pressure or it will leak. It might work temporarily with a very tiny leak but of course have a Mechanic extract the bolt as soon as possible and replace it. The coolant leak, whether at the pump flange or elsewhere, can be diagnosed using a pressure tester. Leaks are either internal or external.

If external, it will definitely show up under pressure if it is of any significance. If its an internal leak (to oil or to combustion chamber), that means there is an issue with either the head gasket or intake manifold gasket and that would have to be diagnosed. In your circumstance, inasmuch as you mention use of a "sealant", the overheating could be due to a head gasket failure that allows exhaust gas to be blown into the coolant. Such will overheat the car.

On the other hand, the sealant itself can potentially plug up the radiator, and heater core, causing, or aggravating, overheating. The Factory Service Manual for your car does not specify, indeed in some manuals specifically prohibits, use of such unapproved aftermarket sealants and consequently Certified Mechanics will not use them in repairs. If your head gasket "was" leaking, the only Toyota sanctioned repair is to replace the head gasket. In your circumstance, I would test the flow rate of the radiator, to see if it is plugged, determine where the leak is, and try to understand your prior issue with the head gasket and its current status to see if that needs to be replaced as well. Fortunately, you have a fairly simple, common and straightforward car to work on. Any number of certified technicians at YourMechanic can get your car back to top condition and diagnose the overheating issue. Hope this helps.

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