Q: Coolant leak from a black box (HVAC box)?

asked by on October 19, 2016

Hi my name is ray. I need advise on 78 mark 5. it has coolant leak between the black box(HVAC box)and the fire wall. I didn't open the box yet but it starts leak when I turn on the heater so I just guessing it is heater core or the piping concerned. I just want to stop the leak so I'm planning to by pass the piping. It will cause only no heater? If it is leaking form the heater core, It will solve the problem?

The most likely cause of your leak is the heater core inside of the car’s heater case. The leak will come out of the A/C’s drain. If you are going to bypass the heater core then I would recommend connecting the two hoses together or just running a new hose from one pipe to the other pipe on the engine. This will ensure the coolant circulates through the water pump and cooling system well. The heater core can be replaced at any time in the future. If you need some assistance with this, consider YourMechanic, as one of our mobile technicians can come to you to diagnose the coolant leak and help you install a new heater hose to ensure good coolant circulation.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Floorboards wet from coolant leak.

There are a few things that could cause a wet floor. A clogged evaporator drain if you are lucky and a leaking heater core if you are not so lucky. To address the leaking coolant, I would have a technician,...

Over heating

This can be caused by a number of things such as low coolant levels, a faulty thermostat, or a failing coolant fan switch. As you may know the coolant fan switch helps to maintain the proper coolant temperature by turning...

Loud tapping under valve cover

Hello. If the noise is coming from under the valve cover I am certain there is an internal engine problem in the cylinder head. The easiest way to test engine internals is by performing a compression test. However, a compression...

Related articles

How To Keep Your Car From Overheating
Monitoring your coolant level, turning the A/C off in very hot weather, and regular inspections will help you avoid having an overheating car.
Is it Safe to Drive With a Radiator Leak?
The radiator helps to keep your engine cool. If your radiator is leaking, coolant will be lost and the engine will have the potential...
How Serious Is It When a Hose Is Leaking?
A leaking hose in your car could indicate different problems. Some leaking hoses are more serious than others, but all should be checked and repaired.