Hey all, so the hose on the right (new one, not old one) is leaking both inside the car and outside. Probably lost about a quarter cup of fluid. I tightened the hose clamp, but just wondering if there is anything else that could cause this? Is my heater core toast?

Just when you think everything is good, something else pops a leak...

 

I think the hoses are connected thru the firewall with a metal pipe. Any chance this is damaged? Its just held in place with the rubber bung in the firewall and should be fairly easy to remove and inspect...

The fact it leaks on BOTH sides does not suggest the heater core is the problem. That said, I think this hose hooks to the heater control VALVE at the inside of the heater, and these do fail. But that would result in a leak in the passenger comp, not engine side...
Stu A
80GS
AZ

 

Thanks for your response. I DO in fact have a leak both outside/firewall and on the passenger floor board...

Two questions for everyone:

1. To get to the heater control valve, do I have to remove the heater core itself?
2. Can I remove this heater hose without draining the coolant? (I'm guessing no, though it is pretty "high" up in the system)

 

Does it still leak after tightening the clamp?

If it's leaking outside and inside, I think the pipe itself may be deformed. Water is flowing towards the interior on that pipe.
There's another hose and pipe connection to the heater valve on the inside. If you smoosh your face to the gas pedal you can see it.

 

I tightened the clamp, and looked under the car 24hours later. There was still a small puddle, but I haven't started the car yet. Hard to tell whether it was residual fluid making its way down, or if it's still got a slight leak.

FML - may have to just bypass the heater for now.

 

If it is inside and out it is probably the hose connection. If it is still leaking after tightening it up, I would suggest getting some form-a-gasket (#3 I think) and gooping it on the metal tube before slipping the hose back over. I have used that on other coolant leaks where the metal part of the connection was badly corroded and it worked fine. In the attached picture you can see the metal connections to the heater core. They are pretty long, so it is unlikely that the heater core is causing a leak in the engine compartment.

Carl

 

Maybe take the hose off and check its inner diameter for a split or crack? I had a fuel hose I overtightened and split the hose. Would leak even more as I tightened it.

Does hose diameter seem to be correct? The new hose doesn't look OEM. Your local Mazda dealer can get you new OEM hoses in a few days if required...

 

Thanks for the pic Carl, that helps.

yes, the hose is OEM I replaced it when I fixed beehive cooler leak. But the metal pipe is likely corroded as the car sat for a long time. I’ll try the form a gasket and see if that helps.

full disclosure, there is also a good chance a mouse lives in my heater haha. I keep poison in the car, but I’ve been seeing some nests in the vents and droppings recently.

 

For the possible mouse, you can drop your blower motor assembly pretty easily. It's 3 nuts accessed with a 10mm socket in passenger footwell. Might be worth to take a look!

 

Great idea, thanks! I'll drop it this weekend.