Overheating but not really? Air in system or other problem? Need help diagnosing (Page 4/14)
cebix NOV 09, 07:55 AM
Can't get those heater hoses off so I'm gonna cut the bigger, upper one and install a bleeder valve. I have an AC car. I bought this one:



Wondering where to cut the hose... I guess the higher the valve is the better. Does it hurt if it won't be pointing upwards but rather at an angle? Or will it not do its job at all?

Say if it was installed like shown below with the blue arrow being "up":

[This message has been edited by cebix (edited 11-09-2019).]

olejoedad NOV 09, 09:15 AM
I wouldn't add that fitting.
Pull the thermostat and drive it a bit.
The heater core and the rest of the system will work the air out and trap it in the top of the radiator so that it will self-burp.
cebix NOV 09, 10:05 AM
It's just not burping itself. I don't know why but it doesn't. Driving it regularly and still hear hissing from heater core on deceleration and coolant sloshing around there on startup. Still all my symptoms remain except for the reservoir tank - that doesn't overflow anymore I guess thanks to the new rad cap.

In fact I think with every drive I see the temp gauge go higher and higher a little. Why wouldn't you add that fitting?
Gall757 NOV 09, 10:20 AM
Hissing from the heater core.

I bet that is air being sucked into the system. Apparently the leak is so small that coolant does not come out, or comes out in a spot you have not found yet.

[This message has been edited by Gall757 (edited 11-09-2019).]

cebix NOV 09, 10:36 AM
Is it possible it's just air that is already trapped in the system? No leaks whatsoever, checked and rechecked. Or if there's one it's so small I can't see it.
Gall757 NOV 09, 10:49 AM
Because the cooling system does purge itself of the usual air pockets, it appears that your cooling system is somehow gaining air. It could be a head gasket, but that does not explain the hissing sound. A pin hole in the rubber hose at the heater core (or a loose hose clamp) might do it.

[This message has been edited by Gall757 (edited 11-09-2019).]

cebix NOV 09, 11:07 AM
Damn. That's gonna be a tough one. Might have to take the car to a shop for a pressure test, that's gonna be expensive I guess because nobody here knows those cars. The hissing sound doesn't actually come straight from the heater core, it's just all around if I walk around the car. It even sounds like it's coming from the engine when revving up and down so that must be air. And it's always straight in pitch, doesn't change with the revs or anything. And it only happens when throttling down or moving at part throttle. It's a deep hiss though, not like a tire inflating sound, kinda Darth Vader if you will.

Still don't understand how that fitting can hurt anything? Is it not a good idea to try it anyway? What I'm trying to achieve with this is burping the heater core as the cave states but without removing the hose and using a bleeder valve.

[This message has been edited by cebix (edited 11-09-2019).]

olejoedad NOV 09, 11:57 AM
The heater core has constant coolant flow whenever the engine is running, not dependant on thermostat position. It has no choice - it has to push the air out due to flow, unless that flow is greatly restricted by a crushed supply tube, a kinked hose or a hose that is delaminating internally.

Even if there was a bit of air in the core, it would have absolutely no effect on the overheating of the engine, if indeed that is still happening.

I would not add the fitting because it is not needed.
cebix NOV 09, 12:13 PM
Damn. No idea what to do now. Maybe there is a blockage somewhere but just a slight enough one to be overthrown by the pump when at moderate throttle?

Would a pressure test show that?

I do get a lot of heat from the heater and it is HOT but only while at some throttle. Idling for a minute or so and it gets cold.

[This message has been edited by cebix (edited 11-09-2019).]

Patrick NOV 09, 01:58 PM

quote
Originally posted by cebix:

I do get a lot of heat from the heater and it is HOT but only while at some throttle. Idling for a minute or so and it gets cold.



Obviously not normal.

If it was my Fiero, I'd remove one of the hoses from the heater core and flush and then back flush the system with a garden hose. This would at least tell you if you have a blockage somewhere in that part of the system, and maybe it would also push out whatever the blockage is.

Keep in mind that you don't necessarily need to disconnect a hose up front from the actual heater core. If it's easier to disconnect a heater hose in the engine bay, do it there instead.

[This message has been edited by Patrick (edited 11-09-2019).]