Overheating but not really? Air in system or other problem? Need help diagnosing (Page 7/14)
olejoedad NOV 11, 08:05 PM
Be sure to monitor the coolant level in the expansion tank also.
cebix NOV 12, 01:40 AM
Yes, that level is good too.
olejoedad NOV 12, 09:02 AM
That is a good sign that your coolant system has stabilized, no leaks and no gains...
cebix NOV 16, 06:12 AM
All right, the Superstat came in. Checked it in boiling water and voila, it opens! I put it in, go for a drive and nothing's changed... Almost pegged the gauge to red however after that it seemed to settle a little. I got into heavy traffic and was fluctuating wildly between 220 and the middle spot between the second mark and 220. After a while it kinda settles there in that middle spot between those lines. So I guess it's somewhat better? Still the gauge is not steady and kind of wobbles when without the thermostat it was very fluent. Any ideas about these symptoms? Still air somewhere or a blockage? Thanks.

[This message has been edited by cebix (edited 11-16-2019).]

olejoedad NOV 16, 08:24 AM
If there is any air left in your system it will burp out, just keep driving it and monitor the coolant tank level.

The gage is not known for its accuracy. Do you have a way to verify what it indicates, possibly an infrared thermometer?
cebix NOV 16, 08:49 AM
Not really at the moment. Going to look them up, if they're not too expensive, maybe I'll get one. Still all the hoses are plenty hot and stiff under pressure, rad cap too is hot. There's heat from the heater but it's going a little cooler when idling, not cold though like previously. When revving it gets somewhat hotter. I'm still thinking there is an air bubble. After cooling down and starting the engine again it does go above 220 and then it "kind of" settles down from there but a lot of fluctuation. Without the thermostat there was no fluctuation at all, just steady rising and falling down slowly like in newer cars I guess.
Gall757 NOV 16, 10:02 AM

quote
Originally posted by cebix:
After cooling down and starting the engine again it does go above 220 and then it "kind of" settles down from there but a lot of fluctuation.



There are cold and hot spots in the cooling system because it is so big. The thermostat is closing when the coolant is cold....it heats up and the thermostat opens...in comes more cold coolant....thermostat closes again. It's a special Fiero feature with the engine and radiator so far away from each other...
cebix NOV 16, 12:44 PM
So this is normal behavior for your Fieros too? I'm not sure they acted like that from the factory in the 80s, people would go nuts. I think I'm going to try to shoot a video of the gauge while driving so maybe you guys can judge how it's supposed to be.

I'm looking at some youtube POV videos and most guys' gauges either don't work or they're running dead cold. I don't know.

[This message has been edited by cebix (edited 11-16-2019).]

Patrick NOV 16, 02:37 PM

quote
Originally posted by cebix:

There's heat from the heater but it's going a little cooler when idling, not cold though like previously. When revving it gets somewhat hotter.

So this is normal behavior for your Fieros too?



None of the several Fieros I own has ever acted in this manner.

Have you tried this yet? If not, why not? It's a simple process.


quote
Originally posted by Patrick:

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.
cebix NOV 16, 02:52 PM
I also guess your gauge is pretty steady and moving fluidly and not going into the red just to fall down with a blip of throttle down to 220 and less?

Haven't tried to flush the heater yet. Can't get those hoses off anyway, and would probably have to cut them.