Overheating but not really? Air in system or other problem? Need help diagnosing (Page 9/14)
Patrick NOV 23, 02:17 PM

quote
Originally posted by cebix:

Got a feeling I got lucky with the reservoir crap as it probably was added to that tank and never got sucked into the system.



It would make absolutely no sense for "stop-leak" to have been added to the coolant reservoir... but I suppose some people are capable of doing anything.

fierobear NOV 23, 02:22 PM

quote
Originally posted by fierobear:
The gauges, especially at their age now, are notoriously inaccurate. I’ve changed senders and temperature gauges in my 88GT more than once and it still goes nuts. The way I test the real temperature in the system is I put a scanner on the ALDL and see what the ECM is seeing. Do you know anyone with a real time data scanner?

Edit, remove scanner link.

Any time I’m reviving a long dead car or I need to be sure everything is working properly, I put the scanner on and see what the ECM is seeing.




Sorry, dude, I messed up. The link I gave you was for my OBD2 scanner for my Escalade. I use an AutoXRay OBD1 scanner for Fieros. They don’t make them any more, the company looks like it went out of business. I recommend getting a real time/live data scanner. Just this morning, I got another long dead Fiero running, and when I got it running well I put my scanner on it and it showed the coolant temp sensor is reporting to the ECM a temperature of -37 dF, which will cause all sorts of running issues. I now know to replace that sensor. Scanners are highly recommended .
Patrick NOV 23, 02:31 PM

quote
Originally posted by fierobear:

Scanners are highly recommended...



...and/or software such as WinALDL used with a laptop and appropriate cable.

Yeah, without knowing what the sensors and ECU actually "see", it's awfully difficult to properly troubleshoot an issue.
fierobear NOV 24, 11:17 AM

quote
Originally posted by Patrick:

...and/or software such as WinALDL used with a laptop and appropriate cable.

Yeah, without knowing what the sensors and ECU actually "see", it's awfully difficult to properly troubleshoot an issue.



That’s true, WinALDL should work as well. I’d forgotten about that program.
cebix NOV 26, 12:34 PM
Been driving around just to see what it does and it is kind of more civilized now I guess. Only shoots up some above 220 and then goes down quickly even without hitting the throttle. Then it still kind of oscillates but it looks a lot better. Also there's no rad cap hissing so I guess that was indeed the overflow hose sucking in air. Maybe _now_ it's just time until it burps itself?

Got a multimeter with a thermocouple and measured the temperature where the gauge sensor goes into the block and it pretty much confirms what the gauge says. It's not as fast as the gauge but it settles at what the gauge says. On hot shutdown it soaks to about 220 which is what the gauge shows when after shutdown I turn on the ignition. Hot engine running seconds before shutdown it was at the second mark. Couldn't really get to measure it where it was shooting up days before due to traffic and the gauge not pegging that high anymore... for now at least.

No reservoir overflowing, level changes hot/cold good so the hose is flowing. No rad cap hissing. However I noticed after shutdown my thermostat cap now is hissing a little bit... Is that normal? Or should I replace it? It has been opened up and closed a lot of times this past month so I guess it can wear down.

EDIT: I did mention before that my thermostat was loose in the housing. The Stant new one is snug so I guess the Gates one was a little less in gasket diameter.

[This message has been edited by cebix (edited 11-26-2019).]

olejoedad NOV 26, 03:09 PM
The hose between the radiator and the expansion tank could well be the cause of your problem.
Sounds like your issues are resolved.
Good deal!
Patrick NOV 26, 03:18 PM

quote
Originally posted by cebix:

I noticed after shutdown my thermostat cap now is hissing a little bit... Is that normal?



No.


quote
Originally posted by Patrick:

The top of the thermostat housing can get bent from improper removal of the cap (ie using a big honkin' pipe wrench to remove it), so you need to make sure it's flat. I've used sandpaper on a flat surface (when the housing was off the engine) to see where the high points were, but something similar can probably be done while the housing is still on the engine. You want the top edge of the housing to eventually be corrosion free and flat, otherwise even a new cap won't be able to seal. And when the cap is put on, push down while turning to make sure it's turned all the way (past the first click and to the end).


[This message has been edited by Patrick (edited 11-26-2019).]

cebix NOV 27, 07:26 AM
Noticed today that the thermostat cap started leaking, so yeah. The hissing was a sign.
fierobear NOV 28, 02:09 AM

quote
Originally posted by cebix:

Noticed today that the thermostat cap started leaking, so yeah. The hissing was a sign.



Any loss of pressure will cause problems.
cebix DEC 04, 12:53 PM
Still fighting with it, driving around, no change. Made a rubber gasket to seal the thermostat cap. Now the thermostat housing is leaking where it attaches to the block... Guess now it's a leak hunt.

Anyways another question - how much should the reservoir tank level move? It's at "ADD" level at cold and goes up about half an inch maybe when hot. Should it go all the way up to "FULL"? That's about a 3 inch difference I guess. I'm wondering if my leaks are excessive pressure related since they weren't there before and if my rad cap is actually opening or has the little hose clogged itself... Many thanks.

EDIT: Then again I think because of a leak there might never be enough pressure to push the rad cap open? I guess I'll post again when I get rid of the leak(s).

[This message has been edited by cebix (edited 12-04-2019).]