Found another coolant leak - heater core (Page 4/4) Patrick OCT 04, 03:46 AM quote Originally posted by Cliff Pennock: No wait, it's called the "Glass Roof Vent Storage Cover". That makes a whole lot more sense than the other name. Vintage-Nut OCT 04, 10:36 AM I tried to find the GM part in my P22 Parts and Illustration Catalog, but I didn't have any luck..... Cliff Pennock OCT 05, 07:41 AM Replaced the heater core today and I'm happy to say that that fixed the problem! So fortunately, there were no other leaks. This was probably the easiest repair I've done to my Fiero so far. 😊 Haven't tested yet if this also fixes the temperature gauge going all over the place, but it could very well be. The leaking heater core of course not only leaks coolant, but also sucks air into the system. theogre OCT 05, 09:12 AM Likely Will need a few heat cycling to get all air out. No matter how follow "burping" methods many still believe you need. Likely Won't help the gauge bouncing. All "Dumb" Gauges can/will bounce depending where/how you drive, weather that day, etc. & more so on Fiero w/ ~ 3x system capacity. Cliff Pennock OCT 05, 11:29 AM quote Originally posted by theogre: Likely Won't help the gauge bouncing. No, I meant the temperature quickly rising to beyond the red, stay there for a few seconds, then drop again. Which might be caused by an air bubble in the system. If I drive normally, the temperature stays pretty constant (around 175*F). But I only had to floor it once and the temperature would immediately rise to beyond the red. After which it would drop within seconds to 175* again, only to slowly rise to beyond the red again. theogre OCT 05, 09:27 PM quote Originally posted by Cliff Pennock: No, I meant the temperature quickly rising to beyond the red, stay there for a few seconds, then drop again. Which might be caused by an air bubble in the system. If I drive normally, the temperature stays pretty constant (around 175*F). But I only had to floor it once and the temperature would immediately rise to beyond the red. After which it would drop within seconds to 175* again, only to slowly rise to beyond the red again. Bouncing like that can happen w/ OE type T-stat & 175°F isn't even opening the T-stat. & Again you cannot trust that gauge. Should use ECM scanner that reports all sensors Way Better then Dash Gauges that often have crap power, crap grounds, crap 1 wire to whatever sender, or all three. Air in the H-core is purge when you start the car & have T-stat In. Sometimes... If H-core is installed wrong may trap air but only problem is little to no heat to cabin. H-cores have 2 sizes of hose/tube joints to prevent that. Air in the system then is pushed to the Radiator then out thru Overflow tank as system gets heat cycled. see cave coolant section. Now Stant is gone for aftermarket so Can't get the SuperStat that was made to stop or reduce gauge bouncing.