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| Overheating but not really? Air in system or other problem? Need help diagnosing (Page 13/14) |
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Patrick
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JAN 12, 05:52 PM
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| quote | Originally posted by cebix:
So I took the rad cap off (maybe shouldn't have done that?) to see if the hose is flowing. It is. I'm wondering if I might have messed up the burping by removing the rad cap and introducing air back to the system. Is that possible?
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On level ground, the rad cap is not the highest point of the Fiero's coolant system. Check your coolant level in the system by removing the thermostat housing cap. Also make sure of course that coolant is at the proper level in the reservoir.
It wouldn't hurt to burp it one more time... but in the future leave the rad cap alone!
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cebix
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JAN 13, 11:17 AM
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All the old symptoms came back...
The reservoir tank filled up an inch moments after engine shutdown. So I'm guessing back pressure because of a clog. Damn this thing must be still clogged somewhere. I just can't believe it ran so well the first day - it was textbook normal temperature behavior. I must be pretty bad at flushing this thing. I guess the symptoms don't mean air in the system?
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olejoedad
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JAN 13, 11:36 AM
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That would be perfectly normal.
The hot engine transfers heat to the coolant, causing it to expand.
This also burps the air out of the top of the radiator.
The level will drop as the car cools.[This message has been edited by olejoedad (edited 01-13-2020).]
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cebix
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JAN 13, 12:05 PM
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The level didn't rise when the engine was hot. Dead cold/operating temperature was exactly the same, rad cap and reservoir hose were both cold.
Only after I shut it down it filled up an inch in seconds and the rad cap and reservoir hose became warm.
Does that still make sense in an air bubble situation?
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cebix
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JAN 15, 01:34 AM
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Story is now as follows:
1. Reservoir is being filled up an inch or so in a few seconds after hot engine shutoff. Level doesn't rise one bit when engine is running dead cold/hot.
2. The reservoir level is not dropping, it's not being sucked back in. Every heat cycle I have more coolant in the tank.
Could air be sucked in only through a loose overflow hose or basically any leak in the system anywhere? I'm not observing any coolant leaks whatsoever. If there's a small enough leak to not let coolant out but let air in, would a pressure tester show this?[This message has been edited by cebix (edited 01-15-2020).]
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olejoedad
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JAN 15, 07:34 AM
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The radiator to tank hose must be tight at both ends, free flowing and leak free.
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cebix
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JAN 29, 02:51 PM
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Didn't really have much time to tinker with this issue so I'm just driving it and seeing no real improvement. Tightened some hoses, pretty sure there are no leaks. The coolant level still rises in the reservoir with each heat/cool cycle. I guess no self-burping is occuring so I have another question about it.
Since the system is "full" it's just not possible for me to get the thing running with the thermostat cap open. It sprays it out all over the place. How do I go about this? Should I drain some coolant and add it again while burping? Should I drain the system dry and refill it again? I just miss that one day it ran perfectly fine and I don't know if it was the one time I did the burping right. Thanks.
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Patrick
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JAN 29, 03:36 PM
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| quote | Originally posted by cebix:
The coolant level still rises in the reservoir with each heat/cool cycle.
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Well, the coolant level is supposed to rise during each heat cycle... but does the coolant level in the reservoir not also lower again when the engine cools down?
| quote | Originally posted by cebix:
Since the system is "full" it's just not possible for me to get the thing running with the thermostat cap open. It sprays it out all over the place.
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That's normal. Why do you wish to run the engine with the thermostat cap open.
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cebix
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JAN 29, 04:12 PM
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I meant to run the engine with the thermostat cap off just during burping. It's not possible now even with the rear elevated (about 5 inches I'm guessing).
When I tightened some hoses and burped again the system about two weeks ago the coolant level was rising when hot and was lowering when cold, so it was operating normally. I'm checking the tank level every time I drive cold, hot and immediately after engine shutoff.
3-4 cycles after that the level was rising still when hot but lowering less and less back into the system. 2-3 cycles later it does _not_ go up when hot. Only goes up a few seconds after shutdown. Hissing can be heard from the rad cap when it does this. Now it's not lowering back almost anymore at all.
Two weeks ago the tank was halfway full cold. Now it's at the full line when cold in about let's say... 6-8 cycles? Didn't add any coolant to that tank manually, it filled up on its own. Does this give you guys any ideas on what to look for next? I though I would have had it with fixing this system but I'm now genuinely intrigued.
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Patrick
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JAN 29, 04:28 PM
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| quote | Originally posted by cebix:
I meant to run the engine with the thermostat cap off just during burping.
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Again I ask why? That isn't the way to burp the system.
| quote | Originally posted by cebix:
Now it's not lowering back almost anymore at all.
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I guess the question is whether the coolant is for some reason being prevented from being drawn back into the radiator while cooling down... or is there something (air) being added to the cooling system (from an internally cracked head?) that's displacing the coolant?[This message has been edited by Patrick (edited 01-29-2020).]
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