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| Engine temps all over the place (Page 6/9) |
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Patrick
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DEC 25, 04:39 PM
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And Merry Christmas to you too! 
I'm surprised The Ogre didn't chime in on the thermostat modification. I suspect there's more going on with your cooling issues than what a small hole in the thermostat might rectify, but I didn't think it would hurt to at least try.[This message has been edited by Patrick (edited 12-27-2022).]
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theogre
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DEC 26, 11:29 AM
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I didn't read all of this thread for several reasons....
Most Often Cliff and most others in recent treads has No Problem w/ temp swing driving in cold weather.
If the engine really is over heating, the coolant system has problems w/ crush pipes, crap plugging the rad, heater, or both, or worse problems. And big temp swings to boil over will keep happening when drive in warmer weather like ambient > ~ 40°F/4°C
Pulling the T-stat Often Proves Nothing when testing for problems in most vehicles.
T-stat is a Metered Opening even when Full Open and keeps the Heater Loop Working.
If/When have Heater loop w/ a plugging problem, this maybe disables that but still doesn't really say heater is your problem or where the problem is most times... plugged core? plugged/crush pipe(s)? F'd fitting in some areas? Heater Pipes are Aluminum and easy crushed. See my Cave, Heater
The "T-stat mod" does Not do what said the archive post and many others.
Because Those had no clue how the coolant system works.
So adding adding ~ 1/8" hole or metric equiv doesn't matter.
"But Everyone said most other had this." Wrong. Very Few T-stats for any other engines Do Not have "air bleeder" "Weep holes" and whatever other name for this. Most T-stats main openings are not "gas sealing" and enough trapped air will pass thru them just when filling the system.
If you see anything w/ this "mod" is often because:
just band aid for real problems like heater is "plugged."
Weather and/or driving changed and system doesn't show temp swings right now.
Even w/ Super stat, the engine temp can swing some when driving in ~ 0°F/-18°C or lower but doesn't swing so widely as OE T-stat types. Again, Fiero has 2 to 3 times the coolant capacity then Front Mounting Engines including many big V8 engines and This Is What this T-stat was design for including Super Stat.
"Air" trapped under the T-stat only happens maybe first time after a flush etc that let a lot of air in the system.
Most Engine Setups and When the coolant system works right, will Self Purge All Air Out after 1 or a few heat cycles.
Even the Radiator will purge air out to reach 100% wet when overflow and cap seals the system.
See my Cave, Coolant Fill
(Very Few engine will benefit by pulling a vacuum to fill the system or do other things to "burp" the system.)
Every Time you Open many radiators including Fiero you let air in the system. Bottom of the port neck of Fiero and others spills some coolant formerly filling the top tubes. The system will then repeat the self purging but air will not get in the engine.
Air or or worse engine fumes in the engine then has big problems.
Get/Have Coolant Exhaust Testing done and to see if test fluid/strips changes color. Because often Exhaust gets in coolant before coolant gets in the cylinder(s)
Air can suck into the WP Seal and some other places w/o leaking coolant. Worse when have the Wrong Rad Cap and parked "nose down" even a small grade because Coolant is draining into/thru the overflow tank.
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PhatMax
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DEC 26, 02:30 PM
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Or your water pump could look like this…
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Cliff Pennock
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DEC 26, 03:30 PM
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| quote | Originally posted by theogre:
Most Often Cliff and most others in recent treads has No Problem w/ temp swing driving in cold weather. |
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It actually gets worse in cold weather.
| quote | | If the engine really is over heating, the coolant system has problems w/ crush pipes, crap plugging the rad, heater, or both, or worse problems. |
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It is really overheating, but only during the first 10-15 minutes when I drive the car. After that, temperature stabilizes at "normal" values.
| quote | | The "T-stat mod" does not do what said the archive post and many others. Because Those had no clue how the coolant system works. So adding adding ~ 1/8" hole or metric equiv doesn't matter. |
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Apparently, it's a mod used on many cars. And it makes sense. Not only to prevent a gas bubble forming under the T-stat, but also to allow some coolant to flow even when the T-stat is closed, causing the temperature difference on both sides of the T-stat to be smaller which in turn will prevent huge temperature swings.
Which is the reason I thought it was worth a try.
| quote | | Every Time you Open many radiators including Fiero you let air in the system. |
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When I open the radiator cap, air escapes until after a while coolant comes out. So I'm pretty sure it's not sucking air in.
Let me repeat what happens each time I drive the car.
After a few minutes of driving, temperature rises quickly up to the point where the needle is pegged to the right and the overheating warning light comes on.
It stays this way until after a few more monutes, the temperature drops in just a few seconds to below normal temperatures.
It then again rises quickly, again pegging the needle to the right and the overheating warming light lighting up
This repeats itself for about 15-20 minutes until the temperature drops to "normal" values where it stays for the remainder of the trip. So from that moment on, there are no temperature swings for however long the trip lasts.
Now to me, it's obvious that the reason it overheats, is because coolant is not reaching the T-stat causing it to stay closed for too long. After a while it warms up enough (through hot air, or maybe because the t-stat housing warms up) for it to open. Very cold coolant now flows through the T-stat causing it to cool off and close again after which the cycle starts all over again. But the temperature difference of the coolant on both sides of the T-stat will become less and less with each cycle until the point is reached where it will not close again, and coolant is allowed to flow normally through the coolant system.
This also explains why the problem is worse in cold weather. Because the coolant behind the T-stat cools off significantly faster than in warmer weather. So it takes much longer for the temperature difference to become low enough that the T-stat wil remain open.
Now the question is, why isn't the coolant reaching the T-stat? Not even after I add coolant? Is there a big air bubble trapped somewhere that moves to the T-stat when the engine is running?
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Cliff Pennock
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DEC 26, 03:34 PM
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| quote | Originally posted by PhatMax:
Or your water pump could look like this… |
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I have replaced the water pump two years ago and it's working properly. I tested that by opening the T-stat cap immediately after starting the car in the morning. Which, I might add, was a stupid idea. It was spraying coolant like a geyser. Also, if the water pump wasn't working (properly) engine temps would never stabilize. It would overheat and stay overheated.
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sanderson231
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DEC 26, 05:57 PM
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Check the coolant temperture with a scan tool or data logging program to verify that the dash gauge is reading correctly. If it is I would have the coolant system pressure tested. ------------------
formerly known as sanderson
1984 Quad 4
1886 SE 2.8L
1988 4.9L Cadillac
1988 3800 Supercharged
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Patrick
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DEC 26, 06:28 PM
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| quote | Originally posted by Cliff Pennock:
When I open the radiator cap, air escapes until after a while coolant comes out. So I'm pretty sure it's not sucking air in.
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That's just not normal. The coolant in the radiator should be right up to the cap. That air has to be coming from somewhere. If it's not being sucked in, then I suspect it's being forced in from one or more combustion chambers due to a head gasket issue... but this is beyond my competent knowledge level.[This message has been edited by Patrick (edited 12-27-2022).]
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sanderson231
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DEC 26, 10:26 PM
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This smells more and more like a head gasket. I have not done it but there are chemical test kits that will detect the presence of comustion gases ine the coolant system. Google for more info.
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formerly known as sanderson
1984 Quad 4
1886 SE 2.8L
1988 4.9L Cadillac
1988 3800 Supercharged[This message has been edited by sanderson231 (edited 12-26-2022).]
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Notorio
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DEC 26, 11:36 PM
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Cliff, when I had a temp gauge cycling problem similar to yours, I got an inexpensive dial thermometer and used it to measure the temperature directly in the fill neck. I'd stop engine when the gauge pegged high, then pulled off the cap, yanked out the stat, and dipped in the probe, which proved the stat to be grossly inaccurate. I had hesitated to replace this new stat because the resistance readings were correct per the manual. In view of the hard temperature data from the thermometer, I got another stat and the gauge then worked perfectly.
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theogre
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DEC 27, 02:05 AM
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Cliff... Read that again... All of it...
Very Likely You don't have Air in the system but Exhaust.
Because Cold Engine can let crap parts leak until whatever heats up. Even when warm likely still leaks but less.
Cylinder Pressure just doing basic pressure tests reaches 150-170psi or 10+bars.
Engine runs gets way higher Cylinder Pressure.
Vs. 0-15psi or 1 bar coolant pressure w/ that limit set by rad cap.
"Air" then tries to find the lowest flow area that is the Radiator and why pull the rad cap you get "Air" even when T-stat tube is full.
Ounce Exhaust pushes a bit of Coolant, more exhaust just exit thru same tube and O-tank.
IOW the coolant system is acting sim to a normal purge cycle but one that never ends.
Iffy Head Gaskets etc Does Not = Milky Oil in a lot of cases and for same reason... cyl pressure vs coolant pressure.
Again
Get coolant exhaust test done and watch for color change when coolant has exhaust contamination.
Example: https://www.youtube.com/watch?v=x2f5qEhaFdk
If that test fails Then to see what/where is leaking... Use a coolant pressure tester that's covered above too and bore scope in the spark plug holes to watch for tiny coolant leak(s), 1 or more piston cleaner then others, etc. May get lucky and 1 or more spark plugs are cleaner/different then others. Bore scope may show even w/o the coolant system pressurized if has "clean" piston(s). Or may get lucky just w/ cyl pressure test but don't hold your breath if engine runs fairly well.
⚠️ Warning: If the pressure tester even pumps up to 15-17psi, do not push pass that... If test w/ T-stat adapter and rad cap on you can't. But tester to replace the rad cap then can and blow up the rad or whatever is weaker > 19-20psi.
"T-stat Mod" is 100% crap. Same BS is still pushed for people w/ bent up T-stats when cars really had bad heater plumbing.
And the Fiero T-stat like many others can't trap air bubbles under the valve. Valve etc may look tight to you but air finds any tiny place to get out.
Often Doesn't even stop all coolant flow around the valve seat because how made and often other small holes were parts meet. The O-ring is there to keep the thing in places and easier to make because tube and T-stat don't need tight tolerance to work.
So if "air" seems trapped there then often is Exhaust not air trying to get thru a closed T-stat.[This message has been edited by theogre (edited 12-27-2022).]
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