My engine overheats until I turn on my heater I only have to leave it running for a couple seconds and then can turn it off and it won't overheat for the rest of the drive. 85 gt 2.8l
Something strange happening there......maybe it has to do with a bad electrical contact. Is your coolant really hot or does the gauge just say it's hot?
[This message has been edited by Gall757 (edited 05-19-2020).]
It sounds like there is air in the cooling system or the heater coil or possibly not enough coolant (which would mean air in the system). I had a similar problem until I followed the steps to refill that can be found in Ogre's Cave. I was also parked nose down at a 30-degree angle (steep driveway) when I refilled. Haven't had a overheating problem since.
Something strange happening there......maybe it has to do with a bad electrical contact. Is your coolant really hot or does the gauge just say it's hot?
I don't know I always forget to check my coolant tubes when its happening, although the thermostat cap in the back gets hot.
It sounds like there is air in the cooling system or the heater coil or possibly not enough coolant (which would mean air in the system). I had a similar problem until I followed the steps to refill that can be found in Ogre's Cave. I was also parked nose down at a 30-degree angle (steep driveway) when I refilled. Haven't had a overheating problem since.
I followed those steps to refill as well, and I fill it with coolant although it seems like it might be leaking from somewhere. Looks like the front so maybe the reservoir is bad ?
...it seems like it might be leaking from somewhere. Looks like the front so maybe the reservoir is bad ?
No offence... but if there are signs of coolant leaking, you are the one who's going to have to find the actual location... because the view from where the rest of us are is rather poor!
So in regards to earlier comments, it is definitely overheating, spiked to full temp then shot coolant out a hole in the reservour up front like a jet, pretty much emptied my coolant, had to re add and re burp the system, it will still sometimes get hot and then I have to turn heater on to get it to go back down
Does your radiator fan come on when the temperature spikes? Does the fan come on when the air-cond is on? If the fan doesn't come on when the coolant temperature goes up with the air-cond off, you could have a wiring or switch issue with the radiator fan. I'm pretty sure the radiator fan should run when air-conditioner compressor is operating regardless of temperature. Does that happen?
Obviously you are really overheating- Number one thing to do before anything else is Step 1, let engine/coolant cool down, then step 2, Pop the thermo cap and pull the thermostat, then fill that opening with more coolant and reinstall the cap...Take it for a drive and see if it overheats....this will check a couple of things- A) your thermostat, and B) your waterpump....I replaced mine 20 years ago with a pump with a PLASTIC impeller- the engine overheated 3 times in a row going to work....found out the plastic impeller was slipping on the shaft (Plastic impeller expands faster than steel shaft)
When refilling coolant system, you have to "Burp" the system and top off several times- never pull the radiator cap except when draining the system.....Fill at the back until it flows out of rad' cap and then install cap....Then continue to fill at the back.
Obviously you are really overheating- Number one thing to do before anything else is Step 1, let engine/coolant cool down, then step 2, Pop the thermo cap and pull the thermostat, then fill that opening with more coolant and reinstall the cap...Take it for a drive and see if it overheats....this will check a couple of things- A) your thermostat, and B) your waterpump....I replaced mine 20 years ago with a pump with a PLASTIC impeller- the engine overheated 3 times in a row going to work....found out the plastic impeller was slipping on the shaft (Plastic impeller expands faster than steel shaft)
When refilling coolant system, you have to "Burp" the system and top off several times- never pull the radiator cap except when draining the system.....Fill at the back until it flows out of rad' cap and then install cap....Then continue to fill at the back.
Ya so I did the correct burping afterwards but unless I am running ac/ heater it will start to overheat, also whenever I start up the car it whines, alternator is tight belt is new, alternator is also new, but it whines for a while probably thirty seconds which makes me think waterpump? Thermostat is new as well
If your water pump impeller is slipping like mine was, by removing the thermostat you eliminate drag on the system, so then the impeller will continue to spin (Unless the inside worn so it slips all of the time) This is a temporary test/fix....Also, when filling be careful that you don't have any air pockets in the heating system- that may be why yours stops overheating when you engage the heater/AC.
I don't have AC, so I have never had to deal with any special ventilation system procedures while refilling the coolant.
One other odd thing that once happened to me (But may not apply to Fieros)...My 1973 mach 1 started overheating on the freeway but as soon as I slowed it would cool down....I had replaced everything including radiator and hoses....Finally found out that on Mustangs the SUCTION side radiator hose has a spring in it to keep it from collapsing during high rpm pump operation.....Every time I got on the freeway, the hose was pinching off because that spring was SHORT! Wrecked the 351C in the car, so I installed a 5.0 FI engine.
...air pockets in the heating system- that may be why yours stops overheating when you engage the heater/AC.
Just so we're all clear on this, engaging the heater/AC makes absolutely no difference whatsoever in regards to coolant flow.
Sorry, but I find it impossible to believe that the tiny little bit of heat removed by air going through the heater core would make an appreciable difference in coolant temperature... especially in the span of "a couple seconds"!
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Originally posted by Monkeybean007:
My engine overheats until I turn on my heater I only have to leave it running for a couple seconds and then can turn it off and it won't overheat for the rest of the drive. 85 gt 2.8l
...but unless I am running ac/ heater it will start to overheat, ...
I'd be will to bet the sheep station that you have a faulty radiator fan switch in the engines water jacket. When the AC is turned on it overrides the normal fan switch and turns on the radiator fan, regardless of temperature. When the heater is used it circulates coolant through the heater core which in effect is a radiator and, yes, that small amount of additional "radiator" will lower the temperature.
Quick question for you: Does it overheat when you are driving at speed on the freeway when the AC is off or when it's driven around town in a stop-and-go method? If you don't overheat while driving at speed or the overheating doesn't happen as quickly as when you're doing stop-and-go or tooling around at low speed, you're likely to have a faulty fan switch or wiring issue.
When the heater is used it circulates coolant through the heater core..
Mike, quit spreading FALSE information!
Coolant is constantly circulating through the heater core in a Fiero. How many times do we need to go over this?!!! (This was discussed just recently in This thread.)
[This message has been edited by Patrick (edited 06-03-2020).]
Patrick, don't blow a gasket, Mate. Yes, coolant is circulating constantly through the heater core. Increasing airflow to the core by turning on the fan does improve heat transfer through the core so, yes, using the heater will lower the temperature in the coolant to some degree. It's the same principle as the fan on the primary radiator.
Love you, mean it. I appreciate your input and comments.//www.fiero.nl/forum/icons/icon10.gif
Mike, the "tantrum" fella is still a smiley face. I wasn't choked.
But back to the issue... I cannot believe that running the heater, rad fan, or whatever for two seconds makes a lick of difference with the actual coolant temperature!
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Originally posted by Monkeybean007:
My engine overheats until I turn on my heater I only have to leave it running for a couple seconds and then can turn it off and it won't overheat for the rest of the drive. 85 gt 2.8l
Patrick- That is what I thought.....But my 1972 Merc Comet had AC and had a VALVE that shut off flow thru the vent system while in AC mode.....Wasn't sure about Fieros.
Is there a (Crazy) possibility that the radiator fan is not running until he turns on the AC? How quickly does it overheat? And at what atmospheric temps?
Originally posted by Mike in Sydney: I'd be will to bet the sheep station that you have a faulty radiator fan switch in the engines water jacket. When the AC is turned on it overrides the normal fan switch and turns on the radiator fan, regardless of temperature. When the heater is used it circulates coolant through the heater core which in effect is a radiator and, yes, that small amount of additional "radiator" will lower the temperature.
Quick question for you: Does it overheat when you are driving at speed on the freeway when the AC is off or when it's driven around town in a stop-and-go method? If you don't overheat while driving at speed or the overheating doesn't happen as quickly as when you're doing stop-and-go or tooling around at low speed, you're likely to have a faulty fan switch or wiring issue.
Patrick- That is what I thought.....But my 1972 Merc Comet had AC and had a VALVE that shut off flow thru the vent system while in AC mode.....Wasn't sure about Fieros.
Is there a (Crazy) possibility that the radiator fan is not running until he turns on the AC? How quickly does it overheat? And at what atmospheric temps?
Nah my radiator fan runs almost consistently all the time except for upon cold start but turns on relatively quick and a couple seconds meaning like 15 - 30 sec my bad, as Patrick is aware I'm bad at explaining things lol
...my radiator fan runs almost consistently all the time except for upon cold start but turns on relatively quick and a couple seconds meaning like 15 - 30 sec my bad...l
Something is not making sense. Are you sure the fan is running? In a previous post you said it heats up at stop and go but you're also saying the fan runs almost continuously so that would tend to rule out an fan issue. Good T'stat? How bout the water pump? Impellers can slip if they are plastic.
Some may disagree, but if you remove the t'stat does the car overheat?
Something is not making sense. Are you sure the fan is running? In a previous post you said it heats up at stop and go but you're also saying the fan runs almost continuously so that would tend to rule out an fan issue. Good T'stat? How bout the water pump? Impellers can slip if they are plastic.
Some may disagree, but if you remove the t'stat does the car overheat?
The fan is definitely running can hear it loud and clear, and it does heat up at stop and go especially if I am at a drivethru then it will start to heat up moderately fast. And it's a new thermostat, didn't have one when I got the car so it was always cold, and then found out I didn't have one tossed it in and it let the engine heat up lol. The water pump is what I am thinking due to , squealing upon startup that definitely isn't alternator.
....And it's a new thermostat, didn't have one when I got the car so it was always cold, and then found out I didn't have one tossed it in and it let the engine heat up lol. The water pump is what I am thinking due to , squealing upon startup that definitely isn't alternator.
So the problem started after adding a t'stat? Maybe the new thermostat is faulty. Squealing on start-up is usually a loose belt. The belt drives the alternator, water pump and a/c compressor (if you have a/c). Not sure if a loose belt is the problem, but you should check the tension or maybe even replace the belt.
So the problem started after adding a t'stat? Maybe the new thermostat is faulty. Squealing on start-up is usually a loose belt. The belt drives the alternator, water pump and a/c compressor (if you have a/c). Not sure if a loose belt is the problem, but you should check the tension or maybe even replace the belt.
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How tight should the belt be ? Right now I have it where you can pluck it like a guitar string but you can still twist it, is that too loose? And it wasn't an issue for a little bit after replacing the thermostat , like month maybe till it became an issue.
Hello Monkeybean, does your new thermostat have the tall upper loop? The cap presses on the loop to hold the 'stat in place. A regular type T-stat would come up and possibly block the return line to the rad. You said that with no T-stat the engine stayed cold. Has to be a T-stat issue IMHO.
Hello Monkeybean, does your new thermostat have the tall upper loop? The cap presses on the loop to hold the 'stat in place. A regular type T-stat would come up and possibly block the return line to the rad. You said that with no T-stat the engine stayed cold. Has to be a T-stat issue IMHO.
Excellent comment from 88Fingers. Your thermostat should look like this: https://images.app.goo.gl/NhHSHwQNJ1YFVKxHA If it doesn't have the big loop at the top, it's the wrong one. The loop holds the thermostat in place when the coolant filler cap is on.
------------------ Mike in Sydney
[This message has been edited by Mike in Sydney (edited 06-07-2020).]
If your radiator cap is old it may not hold pressure and that leads to overheating too. Also they leak, the leak gets bigger over time and one day you will get to your car and there will be a giant green puddle under the nose.
------------------ 86 GT built 2.2 ecotec turbo rear SLA suspension QA1 coilovers on tube arms
Check to make sure it's a non-vented rad cap as well.
From Ogre's Cave...
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Warning! There is an error in Stant old listings. Which means all catalogs, including some brands catalog, listing Stant parts share the same error. The correct caps for Fiero are Stant part numbers 10230 or 10330 non-vented caps.
Yes the thermostat has the big loop I made sure to look up correct type when I got the new one, and there is no leakage from radiator cap and dosen't appear to be vented how would I check ?
If the belts squealing, something slipping and not turning at full speed. Like your water pump, change the belt- cheap test. Maybe scuff up the pulleys w some sandpaper for better bite. Good luck
(This was discussed just recently in 
I wasn't choked.
