Stock 87 2.8L ... I replaced my temperature gauge sender/switch so I could read my gauge and it works fine but as soon as I start the car and let it idle the needle on the gauge slowly creeps up all the way to the red then I shut it off. I don't think the thermostat is opening cause the thermostat housing tube and cap get super hot also the radiator hoses dont get hot. Is this just a defective thermostat or something bigger??
Thanks

------------------
'86 2m4- Auto, Daily Driver
'87 GT - 5spd, Project Car
--------------------------------------------------------------------------
So now you'd better stop and rebuild all your ruins,
For peace and trust can win the day despite of all your losing

quote Originally posted by FIER086: Stock 87 2.8L ... I replaced my temperature gauge sender/switch so I could read my gauge and it works fine but as soon as I start the car and let it idle the needle on the gauge slowly creeps up all the way to the red then I shut it off. I don't think the thermostat is opening cause the thermostat housing tube and cap get super hot also the radiator hoses dont get hot. Is this just a defective thermostat or something bigger?? Thanks

W A T E R P U M P

[This message has been edited by randye (edited 06-11-2008).]

Alright, I took the thermostat cap off and rad. cap off and started the car and the coolant obviously is flowing cause it bubble/shot out pretty quick onto the side of the motor. Does this mean my water pump works? Also does my gauge need recalibrating since i replaced the temperature gauge switch/sender? When I turn the key to ON the needle goes to 100 like it should but when i start it it pegs and gets stuck until I hit the dash n it comes down.

Put the thermostat cap back on without the thermostat inside, see if it still gets hot on the guage. If it does then something's blocking flow or the water pump isn't pumping fast enough. Look under the car at the cooling tubes, see if they're crushed. Look at the hoses to see if one's collapsed. Have you ever had the radiator cleaned out?

JazzMan

I put the thermostat cap on w/o the thermostat in, and left the radiator cap on but the gauge still went all the way up. It seems like the water pump works because of the eruption of coolant out of the thermostat housing when i started the car. I glanced at the coolant lines under the car but they aren't crushed but a little dinged up in places. I could have a air bubble. Does my gauge need to be set in some way? And my fan never comes on once it gets past 260*.

Its not the water pump, 99.99999.9% of the time waterpumps just fail because the bearings go out, they still work, just leak. There are some plastic impeller WP out there than can fail, but its almost on the verge of an urban legend at this point.

You probably have an air bubble. You need to burp the cooling system.

Park the car with the nose slightly down, or level.
Open the thermostat cap in the rear, remove the thermostat and leave the cap off.
Crack the front radiator cap just a little so that the air can get out, put it back on when coolant starts coming out
Top of the thermostat area.

Some Fieros will run with the thermostat cap off, others just spew coolant everywhere. If you can idle with the cap off, do so.
Top off the rear and start the car for 30 seconds, then turn off and top off again.

If your car will run with the cap off and not spew coolant, you dont need to do all this off and on, just run the car and let it heat up, keeping the coolant full, Once it really starts to warm, the coolant will expand and start slowly dribbling out. At that point put the cap on and take it for a drive.

Then let the car warm up a little, and carefully remove the cap, it doesnt take much to build up pressure, so you might want to let it cool off. all the air should accumulate in the thermo housing.

Then take the car for a drive, bring it back and let it cool off and top it off. That should be about it. You can also squeeze the radiator hoses hard, this will move coolant around and might dislodge an air bubble.

Keep the heater on full, if its blowing warm air, then you dont have a circulation problem. If it ever goes cold, that means coolant has stopped flowing. It could also be either a plugged radiator or maybe just a bad guage, but Id try burping first, these cars can be tricky.

[This message has been edited by 86GT3.4DOHC (edited 06-11-2008).]

Wow thank you for that write up! This is my plan, first I will buy a new thermostat, get some more coolant, burp the system, and install the new thermostat. I am unaware of the water pumps condition because I just bought this car. It doesn't leak or make any noise and the belt is tight and I think I have flow because it went spewing all over when I started it up. (does this mean the pump works?) Also my heater blows hot.

And my rad fan won't come on so I looked at the fan switch and the connector looks broken will this affect anything until I get it fixed, the fan doesn't kick on till it gets real hot anyway?
Thanks

Ok, I burped the cooling system and put in a new t-stat with no change. Within a few minutes the temp. gauge heads towards the red then I shut it off. Does this mean a bad water pump? It doesn't make any noise or leak though. Also while I was burping it when I took the t-stat cap off after letting it run for a minute to get the bubbles out the coolant was all foamy and frothy. Does this mean head gasket? My oil is fine with no coolant in it. I am lost, please help.

Do you get heat out of the heater when its warmed up?

Have you had the car awhile and it just started this, or did you just get it?

Have you had it raised up about the time this started? The under body cooling tubes are easily crushed if lifted or jacked improperly. Also these can just be bent a little, look fine, and cause probelms. What I had one time, I had the car for years and all of a sudden it started overheating. Long story short the coolant tube was bent, but not too much, eventually when the hose got soft, the bend was enought to cause it to collapse under pressure, but not when the engine was off. So it would overheat but there would be no sign of a problem. That was a fun one to figure out.

If you've gone through the whole burping thing, a more aggresive burp may be needed. If you didnt have antifreeze in it, I would suggest cramming a hose in the thermostat neck, and opening the radiator.

You are doing this burping without the thermostat right? The thermostat will keep it from burping properly, dont even bother putting it in until you have it running right. All the thermostat does is regulate the minimum running tempature of the motor, it has no effect on overheating.

So if you really cant get it working, start by taking out the thermostat (again, dont bother with it in yet) with the front end parked higher than the back, take the drivers side hose off the radiator, try to keep coolant from falling out of it. Start the engine. If you have coolant rushing out, then put it back on. You might try topping off into the radiator and the hose first. If you get no coolant, make sure there is as much water in the system as you can get in there.

Mainly we need to know if the heater blows hot or cold when overheating. Hot heater and overheating engine means there isnt enough heat getting pulled out through the radiator, usually a plugged rad. Cold heater when warm means no coolant flow. Again, there is the far out possiblilty of the WP being a plastic impeller and not working, but its far from likely.

quote Originally posted by 86GT3.4DOHC: Its not the water pump, 99.99999.9% of the time waterpumps just fail because the bearings go out, they still work, just leak. There are some plastic impeller WP out there than can fail, but its almost on the verge of an urban legend at this point.

Grr.... Urban Legend? I was one of those poor bastards that had his plastic impellered waterpump fail. I will say this. When it worked, it ran AWESOME. I mean, it ran cooler than any Fiero I've ever had and the temperature was always at least 1/10th cooler than it was before or when almost new.

It was the Coltec brand of water pumps (from Holley I think).

------------------
Todd,
2006 Pontiac Solstice
2004 Volkswagen Beetle Convertible (Wife's Car)
2002 Ford Crown Victoria LX
1987 Pontiac Fiero SE / V6 (3.2) 5-Speed
1984 Porsche 944 5-Speed
1981 Pontiac TransAm (Olds 455BB)
1981 EZ-GO Xi875-A "Miami Dolphins" Medical Cart
1973 Volkswagen Type-2 Transporter

Thanks for the help 86GT3,

The heater blows warm, I dont know about hot but I turn the car off within 4-5 min. because the temp. goes into the red w/o the SES light coming on. When it starts overheating the engine runs fine, no sputtering or stalling either. I cannot tell if the rad. hoses get hot or have coolant circulating because I shut the car off because the gauge goes into the red. The solid lines under the car look great, pass. side has a small dimple in it so that isn't the problem. I just bought the car but i dont talk to the previous owner.

You need to examine with your fingers the coolant pipes, especially the area where they turn upwards at the back just before connecting to the rubber hoses going to the engine. Often times they get bent upwards and look just fine to the eye, when in fact they're folded and nearly closed off. They should feel fairly round all the way to the hoses.

With the engine running and warmed up you should feel the metal lines at the front, and feel the hoses or tank either side of the radiator. Are they hot? The heater core should blow fairly hot, especially if the guage is getting that hot. Are the heater hoses hot?

The cooling system in a Fiero is easy to troubleshoot and fairly robust, it's a simple system. Either coolant is flowing or it's not. Air isn't as big a problem as it's made out to be, a bubble or pocket in a properly function system will get pushed out to the radiator in no time. In a system with a weak pump or clogs it won't, but in those cases the pump or line problem is the real issue.

JazzMan

So it could be the radiator is clogged, one of the lines/pipes is cutting off circulation, or the water pump. And it can't be the water pump if the heater blows hot??

Also how come the car doesn't run like crap or shut off once it gets so hot on the gauge, btw the temp. gauge sender is brand new w/ new connector?

[This message has been edited by FIER086 (edited 06-13-2008).]

Engines could care less about operating tempature, it would continue running smooth clear up until the pistons seize in the cyls or the crank locks up.

After reading most of this thread I would put my money on a clogged radiator.

I forgot to mention that most of the front end got ripped off when the PO tried towing it from the front. This left me with no front bumper, air dam, or anything holding the radiator up, basically its just hangin there, but all the hoses around it look fine. The rad. looks like crap so it is possible it doesn't work good. I will start it again and feel all the hoses for heat today.

quote Originally posted by FIER086: When I turn the key to ON the needle goes to 100 like it should but when i start it it pegs and gets stuck until I hit the dash n it comes down.

I just noted this statement you made. I missed it earlier.

If I understand you correctly, you hit the top of the instrument pod and the needle on the temp gage goes down?

You really need to determine if the car is actually overheating before going further.

Fiero gages, (especially the water temp and oil pressure gages), have been notorious for being inaccurate, at least in my experience. I had a temp gage that did exactly what you describe. Have you fixed the pegging temp gage problem? There are numerous threads on the forum on how to do this.
If your temp gage has been pegging, over time the needle can become loose or slip and give wildly inaccurate readings.
Hitting the top of the instrument pod and having the needle move down is a good indication of a gage problem.
After I finished my 3.4L engine swap I thought I had an over heat problem and after replacing nearly everything in the system, including a new radiator, hoses, t-stat all to no avail, I finally had a shop with a SnapOn scanner read the ECU to get a water temp from the other sensor: NORMAL
I replaced the temp gage, and while it is still not nearly as accurate as I would like, I at least have a better indication of the engine water temp.

Certainly check all the other things that others have suggested, but it might be worthwhile to determine precisely what temp the engine is actually running at this point.

[This message has been edited by randye (edited 06-14-2008).]

Yeah I need to fix that for sure, it only gets stuck sometimes though. I figured since it starts out at 100* it was accurate??

Anyway I just started the car and let it run for about 5 minutes until the temp. gauge went into the Red. The heater in the car blows hot, but both of the radiator hoses (upper & lower) stayed ice cold while the car got hot. So is the radiator clogged or look at the water pump still?

quote Originally posted by FIER086: Yeah I need to fix that for sure, it only gets stuck sometimes though. I figured since it starts out at 100* it was accurate?? Anyway I just started the car and let it run for about 5 minutes until the temp. gauge went into the Red. The heater in the car blows hot, but both of the radiator hoses (upper & lower) stayed ice cold while the car got hot. So is the radiator clogged or look at the water pump still?

I just replaced my radiator in my 2.8l 86 Fiero. I got lucky this time and found a nice used radiator that I could have rodded out while still using the old radiator to reduce down time. I have not finished burping the system but after draining the old coolant from the radiator I have been using it would appear that it could very well have been the problem. There was a lot of gunk floating around in there. Then I filled one radiator tank with water and let it run through the pipes to the other tank. It only dribbled through the tubes. I hope that putting in a good radiator fixed my problem. The last time this happened I had the same symptoms as you. The coolant temp gauge showed hot and the heater made hot air but the pipes to and from the radiator were relatively cool. Easy to hold my hand around the hose and not feel more than a little warm while the engine was over 220 degrees. When I put a clean radiator in that time the problem was solved. This a long way of saying it looks like it could be your radiator.

quote Originally posted by FIER086: When I turn the key to ON the needle goes to 100 like it should but when i start it it pegs and gets stuck until I hit the dash n it comes down.

Fieros temp gauges are wired incorrectly from the factory. Look here for a fix.

Update:

I did a quick burp of the system and went out driving. The rodded out used radiator once again fixed the problem. I am surprised to see that my last radiator only lasted approx 2 good years after being rodded out and started getting plugged up again last year. This year it was not going to handle the heat with the A/C on but now it looks fine. Good luck with yours.

If the radiator is only being held up by the hoses, it wont work for sure, and if its bashed up thats a bad sign too. I would fix it right before you try chasing problems. If the coolant cant flow through the radiator, it wont move down the pipes, which means everything from the motor up will stay cold regardless of how hot the engine gets.

quote Originally posted by 86GT3.4DOHC: Its not the water pump, 99.99999.9% of the time waterpumps just fail because the bearings go out, they still work, just leak. There are some plastic impeller WP out there than can fail, but its almost on the verge of an urban legend at this point.

it's no legend. the one I took out had a plastic impeller, it too would gush the tstat housing, but the car would still over heat. the impeller spins on the shaft, and with any type of load on it, will not flow water. The new one I put in was an acdelco from the fierostore, and it also had the plastic impeller. brand new pump.
failure scenario was you had lots of heat at the heater core, but the motor would overheat unless the car was moving and it was very cool out.
it got worse from there.

now for the easy method to fill the fiero cooling system.
open the radiator cap and fill at that tstat with no tstat in until it overflows at the radiator. cap the radiator. top off the tstat housing. put on the cap (no tstat). start car and run for 30 seconds or so, blip the throttle a couple of times. shut off. open tstat, top off. cap it and restart for another 30 seconds, blip it a few times. shut off. top off should only take a quart or less at this point. if so, top it off put in tstat and drive.
be sure you have the reserviour holding collant to the cold line intially, and check it a few days later when hot.
simple. takes under 5 minutes. no need to raise the nose. I previously pointed out with a diagram you would need to get the nose about 3feet off the ground in order for any air to move thru the system.

for this issue, if you are 100% sure you got it burped right, it is either the radiator clogged, or the wp is a plastic impeller that failed. if you have any radiator shops in your area, you can take it in and they can flow test it for you. if not you can try removing it and backflushing it directly with a hose. try the non cap side first, that is normal flow, if it flows enought to let the hose go thru it wih just your hand holding the hose end in the input, it probably isn;t that bad. go from the opposite side and see if you get any gunk out. a decent radiator should be able to flow the output of most garden hoses with almost no backpressure.
unfortunately there is no way to tell if the wp is plastic or not on the car. best to eliminate what you can before going for the pump.

Im not saying its a legend, im just saying everytime someone posts with a cooling problem, several poeple start saying plastic impeller, but thats hardy, rarely, ever it. Just like whenever someone has a drivability problem several people pop in saying it must be the cat, and yes, it happens, just the majority of the time its not it, and usually it doesnt even fit the symptoms.

But you gave me a great idea I've used in the past. Just take the lower passneger hose off the underside pipe, at the engine, cram a hose in the lower drivers side pipe, at the engine, and see if you get water shooting through the system (through the radiator not the engine), or just squirting out around the hose. You will loose a lot of antifreeze, but its starting to look like youre going to be opening the system anyway. This is a fool proof way to see if you have a blockage. Make sure you shoot the water from the drivers side to the passneger side first, in the normal flow. If that doesnt work, you could then try backflushing. But again, if the radiator is flopping on the rubber hoses, there isnt much point in testing anything until you get that fixed.

Right now I got the radiator sitting up in place with bungee cords, I know its white trash. That sounds like a good idea with the garden hose deal to test the flow and clear any blockage. Should I try just removing the radiator first and flush that or should I flush the lines as well? For now I think I'll just do the easier stuff first.
Thanks again guys for all the help, I am new to the cooling systems but I will let you know the progress in a couple of days.

one other thing to check since you bought the car from somebody else and dont really know what they did, make sure your radiator cap is a NON VENTED CAP. this happened to me. also if you do pick up a new cap DISCOUNT AUTO HAS THE PART #S WRONG. THE ONE THEY HAVE ON THEIR COMPUTER IS FOR A VENTED CAP. i DID NOTIFY THEM BUT SO FAR NO CHANGE ON THEIR COMPUTER........

I would do the flow test with it in the car, and test through the underbody tubes, just use the lines in the engine bay. This way we can check the whole system in one shot.

Thanks everyone, especially 86GT3!

The radiator cap looks original but I will probably replace it soon. This week I will test the flow like you instructed through the pipes. But I am a bit confused cause you said...
Just take the lower passenger hose off the underside pipe, at the engine, cram a hose in the lower drivers side pipe, at the engine, and see if you get water shooting through the system (through the radiator not the engine)

If I do this the coolant will just come out the passenger side by the motor right, and not through the radiator??

hey fiero86 if you need a differnt radiator i have one from my project car you can use, i work right down by you (i think) so i can bring it to you if you want.

If you put a garden hose into the drivers side under body tube, facing foward, the water will go up through the radiator, down into the passenger side tube and run out on the ground.

quote Originally posted by 86GT3.4DOHC: If you put a garden hose into the drivers side under body tube, facing foward, the water will go up through the radiator, down into the passenger side tube and run out on the ground.

In addition, if you have a helper handy, have them hold the hose and you look into the radiator cap hole. See how the water is flowing out of the tubes. You should get an idea if it is flowing freely or not. I drove my car some more and it was definitely 100% a clogged radiator causing the problems. The radiator that was clogged did not take very long to get that way so don't be too surprised if that is the problem.

...one thing I noticed in reading through this, he said that the car hits the red on the gage in 5 minutes - now this seems a bit odd to me that the engine would heat up that fast? Both of my cars (stock and 4.9) take a lot longer to show any indication on the gage never mind over heat.

If you have access to a scanner, what temp do you read coming from the ECM and does it match the gage reading (separate sender for the ECM)?

...could be a bad sender (wrong one) or some sort of wiring issue...

If the car is overheating without the thermostat in, than you have a blockage or the water pump is not working correctly. Sometimes it is really hard to get all the air out of the system.

Also meationed that the coolant was all frothy at one point - this would indicate an issue with the water pump cavitating (bad pump or air in the system).

Flushed entire systm with hose described above including pipes under the car and the radiator. I was checking for blockage in system. After all the old coolant was out the water via the hose had good flow up the driverside thru the rad. down the passenger side and out.

So I refilled the cooling system with 50/50 mix, burped the system, used a new t-stat.

I should mention my Temp gauge does NOT work right now after I did the pegging temp gauge fix via instructions from fierosails.com, refer to this thread if you can help with this problem please--- https://www.fiero.nl/forum/Forum2/HTML/092965.html

After burping the system I started the car and let it warm up while I walked around the car checking all the hoses/pipes for heat. The upper rad. hose (driver side) now gets warm, before the flush it stayed cold. The pipe under the driver side now gets warm. The passenger side cooling pipe gets warm, but the lower rad. hose seems cool to me?? After about 6 minutes of the car running I shut it off because it was smelling really warm and the T-stat cap got really hot, b/c my temp. gauge does not work I shut it off for fear of overheating! **ALSO MY RADIATOR FAN SWITCH IS BROKE CAUSE IT NEVER COMES ON EVEN WHEN I TURN THE A/C ON.

All in all, it seems that my cooling system is not clogged, at least anymore but I'm not sure if I solved the problem. My water pump seems to work as well if it is moving fluid thru the system correct? (pipes get warm) I really need to fix the temp. gauge and fan switch next, but I thought I would keep you guys posted on the progress and maybe you fellas can give me some free advice

quote Originally posted by FIER086: Flushed entire systm with hose described above including pipes under the car and the radiator. I was checking for blockage in system. After all the old coolant was out the water via the hose had good flow up the driverside thru the rad. down the passenger side and out. So I refilled the cooling system with 50/50 mix, burped the system, used a new t-stat. I should mention my Temp gauge does NOT work right now after I did the pegging temp gauge fix via instructions from fierosails.com, refer to this thread if you can help with this problem please--- https://www.fiero.nl/forum/Forum2/HTML/092965.html After burping the system I started the car and let it warm up while I walked around the car checking all the hoses/pipes for heat. The upper rad. hose (driver side) now gets warm, before the flush it stayed cold. The pipe under the driver side now gets warm. The passenger side cooling pipe gets warm, but the lower rad. hose seems cool to me?? After about 6 minutes of the car running I shut it off because it was smelling really warm and the T-stat cap got really hot, b/c my temp. gauge does not work I shut it off for fear of overheating! **ALSO MY RADIATOR FAN SWITCH IS BROKE CAUSE IT NEVER COMES ON EVEN WHEN I TURN THE A/C ON. All in all, it seems that my cooling system is not clogged, at least anymore but I'm not sure if I solved the problem. My water pump seems to work as well if it is moving fluid thru the system correct? (pipes get warm) I really need to fix the temp. gauge and fan switch next, but I thought I would keep you guys posted on the progress and maybe you fellas can give me some free advice

I just had the same problem today... never happened to me before and on the highway. Shooot... so what's the verdict, what should I do with this overheating problem?

------------------
1986 GT Fiero Owner & Enthusiast
For Fiero updates, visit my site and don't forget to click on the ads!
http://educatorstop15.we.bs/fieropage.htm

Alrighty, now my TEMPERATURE GAUGE WORKS FINALLY!!! So I started the car this time and the needle rose slowly as it warmed. As it warmed, I rechecked all the pipes/hoses and the only one that is cold to the touch is the lower rad. hose and cooling pipes under the passenger side, the only spot on the passenger side cooling pipe that gets Hot is where it goes up into the motor, the rest of the pipe forward towards the front is cold. What is the deal?? The needle on the gauge soared passed when the t-stat should open but kept rising to the Red before I shut it off too.

I have the exact same symptoms you describe. I wasn't able to figure out the problem and lost the space where I work on the car so I had to take it to the mechanic. I should be getting the car back this week sometime, so if you don't figure out what's wrong I will post the solution when I find out.

bump

Pull the single wire off your fan switch, green wire maybe stripe green and ground it out to your block, the radiator fan should come on. The fan switch is on the intake under the thermostat housing, if fan comes on that indicates a bad switch.

Make sure that the rear of the car is slightly elevated, pull thermostat out and re-burp the system. Leave the thermostat out, run car again with cap on tight, if the car gets hot on the gauge quickly then you're looking at a clogged radiator or defective water pump.

I would also take a look at the cooling fins of the radiator as we have those stupid cotton wood trees here in Michigan and they clog up the cooling fines big time. In that case, a high pressure hose will clean that out for you.

------------------
jetman
Silver 86 SE 2M6 4-speed, with "check wallet light"
Now fortified with 8 essential slices of bacon goodness