It all started with the temp gauge. I replaced the temp sender ( twice actually) and the temp gauge. I also ending up patching the radiator tube that runs to the back. I must have disturbed it when I drained off some fluid by taking the rubber radiator hose off that goes up to the motor. But now my fan doesn't start up when the motor gets hot, that is into the red . I replaced the fan switch and the connector end but still nothing. I know the fan works because when I put on the air conditioner the fan runs. Also I shorted the fan switch wire to a ground and again the fan runs. Where do I go from here? The only thing I didn't replace was the temp sensor but from what I have read, that shouldn't stop the fan from running. Help, I'm getting frustrated. Centervilledon

You've got a airlock in your coolant system. It needs to be burped at the thermostat.

Could an air bubble cause the fan to not kick on? I would be very happy if that was it. How do I burp it? Don

yup air pocket sounds most reasonable.. I jacked up the back of my car, pulled the thermostat out, and filled it.. started it for a min and rechecked it while jacked up.. I'm sure there is a proper procedure for this but this way worked for me.. good luck to ya.

To "burp" the cooling system, you remove the thermostat and go through a cycle of running the engine for a few seconds (10-15 seconds is enough), shutting it off, and topping off the coolant. It may take 4-5 repetitions to get most of the air bubbles out.

Just out of curiosity, what type of sealant (if any) did you use on the fan switch? If you use Teflon tape on the threads, it can interrupt the flow of electricity through the switch (it's grounded via the threads).

I didn't use teflon tape, but I did use a very small amount of gasket sealant. I did a search after I posted my message about "burping" the system. There is a lot of opinions about this. One invollves taking off the front radiator cap. I haven't been able to take that cap off as yet. It is stuck on there pretty good. Is it necessary to get that cap off? I did lose a lot of fluid on my floor from the leak and from not being able to catch all of the fluid when I drained some off to put in the fan switch. So, I'm thinking maybe everyone is right and there is some air in the system because it is full of fluid at the t-stat and only down a couple of inches in the reservoir tank. I tried to pull the thermostat out and It didn't come. Are they all hard to break loose? Do you need pliers to get it out? Centervilledon

You don't need to remove the radiator cap since any air trapped there will eventually vent into the reservoir or find it's way rather quickly to the thermostat neck once the thermostat opens properly under normal operating conditions. You do, however, have to get the thermostat out of the housing since this is where the trouble is. Since the theremostat housing is the highest point in the system, any air in the system will accumulate there. Any air trapped under the thermostat prevents the coolant from touching the bulb which prevents the theremostat from opening which prevents the coolant to circulate to the radiator.

Thermostats can be hard to remove because there's a tight rubber o-ring so you may have to use pliers... twist it a bit first to get the o-ring to release. You should plan on buying a new one before you remove the old one since the basket handle can break off. Once you get it out, back fill the engine block until it spills over into the large tube at 90* to the housing near the top. Then keep filling until the large tube is full, then you can either take your chances and replace the thermostat and cap and hope for the best (works 90% of the time), or replace just the cap, run the engine for a minute or two, and do a final top up before reinstalling the thermostat and cap. Good luck!

I wouldn't worry about the radiator cap, or jacking up the rear end, or any of that stuff. People seem to like over-complicating the coolant filling procedure, for some reason.

However, you do need to get that thermostat out. You can pry on it with pliers, or a big screwdriver. Just be careful not to rip the handle off the thermostat. When you re-install the thermostat and its cap, a light coating of Vaseline (or axle grease) will help prevent the rubber seal from sticking in the future, and will help seal the cap to the thermostat neck.

I did get the t-stat out okay. It was still full of fluid. I left the t-stat out and let it run for a couple of minutes and took off the cap to refill it again. What happened was kind of a surprise. Fluid came out an over the top! I looks like a cup or two came out and onto the floor.. I put the t-stat back in and took it for a ride to see if the fan would kick in. After I got back, it was hot, I think it was about 220 according to the gauge. I let it idle for 5 minutes or so more and the temp went into the red to almost 260 degrees, but the fan never started. I filled the front reservoir to check hot line. I shut it off and let it cool down pretty much. When I opened the cap, fluid started coming out the top again! What do I do now? Centervilledon

Just my 2 cents. Have you confirmed that the gauge is giving you the correct reading? I suggest this only because I suffered from a very similar issue and I spent plenty of money and lost allot of time in changing out parts and sensors, when it really came down to a bad ground that would give a bad signal to the temp gauge. I suggest you get a multi meter and test the gauge sending unit at the block head for a true and accurate reading of the engine temp.

Abe

Tell me, when the the engine is hot, is the upper radiator hose at the radiator hot to the touch? If not, then your t-stat isn't opening. You could try putting it in a pot of boiling water to see if it pops, if it doesn't, then replace it.

Good idea Bloozeberry. I don't think I checked that hose. The front hose was hot. I'll have to check that out next time I drive it. I'll try the thermostat in boiling water test tonight. Centervilledon

Hmmm, radiator fan not working after messing with temp sensor and trying to fix the temp gauge...?

I cannot assume how much you know about the wiring diagrams and the coolant fan wiring. Can you please elaborate on what year the car is? What engine does it have?

I suspect that you changed something when trying to fix the temp gauge. Maybe not but it is the highest likelihood versus something like the radiator fan temp sensor suddenly stopped working at the same time you were working on the temp gauge temp sensor. As Blooz and the others suspected it may be that the system has an air bubble and the radiator fan temp sensor is not getting hot water on it. More likely after what you have done so far is that either you changed the wrong sensor or it just gave up and quit... For the 2.8L v-6, when the engine is hot you should have a short to ground on the temp sensor above the water pump. The temp sensor by the ignition coil is for your temp gauge and light. If this is the correct engine type and you already knew this then put an ohmmeter on the sensor over the water pump and see if it shorts to ground when the engine is hot enough to turn on the radiator fan.

Charlie

To Bloozberry, I did the thermostat test in boiling water and it popped open. To cptsnoopy, The car is a Fiero '85 V-6 GT. I changed the temp sender which is underneath the ignition on the left end of the motor as you face it. I changed that part (actually twice as the first one made the temp gauge act a little wild) I did not change the temp sensor which is on the t-stat end. I did change the fan switch and the connector end which is close to the temp sensor near the t-stat. I got my information on the Fiero Store site. I was very careful to put in the correct part. These are the tests I have done. I used a wire with sharpened nails on each end and poked it into the wire after the connection I did going to the fan switch and the fan ran, so the wiring is OK. On the fan sender I grounded one prong of the sender connector and the temp gauge went all the way right. The light did not come on when I grounded the other prong. I may have knocked the bulb loose when I changed the temp gauge, I changed the temp gauge because of the wild readings I was getting. When I put the replacement gauge in, the gauge was still kind of wild. That's when I exchanged the temp sender and things settled down. Here is another test I did. I put a couple of resistors onto the one prong that moved the needle to fhe far right With a 1600 ohm resistor set the reading was 100 which is where it started and it did not move and with the 68 ohm resistor set I got about 230-240 degrees on the gauge. Thats where I am now . I know this is long and little confusing and if you have any questions let me know. I don't have a good multimeter to do that test. Centervilledon

You are doing very well. It has to be something simple, maybe even the gasket sealant you put on the fan switch. Can you ohm the fan switch when the temp goes above 230*? It's very hot there and a bit hard to get at so you would need to setup a wire ahead of time. You would be looking for 0 ohms.

Before I changed to the 7730 ECM I checked mine at 228*F when the fan came on using WINaldl software, an ALDL-Serial Port cable, and an old serial port equipped laptop.

You really don't need any sealant on those particular threads. It's a tapered thread design that gets tighter the farther it's screwed in.

Someone told me a small amount of sealant wouldn't stop the connection from being made. What I could do about that is do a continuity check between the fan switch body and the block, if I can get to it, and make sure that the ground is being made. Some how I don't think that is it since I used such a small amount of sealant. The multimeters that I have are simple and only have one range on it. And to be honest I can't figure out how to use either one of them. The digital one just says OL all the time. And the analog one 's readings don't jive with the resistor's numbers I have checked. I do have a friend who says he has a good one. I could pay him a visit I guess, next week. This weekend is jammed up. Thanx foe trying to help. Centervilleon

You might have to move the red test lead from one socket to anouther in your meter to read ohms - the common lead (black) won't have to move.

It seems you have a pretty good idea of what is what. My next thought is (this has been sort of touched on...) that maybe you are just not getting the coolant hot enough to trip the fan switch. From what I have read so far you do not mention the coolant boiling over and if that is the case, do you have any way to accurately measure the coolant temp?

Charlie

All good suggestions here for things to check but I'll add one more. Make sure your heater circuit (core, lines & hoses) isn't plugged. The coolant has to circulate through the heater core anytime the engine is running, even when the thermostat is closed. It's a bypass for the coolant to circulate and warm up the thermostat until it opens. If yours is plugged or blocked off it can cause symptoms exactly like what you are describing. My '86 GT had a kink in a heater hose line and it caused the engine to overheat but the radiator fan would not come on. The hose at the radiator was cool to the touch. After repairing that line everything worked normally again.

Mike

Okay, First, my multimeters only have one red socket and one black socket.These are the things I have yet to try... Ohm the fan switch when the motor is hot, check the hose at the t-stat to see if that is hot ( I believe it was), check my ground of my fan switch, check for heater core hose kinks, and check actual temperature of the coolant. I'll have to buy a good multimeter with several OHM reading ranges or borrow my friends. Most of the checks I think I can do except checking the actual coolant temp. I could buy a temp gauge from Auto Zone (about $20) and hook that to my temp sender, How do you ohm the fan switch? Do I poke a small hole in the wire with a straight pin coming from the sender and put one probe there and the other on a ground, when the motor is hot? Thanx guys, I appreciate the ideas, Is there anything I'm missing? Centervilledon

quote Originally posted by centervilledon: How do you ohm the fan switch? Do I poke a small hole in the wire with a straight pin coming from the sender and put one probe there and the other on a ground, when the motor is hot?

Yes... or just unplug the connector if you can. Don't forget to check for crushed coolant lines running to the front of the car too.

Thanx Bloozberry, I don't want to disconnect that connector. I've ruined one already. I'll go with the straight pin idea. I will check the coolant tubes for sure. Centervilledon

There is another option, though it might sound a bit drastic. What I did on mine was to buy an electric fan controller that triggers off the rad/coolant temperature and has an adjustable turn-on point. This way it is all more or less self-contained right in the fan/rad area and doesn't rely on anything running back to the engine. Foolproof that way.

Rick

With the key on have you shorted the fan switch wire to ground to see if the fan comes on?
You may have gotten a bad switch or even a bad pig tail.
I know you don't want to take it off but if it were me, I would just to see.

Indiana_resto_guy Yes I did that test and the fan ran. To- CouldahadaV8 The is a sure way but kinda of expensive I would guess. Thanx for the suggestion anyway. Centervilledon

Off topic but.....I replaced the stock fan with an aftermarket fan. My question is what direction does the stock fan turn? The fan I installed is running counter clockwise.....I would just go check my other car but I am at work.

quote Originally posted by MstangsBware: Off topic but.....I replaced the stock fan with an aftermarket fan. My question is what direction does the stock fan turn? The fan I installed is running counter clockwise.....I would just go check my other car but I am at work.

As long as its pulling air through the radiator it doesn't matter what way it turns but pretty sure stock in clock wise if your looking at it sitting in the car.

You are aware the fan isn't supposed to come on till the coolant reaches 230* (almost in the red) or so and runs till it cools to 220*.
That is unless you installed a lower temp switch.

[This message has been edited by Indiana_resto_guy (edited 06-12-2010).]

If it were me, I'd compare the temperature gauge reading to the ECM temperature sensor (the one below the thermostat neck) to see if your gauge is off. You can do that with a multimeter measuring Ohms (refer to chart below), or with a laptop using WinALDL.

You may have accidentally tweaked the temperature gauge when you replaced it.

Anyway, here's the chart.

I took it for a drive and then parked it in the driveway and let it idle. The temp went all the way up into the red and the fan did not kick on. It is possible that the temp reading is wrong, It is a replacement gauge and a new temp sender (actually its the second sender, the first one seemed to be faulty, so I returned it). Centervilledon

Posting this for people who don't know where the fan switch is. The other temp sensor is for the ECM.

The sensor for the temp gauge is at the distributor end of the head near spark plug #5.

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I don't have a multimeter with that kind of capacity. I read that you can do the same check on the temp sender that goes to the gauge, located on the left end of the motor. I did do this test. I put 2 resistors together that totalled 1600 ohms and touched them to one prong at that sensor and grounded it and the needle was right at 100 degrees. And with a set of 2 resistors that totaled 68 ohms I got a reading of about 240 degrees.. So the gauge is off some. I would guess that means it is reading little too low. Right? How do I deal with that? Centervilledon

Probably. Gotta be there somewhere. From the 86 Service Manual http://www.fieronews.net/fusion/downloads.php

It's not so easy to see with everything in place: (Disregard the cam sensor wires just to the right of the ECM temp sensor. It's a 3.4L engine using the Fiero intakes)

[This message has been edited by Hudini (edited 06-13-2010).]