[TheFoxRocks]

Hey guys,

I have been pretty busy the last few months. I lost my father that was actually helping me work on the car to Covid last month. There are no words to explain what I am going through. I am trying to keep myself busy to keep my mind off it. I want to finish or at least get this project that my father and I started together running.

Anyway I am in the same boat that I was later last year. I have an overheating problem and cannot figure it out. I took it in today for state inspection and my friend gave me a list of things that needed resolved that was mostly tedious stuff like lights and wiper blades.

However, I drove it all the way home and the dash read at 185 degrees almost exactly all the way home. This is the 1/4 tick mark on the gauge I believe. It took me about fifteen minutes to get home but the way was warm before leaving the shop. When I got it home I noticed a boiling/bubbling sound. So I popped the hood and sure enough I could heat it at the top of the radiator and overflow reservoir boiling pretty rapidly. It lasted a few minutes but then seemed to level off. So hopefully I didn't do any damage.

So the shop mechanic said he would work on it if I wanted him to but said I would like to try to figure it out myself. He is the head of the shop and pretty good with cars and he told me the radiator fans were definitely not kicking on. I know one of them is suppose to kick on after it gets somewhere past the 210 mark and both are suppose to kick on when it gets somewhere past that and guess the shop guy knew that as well. I will leave it at this before this gets too out of control but that is where I am now.

I bought a bleeder funnel as suggested by another user and just received it today as well. Having that said, I really doubt that is my issue now and will move straight to the radiators which is most likely my problem. It seems like there is an obvious issue with the gauge/sensor as well. Because it seems like the car was obviously overheating well before I got it home. I am not sure if I possibly damaged the radiator fans when I removed them or what but seems like the heating situation with this car is going to need some work.

I began learning how to diagnose these fuses last year as well and will probably continue down that road. As always any advice on possibly where to start and locate my problem would be appreciated.

 

[ZumpTA]

Saddened to hear about your father. Truly I am. Keeping busy helps short term, but this is something that needs faced head on. Ignoring the situation and burring grief might appear to work but it will affect you and those you interact with in ways you will never notice, potentially until its too late. Do your best to be open to emotion especially around friends and family. It's very hard, but it's the first step to healing.

...

Water, 100% water, doesn't boil until 212F and a 50/50 mix of water and antifreeze raises boiling temperature to 223F. Pressurizing a system like our cooling system to 15psi raises the boiling point of 100% water to 257F, and the addition of antifreeze raises that even higher. So, first... If you only saw "185F" on your temperature gauge and experienced boiling, your gauge is clearly wrong and the sender needs replaced. The temperature gauge reads the temperature of the head and has absolutely nothing to do with your cooling system. It's just there for your piece of mind, it's informational only. The computer on the other hand reads the temperature from a "wet" sensor at the water-pump. This sensor tells the computer what the coolant temperature is and the computer controls the activation of the cooling fans. Fuses aside, there are also relay's.

I think you're incorrect on how you think the fans operate. If I'm remembering correctly, and for once I think I am, your year uses 2 different fan speeds to control temperature. At a given temp, both fans operate at low RPM, and at high temp, they both operate at high RPM. This is vastly different to the older configuration like mine where one fan comes on at the lowest limit and the second fan comes on at the higher limit. I have no experience with the setup your '97 uses "electrically". You will need to use the diagnostic flowcharts in the Factory Service manual.

What I did when I suspected my fans weren't working was a simple voltage check. I lifted the front of the car, started it, and let it come up to temp. I unplugged my drivers side fan and shoved the leads to my multi-meter in the harness. When I saw 12v on my multi-meter, I plugged in the fan. ...nothing. Tested the harness again, 12v. Clearly a burnt out fan motor as it's getting full power. $20 at AutoZone. Solved. However, my system is the simple 1-fan/2-fan system not the 2-fan/2-speed system you have. I do not know the location of the fan relays, I'm guessing the under-hood relay/fuse box, but I'd suspect that's where you should start. One or both of the relay's may be bad or unplugged. ...the fans are plugged in? Yes? Engine Coolant Temperature Sensor plugged in too? ...all the way? I would think if the ECT sensor was unplugged you'd have a code set and the Service/Check Engine lamp would be illuminated, or maybe the computer would only run in "Limp-Home" mode or something, but I've learned never to assume things like that with my 1993. Best to check!

You need to follow the power. A fuse or fusable link probably provides the 12v "high current" power to the relays, and the computer turns on/off the relays with a low current signal, the relays switch power to the fans. This is what relays are, they are switches, except instead of physically flipping a switch, they use a small electrical current to "connect" power across the relay. If "high-current" power doesn't get to the relays, it can not be routed to the fans. if the high-current lines are powered, but the relay is not seeing the signal to transfer power to the fans, that will never happen either. If the relays are bad, power will not flow.

A question to ask is, "do the fans come on at high temp?" if so, that points to a failed relay. If there is no operation from the fans at all, it sounds like a "main power" issue as in power is not making it to the relays (fuse/fusable link), or the relays not getting the control signal from the computer to transfer power to the fans. From experience, I can tell you it is not easy determining if the fans are on or not unless you're under the vehicle. There is so much noise and air movement when the fans are off, you're really guessing if they are operating or not if observing from above.

If you bled the cooling system, that shouldn't be it, but it does not hurt one bit to allow the engine come up to temp and crack open the bleed screws a little.

I seriously advise you to use the Factory Service Manual. It will walk you through the proper steps in the correct order to diagnose this problem. You should only require a volt-meter. If you do not own one, they're about $10 anywhere local to you such as Radio Shack, Lowes, Home Depot, ACE hardware, Harbor Freight, Northern Tool, and maybe Best Buy. Any cheap volt-meter is fine. You don't need anything more than $10 (as low as $6) or one with a fancy display unless that's what you want. As long as it displays voltage, it's good enough.

Here is an excerpt from another forum with regard to fan temperature operation:

The PCM operates the coolant fans based on input from the Engine Coolant Temperature (ECT) sensor, A/C Pressure Sensor, Vehicle Speed Sensor (VSS), and various other inputs. The F-Body coolant fans operate at the following temperatures and pressures:

Fan Mode Temperature A/C Pressure
==========================================================================
Low-speed Fan(s) ON: 108 C 226 F 248 psi*
Low-speed Fan(s) OFF: 105 C 221 F 208 psi*
--------------------------------------------------------------------------
High-speed Fan(s) ON: 113 C 235 F 248 psi
High-speed Fan(s) OFF: 110 C 230 F 208 psi

*Note - this information is probably incorrect, although it is quoted from
the service manual.

Additionally, the PCM will turn off the fans at higher vehicle speeds (above 70 MPH I believe) since running fans can actually impede airflow through the radiator at high speed. Each fan or fan mode has a minimum running time. Once activated, the primary fan or dual low-speed fans will run for a minimum of 50 seconds, and the secondary or dual high-speed fans for a minimum of 30 seconds. Finally, certain Diagnostic Trouble Codes (DTCs) may cause the PCM to turn on one or both fans.

All LT1 F-Bodies with automatic transmissions also have a transmission oil cooler as standard equipment. The transmission cooler is an oil to water type mounted inside the RH radiator tank.




...and the electrical schematic which I have not studied:

Don't let that schematic scare or intimidate you. If you use the Diagnostic Flow Chart for this condition in the Factory Service Manual, it will walk you through everything with words you can understand. If you can count to 10 and recite your ABC's, you can follow the diagnostic flow charts. If you throw up your hands and decide to let the mechanic solve this, so be it. But maybe pass on the FSM to them, if anything it will shorten the time the need to resolve it.

...but, YOU GOT THIS!!!!

...also looks like you got THREE fan relays.

Sorry it took a couple days to get around to this, and again, my deepest condolences. I know the pain. I can't say it goes away, but it does get better.

 

[TheFoxRocks]

Saddened to hear about your father. Truly I am. Keeping busy helps short term, but this is something that needs faced head on. Ignoring the situation and burring grief might appear to work but it will affect you and those you interact with in ways you will never notice, potentially until its too late. Do your best to be open to emotion especially around friends and family. It's very hard, but it's the first step to healing.

Sorry it took a couple days to get around to this, and again, my deepest condolences. I know the pain. I can't say it goes away, but it does get better.

Hey Tony,

Thanks for your words. My dad had a lot of friends and there really are not words to describe this so I really only get the "sorry for your loss" and to be honest it is getting old. I do not blame people, they do not know what else to say. You, a guy I only know from the Internet (no offense) has already said more and given more advice than most people I know. My father read a lot of posts from you and Fred, for what little he and I knew about you guys we really liked you guys. We also obviously very much appreciated the help and I still do. I appreciate the advice and guess you are not new to loss because you hit the nail on the head. I am going to have to find a way to deal with it. Keeping busy works for the now but it does not work when things slow down and my mind has time to go over it. I am driving dads Camry and looting his wallet for information I need and it just feels straight wrong.

I am going to slowly go through your post and start with diagnosis.

1.) A couple years ago dad drove the car back from Virginia and it was an hour and a half or two hour drive. It was cooler out (cannot remember exactly when it was) but trying to figure out if it was possible that the fans were not working then. Because if they were it means that it is probably something I did not plug back in or crimped while working on the car and might be an easy traceable fix.

2.) I just had the car jacked up again and my gut was telling me to mess around with the radiator fans before taking it off but I wanted to take it in and get it lined up. I guess it is time to jack it up again.

Also just to throw it out there I am getting catalytic converter codes as well. One is P0420 and the other is P0430. I cleared them out and so far they haven't came back but I have not taken the car out of the driveway yet. I hope that is something that I can put on the back burner for now as well.

Regardless I have plenty of information now, I found another forum on here where Gary and Fred were trying to help someone with I think the same bird. So I now think I should have more than enough information to get started.

I am pretty certain the system is free of air but could be wrong. I let it get pretty hot before and opened those bleeder screws and all I get is coolant. I could always try the bleeder funnel I bought and try a combination of it, the bleeder screws and/or starting the vehicle. However, I think at this point knowing the fans are not working it the obvious culprit.

 

[1993TransAm]

I know what it's like to lose a parent. Your life is never the same afterward. I am truly sorry for your loss.

 

[TheFoxRocks]

I know what it's like to lose a parent. Your life is never the same afterward. I am truly sorry for your loss.

Thanks, nothing can make this situation possibly worse either. My father lost his job due to Covid in early 2020 so we spent a lot of time together. We mostly got on each others nerves but we did have a lot of fun together, like working on this car together for example. I would do anything to get him back. I just turned 33 this month so I guess I am fortunate enough to be old enough to take care of these affairs myself and was old enough to know my father.

 

[1993TransAm]

I realize that we have had more than one thread on this issue, so forgive me if we have already covered these issues. With regard to your cooling fans:
(1) Does the car have a functioning A/C compressor?
(2) If yes, does the system have refrigerant in it?
(3) If yes, when you turn the air conditioning on, the cooling fans should come on immediately to cool the condenser. Do they? This is a simple means to determine whether your fans are getting voltage, assuming the A/C system is properly charged and functioning.

Also, did we broach the subject of a combustion leak test in the earlier discussion? The bubbling you describe can be combustion gases in the coolant, typically indicative of a head gasket failure or in the worst case, a cracked block. If we've already been over all this, I apologize.

 

[TheFoxRocks]

I realize that we have had more than one thread on this issue, so forgive me if we have already covered these issues. With regard to your cooling fans:
(1) Does the car have a functioning A/C compressor?
(2) If yes, does the system have refrigerant in it?
(3) If yes, when you turn the air conditioning on, the cooling fans should come on immediately to cool the condenser. Do they? This is a simple means to determine whether your fans are getting voltage, assuming the A/C system is properly charged and functioning.

Also, did we broach the subject of a combustion leak test in the earlier discussion? The bubbling you describe can be combustion gases in the coolant, typically indicative of a head gasket failure or in the worst case, a cracked block. If we've already been over all this, I apologize.

No need to apologize at all. In a perfect world I guess I would have went back and found the earlier forum instead of starting a new one.

1.) I tried turning the AC on while the car was jacked up and fairly certain the fans never came on at low speed. If I remember correctly I stuck a piece of newspaper in there while I messed with it to see if it moved. I am not sure if it is "functioning". I know it creates a squeaking sound.

2.) Sorry I have no clue.

3.) Not sure for the same reason as before. I guess I could try it again.

4.) The subject may have came up before because I had some 'milkshake' residue in my oil cap. However, none whatsoever on the dipstick.

My thoughts are that the car genuinely overheated. I also haven't tried starting it since then either. The guy at the shop was trying to diagnose the issue so I am guessing he let it get at least begin to overheat to see if the fans would kick on. Like I said though, when I got in the car to take it home it was at the quarter tick which I think is 185? It came up to about operating temperature (around 210). I kept an eye on it the entire time. Then when I got it home and got out I noticed the boiling sound coming from the radiator and overflow reservoir. I went back to the car and the gauge did say that it was now close to or actually overheating. So my gauge is definitely sticking or my sender is not working like Tony mentioned?

 

[TheFoxRocks]

Okay so I am getting ready to jack the car back up. I have the FSM on another computer and going to start seeing if there is anything that makes sense in there soon. I have been trying to think of something that might explain this and I did come up with something.

The only thing I can think of is when I was soldering the PCM to try to resolve the radio and window issues. Perhaps there is a chance that I screwed something up when I either removed it or was soldering on it. The only other obvious thing I can think of is that while I was doing all this work I damaged something that is critical to make the fans function. I believe I am going to let the car come up to operating temperature (whatever I find in the manual) cram just a little newspaper in there and see what happens. Most of you gentleman were present for that but I completely realize you cannot remember everything about every person here.

I also know my way around a multi meter as well. Sometimes I have trouble figuring out where the leads should go but I hope the FSM can help with that.

If this gets to be too complicated (not sure if it will) is it reasonable to just rig a toggle switch into the car to run the fans when the car gets a little above normal operating temperature? I am also going to look into the "fusable" link thing. I found a thread where one of you guys (I think Fred) was giving someone else advice and linked a couple things from ShoeBox but I since lost the thread but still have the picture for something reason.

 

[1993TransAm]

You would have soldered the BCM to solve the radio/power window issue, not the PCM. The BCM has nothing to do with cooling fan operation.

 

[TheFoxRocks]

You would have soldered the BCM to solve the radio/power window issue, not the PCM. The BCM has nothing to do with cooling fan operation.

Thank you for correcting me. Just trying to make sense out of all this. We drove the car home down back roads when I inherited it. It was night and the weather was cooler. I guess it is possible the cooler air was able to keep the car cool on the trip. It was about an hour and a half trip. I would have thought the fans would have been working then. So trying to think of something I may have did to have caused this.

 

[TAman]

Hey guys,

I have been pretty busy the last few months. I lost my father that was actually helping me work on the car to Covid last month. There are no words to explain what I am going through. I am trying to keep myself busy to keep my mind off it. I want to finish or at least get this project that my father and I started together running.

Anyway I am in the same boat that I was later last year. I have an overheating problem and cannot figure it out. I took it in today for state inspection and my friend gave me a list of things that needed resolved that was mostly tedious stuff like lights and wiper blades.

However, I drove it all the way home and the dash read at 185 degrees almost exactly all the way home. This is the 1/4 tick mark on the gauge I believe. It took me about fifteen minutes to get home but the way was warm before leaving the shop. When I got it home I noticed a boiling/bubbling sound. So I popped the hood and sure enough I could heat it at the top of the radiator and overflow reservoir boiling pretty rapidly. It lasted a few minutes but then seemed to level off. So hopefully I didn't do any damage.

So the shop mechanic said he would work on it if I wanted him to but said I would like to try to figure it out myself. He is the head of the shop and pretty good with cars and he told me the radiator fans were definitely not kicking on. I know one of them is suppose to kick on after it gets somewhere past the 210 mark and both are suppose to kick on when it gets somewhere past that and guess the shop guy knew that as well. I will leave it at this before this gets too out of control but that is where I am now.

I bought a bleeder funnel as suggested by another user and just received it today as well. Having that said, I really doubt that is my issue now and will move straight to the radiators which is most likely my problem. It seems like there is an obvious issue with the gauge/sensor as well. Because it seems like the car was obviously overheating well before I got it home. I am not sure if I possibly damaged the radiator fans when I removed them or what but seems like the heating situation with this car is going to need some work.

I began learning how to diagnose these fuses last year as well and will probably continue down that road. As always any advice on possibly where to start and locate my problem would be appreciated.

My problem with my 94 Z28 with overheating was an air bubble. Since the radiator is so low, air can get trapped. I raised my front end up high, rand the car 5 minutes with cap off,Bubble came out and no more overheating. Good luck.

 

[TheFoxRocks]

My problem with my 94 Z28 with overheating was an air bubble. Since the radiator is so low, air can get trapped. I raised my front end up high, rand the car 5 minutes with cap off,Bubble came out and no more overheating. Good luck.

Think we have confirmed my issue is going to be a little bit more complex than this. I will confirm when I am able to get the car jacked up. I need to confirm that the radiator fans are not working. I already checked them once and believe this to be the case and I believe the mechanic checked them and confirmed they were not turning on as well.

 

[ZumpTA]

Disconnect the drivers side fan, shove your multi-meter leads into the harness, start the car and let it idle until it gets hot enough the fans should kick on. Check voltage. If there is voltage but no fan movement, the fan motor is bad. If there is no voltage, move up the circuit to the relays. Test them. If all of the relays are good, test for continuity between the relays and fan motor. If all wires are good, move up the circuit. Probably looking at fuses now, which, should have been checked first.

There are other things that cause overheating too. In general, a plugged or low flowing radiator, head gasket failure, bad thermostat, bad mechanical fan clutch / electric motor... LT1 specific items would be air in the cooling system which has been discussed several times and recently brought up again, fuse / relay / harness failure. ...and way out from left field, it is possible for plastic bags to get sucked up the air-dam and block the opening air flows through, or actually cover most if not all of the radiator.

I doubt there is an issue with the fan motors. Your fans operate together in a high speed / low speed configuration controlled by the PCM and relays. Odds of 2 motors burning out at the same time isn't non-zero, but near enough it makes no difference. I suspect a problem with a relay, a fuse, or the harness. Most likely a relay. Looking at the schematic, it appears Fan relay #1 could prevent both fans from operating although I'm certainly not knowledgeable with this circuit. My '93 has a much simpler circuit to troubleshoot.

Including a video on testing relays. It's easy stuff... Relays are cheap too.

 

[Injuneer]

The fans are powered in series for low speed, running slower since they are only getting 6 volts each. The relays switch them to a parallel circuit, so they each see 12 volts and run at full speed.

 

[TheFoxRocks]

Okay so I finally made a tiny bit of progress today. I went out and checked the terminals at the relay box for battery power. So the first fan relay only showed 12 volts on two terminals. The second and third fan relays showed 12 volts at three terminals. I now have those three relays inside and looking for a way to test them with 12 volts power. I think this is good news because it shows that there is no problem between the battery and fuse block for the fans.

Is there a tester battery of sorts or something that I can buy to supply 12 volts to the relays to test them? I know I have a battery pack that is for jumping vehicles that I am guessing is 12 volts. I am going to lookup the specifications later and see if there is a way to run terminals to it and the relays. It would be really really cool if like Tony said it is just a relay that needs to replaced.

 

[1993TransAm]

I suggest you invest in a Power Probe. They are indispensable when it comes to testing electronic circuits. I used one when I worked in a repair shop (I still have it) and it was worth every penny.

PP3 I POWER PROBE 3

PP3 I POWER PROBE 3 I The right tool makes a world of difference

www.powerprobe.com

 

[TheFoxRocks]

I suggest you invest in a Power Probe. They are indispensable when it comes to testing electronic circuits. I used one when I worked in a repair shop (I still have it) and it was worth every penny.

PP3 I POWER PROBE 3

PP3 I POWER PROBE 3 I The right tool makes a world of difference

www.powerprobe.com

I think my father had one and I believe I know where to find it. Forgive me though, what advantage would I have over the multi-meter in this situation?

 

[TheFoxRocks]

I just looked and my Gooloo GP400 jump starter has an output of 12v. So could I realistically connect the jumper cables to the jumper box and then connect leads to the relay for testing purposes?

EDIT:
I just used my jumper box to test the relays like I planned. So I could not use my multi-meter as well because I had to use the leads from the multi-meter to provide battery power. So when I connected to the correct terminals on the relay (85 and 86) you could hear a clicking noise. This leads me to believe that the relays are good. However, like the video mentions it is not 100% so I am going to purchase some alligator clips and try again so I can check the other side of continuity. At this time though it is looking like my problem is going to wires going from the relay box to the fan motors, the fan motors themselves or one of the other fuses that the diagram mentions.

So what else should I start looking at? As it was mentioned it uses data from the PCM and one of the coolant sensors to tell the fans when to turn on correct? I am just trying to run through what I consider easier right now to see if I can locate a problem.

 

[1993TransAm]

Power Probes test for voltage, grounds, continuity, have a digital voltmeter display, and can provide 12V or a ground to a circuit at the touch of a button.

 

[TheFoxRocks]

Power Probes test for voltage, grounds, continuity, have a digital voltmeter display, and can provide 12V or a ground to a circuit at the touch of a button.

Then I misunderstood. I thought you were just talking about the little probes that have a needle and a tester light for power. I clicked the link right after I made that comment and saw it looked like something more.

My Gooloo battery jump starter can provide 12 volts. I am going to get a set of dual sided alligator clips so I can also check for continuity once the switch is activated. Like I said I can hear it engaging when I give it 12 volts.

Either way it looks like my problem is going to be another fuse somewhere, fan motors, or the wires than run from the relay box to the fans. It could also be the computer or something else.