Iroc Overheating Badly

[pr1689]

Ok, I will try and check it out with a scan tool, but I do know that if I don't get it shut off and the temp gauge shows it going into the red zone, the radiator will boil over into the expansion tank. This is why I think the whole temp gauge and sending unit is accurate. But I will try and get to this this weekend to have the scanner put on it. There is a local performance shop which can help me with that.

I am seriously thinking about trying this new fan switch though. Here is a link for you all to check out: www.jetchip.com At this site they have additional performance stuff, but also the fan switch which will turn the fans on at 195 and turn them off at 185. This isn't an add-on switch, it's a replacement for the stock GM one.

Sorry about the confusion about which switch replaced. The coolant temperature sensor is the one by the water inlet on the front of the car. That one has been replaced and is new.

In summation, I honestly don't think the gauges are wrong, but that they may be more accurate than originally thought. Since these fan switches were designed to keep the engine running hotter, it makes sense to me that this is the issue. The switch is actually a thermistor and that could be failing thus causing the fans to kick on later than they should.

I honestly appreciate everyone's input here and will keep on posting with what I find. I surely hope this is it, but if not, I'll keep on looking. I have found some fairly creative ideas at www.thirdgen.org about wiring in your own switch to turn your fans on and off, but I just don't think it should have to be that way.

Let me know what you all think please!!

Thanks,

Pat

[pr1689]

Sorry guys, forgot to mention that all of the air dams are in place.

Thanks,

Pat

[wrightz28]

I hear ya about the temp, I don't like it either. My issue, the ECM controls mine through input of the CTS, no fan switch on a '85. So I have to put in a complete stand alone system to run the fan.

[pr1689]

Latest Findings...

After reading all about this fan switch and looking at electrical diagrams, I was convinced this was the culprit. That is until I crawled under the car and looked between cylinders 6 & 8 only to find that I didn't have a fan switch there, only a plug. So that shot that idea to pieces.

After more review, and reading more postings, it appears that most people are adding a separate toggle switch to turn their fans on and off when they want to, like in stop and go traffic. It just seems to me that this should not have to be done, that there is just something that was bad in the design, or a setting in the computer set to high, etc.

I still believe that for those of you who have a fan switch between cylinders 6 & 8, that my previous thought-about solution will/may work for you. Here is my other solution which should work for everyone who does not have a fan switch in addition to the coolant temperature sensor.

What I did was pick up a 1K ohm pots (potentiometer) at Radio Shack. I removed some of the insulation from both wires of the coolant temperature sensor (black and yellow wire) and soldered on the potentiometer. There are 3 legs on the pots. The middle leg should be soldered to the black wire and then either of the outside legs will be soldered to the yellow wire. Then turn the pots in the opposite direction of the yellow wire until it stops. I should interrupt here and state that I also picked up an infrared thermometer so I could take temp readings of various parts of the car (engine block, radiator hoses, etc) to help me in deciding at what temp the fans should come on. Once determined, start turning the pots until the fans come on. This will take some minor adjustments, but when the fans cycle on and off like how you want, shut your car off. Then unsolder the pots and take an ohm reading between the two legs of the pots that were soldered. Then head back to RadioShack and pick up a 1/4 watt resistor that is as close to that ohm reading as possible. Don't go lower, get the next one higher.

To date, this has been working just fine. What it's doing is tricking the computer into thinking it's hotter than it is and it is turning on the fans appropriately, only at a lower temperature. This can be done because the computer is reading voltage from the coolant temp. sensor rather than the actual temperature.

If anyone else cares to try this, let me know and I can send you the RadioShack part #'s that I picked up. Oh and total cost was less than $5, with the only exception being the infrared thermometer which was close to $40.

Thanks to all who have replied and checked this link. I think these forums are great and I know they've helped me a lot along the way.

Thanks for all the advice and help!!

Pat

[Genopsyde]

that plug between 6 & 8 IS the switch, you hafta unscrew it from the block and put a new one in its place. It's not actually a switch that you can turn on and off by hand, it operates as a switch.

[pr1689]

Right, but in my vehicle, I don't even have the wiring for that switch. My car is an 86 IROC with an 87 350 in it. Since I didn't have the wiring to begin with, I needed a different option.

Thanks,

Pat

[pr1689]

Also, I should clarify that by "plug" I mean it doesn't have a connector or anything which can be hooked to it. The face of this plug takes a hex wrench to unscrew it. It is actually a plug and by removing it you can put in this fan switch. I'm calling it a switch as that is the part name. It is actually just like another coolant temperature sensor, except it only has a single wire, so in essence it would work like the temperature sender.

Thanks,

Pat

[pr1689]

One last comment on the solution I implemented. After re-reading the solution, I noticed I left out something. I stated to go pickup a 1/4 watt resistor that was as close to the ohm reading of the pots as possible. I forgot to mention to solder it in place where the pots was on the black and yellow wire. You should then tape up the areas where the insulation had been removed.

Sorry, didn't mean to leave that out.

Thanks,

Pat

[Genopsyde]

i see what you mean now, looks like this is out of my league then.