Hey, folks, I've searched through the boards, but haven't found an exact answer to some questions I have.

I have an 85 IROCZ with the 305 TPI, where the temp gauge goes up to 240 at times. It doesn't go into the red zone; that's 250-260.

Is this normal? The coolant has been flushed 3 months ago.

Also, do I understand this correctly when I read that a 180 thermostat and a chip like Hypertech's are needed to turn the fan on sooner; otherwise, I could force the fan on when I turn on the AC?

Do I need an aftermarket radiator too? I'm here in upstate NY, so its cold more often than hot.


Thanks

 

first of all make sure you still have that piece of plastic that draws air to the radiator (airdam) ...i had the same problem always at 220-240ish and i found out i didnt have that plastic thing in below the radiator....also you can get a fan switch that will turn on the fans sooner....its just a plug on the passenger head between the last two spark plugs ....a thermostat would be another way to lower temperature a bit

 

Thanks Rudy. I do have the airdam, and the temp lowers when the car is moving. When idling though, after a drive on the highway, the temp needles up to 240...

I hear that changing the thermostat without changing the chips can make the car run rich, lower fuel economy and foul the plugs...

 

You can test the fluid to see what the boiling point is with a simple ball/float type device. I found mine was actually lower than 212 and was boiling too soon. A pressurised system and correctly mixed antifreeze should stave off boiling to well over the temp the computer is happy at. Do you hear boiling fluids when you shut off the car at 240 degrees? If the fluid is good Get a new radiator cap.
Also I test my 195 degree stock thermostat this evening in a pot on the stove with a $4 candy thermometer and what I found was shocking. It opens only slightly at 200 and closed at 195 so it is working but how well? when the water was at full boil at 212 the thermostat was only slightly open still. I dropped my new 180 I bought today in the pot and at 185 it started to sneak open and by 200 it was gaping open wide. This is the revers poppett from Advance Auto.
The problem I believe I have with my car is the temp got to 240 and sometimes the fan would turn on but sometimes it didn't turn on untill I shut the car off and and it heat soaked for a few minutes than when I restarted the car at about 230 the fan came on. Now looking at the fact my coolant was green but tested a lower boiling point than water-I was getting boiling before the temp the fan should come on. Well you can't raise the temp above boiling! Remember once the fluid boils it gains energy and changes state to steam but the fluid is still the same temp. That means the stupid computer doesn't think its fan time but the dash readout is engine temp not coolant temp. Now all the troubleshooting was worth it - don't get me wrong. I should have flushed the coolant first since I just bought the car and didn't know the history. but in troube shooting I found
1. The fans were wired together
2. The primary fan (ecm) relay socket was melted the relay discarded
3. The secondary fan relay was disconnected and a jumper was found in the battery tray I believe was the method to starting the fans.\
4. The ac doesn't work so turning it on doesn't help
5. the radiator fan switch wire was broken at the switch do to heat from the exhaust -the plug was dried out and crumbled .
6. After fixing all the above the ECM would sometimes start the fan when I started the car even If I disconnected the 2 wire temp sensor so I changed it too.

 

in short a two fan set up the first fan is controled by the ecm via the temp sensor in the manifold. And the secondary fan kicks on at 240 and shuts off at 220. i found the switch that turns the fan on at 220 and shuts off at 200 in standard...... if any one need email me and i willlet you know what the # is
thats what i learned and Rockauto.com is awsome for looking up the right parts
Meh
Kenny

 

In regards to the air dam. my recently purchased 86 305 TPI does have what appears to be the air dam. However, I am unsure if it is all there. There is a single piece that extends just past either side of the radiator. On the drivers side there is a separate piece that is maybe 10" long, but not one on the passengers side. Should these hang straight down? Also, if the passenger side is missing a 10" piece, is this enough to make it run 240-250? I have taken all other steps to address the problem. Any comments are greatly appreciated.

 

Okay, I popped the hood this morning after a blast along the highway, and turned on the AC. The temp gauge read 220 and climbing. The fan didn't come on though. I tried movnig it, but while it spun freely, it didn't turn on. So back to the mechanics....

 

try jumping the fan relay first with a paper clip ....if your fans still dont turn on then it might be a bad relay .....this same thing happened to me and i thought it was the t-stat at first then i replaced it and broke a bolt to it.....there should be some diagrams on here on where to jump the relay....i replaced mine and worked just fine after that ....but i never had a airdam

 

Okay, I got my car back today, and was told the temp gauge was about 20 degrees too hot. The garage ran some tests that confirmed the thermostat and fan were working correctly. When I tested the fan by turning on the AC, I hadn't given it enough time to build pressure. I'm told it takes about a minute before the fan kicks in, which led to the false alarm.

Thanks for everyone's input!

 

I finished flushing and refilling the coolant and changing to a 180 thermostat. Also put in a FS1 fan switch. Anyone know the temp this is suppose to turn on? Somewhere in another thread it said on at 240 and off at 220. I thought that was more correct for the stock FS3 but the same post said the FS3 is 260-240 which seems too late.
I overheated first time out this time rupturing the overflow hose as steem came out. I re-checked my wiring and the fans were not getting ground. The plug is melted and the wiring on the black (ground) and Blk/red (primary fan) is not making a connection so I cut the plug off and used water tight butt splices. I think this was damaged as part of a previous incedent before I bought the car because the relay socket was burned also. Maybe someone shorted the wiring when trying to connect the fans together/

Anyways the primary fan comes on when I start the car and I think this can't be normal! I finally got the winALDL to work and the temp readout is correct in the car. It takes about 15 minutes of driving with no air dam(have one on order from hawkesthirdgen.org) and the temp stays at a perfect 220. The second fan does not come on yet. I can force the fan on by pulling the wire off the fan switch and grounding it so I know all that is working and the fan switch is new so I will just trust on faith that it will work when needed.
BIG QUESTION: Anyone else ever have the fan come on when the car is started? The resitance to groung seems to 300k so it is not shorted and fear a bad ecm.
SECOND BIG QUESTION: Anyone ever measure the fan motor resistance as mine appears to measure only .7 ohms from the relay blk/red wire to ground. This is hot lead to the fan(12v) so it should be measuring through the motor to ground.

 

12 Volts divided by 0.7 ohms equals about 17.2 amps. Seems like a lot of current...

??

 

I'm surprised no one jumped on the "stock temp guages are notoriously off" thing.

• 180* Stat
• Corvette Fan Switch

That's all I needed for superior cooling. Well, that and a regular flush.

 

I'm not sure the static resistance is accurate as it does give erratic readings when I spin the fan. But since you mentioned your calculation is 17 amps it gave the idea that have a clamp on amp meter somewhere and I will get back with some real measurements.

 

A clampmeter is a better way to measure the amps drawn by the motor. I'd say that calculation is a pretty good indicator of the starting amps that would be drawn by that motor, but once it gets up to speed I think it's resistance would increase, and the amps would come down some.