1991rsblue

this car has a 5.7 with dual fans. the car was in storage over winter and pulled out a couple weeks ago. the fans don't kick on and the temp guage reads 260 and higher. i replaced the temp. switch for the guage and the temp. sending unit by the throttle body and also both relays. i'm at a loss and i'm throwing no codes. please help, and suggestions would be very helpfull. thanks again.

JAKEDPLAYA

THERMOSTAT???

Drunken_Polak

when i had overheating problems... i did this:

https://www.thirdgen.org/techbb2/sho...hreadid=174666

also...if all else fails...u can just put manual switches in your car

1991rsblue

welp, still have the problem and i was hoping to not replace the ecm or prom but if it needs it it will be done. i followed a chart with ohms from the ct sensor compared to degrees Fer. according to the ohms which i got to 200 from the collant temp. sensor the temp of the car was at 215 or there abouts which wouldn't activate the fans but my gauge inside the car read 260 plus. the car didn't boil over which tells me that it couldn't be over 260 because the car would have antifreeze flowing out like a river right? so i replaced the temp guage with a new one and same thing. what the hell. I replaced the temp switch for the guage with a new napa part and warmed the car up and same reading as before. what the hell???? is it really the ecm or am i missing something big??? please help. anything would be good. the fans do work in diagnostic mode and get this. when the car is on and i jump the wires by the fan really and then connect the relay again they stay on and don't turn off until i shut the car off. answer that one. i think the car is possesed.
thanks for the help, keep it coming

05kcilS

ummm... is it leaking coolant???? i'd check for that first and formost.

Danno

You are right. At 260 or so the recovery bottle should be filling fast with coolant. After the engine is stone cold open the rad cap, start it and let it warm enough to get a reading on a secondary thermometer. I use one with a probe dipped in the rad at the cap inlet. When you get a reading compare it with the guage. 5-10 degree difference is normal, a radical change indicates a problem with the guage or guage wiring assuming the reading is much lower from the coolant temp. Winter storage eh, any possibility some chisel toothed rodent got at the wiring. Check the sender wire. The CTS is NOT the same as the guage sender. The guage sender is located on the driver side above plugs 1&3. It is a single wire brass fitting with normally a green wire. Make sure the wire has not drooped and is touching the exhaust manifold. you can pull the wire off the sender, let it warm up a little and see if the guage reads. It should not read at all. If it does, there is a problem in the wiring back to the guage. Grounding that wire should make the guage peg, removing the ground it should drop back to zero. More info on the car in question would help, the info in the sig doesn't jive with the questions.

1991rsblue

i know the car in the sig is not the car in question. i have two camaro's. one is a 1991 rs 3.1 and the other is the one in question. it is a 1988 5.7 automatic iroc-z i've replaced both the sending unit for the guage and the sensor. the guage is fine because i bought a brand spanking new one from gm and it still doesn't work, like it should. the recovery bottle sits on cold when the temp os low but when the car warms up for 30 minutes eating a crap load of gas the recovery bottle sits at the same temp/level. the thermostat is brand new and doesn't have any holes for leakage. there is no leaking from any part of the system either. i replaced the radiator last month on it but didn't remove or unhook any wiring just bolts for the fans. And yes i did check to make sure i didn't jossle anything and make it loose. The car was on jackstands on top of a tarp for the winter. i didn't see any visible wiring chewed away by any animal. thanks for the help but i'm still at a loss here.

1991rsblue

danno what do you mean by grounding the wire at the temp switch for the guage? if i warm the car up the guage doens't move when the wire is disconnected when i put the wire on the sending unit the guage goes up to some temp reading. if i put the wire on the frame rail the guage pegs. That's what i got out of that. Does that mean the guage is fine? This weekend i'm going to put a autometer sending unit and guage on it to get a real freaking temp reading. no more games. i hope the temp reads right with that guage if it doens't i'm really up the creek.

Danno

If the guage doesn't read with the wire disconnected it rules out the wiring from that point back. Grounding it should peg the guage, removing ground it should fall back down. I just wanted to ask if was in fact making a full swing and then back to zero. Rule out the guage for now. You mention in the first post that the fans won't work. 88 should have the primary fan ECM controlled according to my diagram. Turn on A/C if equipped and the primary should come on. Also, if you test for codes from the SES light during the test cycle the primary fan should run. That also rules out the ECM driver that feeds the fan relay. If the fan does not run pull the primay relay and you will see two heavy guage wires and two lighter guage. Jump the 2 heavy guage ones together and the fan should run even with the key off. They get 12 volts directly from a fuse link right off the battery. Both fans are fed from the same fuse link. Usually these things are fairly cut and dry. Keep us posted, Dan

1991rsblue

i've bypassed the fans from the relay's, i know they work because the kick on(both do) when i do the bypass for the diagnostic thing. there are no cut wires or unhooked wires, as far as i can see. i've replaced the CTS and the Temp. switch for the guage. i personally don't think i'm reaching temp and my gauge is screwed up but according to gm they can't help me if the part the sold me was bad. i'll find out what is what this weekend when i install the autometer temp guage and sender. i don't know what else to do. they just don't want to come on. they worked fine last fall and now they are still dormant and th car is begging for coolness.

txhotRS

I had the same problem 2 years ago... it just started overheating one day... I was in a parking lot with the engine running, waiting for my brother at school and steam started pouring out from the hood... I opened the hood and there was anti-freeze spraying EVERYWHERE... I tried everything... I ended up replacing the radiator/ water pump at first... then the fan stopped, THEN I HAD TO REPLACE the temp sensor/ fan-relays/ fan motor/ fan switch.. EVERYTHING.... I got so f#cking tired of messing with it, and not being able to drive anywhere... I jerry-rigged the fan to come on with a switch ... IT WORKED.... I got tired of forgetting to flip the switch EVERY TIME I started my car... so I reverse-wired it... THE FAN RUNS ALL THE TIME, UNLESS I turn the switch off.. (like when I'm on the highway & stuff) It's worked fine EVER-SINCE, (unless I ever need to sell the car either way... AT LEAST I have lifetime warranty on most of the $hit that I had to replace..

1991rsblue

atleast you had antifreeze spraying everywhere. i don't even have that witch tends me to believe that the guage is busted rather than the car actually hitting 270 degrees. you would think there would be antifreeze there, but not a drop anywheres. the car can idle for one hour straight and according to the guage i goes above 260redline but the antifreeze never burts open the radiator cap or the catch bottle doesn't even hit the hot when running mark. just stays at cold. but wouldn't the car be running hot if it idles for one hour or is my water pump and thermostat actually working better than ever???? i don't know till i replace the guage with an aftermarket

AaronIROCZ

iTrader: (5)

Do you have a lever on your rad cap? if you fo replace it now I have never hadone last more than 6 months. If you don't try to replace the rad cap. It could be defective and not letting the motor reach the 16 psi of coolant pressure. Having pressure in the coolant system makes the coolant transfer heat better. I had a overheating problem with a 85 S-10 truck, I replaced the cap on a hunch and it worked!!

1991rsblue

welp this past weekend i put an autometer guage and sneding unit in under the drivers side hole for the guage. i hooked everything up and nothing. no temp at all. so i think the sending unit is bad because when i pulled it out the temp of the water scallded me. brand new sending unit bad already. the fans still won't come on and i'm not going to let it idle for long now. don't want to burn out a 350 tpi.