I bought a 91 rs a lil over a month ago its got the tbi 305 bone stock. I noticed on the highway the car operates at 160 degrees, the temp gauge sometimes wld shoot up to the red line hold for about a minute then shoot back down to 160 and the car wasnt running hot when it shot up. On the street it runs hot cuz the fan doesnt kick on. It has a single fan. idk if they came stock with a single or dual fan setup. if i turn the a/c on the fan will come on, even from a dead cold startup the fan will turn on with the a/c being on. On the street with the a/c on it runs bout 200. I changed the thermostat. I put the stock 195 in it. I drained the coolant and put fresh coolant in it. The car still runs at 160. The temp gauge stopped bouncing around. The fan still wont turn on unless the a/c is on. Any help would be appreciated. Thanx

on the passenger side of the block below the back 2 spark plugs there should be a sensor that controls when the fan turns on. it is common for the plastic connector to break. that is why the fan doesnt come on. when you turn the a/c on it overrides that sensor and turns the fan on. also i would try and change the coolant temp sensor. that should be on the thermostat housing.

ok..ill check that out..now what about it operating at 160 is that normal? i live in missouri. and its been in the 70's the humidity has been up 2 and on the highway w/o the fan running it stay right at 160.

i would say that the thermostat might be stuck open but that cant be it since you chenged it. and 160 on the highway is about right. thats a lot of airflow over the radiator. now for the 200 in town, thats not too far off either. the normal operating temp is 195. you can get a 160 thermostat in there and it will run cooler if you want to. oh and the lo5 did come stock with a single fan. i got a dual fan setup from an iroc and put that in.

ok..at least i know that theres nothing 2 worry bout with it running 2 cool. now i have read that on these cars going 2 a cooler thermostat with having the electric fan will cause the fan switch not close the circuit to allow the fan to come on. is that true..if not then i will change it to a lower temp stat and i will check/replace the fan switch and temp cooling sensor

That's not really true.

However, I recommend the following.

http://store.summitracing.com/partde...5&autoview=sku

Jet fan switch, easy to install as well, it's 195 on, and 185 off, instructions via a PDF on the summit page, the 195 on matches your current thermostat.

However i would recommend a 180 thermostat, 160 if you don't mind your heat not so good during winter.

the fan is programed to come on at a set temp. wither you use the stock sensor or the jet sensor. if you put in a cooler thermostat, the fan will still come on once it hits the preprogramed temp. and as mischief said you can use a 180 if you drive in the winter. i dont drive mine in the winter so i put a 160 in. it is up to you.

There's nothing wrong with your cooling system. My LO3 would run constant 165-170. With A/C on in traffic it might creep up to 195. These motors are supposed to run hotter than I am comfortable with. Normal operating temps are said to be around 200-220. The fan switch is not a cooling fan per say, it's just keeps the motor from completely melting down. Most of the stock switches that I've encountered are set to kick the fan on around 230* and will turn it off around 210*.

if you are going by the stock gauge it is not accurate. my 91 has the same cluster as urs, 160 degrees is hardly about the 100 mark, the line between 100 degrees and 220 is actually 190 degrees, at the 220 mark the car is 210, 220 isnt till the gauge is a little after the 220 mark, i verified this with a diagnostic scan tool. this is not to say ur gauge is going to read the same as mine, but i would double check the actual coolant temp with something more accurate.

I just want to point out that most SBC motors run best with the water (and oil) temperature around 200 to 215 degrees F. But, the air going into the motor needs to be ambient (outside) temperature - easy with the TBI and its snorkel intake; touch for a TPI with a lot of aluminum intake tract that heats the air on its way in.

my cluster does have a 160 mark and thats where it runs at

I have a 91 RS that runs at 160 constantly. All the sensors and things are new on the system so I'm pretty sure it is just where it runs.

I had a thread on this too. Sits bang on 160 even with the car stopped and a breeze blowing in the nose. There have been many threads about the 'correct' running temp with some saying 160 gives more power and others that 195 or so is best. Seems like if the thermostat is a 195 it should run at 195 approximately. If increased airflow causes the temp to drop shouldn't the thermostat close to get the temp back up????

I just got done dealing with the same problem.My fan would only come on if i turned on the AC.Same switch that Racer is reffering too was the culprit on my car as well.Bone stock 305 with one fan.I did notice before i started having this problem my fan would come on at about 206...supposedly there is another switch that can be used to turn on the fans earlier.I think my car had this switch.now with the factory switch it turns on at the line right before the red which is about 230 give or take.With the other switch it would come on just to right of 220 on the gauge,which is about 206 or soo.Our guages are definetly not accurate.The parts store I just bought the switch from said they had the colder switch,I think i will go get it and change it out lol.