Chevy 305. About 230 HP. Renegade's Ron Davis radiator. Renegade's converted MoPar water pump. 160 T-stat.

The motor never gets over center scale on the gauge or over 185 on the laser thermometer at the base of the T-stat, but the fans seem to run more than they should.

My radiator fan comes on at about 160 and off about 140. (laser thermometer aimed at base of the switch).

What are you guys with iron block Chevy V8s seeing on yours and what fan on/off range and T-stat are you using.

Thanks.

My temps depend upon the ambient temp and whether I'm moving or not. On a 90 degree day I can see anywhere from 185 to 210. Where is your fan sender mounted on the engine. On the intake or between the cylinders.? BTW, mine isn't stock either. It's a 327 punched .060 over and has a race cam.

Seconded on the fan sensor placement question. Personally I'd put the fan sensor on the item they have a direct effect on, ie the radiator.

I ditched my thermostat last year after my water pump impeller blades grenaded. I live in a warm climate so I wasn't really concerned with getting it up to temp in a reasonable time.

From what I know about my temp gauge, my fans kick on around 195-210 similar to Kent's.

I have the Renegade radiator setup as well, and my temp sender for the fans is mounted in the radiator itself as installed/sold by Renegade.

These V-8 setups are notorious for being a pain to purge all the air out of the system. Not sure how long you have been running this setup, but if new I suggest running that down as a possible cause. I had air trapped under my temp sender in the intake manifold and was getting false readings - blew a head gasket as a result.

Josh

Thanks for the replies.

My fan sensor is on the rad. It's a cross flow rad and the sensor is on the passenger side tank (same side as the hoses) nearer the top hose than the bottom.

Again, my engine does not get over 180 or so. The gauge stays about there no matter the ambient. I'm not concerned about over heating. My concern is that the fans run too much (in my opinion).

After a cold start and just idling, the fans will come on after about 8 minutes. They'll stay on a minute, then off a minute, then on, etc.

When driving in city traffic, they will be on almost continually. On the highway, they will shut off after about 5 minutes of cruise but come on every now and then...especially if I get on it a little.

I pulled the fan temp sensor and it is marked...

AIRPAX
0518
CLR185

I can't cross this number to anything that will tell me the on/off setting.

What is your experience with your fans cycling, and what on/off fan switch settings are you using?

I did a quick test with mine since it was a good excuse to start her up! Ambient temp here is ~95 degrees. Similar results to yours. Started it and just let it idle to come up to temp. After ~10 minutes the fans kicked on for about 1 minute then off. One minute later they were back on, then another minute to shut off.

Based on eyeballing my temp gauge I would say the water temp was in the low 200's when the fans kicked on. This is based off a test I did last year in the kitchen to correlate my gauge with measured temps.

With that said I don't trust the readings I was getting right now from my IR thermometer. Checking the radiator/switch, temp gauge sender on intake manifold, and the radiator hoses, they all seemed to read fairly low (160 - 180-ish). The highest temp I could find was on the water pump itself at ~195.

When I have it on the road I don't have much awareness of how often they cycle, but I mainly watch my gauge to make sure it doesn't overheat.

I couldn't make out the markings on my fan switch so no help there. Click to view attachment

Thanks!

I think my IR thermometer may be fooling me too. Temps are similar to yours.

I did hook up a little red LED to let me know when my fans are on. I wouldn't know otherwise. I probably shouldn't have done that. I'd be dumb and happy.

I placed my fan temp sender in the intake manifold. I thought, perhaps erroneously, that temps at the radiator would not fairly represent the temp at the engine. When I did IR readings they were always much lower than the sender represented. Which controller are you using Dick?

I have the same renegade setup. In the past I’ve had over heating issues. I had my overflow reservoir draining to the ground. Once I re-routed to a closed system,I’ve never had a issue.temps stay around 185 unless sitting in traffic it will climb to 200.
I wired a switch to turn fans from cabin because I can’t hear fans come on so I wanted to be sure they come on. Burping the system is key as well.

Sounds like you need a higher temp sensor. It says its 185 but it might be lower given your fan kick in temp.

http://airpax.sensata.com/pdfs/5100.pdf

Is your fan sensor connected to the fans directly through a relay or some other controller?

Could it possibly be wired wrong?


I would pull the sensor, put it suspended in boiling water with a digital lazer temp sensor, Put an ohm meter on the sensor and see at what temp it clicks over.

I got the Renegade rad with sensor/switch from the previous owner of the car who had started on a V8 conversion then ran out of interest/talent/money...whatever. The sensor/switch has this stenciled on the probe...



I can't find anything on the net to cross it to so that I can know the on/off settings. I assume the 185 is probably either the on or the off setting.

My temp readings at the base of the probe are also low relative to what I was expecting. In fact, laser temp readings anyplace on the rad, hoses, inlet, outlet are low relative to what I would expect (160ish).

I've not had overheating issues. I have maybe 1,000 shakedown miles on the car since completion. I've always had a closed cooling system. I believe I do get all the air out of the system. There is a "vent" at the top of the rad, and one on my aftermarket intake that I use to "burp" the system.

I also hooked up a switch to turn the fans on manually. I thought I would use it if I saw that I would be sitting in traffic a while to get a head start on cooling, but I haven't used it so far. I'm considering a switch to turn the fans OFF while running down the highway at speed with the theory that the fans block more air than they provide above 30 MPH or so.

What percent of the time are your fans running?

.

Thanks for the contact info for Airpax. My sensor has a different numbering system than what is shown. It is probably an older version. I know my car sat in the previous owner's garage for many years (20?) after being torn down for a V8 conversion. The rad and sensor may be that old. I'll contact Airpax and see if they can decode mine.

Thanks also for suggesting the test. That goes in the "why didn't I think of that" category.

The fans each have their own individual fused power source. The fused power goes to a relay for each fan. The sensor/switch is only the "trigger" to the relays. Relays are wired like this...

Personally I would just spend the $50 and get a new sensor... Lots of headache when you could just solve the issue with relatively low $$ investment.

They are actually less expensive than that and there is a big range of on/off temps available.

What on/off settings are working for you? I'll buy one and try it in my application.

Thanks.

That amount of fan running was what I was expecting.

Do you know the on/off settings of the sensor/switch you are using?

I like adjustable ones. My current one is adjustable via an LCD display, came with my electric water pump.


I would find one thats around 200deg.

On at 160 and off at 140 seems pretty low to me.

IIRC mine was set higher than that, maybe on at 180 or 190.
It was the adjustable type that came with the fans.

My fans come on At 185 then shut off within a minute or so after temp drops below the 185. If the fans running when I shut off the car, they stay on for about a minute or so .

You showed me yours so I will show you mine.

Not a lot to add but this is my set up from Ron Davis but I think it came from Renergrade



Chers,

Bob BClick to view attachment Click to view attachment

I do believe I am getting some bogus laser temp readings anywhere on the rad for some reason. All seem low.

Thanks to Andyrew's post with contact info, I called the Airpax division of Sensata and actually got a real tech on the line. He confirmed that the CLR185 on my sensor/switch means "close on rise 185 degrees (switch closes at 185F). He said the switch opens again at about 165. I'm also going to test it as Andyrew suggests.

Same with mine.

Identical to mine.

Is your car running, and if so how's the cooling?

It is not running but the guy I bought it from 10 years ago said it ran fine as far as the coolness went. This set up was for an old 350.

I had a 283 with cams and headers back in 1979 that I used an aluminum Corvette radiator at an angle and the fans (Duel fans from a Jaguar) where on all the time. It ran just over 200 if the day was very hot or going up a steep grade on the freeway.

This was in LA. Dry hot air.

It used to bug the hell out of me but it did not overheat. It used to get very hot inside the cabin.

Bob B

I tested my sensor/switch. It closes at 185F and opens again at 160F. 25 degrees seems like a big spread, but it is conservative and maybe that's a good thing.

There is a 190-175 available that I might try, but I think what I have is OK. The engine doesn't over heat.

Thanks to everyone for their help.