I let it heat up. therm gun read 200 degrees. had the burp funnel there with 1/3 full of distilled water (rest of the rad was full already) fan hadn't kicked in yet (have to play with damn therm sensor) then suddenly water started boiling bubbles came out and shot coolant as if it were a hose. either alot of air just escaped or it overheated? maybe the therm opened releasing all that air at once. tried it again and same deal. am i missing something? there can't be that much air in there to cause and explosive eruption like that.

i'll try it tomorrow. i was told to drill two 1/8" holes and didn't do it. i'll do that as well.

 

I'm confused. Where is boiling water coming from? The spout below the radiator cap that goes to the overflow tank, or somewhere else?

Are you certain your rad cap is doing what it's sposed to? I use a 15 psi Stant cap that has a manual pressure relief valve.

 

so i have the rad open at the cap with a funnel that's made to burp rads. you fill it with 1/3 fluid and wait for the bubbles to come out. after the temp on the engine reaches about 200, instead of it sending some of the air out via the rad to the funnel, it shoots out fluid as if it over heated thru the funnel.

 

That makes more sense.

Follow the instructions in Post #40 while your thermostat is out, and the trapped air in the engine will go away. With the holes, your rad-fill method would probably work just fine, but why not do both?

 

Lol, the op just needs to put coolant in the engine through the rad cap until full. Start car and top up rad again. Replace cap. Put coolant in the overflow tank at the cold level. Take the car for a long drive. Next morning, add coolant to o/f tank to cold level. Monitor each morning thereafter. The cooling system will burp the air out automatically and replace the air with the coolant from the o/f tank. That's how a PROPERLY functioning cooling system works, period. But if you feel better, put the car on ramps, drill holes in the thermostat, tap the engine block with a rubber mallet, fill through the thermostat opening on the intake, use a water wetter, blah, blah, blah. Then ask yourself if GM did it this way on the assembly line? Then why should you?

 

I am the OP. Lol. So yup burped and good to go. The NPT thermostat the derale comes from doesn’t go in all the way when screwing it in. I mean maybe half way. It does NOT turn the fan on and I calibrated the unit down to 165 just to see if it would kick in. Nothing. I ordered the probe piece to see if I have any luck with that. Electric fan is doing good when I leave the a/c on. Pulls super hot air from the radiator towards the engine telling me it’s working. Only saw it get a hair over 200 once. The rest of the time 185-190. Here’s hoping the probe will work. Cheers.

 

Guys question. I’m concerned still about the therm opening and hate the idea of having to open it all up again. Is it normal foe the upper hose to feel super hot also when I squeeze it when it should already be an open therm it’s squishy. Shouldn’t it be rock hard with water flowing?

 

with a 180f thermostat mine feels like 180f when it opens..
get an IR gun and see what temps really are..
rock hard? eh.. interpretation..

 

in other words I can squeeze the upper hose completely like it’s not installed.

 

Do any of your other cars behave differently? As @interpon suggested, get an IR gun and check the actual temperature of the upper rad hose. It will give you piece of mind. 180 degree thermostat, you'll likely read about 185 with the engine up to temp and running. The top hose will soften, but not collapse since the fluid inside is under pressure. Don't burn your hand.

 

all right. Temp gun shows 185-190 ish. It’s Miami too sooo...
Fan doesn’t kick on no matter how I adjust it waiting for thermostat probe from derale I think the npt is t working. I turn on a/c and boom it’s cold. Thanks all

 

did you actually test the thermostat? It’s normal
for them to be 10-15*F off in temp and usually hotter, my 160 Tstat doesn’t start to crack open till 170.

sounds like u got air in the system. Did you drill a 3/16” hole in the Tstat at 12 o’clock when it’s installed?

also seems like you have a wiring or sensor issue. Im not familiar with your setup but your should verify the sensor is working with an ohm meter if you know the resistance rating of the sensor. Or bypass the sensor which is what the AC override does depending on the sensor if it grounds at a certain temp to tell the circuit to activate then grounding the sensor wires could activate the system. I would verify your coolant temp is accurate, when your Tstat actually opens and work your way back from the sensor through the cooling fan wiring.

To test the Tstat boil a pot of water and add some salt and suspend the Tstat over the pot with a wooden spoon or something and make sure the Tstat is fully under the water and not touching anything (floating fully in water). Use a sensor (cooking thermometer also suspended in water from the spoon) and watch the tstat... record the temp that it starts to crack open and when it’s fully open. You now know exactly when your Tstat will start to
open and be fully open and your engine temps should correlate to those numbers. If they aren’t say your Tstat opens at 185 fully and your engine is running at 200 even tho the fans come on at 185 then your system isn’t adequate (air, size, etc). You should set your fan temps to turn on 10* after the stat opens so say it opens at 185 you set your fans to 195 on and 205 off. That way the Tstat remains open even if the fans turn off (think highway cruising where your fans don’t matter) that way the Tstat isn’t fully opening and closing and the fans don’t run all the time.

 

do you mean on at 205 and off at 195? it'll be on and off all the time. thought 185 on and 205 off was better?

 

no, you want the fans to cycle on and off. If they stay on then they are working too hard. Fan should go from on to off in 10*F span, if you have dual fans then it would be off185/195 on and 195/205 for the 2nd fan. If you kept the fan on from 185/205 it would be on all the time. If yours is the dual speed derale then low speed on at 195 and off at 185 and high speed on at 205 and off at 195. That way it only overlaps for a 10 degree time period and allows the fan motor to cycle.

 

If you are driving, that fan will probably never come on except at a long stoplight. Idling in your driveway it should, though.

I'm assuming that your circuit works the way mine does, and the temp switch closes when hot, grounding the negative side of a powered relay coil, which closes the relay, and provides power to the fan. If that is the case, you should be able to override the fan switch and test the fan relay (and fan), by shorting the fan switch. If you line it up, you should be able to do this with a screwdriver, or just touch the lead that goes to the switch to your engine block.

If that doesn't work, either your system is wired differently, or there is an electrical problem that needs to be fixed.

 

all right I got this nipped in the bud. Two things. that crap therm doesn’t open heated in boiling water or in my over at 250. Original works perfect so put that back. Shorted the npt sensor doesn’t kick on measured the voltage coming out of the derale controller shows 5c which is correct. Heated the sensor the ohms don’t change. I had bought a probe sensor I heated that and the ohms jumped up and down as I heat it up worked. Great. Well I wired that up and nothing. Googled and found that damn derale is known to have this issue. Amazon issued an immediate credit today and I ordered a mishimoto coming Friday. Let’s see what happens. On the positive side the car is idling great. Thanks

 

Happy thanksgiving to you and your loved ones
God bless

 

forgot to update. The mishimoto came in, wired it up and kicked in around 180. Played with the adjustment till I got it to kick on around 200 and shut off around 190. Will play with it again when I have a chance because when I turn the a/c in it lowers the temp to around 180 all the time since the fan doesn’t stop (a/c overide). It cycles on and on perfectly otherwise. So much for people saying electric fans overheat. The trick is a derale 17” and a shroud that covers the entire radiator IMHO.

 

Recently purchased a ‘69 C3 with a 350 and the previous owner installed an aluminum big block radiator. I have recently noticed that the lower hose is dangerously close to the fan. Can anyone suggest a lower radiator hose that will allow proper hose to fan clearance?

 

picture please. Ive noticed calling ecklers or southern car parts directly they will give you the part numbers BUT after market stuff always changes the game. One thing I did learn make sure the lower hose has the spring in it.