Question: 69 vette with air blockage in radiator

[weegie]

a little input would be helpful. 69 vette 350/350 with a blockage or lack of flow. new temperature sensor,new thermostat and guage is working according to the potentiometer i put on it.The ohms on the sensor also appear to be correct . The problem is the car will only warm up to about 150.deg on the guage.I dropped in another 195 deg.thermo and it worked for about 40 mi.or so then it went back to the 150 deg.mark again.there appears to be flow in the radiator but I feel nothing in the top hose at all.If there is an airlock how do you get it out ? I heard some people drill a small hole 1/16 or so in the thermo. and it will slowly work itself out.

 

[68 4 spd]

if you have flow problems with coolant probably would show up as fluctuating temperature. my 68 always runs about 160 180 unless ambient air temperature is 75+.did you check the sensor after a trip?

 

[SVO]

If you are concerned about air in the cooling system, raise the nose of the car using ramps or jack stands. Allow the car to idle with the radiator cap off and add coolant as needed to fill the system. Be careful of hot liquid from the radiator while doing this.

 

[bagger]

You state that you put a new gauge in. Is it one you bought from a vendor or did you have your old one rebuilt? I bought new from a vendor and had the same problem. When I put the new gauge in I put the resistor back on that was there from the original gauge which caused the gauge to read false. A new gauge has the resistor built in so I didn't need the old resistor from the original. If you did what I did, might want to pull off the stock resistor. Good luck.

 

[weegie]

thanks for the input on the airlock.always thought these cars ran hot.I may not have a problem after all.ohms on the sensor after a drive are 175. which is about 160 deg. I put a potentiometer on my guage and it is reading correctly.I guess its time to just drive and enjoy.thanks again

 

[minifridge1138]

I went with the "drill a small hole in the thermostat" solution.

It takes a bit longer to warm up, but provides smooth temperature changes and makes it easy to bleed the cooling system.

 

[Rod75]

I never trust dash gauges for their accuracy. I like to take temp readings at the radiator itself with this tool:
Pelican Parts.com - Radiator Temperature Gauge

Don't start this test with a hot engine, remove rad cap from a cool engine, insert tool, start and let the engine come up to operating temp. Take your reading there.
Watch for hot coolant burping out, especially if you rap the throttle. Just take all safety precautions.

 

[Vettehead Mikey]

Buy/borrow an IR thermo gun to see what temperature you're really running at. The holes in the thermostat is a half-bubba work around.