RickyRick

Hello all, I just joined the forum hoping for some help. I change my head gaskets on my lt1. Previous owner cooked the heads so I had them milled. New thermostat. Now on my first start up while trying to follow the instruction I found and read many post on this fourm the car sky rockets to the red line. Maybe in 2 minutes. The coolant in the radiator isn't hot I can put my fingers in it and not get burnt. The temp gauge sending unit is new as well. I know it's probably air but how I can get the air out if I only have 2 minutes or so before it hits the red. Also I've tried about 4 times now. Thank you all.

94Z28LS1toLT1

Did you make sure that the coupler/shaft was on the water pump,that's one of the things I can think of

RickyRick

Yes I am pretty positive but I can double check

shoebox

Based on your description, it is almost always air in the system. Use the fill procedure on my tech page.

RickyRick

Thanks I've followed it I have a large amount of bubbles coming out of the radiator cap then the temp heads to the red zone. Do I just keep repeating? I've tried w/o the thermostat to no avail same result

RickyRick

Well verified the pump is working. It seems I can't run long enough for the thermostats to open so the radiator remains cool thus the fans do not turn on but the gauge is red. How can I bleed the system if I cannot run it long enough to get the thermostat open and remove the air pockets..?

Injuneer

How did you determine the water pump is working?

And you followed Shoebox's procedure EXACTLY?

Hate to mention it, but..... leaking head gasket?

RickyRick

removed thermostat looked in radiator saw circulation. Removed water pump front cover bared engine over observed pump rotation.

shoebox

Try to see if the engine is really hot (have a temp gun?) Gauge may be lying. Steam pockets will make the sensor in the head go nuts. If engine temp is really not hot, continue to run it. BTW, most all air is purged during filling.

RickyRick

I do have a temp gun I'll take some temps. I suspect it is steam pockets as it isn't boiling and the heat just begins to get warm as it hits the red. The engine doesn't feel like a super hot engine. What temps shot on the sides of the head would be in the range of operating temp? 215 ish? Thanks for the help it's kinda got me stumped!

RickyRick

Ok I have some data temp gauge in car reads near red. IR temp gun reads 110 on the sending unit and around it. ohm'd the sending unit and got a measurement of 48.5 ohms I don't know what the reference is for ohms/degrees but I believe the ohms correlate to the measurement on the gauge i.e. Lower ohm higher reading in degrees on the gauge. Either way surface temp seems way low for what the gauge says.

shoebox

48.5 doesn't sound right.

4th Gen LT1 F-body Tech Articles

RickyRick

Bad sensor? I snapped the plastic bit off the original one removing my manifold.. This is not an ac delco sensor it's a Orileys whatever it's new so maybe defective?

shoebox

I always recommend the ACDelco part for this sensor. The parts stores are notorious for giving out the wrong sensor for this.

RickyRick

I'll pick one up after work. I'm also going to boil some water and ohm the Murphy sensor and post the values vs temps