I just had my engine rebuilt with stock internals except new pistons rings bearings ect ect. stock heads cc503 check the sig. Ok so i searched all over the net for solutions. i replaced my tstat for a 160. Replaced cap and bled system according to shbox instructions. I repeated this process for 6 heat cycles. No mixing of coolant to oil or vice-versa. i got a bleeder valve for the tstat housing that lets you hook up a clear tube so you can see if air is still present. I see alot of little tiny airbubbles and sometimes theres no solid stream of coolant passing through the clear tube. All this while engine is up to temp with the gauge at the 3/4 mark. Both fans are coming on pulling air in towards the engine. i programmed my fans at 179 degrees and 192. During my the first few heat cycles the temp gauge went all the way to the redzone shutoff immediately. Now it stays in the 3/4 mark and wont go down but it sometimes goes up a little but comes back down to the 3/4 which i think is still to damn hot. So im thinking my heads may be warped allowing combustion gas into the coolant thus why i see so many tiny bubbles which never seem to fade. What do you guys think?

 

Were the heads reused or new and were they checked for flatness?

If you suspect such a thing, you can either use a leakdown tester or get a hydrocarbon test kit from an auto parts store.

Do you see flow in the radiator when it's up to temp?

 

Are you sure its not an indication problem?

 

OP never came back to the site to check for replies.

 

Sorry guys but my problem was a bad temp gauge sensor and just had air in the system. I datalogged the car and temp never rose above 190 degrees F. So now I have another issue. The car is misfiring on every cylinder but one only at idle. As soon as I take off misfires dissapear. And bank two is running lean around 6 % while bank one is -5% only at idle. When I accelerate both banks are at -4%. I retrieved codes p300 and p1351. Opti and coil are new.