I have a 91 Rs with a 383 stroker and turbo 350 tranny. out of no where car started running hot hitting 215-225 in 10-15 minutes in 60 degree weather. replaced 160 thermostat with a high flow 180, replaced 4 row no name radiator with brand new 2 row Champion radiator and two 12 inch fan shroud setup, and a brand new napa high volume water pump and the car does the same exact thing. dont really know what to do at this point just know i cant drive it and are down a lot of money.

any help would be useful, also the two 12 inch fans are around 1500 cfm each

 

Have you verified the gauge is accurate, or used a temp gun to confirm the actual temp?

 

Where are you getting your temps from and how are the sensors installed.

 

Are these temps sitting idling or going down the road? If going down the road do you have your front air dam? Those temps are slightly high but not egregious. I agree with the above comments about how you are measuring. A lot of folks are shocked when they use a quality gage and compare it to an OEM one which is incredibly inaccurate.

 

temps are sitting and driving either one slowly creeps up past 210
tested two different gauges both gave same readings and the spot is in the intake next to the thermostat

 

they run from the back of the gauge inside the car to probe in the intake next to the thermostat

 

Is the sensor installed in a bushing to fit the intake? I had an issue with crazy temperature readings and it turned out the bulb for the sensor was not in the path of flowing water so it would read really high when it was not. I changed to a face bushing so the bulb was in the path of the water flow and that gave much more reasonable results.

 

I hear that alot, but I have owned a couple dozen or so GM products and not one of them has had a temperature gauge that was not reasonably accurate.

 

Maybe weakened / soft lower rad hose is collapsing cause flow issues as temp increases? Do you have a spring in it?


Just a thought

 

Currently at a mechanic who says its a head gasket problem. thats about the only thing left it can be

 

Fits the bill. Did they check for gasses in the coolant or just yolo and tear into it?

 

Did the mechanic run a leak down and/or compression check on the cylinders or is he guessing about the head gasket?

Or did he pull the spark plugs and inspect for evidence of coolant getting into the cylinders? And are you losing coolant over a period of time?

Is there coolant in the oil? Or oil in the coolant?

Large amounts of steam coming out the exhaust?

Evidence of a misfire?

There should be noticeable symptoms if you have a head gasket failure. Replacing a head gasket isn't cheap and if he's wrong that's more wasted money.

What's the history on this prior to the issue starting? What temperature was it running at before? How long has the 383 been in operation before the current issue started?

Is your radiator sealed to the radiator support? While you're driving air could be going around the radiator rather than through it (taking path of least resistance)