why does my temperature gauge peg way past hot?

30

Asked by Mar 06, 2015 at 09:06 AM about the 1986 Pontiac Sunbird GT Turbo

Question type: General

I have a rare '86 non turbocharged Pontiac Sunbird GT. After the
engine warms up, the "check gauges" light lights up, and the
temperature gauge pegs way past hot even though the car is not
overheating.  I replaced the temperature sending unit, drove the car
about a dozen miles with a combination of surface streets and
freeway driving.  At about 160 degrees the fault occurred again.  The
next step is to replace the more expensive temperature switch. This
is not the fan switch.  In 1986 Pontiac saw fit to make all Sunbirds
turbocharged, as standard. This 1.8 (112 cu in) engine is in a non
turbocharged  77K mile survivor car. Pontiac produced 118,118
Sunbird two door coupes, including the LE and SE models. Of that
number, I don't know many were GT's and how many were ordered
without a turbocharger. A search across the US and Canada
produced zero '86 Pontiac Sunbirds for sale, anywhere.  So the pool
of people with same car is nil, much less the non turbocharged 1.8
engine.
I sort of chimed in here because I saw that someone was having the
same problem,  albeit with a much newer Pontiac. I have yet to see a
solution here. Has anyone an idea or two?

4 Answers

8,385

have you flushed the cooling system and replaced the thermostat

30

I believe I have solved the problem. I am pretty sure it's the temperature switch. Apparently, the computer freaks out when the cooling fan doesn't kick in when the computer thinks it should. I'll replace the temperature switch tomorrow and test it out. I had already replaced the temperature sending unit. I'll update the results. Thanks for the thoughtful input.

I have one of those 86 non turbo GT convertible and now having the same problem.... I have 2 both GT convertibles one a turbo and one is not.

i have a '83 J200 sunbird convertible with 51k on it, and the same problem. i have replace the fan and temperature switches. (both just below the "radiator cap". , I had the new temperature switch wired in, they don't make the original one. worked for about 3000 miles '. Trying a new gauge next

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