I’m looking for some feedback / insight on a temperature “issue” that has been getting worse over time.
My temperature meter has started to show variations based on outside temperature rather than staying rock-steady at the middle of the range.
So on a cool day when I’m up to temp and driving around the meter will show a bit below the middle of the range. On a hot day it will show a bit over middle of the range, unless I’m in stop and go traffic. In stop and go traffic on a hot day I’ll get a steady increase in temp, right up to the H end >.<
This seems to be a new-ish thing for my car but I’m wondering if others have seen something like this before and if it points to a failing component.
Car details: 428SCJ (3.91 gears), 3-row radiator that is about 3 years old, factory fan shroud and factory C9ZE fan in place, original factory temperature sensor, 195deg thermostat that is about 10 years old, meter has been tested good (using Bill B.'s meter tester), water pump is aftermarket and maybe 15 years old, coolant flush was done last summer.
I do have an NOS autolite temp sensor that I was thinking of swapping in. I’ve also been suspicious of the water pump for a while ~ it is the oldest component left in the system.
Could a failing / sticky thermostat be causing temp variations? Shouldn’t the thermostat be the component that actually adjusts in order to regulate the temperature? So if it is on the cool side it closes down some?
If you have a 351C (with the correct RobertShaw thermostat), your thermostat would fail to close off the recirculation port in the block if it didn’t fully open. This made my 351C act just like that on a hot day. I also would suspect the impeller on an older water pump.
Check fluid level, may be a bit low. See if fan clutch is slipping too much when hot. Could be worn out. Then check for clogged radiator tubes. I agree the pump very likely has had it’s day.
I’ve got no disagreement that a stuck thermostat is unlikely but it could be the easiest to diagnose or just rule out. If it were stuck part way open you should see water flow across the top of the radiator from cold to hot with no real change.
While it is unlikely it was the problem in one of my cars one time. Easy to tell if that is your issue, just boil water then dunk your thermostat in it to see.
Hi!
My suggestion and I do this every time than I flush coolant on my cars,
I always replace the thermostat and the radiator cap (important this $10 part regulates the pressure of the system so the temperature by thermodynamic law).
So those two parts are very easy to replace and inexpensive.
Good luck !
If I were you, before taking anything apart I would verify the actual engine temp is doing what the Temp Gauge is telling you… Get a Infrared Thermometer Gun, they’re dirt cheap and point it where the temp sensor is mounted… Record the temp and compare it to the gauge movement… Could be simply a bad temp sender… Also you mentioned you flushed the coolant, did the problem start after this?? If so maybe you have a air lock in the coolant system… Hate to see you throw a bunch of parts at it for nothing…
