So this is my first summer with mt c4 1986, and I'm scrambling to keep this thing cool but I fear I'm losing the battle. Just before summer hit here in Nevada I replaced the 35 year old radiator with a new OEM 2 row from amazon. I also flushed the engine and installed a 180 degree performance thermostat. By performance it just has a larger hole for the coolant to pass through. Also installed a new fan motor to replace its aging cousin and a new adjustable fan relay from Hayden. So after all that its still getting into the 230 to 240 range while sitting at idle with the AC one. The fan constantly runs with the AC on (i think its supposed to) and I have the relay set for 190 degrees with the AC off. So city driving the temp just keeps rising to that 240 mark, freeway is just fine about 187 to 195. So what I need to understand is if the temps for city are ok or not. Also when I read the outlet temp at the temp sensor up front with a laser temp gun I read 210 and at the radiator inlet about 185, while my gauge is showing 230 to 240. If I take a reading at the temp sensor on the right side of the engine its about 256, go figure. Is it normal to see such a difference in readings? Is the gauge normally off so much? If I do a scanner reading I'm also showing a lower temp them what the gauge is showing. I'm confused and need some help here. Thanks

Tony

 

Hope you don't mind if I piggyback a related question on yours!

I noticed my 1994 C4 sometimes rode a hair over the 180 mark before - I don't remember what happened when I used the AC last year after I bought the car in August (it's possible I was not paying attention) but after having it recharged recently I was unpleasantly surprised to see the coolant temperature gauge had covered almost half the distance to Too Hot mark on the highway! (running a sedate 60 or 70 on a 92 degree day) I turned it off and suffered and the needle drifted back to 180, but now I'm wondering if I should have been worried or merely watchful? In my limited experience cars kept their set point unless there was trouble, but there IS a broad range on the gauge between 180 and the cross-hatches. Is it normal operation to use that range?

 

Let me understand this ... with the AC on at highway speeds your coolant does not get above 195? Sounds like the cooling system capacity is fine (though you don't mention the outside temperature). Also seems there is a cooling capacity issue in the city. Even with the fan on it's not moving as much (relatively) cool air past the radiator as at highway speeds?

That was effectively my question under slightly different conditions, and considering the preponderance of opinion it seemed to me that the 220 I was seeing was acceptable. 240 I am thinking most people would consider too hot.

Forgive me for asking a stupid question, but when you say the radiator inlet is about 185, are you sure you are not looking at the radiator outlet? The coolant going into the radiator is presumably hotter than the coolant coming out of it. You do alert my sleepy mind to the fact that the "coolant temperature" which we see on a gauge is, even assuming it is accurate, measured at a particular point of the coolant loop, in a particular location, whereas first of all obviously the radiator is cooling and there is a different between in let and outlet temperatures and there will also be variation in the temperature as the coolant takes its path by the various heat sources in the loop.

 

Corvettes, Summer, and High Coolant Temperatures

 

Good read, thanks for posting it. One thing is wrong though when the writer states the LT1 Corvette doesn't have an unpressurized recovery tank. My '95 does.