Ok New water pump...10k miles on it. New radiator hoses upper and lower. New thermostat, new radiator cap. Ok i start my car in the morning, after 20 minutes the temp is only at 150-160. Upper and lower hoses are hot, cap is warm, heat is luke warm. I pull out drive way temp reaches 195..then goes back down to 155 then back to 195 then 155...flops back and forth while driving. Ok theres air in the line...bleed the line....no air comes out just coolant now. If i get in my car in the morning and go without warming it up it goes right to 195 then it goes down to 155ish again back and forth with the flexuating...Park, idle, temp goes to 195 and stays...nice scolding hot heat..get out upper and lower hose are both squeezable..no pressure building up?? No leaks, no blown head gaskets no cracks nothing?!?! DRIVING ME NUTS. Any suggestions would be appreciated

 

That is really odd. You don't often see too many times where people have an issue with the engine being too cool unless the t-stat has failed and stuck open.

Since you put a new t-stat in, what temp rating is the new t-stat?

Also, if you've only bled the coolant lines once it might be a good idea to bleed them again. Sometimes you get a pocket of air that takes a few tries to work its way out.

-Riggs.

 

Ill try a bleed again. Thermostat is a 195... Only reaches 195 when idling..and stays at 195 soon as i start driving it flexes

 

Why I wondered. If you had installed a 160* thermostat with the stock fan settings you would get about the temperature range that you're seeing right now (since it's generally really cold out). It would idle at just below the fan turn-on points, but as soon as you got moving and had cold air always rushing through the radiator it would drop right down to 160ish.

Anyways, are you sure that the thermostat is installed correctly?

 

I'm thinking that it's a thermostat issue. Sounds like it's either all the way open or all the way closed. I think it should keep the temp in a smaller temp zone. Driving would make the temp swings greater than when you are parked, because all that cold air (I'm assuming it's cold where you are) is blowing throught the radiator when you drive. When parked, even with the thermostat open, the radiator is a lot less effective.

I think I get one big swing when the thermostat first opens then it moderates somewhat. It does still fluctuate, but I don't think its such a wide range. Of course my temp gauge has no numbers, so who knows.

 

Ok did a pressure test everything is good! It was the radiator cap...new cap was defective replaced cap..still same problem...got a 3rd cap now its good...whats the off of 2 bad caps in a row from 2 different places !!! Now the hoses are firm so there is good pressure temp don't fluxuate...

 

I would try a new radiator cap.