Hi all. my caddy northstar used to stay rock solid halfway on the dash temp guage. Recently it has started to climb WAY up. Twice i got the 'idle engine' 'ac off' etc. I recently had the radiator replaced due to a crack in the plastic side about 5 months ago. The weird thing is that the guage goes up and down. It was in the 90's here at the time. If i gave the car gas to rev the engine, the temp goes down. if its alot of stop and go, it will climb. If i put the climate control to max heat 90, then shut it down, the guage will stay at half. if i put it to 60, then shut it down, the temp goes up and down. It also takes awhile to get heat out of the vents when i put it on 90. if i accelerate then you will feel it get hotter. i checked the purge line and there is coolant flowing from it at the overflow tank. i DO NOT smell or see coolant leaking when it got to overheat condition. There is no white smoke or coolant smell from the exhaust. I have not had to replace any coolant. all the fans are working and come on full blast when its hot. Today its fine with just slightly past half on the guage WITH the ac running. it was 68 degrees today. am i nuts? bad temp sending unit? bad thermostat? water pump failing? where do i start????? thanks to all for any replies as im at a loss.

 

i want to say it seems your low on coolant but then again when was the last time the coolant was flushed and thermostat changed out?

 

Hi Daddylac, my water pump was replaced under warranty about 5yrs ago. dont know if thermostat was changed or not. could still be the original. had the cooling system serviced about 5-6 months ago with a radiator replacement. also had the tranny overhauled about a year and a half ago. my overflow tank is filled to where it should be also and i already checked for coolant from the purge line at the overflow and i do have coolant flowing from it. should i have the coolant sys flushed along with a new thermostat? is this an easy replacement for a DIY person? not even sure where its located. Thanks for the reply as after i posted i realized i may have posted in the wrong area. Thanks again for any help. i figured it wasnt a head gasket failure due to when engine is brought up to 3000 rpm, the temp gets lower. i could be wrong too though. kinda keeping my fingers xed at this point, you know? only other thing i can add is that there is no water in the oil. i DO have a brownish substance in the overflow tank but was told this is the additive that is put in for water pump lubrication. this brown gunk floats on top and the coolant below is clear orange and the coolant from the purge line is also a clear orange. dont know if this makes a diference or not. and i have the normal 1-2 quarts of oil burn between oil changes. been that way since i bought the car with 35,000 miles. it now has 159,000 and still going. i always try to keep up the maint as i do love this car. its a 2000 DHS by the way.

 

most of the time if the water pump is changed out the thermostat should also be replaced since its located in the same area. to change out the T-stat is fairly easy. If you look how the radiator hoses run you have the top one that goes from left to right and the other one is on the right and runs into the water pump housing. You want to disconect the hose from the water pump housing. This will be a bit messy so put something under the car to catch the coolant. Once the hose is removed there are two small bolts that secure a black cover which is also what the hose was clamped to. you remove the 2 bolts and then pull off the cover and the T-stat is right there. If my directions sound a bit confusing let me know i will post pics. With the radiator and water pump being replaced i would assume its a T-stat issue though the black stuff im a little worried about because i had my head gaskets replaced along with the water pump and T-stat 2 years ago and i havent had that black stuff in my coolant. So go ahead and replace the T-stat and see what happens.

 

i've had some of the same issues with my 2000 dts... after changing the water pump themostat.... after all of that hard Labor lol my purge line was clogged.... so coolant was flowing just not enough.. so when i would idle the car would run hot but ever over heat....

i suggest flushing the system making sure there arent any clogs.... make sure you are using orange dex coolant..... i ended up using 4 bottles just to be on the safe side... the caddi engine is very sensitive and now having enough coolant can sometimes cause to run hot when you use half coolant half water.

good luck