Thread: LIM Change Done, Running Hot

Running a 98 GT, it's been an interesting project. After the job the engine gets up to temp at a normal rate, the temperature peaks just above the 235 mark and never goes below about 215. Before I never saw it above 210.

Here is what I've done:
Flush cooling system with water
Remove and clean throttle body, upper and lower intake, valve covers, tensioner.
Remove heater and coolant hoses
Remove water pump, athough I didn't have to, I did it to check the fins
Reinstalled water pump, however without changing the gasket (Though I don't see an obvious leak)
Installed LIM gaskets, applied rtv to the only the 4 corners, Installed LIM, torqued bolts to 12 ft-lbs, new coolant temperature sensor installed improperly (more later)
Installed new tensioner and coolant elbow (my car has only one plastic elbow), new water outlet, new 195 degree T-stat, new coolant hoses, new intake plenum and everything else per the GM service manual. Filled with Prestone coolant
Fired her up no problem, pulled out of the driveway, temperature gage shot up past 210 before I could reach the end of the block.

Coolant temperature sensor was not properly tightened, nut was stripped due to close proximity to exhaust crossover pipe.
Removed crossover pipe, installed another new coolant temp sensor to torque spec.

Flushed cooling system, now running straight water. Engine heats up at a normal temp, stays up at about 230ish. Outside temp in the 90s.

Flushed cooling system with water again, fill with proper antifreeze mix 5.01 liters pure Prestone, rest water. Still hovering around 230ish. Replaced radiator cap, 195 degree thermostat again, same problem. Fans turn on at 230, turning on AC will allow engine to cool to 215, but never lower. Let sit overnight, morning no coolant on the driveway, coolant reservoir and radiator are at proper levels. I drove over 100 miles today (75 degrees outside), never above 240, never below 215, it likes to sit at about 225-230 while driving.

Here is my parts list:
-GM Lower Intake Manifold Gaskets 89017816
-Gates Lower Radiator Hose 22373
-Gates Upper Radiator Hose 22344
-Gates Heater Hose 19109
-Gates Heater Hose 19110
-Gates Drive Belt Tensioner 38152
-GM Coolant Elbow 24503423
-Temperature Sensor Napa ECH TS4020
-Radiator Cap Murray Caps 7616
-Duralast Thermostat 15849
-Thermostat Gasket Felpro 35666
-Water Outlet Autozone “Compressor Works” 815167
-Dutalast/Felpro Water Outlet Gasket 35595
-Felpro Valve Cover Gaskets VS50080R
-Felpro Valve Cover Grommet Set ES72833
-Purolator PCV Valve PV892
-Intake Plenum ineedparts.com GM Intake “Sure Fix” Manifold Kit 17806
http://www.ineedparts.com/auto-parts/intake-manifolds/gm-intake-manifold-kit-17806.html

My ideas are:
-Bad guage/pcm/something and the engine is actually running at proper temp
-Clogged radiator, however there are no cold spots
-The new intake plenum, but it advertises to lower engine temps
-Water pump gasket leak. I do not have a pressure tester to make sure cooling system is about 15-16 psi
-I screwed up somewhere and don’t know it.

I know some would say 180 degree T-stat, but I’ve had 2 T-stats open at the proper temperature (verified by having the bleeder screw open) and I don’t believe that would fix this.

I do not believe it is a bad temp sensor, this does this with 2 sensors. I also do not believe it is a head gasket or LIM gasket since the oil is not milky. When I pulled off the throttle body when removing the crossover pipe, I did not notice any leaks from the upper plenum.
I have the Scantool.net Bluetooth scanner coming in the mail so I can check coolant temp and other parameters with my Android phone.

did you bleed the cooling system?????

i know you said you had it open to see if the thermo opens, but did you keep it open for 5-10 mins to let ALL the air out?

Yes I did. My bleeding procedure is to open the bleed screw, fill the radiator while squeezing the upper hose to bleed air, start the engine, wait for a steady stream then close the bleed screw. rev the engine and have someone fill the radiator and install the cap. Then per the GM manual, drive for 3 heating and cooling cycles and check the radiator level.

Originally Posted by QUICKSILVER462

Clean and reinstall your origianal temp. sensor, then re-bleed the system.
See what it does.
Make sure the front end of the car is higher than the rear when bleeding the
coolant system, level is preferd.
Note: usually rapid movement of the temp gauge is a clear indication there is air in the system.

Unfortunately I cannot, it is broken in 2 pieces. Unless I have a GM part# and go for buying a 3rd temp sensor.

Everything feels like before, just 15-20 degrees higher. Gas mileage is 27mpg @ 60mph, heat and AC feel normal, acceleration feels fine, no dtc codes, no rapid fluctuations of temperature. It rises at a normal rate, peaks at a high temp, and goes down at a normal rate when the fans turn on. It simply will not cool below 215.

I just noticed a recent thread with a similar problem http://www.grandprixforums.net/temp-...ion-49569.html
I do wonder if the wire harness for temp sensor is damaged and sending the wrong value to the gauge, I'll find out when I'm able to hook up a scanner later this week. Just in case, does anybody have a GM part# for it?

My cheap china scanner (ELM327) finally decided to work this morning. The guage reads 230 while the scanner reads 208. Since the wire harness is incredibly close to the exhaust crossover pipe, I wouldn't be surprised if it was burnt even though I have flex tubing around the wires.