99 deville temp keeps jumping up and down

[CaddyWoman76]

My caddy day for 4 months with the alternator down. Now that it's fixed the temp keeping running hot. I've changed the thermostat. Flushed the radiator. There are no leaks. The only way I lose water is through the overflow drain. Sometimes I can go 2 days and it runs at 196, other days it will jump to 240 then down to 222 then up to 230 them down to 215. I pulled the DTC and the only thing I'm getting is P0113. That has nothing to do with the temp from what I read.  Oh and the heads are not cracked or leaking. No water in the oil. I bought a temperature sensor today. I'm not sure if that is the problem though. Any suggestions. 

[BodybyFisher]

Ok no leaks.  Depending upon the outside temps, your temps don't appear to alarming.

What concerns me is that you lose coolant through the cap overflow.

Be sure not to overfill the cooling system, keep it 3 inches from the top when the cap is off.

Here are some things to consider:

Check to be sure you have at least 50% coolant concentration, buy a coolant tester to check the coolant concentration. They are cheap at, pep boys type store.  You said you flushed the cooling system, if you used a hose and flushed it with water, that is a no no because straight water stays in the engine and its hard to balance the concentration to 50/50.  In the future don't flush with water, just drain and refill.  Be SURE its 50/50 or it will boil at a lower temp and pop off at the overflow.

Be sure your radiator cap holds its rated pressure, if its only holding 8 psi instead of 15-16 psi, it will release pressure and the coolant will boil at a lower temp.  If you cant test it, if its old just replace it.

The cooling system must get air out or the water pump will cavitate and stop pumping coolant.  Check it as follows.  Make sure the engine is cool. On top of the coolant tank is a hose that runs toward the engine, that is the air purge line.  Gently pull that hose off after removing any clamps, gently, you dont want to break off the plastic nipple.  Direct the hose down and have someone start the car, dont gun it, idle it.  A steady stream of coolant should flow from the hose, if it flows, you are good.  If not let us know.

You need to check your water pump belt for cracking and slipping, if it slips you will pump less coolant.  The tensioner can bind and not apply sufficient tension.

Believe it or not you will see more stable temps with the AC on.  That is because with the AC off they will turn on at 228 and turn off at 217, but with the AC on, the fans run constantly causing less fluctuation in temps. Observe the fan operation and speed.  

Do those checks before we go deeper and check for a head gasket breach.  

P0113 Intake Air Temperature (IAT) Sensor Circuit High Voltage is not related to the cooling system

[BodybyFisher]

This was a good thread that you were looking at

 

[CaddyWoman76]

I had the radiator and and water pump replaced last year and new cap.  Would it go bad that quick? I've had this car for 5 years and I don't think it has ever run this hot before. I have been doing a lot of research and it hasn't been tuned up in a couple years. Oil changes yes. Would the spark plugs and wires being bad cause it to run hotter than normal? I just went and looked and found the purge line. I'm gonna get on that and get back to you. 

[BodybyFisher]

No the cap is fine, I didnt know it was that new

Spark plugs and wires won't cause overheating.

Where do you live, what have the oitside temps been? 

Did you flush with a.hose?

 

[CaddyWoman76]

It's been in the 90s to 100 degrees outside. I'm in Louisiana. It was flushed with a hose but filled with 50/50 coolant. 

[KHE]

Radiator and water pump replaced in the last year - what were the reasons those items were replaced? 

In addition to the items Body by Fisher mentioned, I think you need to have the coolant tested for combustion gasses.

[BodybyFisher]

7 hours ago, CaddyWoman76 said:

It's been in the 90s to 100 degrees outside. I'm in Louisiana. It was flushed with a hose but filled with 50/50 coolant. 

This is what I was afraid of.  Get a tester asap and test the coolant concentration and adjust it to 50/50 asap.  The engine had straight water in it.  Putting 50/50 into an engine that had straight water in it most likely pushed the mix below 50/50, thereby decreasing the boiling point.  

The other problem with flushing with water is that minerals were introduced into the cooling system.  In the future, drain and refill, NEVER flush.

[CaddyWoman76]

Radiator and water pump were replace because they were the original parts and is a 99. 

[BodybyFisher]

I think Kevin was concerned that they were replaced because a mechanic was chasing an overheating problem.  

Were they changed because it was running hot or overheating? 

Did u test for coolant flow at the air purge line yet?

[rockfangd]

5 hours ago, CaddyWoman76 said:

Radiator and water pump were replace because they were the original parts and is a 99. 

Age is not a reason to replace some parts. (like the waterpump). I have seen too many changed for other reasons and had nothing wrong with them.

Radiator I can see though. 

I have done 0 waterpumps on any of my northstars. And have done few compared to other vehicles in general.

Alot of times when people are not sure of what the problem is they begin to assume and throw parts to try to fix it.

It can cause more problems and more money in the long run.

I agree about checking the coolant concentrate. If water was used to flush it will not all come out and will throw off the concentrate of the new coolant.

[KHE]

5 hours ago, CaddyWoman76 said:

Radiator and water pump were replace because they were the original parts and is a 99. 

Absolutely no reason to replace good parts... Most of the time, inexperienced "mechanics" replace those components when a Northstar engine is overheating.  99.9999% of the time in those cases, the radiator and water pump were perfectly good.

[Cadillac Jim]

Yeah, go right to the antifreeze being below 50-50 and the bypass bolt-with-a-hole clogging.  Not only are these free or very inexpensive to fix, they are the source of most overheating problems.

At least we are mostly past the replace-the-module and replace-the-sensor phase.

If the radiator cap is relatively new and everything was fine with it last year, it's probably OK.  If not, make sure that it's the right one for your car and isn't leaking or clogged.  Having the system pressure-tested can bring out problems with the cooling system holding pressure.