Coolant temperature concern?

[Falcon_LS]

On my way home last night, I did a WOT run on the Grand Marquis before pulling off the highway and ended up busting my upper (rubber) radiator hose. This was at the thermostat end, right at the edge of the clamp. Thankfully, I was less than a mile from home when the idle got rough, due to coolant spraying on the driver's side COPs.

I went and got another rubber Motorcraft hose (will be upgrading to baby blue silicone hoses later), and topped up with distilled water after installing it. Then I went ahead and thoroughly dried the COPs. All is well right now, except for a slight coolant temperature concern.

I use my ScanGauge-II to monitor cylinder head and coolant temperature. At operating temperature, the cylinder head has always been 2°F hotter than the coolant, but that balance seems to be upset right now.

Before cylinder head temperature hits 200°F, the coolant is now 3°F cooler. When the cylinder head temperature hits 198°F, the coolant temperature always remains at 197°F without fail. This 1°F difference is always when the cylinder head hits 198°F. When the cylinder head temperature is over 200°F, the temperature difference goes back to normal at 2°F.

I'm not sure if it's something to worry about, but it is bugging me to be honest, and I'm wondering what the cause may be. Just wondering if anyone has any ideas. Thanks!

 

[SteveSRT8]

I would suspect the sensor (either one) has been stressed by the overheating and now reads slightly different.

But watch that closely as a future issue may arise.

 

[yonyon]

Try another WOT run. You might have a little air bubble that needs to be pushed out.

 

[Chris142]

Water is a better coolant than antifreeze. I'm guessing That running more water than antifreeze is why your getting a different reading now.

 

[Falcon_LS]

Originally Posted By: SteveSRT8
I would suspect the sensor (either one) has been stressed by the overheating and now reads slightly different.

But watch that closely as a future issue may arise.


Sorry, I forgot to mention the engine did NOT overheat. Cylinder head temperature was 197-208°F ever since the engine started running rough. It also lost half a gallon (just under 2L) of coolant.

Originally Posted By: yonyon
Try another WOT run. You might have a little air bubble that needs to be pushed out.


I'll give this a try. After I refilled the system, I raised front end of the car so that the front end sits higher, then idled the engine briefly with the cap off. A bit of air came out, but it wasn't much.

Originally Posted By: Chris142
Water is a better coolant than antifreeze. I'm guessing That running more water than antifreeze is why your getting a different reading now.


I topped off about 13% of the total capacity. Would that be enough to make a big difference? The coolant to distilled water ratio is now about 38 (coolant):62 (distilled water) instead of the original 50:50.

 

[SteveSRT8]

Good details. Hope there is no steam bubbles, they can damage HG.

Chris142 is right on it. That may explain the difference!

 

[Donald]

You should have 50/50 at a minimum. I am not aware of using a lower ratio of coolant just because you are in a hot area. In a very cold area, you can go to 60% coolant and 40% water.

 

[Falcon_LS]

Originally Posted By: SteveSRT8
Good details. Hope there is no steam bubbles, they can damage HG.

Chris142 is right on it. That may explain the difference!


Now you got me worried. How can I check for steam bubbles?

Originally Posted By: Donald
You should have 50/50 at a minimum. I am not aware of using a lower ratio of coolant just because you are in a hot area. In a very cold area, you can go to 60% coolant and 40% water.


This is just temporary, as the vehicle is going in for a heater core replacement on June 3. A complete coolant flush and refill will be done with Motorcraft G-05 and distilled water.

 

[mechtech2]

Are you really concerned about a 1 deg F change in temperature?