Coolant temperature fluctuations normal??

NardDog · Nov 25, 2024

If no coolant leaks to the ground then its a possibility its leaking from the inside , keep an eye on it and if its a drastic leak that you cant see puddling on the ground then you make have a bigger issue.

rdezs · Nov 25, 2024

Scary thought. Low on coolant and an oil pressure gauge not working. Is it really not working? Or do you have coolant mixed with the engine oil thinning it out to where you have no oil pressure? Better start checking things out. I'd start with an oil change and see what comes out from the drain plug first.

mountie · Nov 25, 2024

In my '05 Yukon, the temp gauge ( at running temp - 200 ) , has never been different no matter the ambient conditions or speeds.

( I flushed the coolant twice, since I owned it.... replaced the overflow canister to see the levels better.

Jman2 · Nov 25, 2024

Definitely going to keep an eye on the coolant level. My oil pressure is having the issue where it’s always reading 80, but it jumps to 80 automatically with only battery power. Plan on changing that sensor sometime soon.

Jman2 · Nov 25, 2024

Since filling up the coolant, temp holds steady at a tick under 200 with no fluctuations at all.

Fless · Nov 25, 2024

Is this an electric fan system, or the clutch fan system?

Think about having a scan tool on it to view the ECT PID so you have the exact temp the sensor is reporting. You'll see fluctuations with that setup that you don't see with the gauge that's made to remain steady.

mountie · Nov 25, 2024

Jman2 said:
Since filling up the coolant, temp holds steady at a tick under 200 with no fluctuations at all.

If all's good, it will stay there.

petethepug · Nov 26, 2024

Jman2 said:
The coolant level was low……

Yup, and you probably need a new coolant reservoir too. The integral level sensors probably dead.

Now start looking for your coolant leak. Probably the plastic side tank in the radiator or cracked reservoir tank. When new leaks occur they only leak under pressure.

Meathead16 · Dec 1, 2024

How long have you owned the truck for? Any known history? Is it the 5.3? Certain heads used on that engine have a known defect that results in a cracked head and subsequent internal coolant leak. Heads manufactured by Castech wirh the casting number 706 was the most common one to be affected by this.

TSB

rockola1971 · Dec 2, 2024

Fless said:
Is this an electric fan system, or the clutch fan system?

Think about having a scan tool on it to view the ECT PID so you have the exact temp the sensor is reporting. You'll see fluctuations with that setup that you don't see with the gauge that's made to remain steady.

Absolutely true. The temp signal fed to the temp gauge is averaged to keep the temp gauge needle from being erratic and catching every little temp swing. I cant remember on our gen whether its averaged in the BCM or in the Cluster itself.

Coolant temperature fluctuations normal??

NardDog

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rdezs

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mountie

Jman2

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Jman2

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Fless

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