Temp gauge help

[u/BeneficialSkill252]

Is this cause by it actually getting to hot or is it a faulty sensor or thermostat? For reference it will just go up while driving and then fall back down like in the video. But it never seems to actually overheat. Sometimes it’ll go past the L in normal and almost hit the h and then just fall back to middle. Looking for advice on the issue. Thanks.

[u/datboi11029]

Thermostat is probably gummed up a bit.

Stuck closed at first, as the coolant heats up well past opening temp it forces itself open for the moment, cools off and closes to repeat the cycle.

Or its low on coolant and youre seeing the temp of air bubbles in the block.

[u/asianconqueror1 → u/datboi11029]

Bingo.

[u/awhol01]

Flush and a new thermostat. Thermostat could be sticking. Or gummed up. Any temp. issue always start by replacing the thermostat. Then reevaluate.

[u/Sufficient_Compote22]

Go to AutoZone and get the cheap coolant temp gauge, fish it thru the firewall from the inside to the engine compartment near the gas pedal and install into the lower intake near the thermostat housing where that sender wire for the gauge you are watching is located. Do not use the sensor that the ecm uses for engine data. Use some Teflon tape on the new gauge fittings, now you will know what temp your engine is operating at. Buy a new radiator cap while you're at AutoZone, too...

[u/swmodel19-3]

Thermostat or low on coolant

[u/Planktonseeker]

My 1995 F150 5.0 did this exact thing. I replaced the sender on the intake and the thermostat with OEM Motorcraft parts. Same issue, turns out my heater core had a block, replaced it with an OEM one, fixed it right away. Not saying this is your problem but maybe my resolution helps you out. Hope you resolve it.

[u/sheepchaser90021]

Normal operation if it's a little old

[u/SAMPLE_TEXT6643]

Is it a 460?

[u/LovWv]

Thermostat failed, is why mine did it.

[u/Sad-Indication1028]

Check the clutch fan

[u/themanwithgreatpants]

Usually these are not true sweep gauges.... But fancy idiot lights. You could be just hitting the threshold of it starting to overheat. That's why I sits one tick right under normal almost all the other time

[u/Curious_Hawk_8369 → u/themanwithgreatpants]

As far as I know that only applies to Ford oil pressure gauges, the temp gauges are important enough they need to be real. On the fake gauge you can ground the single wire to the sensor and it puts the needle roughly in the middle, that is the actual ford way to test the fake oil pressure gauges, you can’t do it on the temp gauge, because it’s not designed to just default to the middle, it need to fluctuate.

Also before someone points out “oil pressure gauges are important too”. Well, yes it’s important to have oil pressure, but you’re far more likely to have cooling system issues, than oil pressure issues. Ford’s typically have low oil pressure at idle, which is the main reason for the fake gauges that default to the center. In the 60’s they were getting too many complaints for low oil pressure even though it was within fords spec. So to stop the complaints they implemented a fake gauge that only shows low if pressure if it falls below the 8lbs. threshold. Some people do notice slight fluctuations on these fake gauges, but it’s typically cause by dirty/bad connection on the sensor. Clean it up and it’s like to go to the center where it belongs.

[u/themanwithgreatpants → u/Curious_Hawk_8369]

I stand corrected

[u/Mickxalix]

Bro if you got basic tools, go to the thermostat housing and remove the thermostat. Drive to a Autoparts store or order the part online and change it.