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bill
bill, chrysler master tech
Category: Chrysler
Satisfied Customers: 1567
Experience:  25 years with chrysler drivability and electrical expert
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Yesterday the temp gauge in my 2005 300c 5.7 started

Customer Question

Yesterday the temp gauge in my 2005 300c 5.7 started climbing above the middle tick mark, then after 30 seconds to a minute would drop back down.. Car was either at idle or slow speed. AC on. I did hear at least one of the fans going. BTW, what temp does each tick mark represent?
JA: Where exactly do you think the noise is coming from? And how long has this been going on?
Customer: No noise........
JA: What year is your C?
Customer: 2005.
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: Nothing yet. This morning I will check the coolant level and make sure that the electric fans are running.
JA: Anything else you think the mechanic should know?
Customer: Water pump & egr valve were replaced about 2 months ago.
Submitted: 4 months ago.
Category: Chrysler
Expert:  bill replied 4 months ago.

#1 question i have for you what was the OUTSIDE temp when the gauge moved above the "normal mark" ?

the NORMAL operating temp in ideal conditions is 220 degrees that"s the APPROXIMATE middle point on the gauge, the gauge has tick marks now BECAUSE of the high operating temp of modern engines ( more trouble would be caused with an unknowing driver if there was an actual number, older cars used to be overheating at the normal operating temp of a modern car, plus the gauge would need to be super accurate, read super expensive) center is ABOUT 220 1 tick above is ABOUT 230 1 tick below is ABOUT 200, all this info and gauge position is determined by a communication BUS which communicates the engine temp and car vitals to the instrument cluster which is NOT a traditional cluster it's a master computer that "talks" to the up to 30 other computers in your car

Customer: replied 4 months ago.
It was about 90 with heavy rain
Expert:  bill replied 4 months ago.

with that high of an outside temp it's very possible to see the gauge climb slightly above the normal center point until the fans kick on, the first thing to do is verify the coolant level is in the OK range (COLD ENGINE PLEASE, the cooling system on a HOT engine is under pressure and will burn you if you pull the cap off while the engine is hot) there are marks on the coolant bottle and the level should be ABOUT 1/2 way up the bottle (a half full bottle is the correct level) next you have 2 fans and they BOTH must be coming on to properly cool the engine (they both come on at the same time) it's not uncommon to see one fan motor fail and only have 1 fan trying to cool the engine. the BEST way to see this is start the engine and turn on the A/C BOTH fans must come on soon after the A/C is turned on and at ABOUT the same speed if one is not running or turning slower the fan motor(s) need to be replaced

Customer: replied 4 months ago.
OK, thnaks. Made a quick run to the store earlier, no problems but ut was a short trip. I'll check both the coolant and the fans when the engine gets cold. Thanks!
Expert:  bill replied 4 months ago.

no problem once your satisfied please rate the service if you need further help please ask,

as a side note if you notice the gauge moving more than is normally does it's a good idea to replace the thermostat if it wasn't replaced with the water pump on a HEMI it SHOULD have been but if an aftermarket one was used they DO end to be less reliable than OEM ones

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