Erratic oil temp reading on the speedo
#1
Junior Member
Thread Starter
Erratic oil temp reading on the speedo
Sometimes when I'm driving the oil temp readings is erratic going from stable at 97-98 C and then it starts blinking to 75,78,84,92 and so forth it just jumps for a good 5-10 mins of driving then back to normal
Am I suppose to be worried about this ? Or is this normal
I have changed the engine temp sensor recently ( there's 2 of them if I'm not wrong, what other possibility of things broken there might be ? )
Am I suppose to be worried about this ? Or is this normal
I have changed the engine temp sensor recently ( there's 2 of them if I'm not wrong, what other possibility of things broken there might be ? )
#3
I have no idea why, but I see a similar thing with both the oil and water temp.. The majority of the time my water temp will be at 197 and then for no reason it will drop to 175 or so then slowly work its way up to 197... I see the same behavior with the oil temp reading.. In both cases this is after the car has been running for a long time and outside temperature does not seem to matter.. Almost completely random..
#5
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Thread Starter
I don't think it's due to the fan as it drops before it reached any high temp and it stopped after awhile and back to normal
I assume that the fan will stay on or comes on at a certain temp , these drop are intermittent and erratic and then it goes back to normal
I assume that the fan will stay on or comes on at a certain temp , these drop are intermittent and erratic and then it goes back to normal
#6
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2012 P31 C63 Coupe Trackrat, 2019 GLE63S Coupe Beast
I have no idea why, but I see a similar thing with both the oil and water temp.. The majority of the time my water temp will be at 197 and then for no reason it will drop to 175 or so then slowly work its way up to 197... I see the same behavior with the oil temp reading.. In both cases this is after the car has been running for a long time and outside temperature does not seem to matter.. Almost completely random..
#7
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For water temp, that's completely normal. That's what thermostats do. There is a wax pellet inside that begins to melt when coolant reaches a certain temperature, this opens the valve and allows coolant to flow through the radiator, then when the coolant drops below the melting point of the thermostat (190F in our case), the pellet hardens and shuts the valve, recirculating coolant without the radiator and heating it back up again. Cycle, repeat. (or roughly like that, it's been awhile since I studied the mechanics of a thermostat)
Here's a good cutaway demo of thermostat operation:
If people are seeing big and sudden drops in water temp, could that be a result of changes in heat load and a stuck-open thermostat?
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#8
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I've been noticing this too. Started recently on my car. Oil temp goes from 95 celcius to 75, back to 95 and so on. All within 10 seconds. I'm guessing oil temp sensor needs replacing...
#10
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Your temp readings sound normal
#11
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I didn't notice how low the OP said his oil temps were dropping.
Dropping below the "safe" 80°C after it has already reached operating temp is not normal.
Dropping below the "safe" 80°C after it has already reached operating temp is not normal.
#12
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That's true, I was thinking water temp and not in C either. Duh. So the OP is saying that his oil temp gauge goes back into the blue during normal driving, which is below 175F?
Last edited by BLKROKT; 01-08-2017 at 11:05 AM.
#14
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There are two ends to the system. The sensors and the gauge or readout. Away from home and I cannot recall the exact nature of the readout but could it be the readout end that is faulty?
As to temps I was going to make the same comment re thermostats. They are modulating device not an on or off situation. Usually they will fail open so the engine does not heat up properly. The fan only comes on when there is insufficient air flow through the rad to control temperature in the system e.g when at idle. At road speeds in moderate climates they don't run that much to reduce load on the engine and save fuel.
As to temps I was going to make the same comment re thermostats. They are modulating device not an on or off situation. Usually they will fail open so the engine does not heat up properly. The fan only comes on when there is insufficient air flow through the rad to control temperature in the system e.g when at idle. At road speeds in moderate climates they don't run that much to reduce load on the engine and save fuel.
#15
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Thread Starter
Pardon me for the noob question but thermostat is for Water temp or oil temp ?
My water temp very stable readings just the oil temp goes crazy it can be on normal operating temperature then it drops for like 2-3 seconds back to cold then goes back up really weird
My water temp very stable readings just the oil temp goes crazy it can be on normal operating temperature then it drops for like 2-3 seconds back to cold then goes back up really weird
#16
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Thermostat is for water (coolant) temp.
What is the temp gauge doing? Not the digit readout on the dash the actual gauge.
What is the temp gauge doing? Not the digit readout on the dash the actual gauge.
#17
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This is an oil temp reading issue, not coolant temp. That eco user (who I meant to quote earlier) had a completely unrelated coolant temp comment in this thread.
#18
Member
Sometimes when I'm driving the oil temp readings is erratic going from stable at 97-98 C and then it starts blinking to 75,78,84,92 and so forth it just jumps for a good 5-10 mins of driving then back to normal
Am I suppose to be worried about this ? Or is this normal
I have changed the engine temp sensor recently ( there's 2 of them if I'm not wrong, what other possibility of things broken there might be ? )
Am I suppose to be worried about this ? Or is this normal
I have changed the engine temp sensor recently ( there's 2 of them if I'm not wrong, what other possibility of things broken there might be ? )
I have the same trouble today, the oil temperature is fluctuating as yours whereas it used to be very steady once hot.
#19
Member
My ML 550 did the same thing, but it was the water temperature, so may or may not be helpful. It would roll up to normal temp and then all of the sudden drop by ten degrees or so followed by a similar jump up. I changed the temp sensor and the thermostat to no effect. The water pump and circulator pumps were definitely working as well. Turns out it was the fan which did still run, but apparently there is some connection between the temp indicator and the motor controller electronics in the fan motor. Replaced the fan and all was good.
#20
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Has anyone with the fluctuating oil temperature issue on the dash read out solved it? Mine has been doing this for about a year now. Definitely not the normal jumping around in temps.. it could be reading 199 F to 201 F then jumps to 170 F and will blink since it is below the warmed up level and then jump back up to normal. This happens on and off. Doesn't matter whether the car is moving or not.
#21
MBWorld Fanatic!
Has anyone with the fluctuating oil temperature issue on the dash read out solved it? Mine has been doing this for about a year now. Definitely not the normal jumping around in temps.. it could be reading 199 F to 201 F then jumps to 170 F and will blink since it is below the warmed up level and then jump back up to normal. This happens on and off. Doesn't matter whether the car is moving or not.