Correct temperature reading

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rossie11
C Class
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Correct temperature reading

Post by rossie11 » Sun 18 Dec, 2016 7:53 am

Having had some issues with my rising temp, over the last couple of months, change WP, Thermostat and flushed the system, i still have no idea where the temp gauge should sit on my 2004 ML500. After all the messing around with the problems, it sits just slight above halfway between 80 and 100, is this right, or do i still have a problem.

The thing i am finding out about this car, and the reason i disposed to get rid of it, is the fact that the service book and the log book gives you no information on basics on how the car is supposed to run. The other thing is parts and servicing, i have done a load of work myself because the jobs i have done are basic things.

What concerns me about the temp gauge is just not knowing where its supposed to be, my old ML320 sat tight on 80 and never moved, this thin is all over the place and doesnt really settle, anybody any ideas, please.

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TheMadRacoon
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Re: Correct temperature reading

Post by TheMadRacoon » Sun 18 Dec, 2016 11:53 am

Could it be the temperature gauge that is at fault? I've had a loose wire send the gauge instantly to maximum travel into the red, but is it possible that a poor connection is getting yours to fluctuate depending on the contact it makes? Alternatively the gauge might be faulty and not zeroed correctly, so is reading 90 instead of 80.

I don't know the chances of finding a replacement gauge (and other components) at a wreckers.
Emad,
TheMadRacoon
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rossie11
C Class
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Re: Correct temperature reading

Post by rossie11 » Sun 18 Dec, 2016 2:16 pm

Thanks for your reply, but we have change the temp sensor and done what can only be describes as, going bald by pulling out hair i dont have left lol.

CraigB
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Re: Correct temperature reading

Post by CraigB » Sun 18 Dec, 2016 3:37 pm

I wonder if one of those 'point and shoot' temperature readers might help in trying to determine if the temperature is really changing or just the guage. Also how quickly is it all over the place. If it is quite quick that it jumps about i would have thought it unlikely that it could change so quickly and would suggest some fault in the guage system. In the old days you would just pull out the sender and bolt in a cheap capillary type guage to find the real readings - it is possible to try that? I doubt anyone has a textbook answer for you, we are just chucking thoughts around to try and help.
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T-Modell
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Re: Correct temperature reading

Post by T-Modell » Sun 18 Dec, 2016 6:55 pm

Hi,

imho you don't have a problem at all. The 320 is a V6, so a lot of space between the motor and the cooler. I changed in 2002 from a 320-V6 to a 430-V8, the latter completely filling the space. The V8 always had a bit higher temperature than the V6.

Thomas
---------------------------------------------------------------
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fonzi
Dernburg Wagon
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Re: Correct temperature reading

Post by fonzi » Tue 20 Dec, 2016 12:10 am

Keep an eye on it. Any DIYer should have one of those IR thermometers. They might not be 100% exact, but you can check it by boiling water and performing other tests. I have a 1992 500sl with a wonky gauge that will read 100 C or even just bounce into the red due to some issue (electrical ground I assume?). So I keep the gauge in the car in the summer and if it goes nuts I can actually pull over to the side of the road and make myself feel better.

We all like them to sit right at the temp our thermostat pops at. But I also discovered with the above car that the thermostat only starts to open at 80 C and isn't "wide open" until it's at a higher temp.

I'd probably citrus flush your cooling system or use something cheap like prestige radiator flush, but don't go nuts over 90 C.

https://www.walmart.com/ip/35764365?wml ... 3=&veh=sem

I used that, and thought I saw results, but honestly don't think it made much of a difference.

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AMG
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Re: Correct temperature reading

Post by AMG » Tue 20 Dec, 2016 12:50 am

T-Modell wrote:Hi,

imho you don't have a problem at all. The 320 is a V6, so a lot of space between the motor and the cooler. I changed in 2002 from a 320-V6 to a 430-V8, the latter completely filling the space. The V8 always had a bit higher temperature than the V6.

Thomas

Agreed.

90 degrees is normal. especially when the thermostat opening temp is approx 87 degrees.
Thermofans will kick in at higher temps to bring it back down.
If you're worried, check the operation of the aux fan. Get the car hot in traffic, you'll watch the gauge plummet as the fans punch air through the radiator.

Coolant change is every 2 years - stick to the factory service schedule for this.
Current:
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Mercmad
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Re: Correct temperature reading

Post by Mercmad » Fri 30 Dec, 2016 10:12 am

90 is the factory recommended average temp for a 500.

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