M103 Engine Temp Fluctuations
I am having a problem with my 300GES - Driving home this evening the engine temperature gauge was sitting at the usual 80°C when it suddenly rose sharply up to the red line at 120°C. It stayed there for 30 seconds then dropped equally rapidly back to 80°C. This happened one more time on my 30 mile drive home. Once at home I left the car to cool then checked the coolant level and it was fine.
Does anyone have any suggestions as to what is happening to cause this? Unfortunatley, I have to use the car again tomorrow....
Most likely this is your viscous fan coupling needing to be replaced. The symptoms you mentioned mirror what happened to mine: I replaced the viscous coupling - never a problem again (even in mid-August Athens traffic jams). Good luck/Ph
ME again. Could also be your thermostat switch sticking. Depending on when both the thermostat and the viscous fan coupling was last changed, these are good routine items to change for an upcoming summer (might be more than the present 'winter' we just had).Ph
Perhaps one of those infrared thermometers with a laser beam would be useful, to check the temps in different parts of the system. The rise and drop sounds very fast - could it be an electrical problem with the guage?
Most probable scenario is a sticky thermostat, whilst checking out the thermostat, you can test out the viscous coupling at the same time and replace whatever, as necessary.
From cold, start your engine taking the necessary precautions of applying handbrake and selecting Park if you have an automatic.
The test would take up to 20-30 minutes to conduct. Start the engine and feel for the temperature rise in the top-radiator hose; naturally taking care you will be working near moving parts!
Check the temperature gauge reading to see what the needle is doing. The hose will gradually warm up relative to the gauge temperature. At the point, should the temperature rise above 90 degrees the viscous fan should be kicking in, you will need to increase the idle speed a little say rev to about 1500 rpm for a good result, to test the fan.
You will know of the kicking-in because there should be a loud noise from the fan, followed by a blowing of a strong gush of air. The hose would be quite hot so you would not be able to touch it, but if the hose feels as hot as it was at when the temperate gauge read just below 85 degrees, i.e. the needle sitting at the top part of the digit 8. Then it could be you are getting a false reading from the gauge.
After you have satisfied or got your result, switch off the engine, remove the key from ignition so no one may inadvertently start the vehicle. Carefully, feel your hand through the fan and feel the radiator surface. The whole surface should be hot and have no cold spots, this would indicate a blocked radiator.
Do take care at all stages.
Cheers,
It sounds more like an electric fault of the temperature sensor. The deflection of the needle of the temperature gauge is controlled by the voltage output of the thermocouple. Disconnect the cables and start by cleaning the contacts. If for some reason there is a shorting, ( check with your ohmmetter) you will get a full deflexion, then you will have to replace the sensor. Lot cheaper than then replacing a viscous coupling.
Using our good friend google (not verified):
http://www.flickr.com/photos/47126958@N00/2036556061/
Latest update - the temperature problem is still with us. The thermostat changed, water pump removed and checked OK. The expansion reservoir cap was found to be leaking and not holding pressure, so tank and cap were changed and the cooling system was refilled and checked for air locks.
Mechanic now saying it does look like the radiator is blocked, so new radiator (£720 from MBZ) or a recore - approx £275 + car off the road for a week. The local MBZ dealer has offered to do the job for £1,000 all in - at a reduced "older car" labour rate of £70/hr.
Anybody got any advice where to find a cheap radiator??
Hello Big Al,
It seems my instructions have not been understood, as sent to you on your PM. I covered the radiator previously and am surprised your mechanics are coming to the conclusion of the radiator, after doing all this work.
Never-the-less, the price you have for a re-core is average, the URL addresses I had sent to you with respect to a new radiator is slightly over £300 including VAT; you will not get any cheaper.
Cheers,
A nice new, or re-cored radiator is nice to have, but at £1k I am not sure I see how it explains the symptoms? If the temp rises suddenly, then drops back, it suggests an occasional blockage which then is released (hence the sticky thermostat idea) or a sensor playing up?
Assume you/they have done a coolant flush to empty out the crap that could be circulating - when the rad is emptied, an air line up the reverse direction to blow out what is left might work
The viscous coupling could be 'slipping' (already suggested), but again I'd think that would be more of a gradual and sustained higher temp rather than up and down?
There's a good Rad-specialist in Reading, but that's a long way from you up the top there.
REPLY TO THREAD NUMBER 10
Hi jdring,
I think the £1000 will be at the cost of new radiator of £720 from M/Benz plus labour of £70 p/h at approximately 2.0 hrs of labour and anti-freeze.
Big Al can fit a re-cored one, at some £300 plus, say 2.0hrs labour, at an independent garage rates of; in that area, of around £50 p/h. That should be a little less than £500.
Depending on the type of blockage in the radiator cores; honestly, flushing does not do anything to aluminum radiators. I have actually cut open a blocked radiator core of this type and the blockage is of a solid metallic material, flushing with the acidic or alkaline solutions will not dissolve this material.
Some one the forum, some time ago, was brave enough and lucky enough to attempt his own repair, he had to shove a welding rod through the cores to shift this blockage and reverse flushed with a power cleaner to unblock his cores. He was lucky further still, because he claimed to have reused his header seals; these are thin and delicate any way.
Cheers,
Thanks for everybodies further comments and Pm's
The car was check out by a local garage, they were told all the syptoms I had noted thanks to the replies and PM's I recieved from the forum, inc radiator cool spot. They then checked the cooling system over, changed the thermostat and removed the water pump to check its function, they also noticed that the header tank cap was not holding pressure so they changed the tank and cap. flushed and refilled the system and pronounced the problem fixed.They said the radiator cold spot was the result of the problems thay had addressed. I collected the car and 20 miles into the 1st drive up went the tepmerature exactly as before.
So I was less than empressed. So, I took the car along to the local Mbz dealers for a 2nd opinion. They did their checks, inc checking out the temperature sensors, thermostat, viscous coupling and when checking the radiator noted an cool area. Hence the conclusion now about the radiator being partially blocked and needing replacing or recoring was reached.
I need the car for my daily commute so putting it off the road while a recore is done is not really an option for me so have been looking at aftermarket radiators.
I can get a Behr Hela radiator for about £400. A Nissens radiator is being quoted at almost the same price as the MBZ OEM unit by their local trade stockist in Aberdeen, but the Nissens UK sales manager is looking to get a better price from one of their web stockist.
I have lots of patience for the car, but not so much for the garages in the area!
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All, thanks for the advice, I will work my way through the suggested diagnostic steps. Can someone tell me where to find the temperature sensor. Thanks