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Hi everyone. My first post in BenzWorld. I have bought a 1992 500SE with full dealership service history but the car is de-registered since 2002 and has not been driven for 17 years. It has travelled 101,000km. I just fixed rough idle by replacing all spark plugs and ignition cables. But the car still has problems of overheating and no ac. The coolant temperature of 1998 S320 that I bought in high school never reach 80掳C 馃槀馃槀馃槀 The gauge on instrument cluster shows 100掳C-110掳C when the car is on motorway and 120掳C in traffic. So I do not drive this car anymore.... After some checks, my mechanics said the thermostat works, the radiator is good after flush and the fanclutch works. So I guess probably the coolant sensor is faulty? I have read many posts, and now know that this car has two coolant sensors and probably the climate control diagnostics will help to determine the faults. Anyone has ideas to sort out this problem? Many thanks!

Cheers,
James

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Get infrared thermometer for troubleshooting.
If the pump works and thermostat opens, fan working yet the engine overheats, that means your radiator has a layer of boiling stone. The flushes can help only so much.
Post some pictures of your AC panel? Is it r12 or R134 system? Did you check the charge?
 

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Get infrared thermometer for troubleshooting.
If the pump works and thermostat opens, fan working yet the engine overheats, that means your radiator has a layer of boiling stone. The flushes can help only so much.
Post some pictures of your AC panel? Is it r12 or R134 system? Did you check the charge?
Hi mate. Thanks for the reply! Yes, using infrared thermometer is also coming to my mind. But where should I use it to test the temperature? The surface of radiator? Should the temperature of the surface of radiator be close to the gauge on instrument cluster? The car is in mechanic's workshop now. I will take pictures of AC panel when I pick up the car. The AC panel is the one with lots of button, not the one after facelift. Have not charged R12 or R134 yet, not sure it is R12 or R134. Cheers, James
 

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Regarding the overheating, do both fans work? I believe one is belt driven and the second is electric.

Does the AC Fan blow? If so it is not the blower motor. If it does not blow, then the blower motor assembly is about $250 from Autohaus or Pelican.

Hopefully your evaporator is not leaking. If so that is a $2500 to $3000 repair as the dashboard has to come out. The 92to 95 were more susceptible to evap problems than the facelift cars.

Take your vin # to the MB Dealer and he can do a search to see if the evap core was ever replaced by the MB dealer. If not maybe(?) a car fax would tell you.
 

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Regarding the overheating, do both fans work? I believe one is belt driven and the second is electric.

Does the AC Fan blow? If so it is not the blower motor. If it does not blow, then the blower motor assembly is about $250 from Autohaus or Pelican.

Hopefully your evaporator is not leaking. If so that is a $2500 to $3000 repair as the dashboard has to come out. The 92to 95 were more susceptible to evap problems than the facelift cars.

Take your vin # to the MB Dealer and he can do a search to see if the evap core was ever replaced by the MB dealer. If not maybe(?) a car fax would tell you.
Hi bro. Yes, you are right. There are 2 fans and both of them are working. AC fan blows, I will charge R134 next week to see my luck. Cheers
 

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Great looking car!

Overheating can really only be a few things; radiator, water pump, thermostat, fan clutch, electric fans. I doubt it's the temperature sensors, as you're more likely to get an erratic reading from a bad sensor than a consistent overheat signal. If I'm wrong about this, someone please correct me. Not saying don't check or do a thermal test, but it doesn't sound likely.

If you're not losing coolant while driving I'd probably rule out the water pump unless you hear it chattering. Check your fan clutch for yourself by trying to spin the fan with the engine off; if you feel resistance and the fan won't spin then the clutch is functional. If the fan spins freely you need a new clutch.

To be honest it sounds like a bad radiator and/or thermostat. I know your mechanic confirmed they were working, but seventeen years is a long time for a car to sit, and radiators can underperform even if they're technically still functional -- ditto the water pump, but they'll usually give you some other sign if they're on their way out. I'd change the radiator just as a precaution. These radiators are only good for about 100k miles, and you're approaching that anyway. Thermostats are cheap and an easy replacement, so may as well get a fresh one too.

My car needed basically the entire cooling system replaced by 150k miles. Everything other than the electric fans. So just be prepared for the probable eventuality that everything is going to need to be replaced in relatively short order.

As for the AC, yes, get the system recharged first and see where that leaves you. Hopefully you just have a leak somewhere and it can be fixed easily. Next best thing would be a compressor or condenser issue. Compressor is pricey but at least it's easy to find. Evaporator core is insanely expensive and time consuming, so let's hope it's not that.
 

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Great looking car!

Overheating can really only be a few things; radiator, water pump, thermostat, fan clutch, electric fans. I doubt it's the temperature sensors, as you're more likely to get an erratic reading from a bad sensor than a consistent overheat signal. If I'm wrong about this, someone please correct me. Not saying don't check or do a thermal test, but it doesn't sound likely.

If you're not losing coolant while driving I'd probably rule out the water pump unless you hear it chattering. Check your fan clutch for yourself by trying to spin the fan with the engine off; if you feel resistance and the fan won't spin then the clutch is functional. If the fan spins freely you need a new clutch.

To be honest it sounds like a bad radiator and/or thermostat. I know your mechanic confirmed they were working, but seventeen years is a long time for a car to sit, and radiators can underperform even if they're technically still functional -- ditto the water pump, but they'll usually give you some other sign if they're on their way out. I'd change the radiator just as a precaution. These radiators are only good for about 100k miles, and you're approaching that anyway. Thermostats are cheap and an easy replacement, so may as well get a fresh one too.

My car needed basically the entire cooling system replaced by 150k miles. Everything other than the electric fans. So just be prepared for the probable eventuality that everything is going to need to be replaced in relatively short order.

As for the AC, yes, get the system recharged first and see where that leaves you. Hopefully you just have a leak somewhere and it can be fixed easily. Next best thing would be a compressor or condenser issue. Compressor is pricey but at least it's easy to find. Evaporator core is insanely expensive and time consuming, so let's hope it's not that.
Hi Thom. Thanks for your advises! I have checked fan clutch as soon as I realised the car is overheating and it works. I will do a thermal test. Hope it is just a faulty sensor. And replacing radiator is the next step I will take. Cheers!
 

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You are a brave man to have bought a 1992. The over heating is relatively easy tp fix (eventually). As for the AC, as Thom says let's hope it's not the evaporator. If so, you will need real money...

Are you anywhere near Atlanta? or Sacramento? or San Diego? or Vancouver BC? reason I ask is very very good W140 techs are rare. I keep track of them... :)
 

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You are a brave man to have bought a 1992. The over heating is relatively easy tp fix (eventually). As for the AC, as Thom says let's hope it's not the evaporator. If so, you will need real money...

Are you anywhere near Atlanta? or Sacramento? or San Diego? or Vancouver BC? reason I ask is very very good W140 techs are rare. I keep track of them... :)
I know buying early model of any cars is risky especially my one is actually built in 1991, very first model and registered in 1992. But I prefer pre-facelift model which I think looks better. I live in Auckland, New Zealand. Cheers
 

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Hi guys. Just confirmed that this car has blown head gasket. My wallet is crying... When I picked up the car it has white smoke from the exhaust, I thought it was just cold weather and the car has long time not driving, and didn't burn the petrol well. The oil was clean so is the oil cap but when I sent the car to to do oil change, I found the oil filter is really dirty. That is a sign of the owner had replaced the oil but did not replace filter. Probably he wants to hide the fact that there is sludge in the oil... Today the mechanics told me there is a little sludge on the oil cap... F**k!
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