My 500SLC has begun to run "hot" in severe stop & go traffic when days are hot (85-95 Farenheit). On the highway and in regular traffic I am always in the 100 C temperature range. Though when driving up long mountain passes (10-15 kms), the temperature does move into the 105-110 C range.
In order to rectify this "running hot situation", I have done the following to the car:
- Installed new water pump
- Installed new thermostat (which opens at 71C)
- Recored the radiator
- Verified if the fan is "sucking" air strongly: it is.
- Verified the ignition timing. correct
- Replaced fan sensor
- Replaced temperature sensor on block
Regardless of these actions, the car still runs "dangerously" hot. We removed the instrument cluster and had it tested to make sure it was not overstating the temperature. The specialized firm that tested the temperature gauge found nothing wrong.
My mechanic (who has rebuilt an M130/PAgoda engine for me in the past and whom I trust is not taking me for a ride), believes I might have a head gasket failure. However, there is no coolant in the oil and the coolant level is NOT going down.
Therefore, and before I redo the engine head, I would like to know if based on the above conditions, can it be possible that I need to redo the engine head.
Wow..that's a lot of time and money spent for no improvement. Faulty head gasket? A compression test or leak-down test could tell you that without embarking on a potentially unnecessary rebuild. I've had cars that ran hotter when the engine oil was overdue for changing, though I'm sure you've already considered that.
I'd want a second opinion on the temperature. Buy yourself a wireless digital oven thermometer like this one (
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For head gasket failure, there was a notion here that engine would run hot until air (sucked/pushed in trough gasket) was relieved by oppening the cap (take care not to boil-burn your self to death).
If there is a small coolant leak (e.g. over hot parts) you may not notice loss of coolant and for good temp maintenance there can be no coolant shortage.
I'd get one of those $20 IR temp sensors of eBay and measure at the same place where the temp sensor is mounted (above thermostat on 500?).
Does the temperature drop when you run heater?
I tried that once (my engine was short of coolant at the time) and it kept the temp in 80-100*C range
If there is air in the system won't it cause the system to run hot? I think I read on one of the forums that bumping the system can help with running hot.
It doesn't hit the red until it gets to 120C is that correct?
It's not unusual for it to run hottish, but if it stays out of the red in "severe stop & go traffic when days are hot" then I don't see that it is running "dangerously" hot.
Also, your thermostat should be 75C, not 71C.
Running about 100C in normal condition seems about right to me.
Are you sure you have a problem?
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Thank you for the input. With regard to your comments I can mention the following:
1. Auxiliary fax (in front of radiator) is kicking-in and sucking air (we placed a piece of paper in front of it and it sucked it)
2. The temperature sensor on this engine is on the farside of the block (near the firewall). We utilized and infrared thermometer and measured the temperature at the hoses and got values that are 100C for the entry hose and 90 for the exit hose. However, the temp sensor which was replaced and the instrument panel (which was verified for accuracy) show a strong rise (from 100C to 115-118C) in coolant temperature (almost bordering the red line) when I am stuck in traffic and on hot days.
Based on this, I am concerned that I may have a obstructed or damaged water gallery and this could be raising the coolant temp at the rear of the engine block. Would this make sense?
3. Will a compression test or leakdown test tell me if I have a head gasket issue?
4. Excuse my ignorance but, how do you test a fan clutch?
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