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overheating 99 sls


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My car has gave me some trouble a few months back with overheating. Since then I have replaced the valve cover gaskets, the main seal, the water pump, and the thermostat. I flushed the radiator with a hose to see if there was blockage, but the water ran freely. Does anyone have any suggestions on what I should do next to fix this problem? To add, I had someone read the temp and it read different on several different spots, which I'm told could be a huge problem.

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:welcomesmiley:

How is it overheating? If it heats up gradually while stopped in traffic, the thing to look at is the radiator fans. A quick check is to turn on the A/C and see that both are running at low speed, which means that the fuse, the wiring, and two of the three relays are OK. If it seems OK but occasionally gets it in its mind to overheat, check the bypass hose, which is the 3/8" hose between the water pump and the surge tank; with a cold engine pull it off the surge tank and start the engine, and it should run out when the motor is idling. Or, the heater lines or heater core could be clogged. Or, the thermostat could be bad - be careful with that one, you must get the right part and temperature for your car and it's possible to insert it backwards.

Another thing is to make sure that the coolant is somewhere near 50/50. If it's too far from that balance it will boil in the heads under load and the steam bubbles will interfere with the thermostat and cause overheating.

If it's OK except when you pull a hill or nail it to pass a car, and then it overheats about 30 seconds later, it could be head leakage. A lot of things can cause the same symptoms, including too little antifreeze, but you can rule this out (or confirm it) by having your coolant checked for combustion by-products. Or, see of you smell coolant in the exhaust, or if you smell exhaust in the surge tank.

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My car has gave me some trouble a few months back with overheating. Since then I have replaced the valve cover gaskets, the main seal, the water pump, and the thermostat. I flushed the radiator with a hose to see if there was blockage, but the water ran freely. Does anyone have any suggestions on what I should do next to fix this problem? To add, I had someone read the temp and it read different on several different spots, which I'm told could be a huge problem.

Pull the hose at the surge tank that comes from the thermostat area with the car running. If it does not have water circulating through it then it is blocked and causing you to overheat. It usually plugs up in the thermostat area. If this is the problem then you get off easy. If not be prepared to check for pulled head bolts.

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