Question--As I said, the coolant actually gets hot. Coolant and steam were coming out of the over flow container. On one of the events the pressure blew the cooling hoses off of the alternator. None of the 3 events happened on hot days. Both electric fans appear to be working. After cool down the car goes a few months and several thousand miles under the same, or worse, driving conditions without a problem. -----------------------
Followup To
Question -
I have a 99 STS with 80,000 miles on it. Over the last 9 months and 15,000 miles I have experienced 3 engine overheating events, 2 at highway speed and 1 during an extended idle, with no obvious cause. In each case the temp. gage rose rapidly from it's normal, mid range position to the full hot position. This was accompanied by all of the associated warnings, idle engine, turn of ac, change engine oil etc. Once the engine was allowed to cool for 20 or 30 minutes with the engine off, the gage returned to normal and no problems were encountered for 3 or 4 months until the next event. It does not appear to be a false indication, the coolant actually gets hot. All of the obvious things have been checked. Any ideas?
Answer -
I need to know if the engine is ACTUALLY overheating via engine coolant being expelled onto the ground or filling up the over flow container.
Determine IF the engine is actualy overheating and then we can perform some tsets for a possible coolant sensor/switch fault.
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AnswerWhat mechanical work or ANY kind of work has been performed on the vehicle recently ?. As most problems that occur after a recent repair was made can be traced back to the area of where the repair was made as a vacuum line may have been knocked loose or a wire connection came loose, Look around in the area where work was performed.
You stated:
"Both electric fans appear to be working.
The electric fans vary in speed depending upon the engines coolant temperature. Have the fans been TESTED to be sure that they are capable of operating at all the varying speeds or has everyone just ASSUMED that they are working properly ?.
Here are some possibilities since I do not have access to the vehicle to perform and or check:
1. intermittent thermostat operation or INCORRECT STYLE thermostat. Some engines REQUIRE a thermostat that utilizes a waxed pellet built within the thermostat.
2. faulty pressure relief in the radiator cap which can cause collapse (sucking flat) of the radiator hoses.
3. intermittent faulty KNOCK SENSOR that can cause the engine timing to change of which will NOT turn ON any check engine lights on the dash and or display any codes.
4. An incorrect or intermittent faulty ECM PROM can cause overheating.
5. Engine timing changing due to intermittent fault in the ignition module.
6. Weak serpentine belt tensioner causing belt to slip on water pump pulley.
7. incorrect 50/50 mixture of engine coolant or WRONG TYPE of coolant.
8. Intermittent faulty cooling fan control relay.
9. Intermittent PRIMARY cooling fan relay.
10 intermittent SECONDARY cooling fan relay.
11. Loose corroded electrical circuits and or electrical GROUNDS.
12. Possibility that one or BOTH of the cooling fans are running in REVERSED POLARITY.
13. Missing radiator shrouds on sides and bottom of radiator.
14. Partially restricted exhaust caused by catalytic converter internal collapse. Causing excessive back pressure in the exhaust.
15. Serpentine belt mis-routed causing the water pump to spin in the opposite direction.
16. An intermittent faulty computer circuit can also cause numerous output signals to relays and mis-interpretation of incomong data from numerous sensors.
ALL these items need to be checked and tested for proper operation.
The biggest problem today is that no one wants to take the time and effort to perform these tests, As even slight variances in each of any of the above can combine to cause your type of problem.
There is one last item that I have only seen a few times and that was where the water pump impeller inside the water pump becomes loose on the water pump shaft causing low coolant flow. It is extremly rare but it does happen.
This should give you some things to test. Now all you have to find is someone who is willing to take the time to perform all the tests PROPERLY and YOU have to be willing to PAY for all the time that it takes to perform these tests.
To many owners only want to pay for the actual time it takes to replace the actual faulty component of which may have only taken 5 minutes to replace, But it took several hours of testing to find the fault that they are NOT willing to pay for. This is the main reason that technicians won't take the time or make the effort to perform all the tests necessary.
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