problem emissions, thermostat, radiator

[cadiDADI]

This is for a 99 Deville.
Some Saturday morning a few weeks ago I started my car and was driving it to get inspected. Check Engine light comes on, car gets failed for emissions. Computer diagnostic comes out with a problem with the coolant temperature sensor. A week goes by, check coolant light comes on, I notice coolant on the street. Take it to a GM dealership/repair shop and they are telling me the reason the check light came on was because of a leak in the radiator. $875 repair job. But the check engine light came on before any coolant was leaking out of the car, I asked them to just fix the thermostat but they are saying that there is no point in just doing that without replacing the radiator, I am going to grab my car today and get a second opinion, just wondering if anybody else had a similiar issue?

 

[ALBUNDY]

Have you checked to see where the leak is comming from and have you tried the bars-leak tablets?

 

[MAC1]

The check coolant light will not come on unless there is a faulty sensor or antifreeze is leaking or is being lost internally, such as a result of a blown head gasket. You might not have noticed a leak but that doesn’t mean there isn’t one. Though I would not necessary believe a mechanic that there is a leak unless I saw evidence of one, such as a need to add antifreeze. If you’re mechanically inclined you could can replace the radiator yourself for about $200.

You mentioned both the Engine Coolant Temperature Sensor (ECT) and thermostat, which are two different things. The ECT sensor monitors coolant temperature, while the thermostat opens and closes to maintain optimal coolant temperature. The emissions problem could be related to a faulty ECT, which works with the Powertrain Control Module (PCM) to adjust fuel enrichment. A faulty ECT sensor may cause various driveability conditions.

I suggest that you try to enter the diagnostic mode and try to determine if there are any codes as follows:

1. Turn ignition "ON." (Not necessary to start car)
2. Depress the "OFF" and "WARMER" buttons on the Climate Control Center (CCC) simultaneously and hold down (about 4 seconds) until the segment check appears on the Instrument Panel Cluster (IPC).
3. The PCM will cycle through the various systems and will alert you to any codes either current or history.

Write down the codes, if any, and feel free to post them. If you see the faulty ETC sensor you should probably start by replacing it.

I’m pretty sure you should be able to enter into diagnostic mode and check for codes as described above.