A message came on that states "a/c off to protect engine". How do I take this off without taking it to the garage? The coolant is at the right level and I changed the thermostat. Also, I placed the extension plug in under the hood like a mechanic told me to do. When this message came on it was not running very long maybe 5 minutes. I drove 5 minutes then shut off and let sit for a few minutes then tried to start again but it would not start. So I let it sit for about 40 minutes then tried starting it again. would not start again until I tried a few times and let it roll over a bit. Message is still on there.

ENGINE HOT TURN A/C OFF
Cooling System Description and Operation

ENGINE COOLANT HOT
The instrument panel cluster (IPC) displays ENGINE COOLANT HOT message when the IPC receives a class 2 message from the powertrain control module (PCM) requesting illumination of this driver warning.
ENGINE OVERHEATED
The IPC displays ENGINE OVERHEATED message when the IPC receives a class 2 message from the PCM requesting illumination of this driver warning.

DTC P1258: Engine Coolant Over temperature - Protection Mode Active
Have it check

check the coolant level at the top tank radiator cap
check for an air lock in the cooling system
run the fault codes to check for problem sensors
have a compression test done to check head gasket and cracks

Time to take it to a Dealer/garage.

leaks to passenger floor
to garage floor,
or you mean, the coolant just disappears like magic.
disappears in the overflow tank?
and or actual radiator. top fille?. (no engine option stated, so...)

if rad has a cap, some dont, we remove the cap , engine dead cold
never hot, and look to see if its full, if it keeps dropping
the coolant loss can be ? (rapid, and 2weeks is rapid)

1: bad head gaskets, or worse cracked block/head.
running 50% antifreeze ratio> , is it cold there,????????????
2: A/T tranny the , tranny cooler can fail too, and put AF in the ATF.
that means look at dip stick on A/T is it pink or UGLY?


is it freezing there, no location stated, so cant guess.
if yes, is the coolant ever allowed to drop below 50% ratio?
got a coolant hydrometer, check it each late summer, ???
no? oops

Did you over heat warning message come on " Urgent shut off engine" or check coolant message? My coolant message came on but once car warmed up, it was late summer. No leakage but coolant level was low; added some coolant. Then it happened again but once car warmed up the check message disappeared. Then a few days later I got the Urgent Shut off Engine message! Thankfully I was able to pull off road and shut down immediately. Had it towed to Caddy shop. My water pump had gone out. New Pump and replaced all hoses. Then a year later check coolant light came on again, once car warmed up, light went off. This time tho a small leak in the radiator. My husbank put in a new radiator. Car has 117K miles and a few weeks ago outside temp 35, running late for work and didn't allow car to warm up but just a minute or two and when I puled away the check coolant light came on; but once the car warmed up (temp gauge needle in center) the light went out. Being the car is 17 years old I try to treat her like a baby and not push her so I do let the engine warm up before driving away. Do you have to add oil between oil changes? This is normal for the Northstar engine; your regular garages or full service stations don't know this; also make sure if you aren't using an authorized Cadillac garage that they put the right amount of oil; they want to put less than what is required. Not sure if this is really a solution more comments than anything... :)

Do not add water - use coolant instead. You don't have to take it to garage - see attached picture (point 3) to get to coolant reservoir.

When you receive this message it means that the computer has put the engine and components into protection mode. This computer has done this to prevent any further damage to the engine or transmission. You have to have the computer of the vehicle scanned to find the problem then you need to get it fixed right away. It could be a number of different causes overheating,Low Oil Pressure,Transmission pump problem, low coolant level, low oil level. Their is really no way of telling from this end without seeing the vehicle.Start by checking all fluid levels, Oil,Coolant,Transmission.If all this is good scan the computer with a OBII scanner or take it to a garage and get it scanned. It may just be something simple or it could be something very serious.Do not drive the vehicle it is worth the cost of a tow truck to prevent further damge if you can not determind the cause and fix it yourself.

Coolant recommendations and cautions:


The recommended mixture is 50/50 ethylene-glycol and low mineral content water. Never use pure antifreeze. Only Mopar Antifreeze Coolant, 5 Year/100,000 Mile Formula (glycol base coolant with corrosion inhibitors called HOAT) is recommended. This coolant offers the best engine cooling without corrosion when mixed with 50% distilled water.


Antifreeze mixture must always be at least 44%, all climates year round. Maximum protection (-90d) is provided with a 68% mixture protection. If the percentage is lower than 44 percent, engine parts may be eroded by cavitation, and cooling system components may be severely damaged by corrosion.


CAUTION: Mopar Antifreeze/Coolant, 5 Year/100,000 Mile Formula (MS-9769) may not be mixed with any other type of antifreeze. Mixing of coolants other than specified (non-HOAT or other HOAT), may result in engine damage that may not be covered under the new vehicle warranty, and decreased corrosion protection.


CAUTION: Do not use coolant additives that are claimed to improve engine cooling.


4.7L coolant capacity:
1999-2000: 13.0 qts. (including 2.3 qts. for resevoir)

Hunnybunny has typed in a step by step way of flushing it at home.

Without knowing the year of your truck, I'm assuming that it is a 2000 or newer and has a message center on the left side of the of the instrument panel.

If it was an orange square, with no writing in it, then it was probably the Battery warning light, which illuminates when there is a problem with the charging system. The engine coolant light would more than likely be a message that says TEMP, and the check engine light would be shaped like an engine (both would be in the message center).

Battery warning indicator.