P1258 Technical Definition: Engine Metal Over-Temperature Protection Areas to Inspect - Possible Causes: Engine cooling system problem (tested the cooling fan operation)all are working correctly. Engine coolant level or the mixture is correct ECT sensor may be out-of-calibration or "skewed"
I can visual see it under hood. so open hood and look
SOURCE: 1994 cadillac deville concours
On my car, which is the same as yours, it is located on the manifold top back left. Pictures in the book just show it on top.
SOURCE: What is the location of my coolant level sensor on
coolant sensor is located inside the extension tank.
SOURCE: 2001 cadillac deville, overheats without loss of coolant
First, provided their are no visible coolant leaks and/or loss of coolant with no signs of leaks, I would thoroughly flush cooling system and replace coolant, then check and/or replace thermostat (you can place thermostat in boiling water to check for proper function), if you have tried these 2 steps and still are experiencing overheating you may need to replace your water pump which can be a tricky job if you're unfamiliar and try to do it yourself, however, I could walk you through it if necessary. Also visually check your radiator hoses for bulges, wear ,etc along with heater hoses etc. You may want to also check radiator fins to see if they are dirty/obstructed and clean if necessary. Let me know if I can assist you further and how it works out
SOURCE: I have a 1999 Cadilac Deville that I replaced a
Are you sure the thermostat was in the wrong way ?.
The thermostat is located in the bottom hose unlike most conventional cooling systems.
The thermostat in the Northstar engine is a dual action device.
One end of the stem is the Thermostat(obviously) and at the other end is a spring loaded pressure valve(the thinner end).
Make sure the thermostat end is nearest the rubber hose and the pressure valve end is in towards the engine.
Also note that the cooling fans don't come on until the coolant temperature hits around 225 degrees.
During normal highway driving the fans will very rarely come on(if at all) due to constant air flow through the radiator.They will only usually come on in heavy traffic conditions on a hot day.
But......if you have the Air Con switched on, the fans will run all of the time.
For overheating problems consider the following......
The most common overheating problem with the Northstar engine is a blocked purge line(small hose).The purge line is designed to purge air out of the cooling system.
There is a small diameter hose coming from near the top of the coolant tank (not the cap) ,this is the purge line.
With the engine idling,pull the purge line from the tank,if there is no coolant flow from this small hose,it is blocked and this will cause overheating.
If the hose is clear, check for blockage at the nipple on the tank.Or trace the hose back until you find the blockage.
The hose goes in to the engine to a crossover and comes out the other side close to the thermostat housing,the blockage may be there.
Testimonial: "Thank you very much for your help. The spring of the thermostat was towards the rubber hose and it was the wrong one. I did have a blockage in the purge line. I also found a small leak somewhere under the crosover pipe. This is my first experience with a northstar 4.6L engine. I realy like the car, I just got to learn how to take care of it. Thank you so much again for your help and if you can tell me any thing else I should know I would be forever greatful. Richard "
SOURCE: where is the ect(coolant) sensor
The engine coolant temp sensor is located just below the throttle body.Just remove the air cleaner tube and you should be able to see it.There will be a black and a yellow wire on the connector.Hope this helps.Good luck.
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