Will etc sensor cause overheating in northstar

Cadillac Northstar owners to those whose vehicle is overheating .My 99 Deville was overheating turns out it was Catalytic Converter.Dont rely on PCM for code.If the Cat converter gets plugged up the heat will not get past converter it will back up into engine block causing overheating.My deville ran at between 190 & 201 degrees this morning.If you have a misfire the unburnt fuel goes into Converter and causes damage to converter (blockage).Alot of people overlook converter when overheating happens.

There is no radiator cap on the Northstar engine.
The only cap is on the surge tank (or expansion tank) and is pressurized.

So the answer is Yes, a faulty surge tank cap will result in the loss of coolant and therefore lead to overheating.

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.

If you have overheating problems with this engine, don't assume it's the head gaskets.

Consider the following first.....

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.

So before you decide to rebuild the engine, check this innocent looking little hose first.
I have solved many overheating problems on this engine and you will be surprised to know that it is very rarely due to a blown head gasket.

When you say thermagasket kit,I assume you mean one of those silly DIY gasket sealant liquids that you put in the engine.

You should not use these type of products on ANY engine let alone the Northstar.

To cure a headgasket leak, replace the headgasket.....there is no miracle cure.

On the Northstar, you will damage the cooling system,plus you will continue to have issues as time goes on.

How do you know you have a blown head gasket?

Here is something to consider.......

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.

That car holds 8 quarts of oil. Thats why its still low. You may have head gasket problems. Find a shop that is familiar with your Northstar engine, its going to be big bucks.

The most common overheating problem with the Northstar engine is a blocked purge line. It's job is to purge air out of the cooling system.
There is a small diameter hose coming from near the top of the coolant tank,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. If the hose is still blocked, trace it back until you find the blockage.
Make sure you refill the system with a good quality LONG LIFE coolant, Dexcool was the original coolant used in the Northstar engine but there are others to choose from now, Just make sure it's the long life silicate free coolant which is designed to last 5 years or 100,000+ miles.

There is no need to purge the air out of the cooling system as it is self purging on the northstar engine.
The most common overheating problem with the Northstar engine is a blocked purge line. It's job is to purge air out of the cooling system.
There is a small diameter hose coming from near the top of the coolant tank,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 further back until you locate the blockage.

There is no need to bleed air out of the system as the Northstar is self purging.

If you are having overheating problems the most common overheating problem with the Northstar engine is a blocked purge line. It's job is 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.

Air locks in the Northstar engine shouldn't be a problem as the system is self purging, given that all hoses are clear.

It is hard to start because the recent overheat causing a gap between the head gasket reducing the compression ratio in each cylinder hence it is difficult for a combustion.
The most culprit of the car overheating is the poor circulation of coolant due to bad pump or/ and clog up radiator. The 2 important things that have not been mentioned are needed to take care of now.

I am assuming you have the Northstar engine.

Check for coolant flow at the Purge line,this is a common problem on the Northstar.
There is a small diameter hose coming from near the top of the coolant tank,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.

Are you running it without a thermostat? If so,then strangely enough,this will cause overheating as the Northstar cooling system is different to most conventional systems and therefore will not help you diagnose the problem.