95 Aurora overheating PLEASE HELP!!!

I have a 95 Aurora with 130k miles in it and the colant temperature keeps overheating to the point were steam start to come out of the colant reservoir. I have replased the thermostat becuse didnt had one in there but didnt fix the problem. Any Ideas???? please HElp!!!!

You'll be well served by doing an exhaust gas test on your coolant resevoir. If there are NAPA auto stores in your area, you can get what they call a "Block Check" kit for about $50.00. This is a chemical test for headgasket breaches. If no NAPA's are available, have a good Caddy Dealer do this for you. It will confirm if the overheating is due to headgasket issues if a positive result is given, or rule this out if negative. At any rate, you'll want to know if your overheating is due to headgasket issues (worst case) or a cooling system component (best case). The Aurora's northstar engine is prone to headgasket issues which can be a very expensive repair. This will save time and money in diagnosing this problem.

Hello,

I have a 1994 STS with the same problem.
Three mechanics said that the overheating is caused by leaking head gaskets.
I believed them and I was going to get rid of the car but first I replaced the belt that drives the water pump and the car stopped overheating. The car may have leaking head gaskets but this did not cause the overheating like they said.
The overheating was caused because the waterpump belt was dry and cracked and not turning the water pump at the right speed causing the overheating. If you can find a spray belt that conditions the belt try this first or just replace the water pump belt if it is cracked. Before I replaced the water pump belt the car was running from 225 - 250 degrees and overheating but now it runs from
198 - 207 and does not overheat. Also check if the water pump belt tensioner is providing enough tension to drive the waterpump. This is cheaper than rebuilding the motor and still having it overheat after spending the 5K.

Mine is not overheating but seems to run hot. 210-220 degrees. What is the reccommended temp for the thermostat?

They say 196 - 235 degrees is a normal operating temp for a Northstar. The stock thermostat will open at 200 degrees. The low speed cooling fan does not come on until 225 and high speed fan at aprox 230 degrees.
After I put a new waterpump belt and tensioner my 94 STS 4.6 with leaking head gaskets ran great for a few days but exhaust gases are leaking in to the coolant and it's game over. If you ever get a coolant hot dash warning pull over right away and get it towed until the problem is fixed. My mistake was driving it until the motor got hot and fuel was igniting early causing the motor to shake bad and now my motor is toast. After the damage was done I figure the original cause of the overheating that resulted in blown head gaskets was the water pump belt tensioner. Northstar motors have a separate belt for the water pump. Most people inspect their main drive belt for cracks but I bet your water pump belt has cracks and the tensioner is weak. The $50.00 new tensioner only takes two bolts to intall. The new tensioner felt like it took 20 pounds of pressure to move the spring and the 14 year old tensioner took only 5 pounds to move the spring meaning the waterpump was not always turning with the motor resulting in high heat and poor circulation. The whole point of this post is to warn people who still have a Northstar to inspect the waterpump belt and waterpump belt tensioner. I think this is the real reason why all Northstars tend to blow head gaskets at 200K miles. Has anyone heard of a Northstar with over 200K miles without major engine work ?
My 94 Deville 4.9 has well over 300K original miles and is still going strong.

Now that's some interesting info.
Wouldn't it be something if that belt was the daddy of the Northstar head gasket problems?
How 'bout it Maxwedge?

My 94 STS factory waterpump belt was cracked and the spring tensioner was worn out that I could move it with a finger. I could barely move the new spring by hand and the old tensioner moved with one finger. The bad tensioner did not make any bad sound, it just caused bad circulation. The tensioner spring has had constant pressure applied to it for over 12 years and time finally gets to it. I was looking at another STS and it idles at 225 with just under 200K miles. I think all the tensioners become soft at 200K miles leading to overheating. If I get another Northstar motor as well as a new waterpump belt tensioner I will also bring volatge from relay 1 to relay 3 on the cooling fan relays and have the high fan turn on when low fan is commanded from the PCM. Also talking about running hot has anyone tried the new racing coolant EVENS NGP that has no water content and boils at 375 not 255 like water at 16psi. I might try some EVENS NGP 9 in the STS with the blown head gaskets for a hot run before she becomes an organ doner.

You've probably got the problem solved by now. But, for the benefit of others you should check for damage to the plastic airfoils under the front bumper. They direct air up through the radiator. I also have a '95, at low speeds or even at idle the car would run at normal temps. However, due to damage and missing fasteners, at highway speeds the plastic would blow up and block airflow causing higher operating temps. A few screws and a few minutes and the problem was solved.

Dave