: 1995 STS Cooling problems?

12-28-07, 01:54 PM

I have read everything I can find on this subject on this forum as well as other forums. Here is a brief history of my cooling problems.

1.) Water pump was leaking fixed by local shop, I personally did a pressure test of the cooling system afterwards and check out fine.

2.) Took car back to shop, for them to help me figure out way the COMPUTER displayed on the dash the car was getting hot. Found that the Rad cap upper seal was missing, replaced cap idiled the car at the shop for over and hour everything was fine.

3.) Again when driving down the road the COMPUTER displayed temp said it was getting hot (around 250) pulled over let it cool check fluid level which was ok.

4.) Checked both cooling fans working fine at 2 speeds.

5.) Now in process of reseting the Computer by disconnecting the Battery for a spell.

Next on my list may be a thermostat replacement? Gold pellets (gold seal same thing) worked well temporary on the leaking water pump? Last on my list would be the dreaded pressure test for head gasket loss? Could the COMPUTER be giving me false information? (the car has not actually boiled over). I understand the STS operating temp is higher than most normal cars, but a temp higher than 230 concerns me.

Any help or Ideas would be welcome. If possible also give me an idea were non obivious parts my be located ie: temp. sensor etc. this car is new to me and do not have a repair manual yet.

Thanks Ian (newbe)

12-28-07, 05:41 PM
BEFORE you start throwing some more money and parts at it, go to any auto store, and buy the kit that tests your coolant for combustion (exhaust) gases. It could definetly be the begining stages of a failing headgasket, or it may not be, but it is better to rule it out as a possibility before you spend any more money. Now some possible other things that could cause your issues. Clogged purge line, this would stop the system from selpf purging any air out of the system. THermostat, cracked radiator (plastic sides), or a clogged line. Theres a good chance that when the water pump got changed it threw some crap into the system. Hope its not the hg's but, always prepare for the worst.

12-28-07, 06:03 PM
Thank you for your reply, I will investigate the possible problems and tests that you have pointed out. I did take the purge line off this afternoon at the coolant tank. I blew into the line (with my mouth) and it did not let any air through However I may have did this in vain (not knowing how to properly check for obstructions). I had read that the purge line is located at the coolant tank, is that correct?

Thanks Ian

12-28-07, 08:59 PM
The purge line is the 3/8" line into the side of the surge tank near the top. It should spit coolant at idle and flow should increase with RPM. If you could not blow into it, that may well be your problem. Locate the obstruction and clear it. It may be where it connects to the water pump housing aka crossover manifold.

12-29-07, 10:56 AM
GREAT NEWS the line was definitly clogged, I still have spiting though which way do the water flow? Does the motor have to be at operating temp. before flow starts?

Thanks so much I am almost there, I can see the light!!!!!!!!!


12-29-07, 10:57 AM
Sorry no spitting yet or flow of water.

12-29-07, 02:46 PM
O.K. I apologize for getting overly excited with my last two posts. I was not very clear. Here is where I am at now.

The purge line was clogged, it was mostly rusty soot in the metal pipe portion of the purge line that runs accross the top of the engine I cleaned it out with a wire close hanger and then water. The two rubber hoses that attach to each end of the metal pipe were clear. I poked a length of 8" non breakable plastic into the flange pipe at the water pump housing area, it seemed to be clear, that was the furthest I could reach (with out taking more things off the motor, air intake area) I again attached a piece of hose to the metal flange pipe at the water pump housing area and blew and it did not allow any air in, I am I trying to force air past a closed thermostat or something to that sort or do I still have a clog.

I started the motor before replacing the purge line. Some coolant came out of the metal flange pipe at the water pump housing area and coolant came out more at the cooling tank fitting? May question is did I need to go further than I did in the water pump housing area? Stupid question number 2, Which way does the coolant flow? (from tank to water pump housing area or visa-versa).

Thanks again for all your help, Ian (newbe)

12-29-07, 05:39 PM
Flow is from the pump to the tank. Sounds like you went far enough. If you pull the line at the tank and get flow (hot or cold, makes no difference), then the line is clear. Flow should increase with RPM.

12-30-07, 09:52 AM
Thank you very much for all your help in solving my cooling problem to say the least it was driving me crazy. I am enthusiastic about my Cadillac, Good wishes for the New Year.

12-30-07, 10:10 AM
Same to you, and remember 95 is the best year for the Northstar.:yup:

Chuck B
05-15-11, 05:03 PM
How do you bleed the cooling system ?

05-15-11, 06:23 PM
If by "bleed" you mean purge the air, you don't. It's self purging, as long as the purge line is clear. Just rev the engine to 3K a few times and check the level again after the first drive cycle.