[JESSEONE]

Hey buds...

(I'll keep it simple and quick...My coolant reservoir sprung a crack/leak) .... details:

Around 3 or so years ago, I purchase a replacement reservoir from eBay to replace my OEM that was developing cracks at the seams, plus the plastic was becoming brittle/chalky (firewall side edge, top) .... but here's the kicker.... the replacement developed the same cracks / discoloration, chalkiness on the edge (firewall side, top) too... see attached images... what do you folks think causes that SAME issue in both..? Is it a design flaw..? An over heating issue...?

I just ordered an OEM GM replacement ... So my plan is once it arrives to..... drain the block (via knock sensors)... flush it entire system, replace water pump (sensor), new 160 Stat ... and bleed it.... should I replace any other sensors, I'm I missing any in regards to cooling..? Attached is the sensor for my water pump ... I heard there's another on the side of the block...? If so GM# kindly ..?

(side note)
The 96' usually runs cool but lately, out of nowhere the temp shoots to the top then drops after a few moments ...got the 9C1 green hoses (all in perfect condition) and the annoying plastic "T" was swapped for a custom made metal one ... no leaks around the radiator and last I check, when i pulled the plug on the water pump sensor, both fans kicked on respectively ...

Thank you my friends ahead of time....
JESSE!

 

[Marky Dissod]

The '96 usually runs cool but lately, out of nowhere the temp shoots to the top then drops after a few moments ... last I check, when i pulled the plug on the water pump sensor, both fans kicked on respectively ...

Quoting Scott Mueller (yes, this is roughly 20 years old):
"B- & D-car coolant fans operate under PCM control at the following engine temperatures and AC system pressures:
Fan …….….…… Mode ….….… Temps ….….… AC Pressure
Primary (RH) .... ON ... ... 107°C / 225°F ... ... 225 psi
2ndary (LH) ...... ON ... ... 111°C / 232°F ... ... 248 psi
Primary (RH) ... OFF ... ... 103°C / 218°F ... ... 180 psi
2ndary (LH) ..... OFF ... ... 107°C / 225°F ... ... 203 psi
Additionally, the PCM will turn off the fans at higher vehicle speeds (above 48 MpH I believe), since running fans can actually impede airflow through the radiator at high speed.
...
Finally, certain Diagnostic Trouble Codes (DTCs) may cause the PCM to turn on one or both fans."
If your pcm still has OEM programming, and you have two electric fans, both will stay off until the H2Opump temp sensor hitss 225°F.
At 225°F, one will turn on. The other one stays off until 232°F.
Some people say Overheat is 239°F. Some say even hotter.
Once you get your pcm reprogrammed, though, if the temp needle reaches 3/4ths, you'll have already pulled over, because it will never normally operate past 2/3rds after reprogramming.

 

[JESSEONE]

Quoting Scott Mueller (yes, this is roughly 20 years old):
"B- & D-car coolant fans operate under PCM control at the following engine temperatures and AC system pressures:
Fan …….….…… Mode ….….… Temps ….….… AC Pressure
Primary (RH) .... ON ... ... 107°C / 225°F ... ... 225 psi
2ndary (LH) ...... ON ... ... 111°C / 232°F ... ... 248 psi
Primary (RH) ... OFF ... ... 103°C / 218°F ... ... 180 psi
2ndary (LH) ..... OFF ... ... 107°C / 225°F ... ... 203 psi
Additionally, the PCM will turn off the fans at higher vehicle speeds (above 48 MpH I believe), since running fans can actually impede airflow through the radiator at high speed.
...
Finally, certain Diagnostic Trouble Codes (DTCs) may cause the PCM to turn on one or both fans."
If your pcm still has OEM programming, and you have two electric fans, both will stay off until the H2Opump temp sensor hitss 225°F.
At 225°F, one will turn on. The other one stays off until 232°F.
Some people say Overheat is 239°F. Some say even hotter.
Once you get your pcm reprogrammed, though, if the temp needle reaches 3/4ths, you'll have already pulled over, because it will never normally operate past 2/3rds after reprogramming.

I remember Scott!

Thank you kindly for the info....

 

[Marky Dissod]

Point is, everything under hood lasts longer if both radiator fans are on by 212°F, vs 232°F.
Including the reservoir(s), that variable restrictor valve that protects the heatercore, and other brittle plastics, among all the other stuff that doesn't need to get so hot ...

 

[MWP]

At least the tank failure was easy to spot!

Sudden temp spike/sudden drop as the only obvious overheat symptom -- most common cause is the thermostat.

 

[JESSEONE]

Hey guys....

What's the correct way to purge/bleed system....?!

I've been bleeding the system non stop! And air is still coming out! ugh.... help!

The fans kick on... the temp maxes so I turn off the car whilst bleeding /purging... frustrating....

Thanks again.... much appreciated

 

[JESSEONE]

Update... purged more air for a while (while car was on, then off) and now temp goes up half way, then primary fan kicks in and drops out down nicely... but now I have a stumble which I suspect its my wires (side note I also changed my plugs and I couple of my MSD wires ends..... the insides where the plugs snap in.... were bent...

 

[Marky Dissod]

Update... purged more air for a while (while car was on, then off) and now temp goes up half way, then primary fan kicks in and drops out down nicely ... but now I have a stumble which I suspect its my wires (side note I also changed my plugs and I couple of my MSD wires ends ... the insides were plugs snap in were bent ...

When you burp the air, you have to take some kind of precaution to prevent the coolant from getting anywhere near the Opti-Spark, because GM took no such precautions.
If enough coolant got in the Opti-Spark, there's your stumbles.

 

[JESSEONE]

When you burp the air, you have to take some kind of precaution to prevent the coolant from getting anywhere near the Opti-Spark, because GM took no such precautions.
If enough coolant got in the Opti-Spark, there's your stumbles.

Again.... thank you kindly for responding boss... and totally agree!

So quick update.... took the SS to a shop with a good mechanic that has that snap-on diagnostic tool ... found the stumble.... turns out the #7 sparkplug wire (MSD 8.5s) was arcing ... due to that GM metal heatshield... so that wire is bad now... I'm gonna have to use a temp and order a single one from MSD...

Thank you Marky & MWP... 👊👊

PS Can that arcing wire be fixed and reused....?