Overheating issue...please chime in

[zephyr429]

I just finished a 433 mile trip to the beach. I changed my oil just before I left. The false low oil pressure warning and zero pressure never popped back up. Maybe a combination of new pressure switch and new oil/filter solved it, at least I'm hoping.

 

[zephyr429]

FYI to anyone with the same issue of dropping oil pressure at idle after checking all possible problems, try changing your oil filter. At soon as I switched to a Purolator (parts store was out of the AC Delco) I started having the issues with pressure after 2k miles. I changed the oil and went back to a AC Delco just before my 866 mile round trip to the beach and the issues never once presented. Just my $.02.

 

[Jasmina]

My issue is very similar to this. I changed the thermostat and I drove it for about 30 minutes and it was fine, but on the way back home, the oil gauge read 0 and the oil light came on, the coolant reservoir was boiling got. I have taken the coolant reservoir out to make sure it wasn't cracked bc as soon as I put coolant or water in it, it leaks onto the garage floor. When I put coolant or water into the radiator, there's no leak at all. Can you guys offer some input. Please and thank you.

 

[Mooseman]

The 4.2 doesn't suffer the same air lock while filling issues like the V8's. It is possible you got a bad t-stat. For the oil pressure, it could be coincidental that the pressure switch is dying.

 

[Blckshdw]

as soon as I put coolant or water in it, it leaks onto the garage floor.

There's an opening in the overflow tank, just behind the fill opening. I tried to get a decent pic, you can see a lip, and the dark area above the lip, is open to the engine bay. This is where your added coolant is escaping from, once the fluid level reaches that lip.

 

[mrrsm]

@Jasmina ... Please Read Everything in this Post First.. and WAIT until the Engine/Radiator are cool enough to touch with bare fingers B4 you head out and start working on the situation. If during your R&R of the Thermostat... you used Straight H2O instead of a 50/50 Mixture of DexCool GM Approved Radiator Fluid... You may have pin-pointed the problem at play here. The GM 4.2L Engine begins it's cooling cycle by First directing the pumped coolant through the Engine Head and then to the lower sections of the Block due to the Higher Compression this engine generates and the need to keep a higher head temperature of around 210 Degrees Fahrenheit.

With this Operating Temp being so very close to the Boiling Point of Water at 212 Degrees Fahrenheit at Sea Level ...and it boils at even lower temperatures when you are at higher elevations.... using 'JPW' (Just Plain Water) inside of this Engine is an invitation to disaster. So the best thing to do right now if you have ANY doubts about this matter, is to Completely Drain the Radiator and the Engine Block of whatever is inside those Water Jackets ...as much as possible...and then Refill the Radiator with ONLY "The Golden Ratio" of either the Pre-Mixed 50/50 Dexcool... or obtain the Pure DexCool and Mix the Stuff with Equal Parts of Water yourself ...and do not fudge on that measurement one single drop.

The Problem with your Leaking Reservoir is that with so much Steam rapidly expanding inside of the Plastic Enclosure...it may have blown out the Return Hose between its clamped location onto the Smalll Tube adjacent the Radiator Filler Neck where all of that spewing overflow is ordinarily supposed to be returning from the Coolant Reservoir right back inside of the Radiator. And as you investigated earlier, the container itself can fail and crack anywhere along the Plastic Weld Line and needs a close inspection to find the leaking spots.

The last consideration here... but an important one over time... is that without the protective chemical balance that Dexcool includes in it's formulation... The reactions between Plain Water inside of the Jackets of All Aluminum Engine (and Head) would create electrolytic corrosion that can become severe enough to grow Stalagmite like oxides that can obstruct the coolant flow and gradually dissolve and weaken the Block...from the Inside Out. With the Water Jackets behaving like a "Pressure Vessel", the Extra Heat and Pressure being generated inside of any Plain Water Column moving through the Engine Block would serve to accelerate those Bad Chemical interactions.

 

[Reprise]

One more thing I'd add...while the owners' / service manuals don't specifically specify distilled water - it's best to use it, as tap water can contain minerals that can accumulate & help clog the system, as MRRSM mentions above.

If you're flushing the system, then tap / garden hose is fine. But for the 'final' fill, use distilled. You can get it for about $1 / gal at the grocery. With 2 gallons of that, and two gallons of full-strength Dexcool, you can mix them together and have 4 gal of premix - more than enough for a refill, and some left over for top-up later on.

The coolant doesn't have to be from the dealer, but make sure it's labeled *as* Dexcool, not 'compatible with' (e.g.; universal coolant.) I know Prestone makes both the premix 50/50 and the full strength; that's what I have in mine (dark silver/gray bottle; orange cap).