96 Monte Carlo Z34 - Cooling issues?

My Monte is having cooling issues.

The low coolant light stays on constantly, from engine start to stop.

The temperature gauge periodically starts hitting almost the redline, particularly when the car is parked or idling. After I get on the road and start moving, the gauge then seems to snap back to normal, but it'll regularly climb up as I'm on the road, then fall back to normal; it fluctuates.

The car doesn't actually seem to be overheating; coolant isn't popping or boiling, no hissing, no unusually hot feel in the engine area.

No coolant appears to be leaking, and the reservoir is full and has remained full for a while. Water pump was replaced around a year ago, but the problem started happening several months ago.

Any suggestions would be appreciated. :frown:

maybe your thermostat has finally died. the shift from winter to summer is hard on them. They can get stuck, that might explain the gauge jumping. Is the coolant fluid fresh or very old? Also, are your fans running when your car gets hot? They will automatically run, and you can hear them, they are loud. I have a 1995 monte z34.

Actually I replaced the thermostat a few days after this started happening, it seemed to help a little but it still behaves the same.

I had the radiator flushed less than a month ago.

The fans are definitely running; at one point one of the fan relays died causing only one fan to spin at any given time, but after replacing that both fans spin consistently (even after I turn off the car because the temp gauge thinks it's near red).

We Are Having The Same Problem With Our 95 Z34. It Was Overheating, Or At Least The Gauge Said It Was, So I Changed The Thermostat And I Was Thinking That It May Have A Lot Of Air In The System, But Its Been Several Days And It Keeps Going From Midway To 260 To Red Line Then Back Down Again, Then Sometimes It Will Run At Midway For A While, Then Run Between That And Redline, And Stay There For A While, Thought Both Fans Were Out But One Of Them Kicked On At The Last Minute, But The Second Never Came On. Not Sure How To Go About Checking These, To See If Its A Sensor Or What. Any Help Would Be Good.

maybe a weak water pump? im running out of ideas.. hmmm

hopefully somone else will see this and help.

This is an interesting issue. I was first thinking an electrical/relay problem and that the engine is not actually that hot. Now, I am wondering if there is a blockage in the coolant system. Of course, it could just be a faulty gauge. The cars mentioned have over 10 years on them. When the coolant system was flushed was the entire engine flushed or just the radiator? I know with the GM Dex-Cool anti-freeze it begins to really gum up after so many miles. Just a thought, did you check the hose between the reservoir and radiator for blockage?

I have a 2003 with similar problem. It's my son's car so I'm not a first hand driver, but I'm trinig to fix it. The car would have no heat and then the temp guage would spike to red line. I put a pressure tester on and it held 15 lbs. I tested the cap and it only held 12 lbs and was difficult to remove so I replaced it. I thought the car was full of fluid, resevoir had fluid and radiator was showing full when cool. I read about bleeding the system so I decided to flush and fill the sytem. Just filled it last night and bled the two valves on the pump and thermostat housing. Temperture was fine and it put out plenty of heat. I took it outh this morning and no heat and it overtemped. It did show full in the radiator and overflow. My next guess it replace the thermostat, not so easy on this model, but I cnat think of anything else at this point.:banghead:

I Understand Your Pain, I Thought That I Had Ours Taken Care Off Recently, The Second Bleeder Had Broken Off When I Tryed To Open It, Went To The Dealer Got A New One And Bled It, But Nothing But Straight Fluid. Shes Been Driving It For A Week Or So And It Seems To Run Midway To 3/4. I Believe That We Have Fan Problems, Because Its Getting Above 225 And The First Fan Never Comes On, Unless The Sensor Is Old And Is Just Not Picking Up. But I Believe The Second Fan Never Comes On, If Someone Has A Quick Way To Check These Sure Would Help. Good Luck With Yours

Hello,
Not sure if you got this problem fixed. I had the same thing happen to me on the 3100. Gauge would go to about half then redline then go back down then repeat. I thought it was the thermostat, replaced the thermostat and it didnt seem to help at all. I figured there was air in the cooling system but i had steady streams at the bleeders. Turns out my upper intake gaskets were leaking...I took it apart and they were pretty bad, I could see light threw them when holding them up. I replaced them and used the black rtv for the in between. Filled it back up with coolant and its been working correctly ever since. It also took care of a misfire on cylinder 3 which was driving me crazy! I had replaced coil, plugs, wires and all and it turns out it was all because of the gaskets. Hope this helps someone.