I have a Meziere electric water pump on a LS1 fbody that has been working fine for years, but this summer I started having an overheating problem. The car gets up to operating temp as normal, then after a minute or two of maintaining the proper temperature, the thermostat starts climbing rapidly. The pump seems to work because I can hear it when the engine is off and the key is in the run position. No signs of coolant leaks. Any ideas on what the problem could be?

 

Stuck/sticking thermostat? Low on coolant? Does the temperature still get higher than normal if you are at freeway speeds of 65+? Are you sure your electric fans are working?

 

Fans work. I was out for a ride when I first noticed the problem, and it was overheating while the car was in motion. I thought it was low coolant at first but saw no signs of leaking anywhere, not even around the heads or sides of the engine. Does parking downhill on an inclined driveway have any effect on the cooling system, such as causing it to somehow get airlocked?

 

Check the radiator for cold spots. Todays coolants contain silicates that easily stick and eventually after a lot of miles or a lot of time…whichever comes first…will clog a radiator in certain areas. Had this happen to me last summer with an Altima. Found the issue by using an infrared thermometer. About half the radiator was cold to the touch after locating this issue. Of course I threw a thermostat at it first….$$$

 

Are you running Dex-Cool? A good friend of mine worked for the largest radiator shop in this part of the state. He said the early stuff would coagulate into a jelly like substance if left in too many years. GM supposedly reformulated it years ago, and the newer stuff supposedly is good stuff. I use it. But I never let my coolant go over 4-5 years, 5 years absolutely the max. It works fine for me. I'm with Che70velle, probably the radiator. That or the T-stat...


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Yeah I am using dex-cool or some equivalent orange stuff. So I should do a full coolant system flush, maybe also using some kind of additive to de-gunk it? I guess if that fails I can try a new thermostat and just reuse the fresh coolant.

 

I run 25% coolant with the green stuff. In the summer, I'll run distilled water and a surfactant with no glycol if I know I'm going to put some miles on the car.

 

We use distilled water and a bottle of RMI 25, minimal antifreeze.

 

The biggest problem with the old Dex Cool was inattentive owners! You leave any antifreeze in for more than 5 years, you're tempting fate! If you don't know what brand, or how old, your antifreeze is, I'd definitely flush and change it ASAP. I'd also change the thermostat. If you're running an aluminum block, I'd use distilled water. Mix ratio is up to you......

 

Voltage at the pump is?
Ground good?

 

It's easy to blame inattentive owners, but you have to keep in mind that GM was marketing Dexcool as a "Lifetime" coolant.

"Lifetime," to GM, being the duration of the warranty period, which in those days was 3 years, 36,000 miles...

They pushed that same line of bullshit with transmission fluid, too. Remember when the "new" Malibus came out in '97.
I specifically remember the commercials saying that you would never need to change the transmission fluid, and that instantly tripped my bullshit detector.

Do you know how many 4T60 transmissions I've changed out because of failures that ultimately resulted from lack of maintenance? More than some guys, less than others, but it's been a few.

 

I was just saying things need to be changed and maintained. I dont recall GM advertising Dex Cool as lifetime. If they did, shame on US for believing it. NO fluid is going to last a lifetime.

 

Sounds like a radiator issue as mentioned above etc.

FWIW - Zerex G05 is 5 year/150,000 miles and holds up very well in my experience. Have seen radiators look cleaner with G05 after ~12 years than other coolants after a year.

 

Might want to pull the pump and look at the impeller.. rare, but there have been cases where the impeller corrodes/dissolves, due to electrolysis that sometimes happens in cooling systems.