I just inherited a 1987 Eldorado, 4.1 engine with 35,000 miles. I backflushed the engine, changed the coolant and thermostat, and put the GM leak tabs in.

The car’s digital engine monitor shows the operating temp at about 150 – 170 degrees at night or in cool weather. During the daytime in 80 degree weather the temp shows 190-200. In hot weather, stop and go driving, the temps go up to 215 degrees on the digital readout.

Shouldn’t the thermostat be holding the temp close to 195 degrees under all conditions or is this normal?

Thanks,

PeteC

completely normal. i don't know about the 4.1, but my 4.9 has electric fans that kick on at 224. so those temps are even below that. they look pretty good to me.

btw, you did use distilled water when you changed the coolant, right? also, after doing all that, you might as well change that t-stat out. they're cheap and easy to replace.

I did replace the thermostat but I did not use distilled water.

Is this a big deal now or should I just use distilled water the next time I change coolant?

How often should I change the coolant?

Thanks,

PeteC

it's not a BIG deal, but regular water introduces minerals and other junk that aluminum blocks don't "care for". Change coolant at 30k on these alum block 4.x motors. just next time use distilled, or de-ionized.

I will probably only drive the car 6-8000 miles per year. Should I change the coolant based on time (like every 2 years) rather than miles, which would take 4-5 years to reach 30,000 miles.

PeteC

yes, i don't know for sure what the time interval is, but i'd say 1.5-2 yrs. antifreeze can turn to a goopy consistency like stuff. if it is set and not run for 6 months or so, i'd change to be safe. these things are picky about their coolant!

Factory Maintenance Schedule states "30,000 mi. or 24 months, whichever comes first."

The car’s digital engine monitor shows the operating temp at about 150 – 170 degrees at night or in cool weather. During the daytime in 80 degree weather the temp shows 190-200. In hot weather, stop and go driving, the temps go up to 215 degrees on the digital readout.

The high end temps are fine but it shouldnt be running so low at night. Sounds like your new thermostat is stuck open or defective. Go ahead and swap it out again.

Steve B.