I just had the engine replaced with a used motor. My oil pressure light is going off constantly, although the engine sounds and runs fine. Absolutely NO knocking. Is the oil pressure sensor the most likely cause? It seems to be plugged in correctly.

Also, the car seems to only heat up to about 140. It used to be around 190, should I just check the coolant for 50/50 mix?

I only have a 30 day warranty on the new engine and I want to make sure I didn't get a bad engine. Thanks

Yes I would suggest a new oil sending unit and it sounds like the thermostat is stuck open. Both are fairly cheap and easy to replace.

Welcome to the forum Tom!
I would recommend that a Delco oil sending unit be used only, as other "brands"... may not work as well.
Thermostat replacement as William mentioned should allow car to run at normal temps again.
Does anyone have the spec for that car'* thermostat correct temperature rating ie: 190 degrees or?

Thanks guys. I'll let you know how I make out

if it were me I would get an oil pressure gauge. Test for the correct oil pressure. is there any warranty on the motor you bought? if so take it back and have them make it right.

I bought the car a little over a year ago, and it was obviously very poorly maintained. It'* been a money pit so far. I also still owe on the loan, so I wanted to do the job as cheap as possible. I bought a used engine out of a junkyard and had another guy do the install. I got the entire job done for $1,000. The engine has a 30 day warranty but it pretty much only covers if the engine doesn't run. The engine actually seems to be running very good, I just think I might have some sensors and stuff like that to replace now. Hopefully it all works out well

I replaced the oil pressure sending unit yesterday, and the "low oil pressure" light has not come back on since. Problem solved.

I still have to replace the thermostat, and hopefully that'll take care of the other problem (car not maintaining proper temp). While researching how to replace the thermostat I came across an interesting question. What is the proper coolant for my car? Sounds like GM originally used Dex-Cool - but there seems to be a large amount of people out there that are very much against using it...

Thoughts???

i use prestone extended life, says any make/model. have done this to every car i have since they started putting dex in them and the brown crap that dex causes eventually fades, after a couple yearly changes its only a little bit of chocolate pudding on the pressure cap, then likely can wait two years because it mostly goes away

I just just use regular green concentrate Peak coolant & distilled water to blend in at -55c.

One thing is keeping any eye out for the LIM gasket updating to aluminum framed gasket & do the UIM gasket when U can if it has never been done before...
https://www.gmforum.com/specificatio...h-fact-288248/

his engine is a 3400 and its all aluminum, you cant use regular green in that situation. 03 is when they started phasing in the felpro gaskets on those, some have them some have the ones that commonly fail. my 03 3400 monte had about 200k before i traded it and no gasket failures. but i changed the coolant to prestone at about 30k when the dex started turning brown, same mileage with my moms 03 impala and going by the above change schedule