97 Buick giving false readings

So I have a 97 Buick Lesabre. Lately it had been saying it’s over heating but when I check it isnt. Water level seems to be fine and oil is fine as well. The dial would slowly rise up to barely where it says overheating then it would drop back down mid way. Well I replaced the thermometer and it didnt fix anything. Well the last few days the oil meter has been going up and down as well, even though I check it it’s fine. But when I’m going up hill it will read that the oil is low and the dial for the thermometer will go way up and the car will start shaking and slow down, but when I go back downhill the oil meter goes back down and the car will still say hot but not as much, and will stop shaking and will speed up now. Any ideas of what I need to do? And how much it would cost?

Where are yu checking the water level? The level in the radiator is what counts. Do you have an infared thermometer>

The fuel pump may be weak, causing the engine shaking. You might have the engine checked to see if there is a head gasket problem.

The “oil meter” as you call it is oil pressure, not level. The level on the dip-stick might be just fine but there is another problem with the oil system. The only way to check it is to have a mechanic install a mechanical oil pressure gauge onto the engine so the pressure can be observed and compared to the gauge in the car.

Same for the water temp. Even if the level is OK, the car might still be overheating. Testing that requires some device that can measure water temp to compare to the gauge.

You need to take it to a mechanic that can do these tests. It will cost $100-180 or so to find the problem. The repair cost is unknown until the problem is determined.

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I know it’s not overheating cause when I pull over I can put my hand on the metal part where the water runs and its just warm not scolding hot like where I’ve seen overheating cars are like. But thank you for your response! I’ll relay this to the mechanic

I’ve changed the fuel pump a couple years ago. But I’ll ask the mechanic about the head gasket!

I checked the water level in the white tub in the engine, where it says water on top, on the side it has two lines, the bottom says engine cool and the top says engine hot, its filled to the engine cool line

That points to the instrument panel starting to fail, or the body computer. It also points to the car not properly warming up either. That itself is a problem.

It also means the oil pressure readings are likely not correct either so the engine should be OK.

Finding parts for this 23 year old car may be more of an issue than finding the problem.

Good Luck

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But will false readings still make the car shake when it says its overheating?

It shouldn’t cause a shake but stranger things have happened.

The plastic bottle where you check the coolant is an overflow bottle. You need to check the coolant level in the radiator after removing the cap and when it’s cold.

The overflow bottle is not part of the pressurized cooling system and only serves to catch overflow in the event the radiator decides to burp some coolant out past the radiator cap.

I assume by thermometer you mean thermostat? As for the oil pressure I would want to run a check with an external gauge to determine if there really is a problem going on; maybe due to sludging.

As for the shaking I might throw a wild guess out there that this could be related to a spark plug or plug wire ignition miss. I say this because back in the late 90s/2000s GM had a campaign going on in regards to spark plug wires on the V-6s in various makes and models. A campaign is a voluntary Recall but it has mileage and time limits so that campaign would long be over by now.

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Thank you everyone for your responses! Turns out when my fiance changed the thermostat he let some air into the system and it was building pressure, and the car was actually overheating but I couldnt tell from the one place I was feeling. But he fixed it and it’s all good!

Wish I saw this comment sooner! It actually was a problem with the pressurization and coolant, from when he changed the thermostat, but we got it all fixed now! It was shaking probably from actually overheating, but if it starts shaking again I’ll be sure to look into that recall campaign, the car only has 69,000 miles so as long as it isnt time based it should be good, again thank you for taking the time to try and help!