Gauge reading questions...

[Loekee75]

'92 Park Avenue, standard model
I have a few questions regarding my car's fluids and the gauges..
First, according to my service manual, it states that the oil pressure should be at 60 psi at 1850 RPMs when using a tool that screws into where the oil filter is located. My gauge reads below 40 psi throughout all ranges, and at high RPM it has reached 40, but only after adding a little more oil than what is needed. Is this normal? I haven't hooked up the tool, just thought I'd ask what everyone elses reads.
Next question is about my temperature. What should be read on the gauge at normal operation? I've driven around town, and even on hour trips on the highway, and my needle just barely passes the "100"..about 1/16 inch above. The actual temperature is just fine, My heater blows hot, the core, radiator / heater hoses, thermostat, radiator and waterpump have all been replaced within the last 2 years. The gauges have both always read relatively low, but again, they might be reading correctly. Note that I'm not getting a low temp code.
Last question, does anyone know how much gas exactly is left in the tank once the red warning light comes on? It'd be nice to know exactly how much I can go for a fill-up on emergencies! Thanks for the input, everyone

[kaspr]

Regarding the oil pressure: if the engine is in great condition and there's not a bunch of sludge plugging things up, you should get 80 psi when you first start it up. At operating temperature, at 1800 rpm's you should have at least 50 psi, but 60-70 would be ideal. If you're truly getting 40 psi at best, that's definitely well below what it should be. I don't think oil pressure sending units cost that much; you may want to replace it. If your oil pressure really is low, I've used Gunk's 5-minute motor flush (get it at any auto parts store, or even Wal-Mart). It does work in getting the gunk out of the engine and off of the oil screen so that the pump can give it proper pressure. Some people will say that this might harm your engine, but with an old car, I think it's a good thing if you have an oil pressure problem. I've used it many times and my engine is much cleaner than it used to be, and therefore running better.

Coolant temp: The thermostat is supposed to be at 195 degrees F. Since all of the indicators are showing you that the fluid is plenty hot, that must mean your engine coolant temp sender is faulty, or possibly the gage. I think the coolant temp sending unit is pretty cheap.

Gas: I'd say that when the warning light comes on, you probably have around 3 gallons. At least I'm going by my '95; I don't know if yours is different.

[Loekee75]

Thanks kaspr
I have heard bad things about engine cleaners, mainly that they are harmful to the seals. I'll look into everything you mentioned, though. The engine is and has been running great, I just changed the oil and still got a low reading. The engine only uses about a 1/4 quart of oil every 3,000 miles. I was thinking possibly the oil pressure sending unit as you mentioned, but at 155,000 miles the oil pump itself could also be a culprit. I'll just start ruling out each little component one at a time and I'll post back with my findings. Thanks again!

[Bassasasin]

I just had to replace my Thermostat.. 175 degree... came out of the original and replaced.. It read 130.. till I replaced it. But if yours is replaced.. it might be a bad new one.. or if there is one, the edge seal wasnt installed.. or the sensor is bad.
The Edge seal? THeres a seal you have to buy extra. It goes around the thermostat plate and then press to set into the socket then the gasket goes to the fittings as usual..

Low Oil pressure.. I had to replace my sensor.. .. 45psi.. after that. otherwise.. if you add oil and it comes up.. you have a oil flow problem.. Main bearing.. or such.

Good Luck.

[Loekee75]

Well just updating on my findings..
I bought a new coolant temp sensor and oil pressure sending unit. The coolant sensor I purchased was obviously the wrong one as it was actually larger in diameter and the electrical connector wouldn't fit! I'll be returning it soon.
As for the oil pressure switch, I replaced it. The ECM was reset beforehand, but I still got a low reading below 40 psi on my gauge. Here another twist: The oil pressure sending unit must also be defective, because now my oil gauge needle shoots way over to the right and down to where it cannot be seen when I get to a stop!! However, it goes right back to normal once the car starts moving again. I also noticed it stays in place if the car is shifted back into park or neutral. Sound like a defective new sending unit? I think I'll just return both sensors, get my 40 bucks back and invest in delco brands. My car seems to hate Murray lol

[mcqueary]

My temperature gauge was reading low on my 93 Lesabre. I wanted to find out if the problem was the temperature sensor or the gauge. The first thing I discovered was that there are two different temperature sensors - a sensor with two leads (the ECT sensor) which sends the signal to the ECM for engine control purposes and then the sensor with one connection (gauge ECT sensor) used just for the temperature gauge.

The gauge temperature sensor is a simple variable resistor that varies its resistance with temperature. The factory service manual specs say the temperature gauge is supposed to read 260 degrees F when the sensor resistance is 55 ohms and 100 degrees F when the sensor resistance reads 1365 ohms. So I got some resistors from my junk box (Radio shack has these) and checked my gauge. I found out the gauge was defective. While I had the sensor out I checked it with some boiling water and an ohmmeter and it seemed to be working fine.

During the course of testing, the gauge got stuck at 200 degrees F which confirmed it was bad.

Another thing I discovered when I was working on my 93 Lessabre dual climate control system is that you can see the temperature being read by the ECM from the ECT sensor (not the gauge temperature sensor). So this is useful if you do not have a laser thermometer or a scan tool that shows temperature readings. I also understand that later models require a scan tool to read the climate control data.

[Loekee75]

Thank you for that info! I have both the electrical system and service manuals for my '92, however I never noticed that there are 2 sensors. That explains why I got a double lead sensor from the store, only to find a single lead in the engine. Would you happen to know if the other CTS is anywhere around the single lead sensor I found?