84wuzmy1st

When letting the car idle and bringing the engine temp up to 170ish (Once engine temp hits 175 the radiator kicks on), the oil pressure never falls below 80 and the oil temp reports back Lo according to the dash.

Is this normal?

I believe out driving previously the pressure fell to lower numbers but I would have expected it to fall at idle once the engine warms.

My car is an 85.

FASTAZU

Stock fans should turn on at 225 and second fan at 235 unless AC is on water temp. This would be with a 195 thermostat. Oil pressure at 80psi after warm up seams to be high, I would think it should be in the 35-45 idle warm.

How many mile on your car?

aj1988

It's been close to 10 years since I had the 80 psi problem and it turned out to be the sending unit on the back of the block. I am sure someone with a better memory than mine will come in and answer.

84wuzmy1st

Car only has 25K miles, I have a feeling the PO put in a Low Temp Thermostat. Car is a Z51 with the heavy duty radiator.

Aj1988, could be the sending unit, but my guess is that would not be what is causing my poor performance, no acceleration problem though right? That is just sending info to the dash, that is not info the ECM is using for anything correct?

J W Drew

My 85 Z51 (stock), has oil pressure in the 60 to 70 PSI when starting and crusing down the freeway. After warm up the oil pressure will drop to 30PSI at idle. Running Castol GTX 10/40. All normal. As far as the fan coming on at 175, I would expect someone has put in a performance chip or messed with wiring. You should be running a 195 stat. The only difference between the 195 and the 165 stat is the coolant from the radiator will start circulating sooner with the 165 there by taking longer than normal to come up to spec Once a stat is open its open.

aj1988

When I first got my car the oil pressure was always 80 psi. I found a post on here that indicated it could be the fitting that went into the block that was bad. Changed it and now shows actual pressure.

DinoBob

Oil temp will not read actual output until it hits 150. This allows the sensor to detect a smaller range and therefore display a more accurate reading.

84wuzmy1st

Ok, so possibly another issue, but probably not one causing my main issue. I guess I should look and see if someone has put in a performance chip... I guess I should at least know.

ps374

A lot of owners will argue this but I found my oil pressure 10 pounds more than what it was reading in the car with a manuel gauge. I think the digital dash is not all that accurate.

Cliff Harris

Actually it's because the sensors are grossly inaccurate at lower temperatures so they hide that by showing "LO" on the dash.

They use the same type of sensor for the coolant temperature and it also shows "LO" for the same reason.

WW7

Most times when a oil sender goes bad it goes to 80 psi as the default, I would look at this first as the problem..If your fans are coming on at 175 degrees, then the previous owner either changed it in the chip, installed a different chip, or installed a piggyback wiring harness that makes the fans come on sooner..If your engine is fully warmed up and you have no reading from the oil temp gauge, then it's either the wiring is screwed up, or the oil temp sensor itself is bad.. I had to replace the oil temp sensor on my 89 when I bought it 6 years ago, the oil sensors aren't cheap, around $80.00-$100.00 for my car. Below is a AC Delco oil temp sensor for sale, this is a good price for an AC Delco......WW

http://www.ebay.com/itm/ACDelco-Oil-...4#ht_866wt_671
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Cliff Harris

I believe the oil pressure sensor will default to 80 PSI if the sensor is bad or there is a bad connection from the sensor to the dash. Try grounding the connector at the sensor and see what the dash reads.