21boy

Got my ac charged up for summer, oil PSI indicator went down to 3psi at idle. Usually stays at 8-10 warmed up at idle. Hooked up mech gauge to oil temp unit (easy enough to access) and mech gauge holds at 8-10 at idle. Replaced the oil pressure unit and the oil pressure shut off switch with BWD brand. Now when car gets to temp at idle, psi goes straight to 0psi.... Is it a bad sending unit now, and was the mech reading from the oil temp unit accurate/could it be that drastically different at the top part of the engine? I would suspect based on the oil flow path of the L98 that it should be valid... Also no knocks or grinding and I have oil on the top of my engine. Holding idle fine too with no issues, mech gauge also read similar to gauge when old one was in there but more responsive and accurate, as expected. Any suggestions would be awesome for my peace of mind

Whaleman

I can't answer you question. What I can say is if your oil pressure is really going to zero your engine will self destruct in short order. Dan

xrav22

I replaced my senders and it did not read correctly for a while. I think it had to fill up or something.
But 0 is not good so you may have to replace with the old one or make sure the connector is solif.

21boy

I had a mechanical gauge on the oil temp opening which I've always heard the mechanical gauges read more accurate then the electronic. I guess the only thing I can think would be bad is if for some reason there's different pressures between the oil temp opening and the oil pressure opening, but the oil flow dynamic doesn't look like it should be.

Other than that I can look for leaks, but I've never heard the filling up part... I'm pretty sure oil press exists just super annoyed I ripped it apart to replace it at the moment.

bud40oz

maybe a bad ground on the new sensor? i would take it back and tell them it is defective. was it a quality part, or a cheap off brand sensor?.. even so 8-10 psi at an idle is pretty low, maybe you should consider a thicker oil. i personally only use 10 w 30 even if it calls for 5 w 30 you might wanna get some 20 w 50 in that thing if the cam bearings and other bearings are worn out that bad to drop so low at idle. what is it 10 psi per 1000 rpm? 8-10 psi at a 750 idle is quite low, like minimum....

i don't know man. just my 2 cents and we all know what that's like..

21boy

It's not AC Delco, just the advanced auto brand BWD. If it's ground, it wouldnt read at all? This seems to break down when oil gets to temp so I'm more leaning towards its the sensor itself. Again no leaks, and seems to be worse with ac on but that's not what the mechanical gauge says... So maybe it is a ground issue?

vader86

If its grounding somehow or the connector on the unit is dead, typically it'll read max, which is 80psi, not zero.

If its showing 8-10psi on a mech gauge I'd be very worried right now.

turtle96

I was going to suggest something similar. Install an external known working gauge to see what's going on. What did the mechanical gauge tell you?

21boy

Mech gauge shows 8-10 on 750rpm at idle, maintains around 10-15psi per 1000rpm at running temps. Not high, but it doesn't make noises and its not gotten worse over the years.

The engine is what it is, id like the gauge to work correctly. FSM offers little on this.. I did break the spade connector and had to solder a new one, could that be the culprit?

bud40oz

yes, that could be it, i would still try a little thicker oil. and also i have used cheap parts store brand oil before and it breaks down fast causing very low oil pressure. i changed oil in a guy's truck once. he hauled a trailer to go into the upper penninsula of michigan to his house up there to go ice fishing with all his gear in the trailer... he didn't even make it to the bridge and said his oil pressure was so low he got scared and checked it... it as full so he pulled into a shop and had them put in better oil. that was the last time we ever bought "parts master" oil i have even seen that happen with castrol gtx oil, i used that one time and had rotten pressure. i honestly have great luck with quaker state oil but i did buy mobile 1 when i changed it in my vette a few weeks ago... 10 w 30. it gives me 40 psi at n idle. i like it to be right there

21boy

Good point. I usually use Castrol GTX conventional. Will try the higher viscosity to see if it makes any difference. Is 20W-50 too high? It lives in fl, would be worried about overheating.

corvette_bob

While scanning over the thread, I started thinking about the possibility that your oil galley to the sensor may have developed
a restriction.
maybe something to look into.
Best of luck with your repair.

bud40oz

i would ditch the castrol , seriously. the more i thought about it after posting that i am pretty sure my gauge would drop to nearly zero when that was in there. it has been several years ago and not in a corvette but still. i ran that crap for maybe 2 weeks n drained it. problem went away. i only paid like 30 bucks for a 5 quart jug of mobil 1 10w 30 and a mobile 1 filter, try it and see what happens. at the very least you will give that engine a bit of a flushing out. 20 50 is maybe a bit extreme. i have used it in a lot of engines though. valvoline 20 w 50 racing oil was my go to oil for years and years when i had a hot rod...back in the 80's n 90's.. i don't know what you are running now. but like i said i like 10 30 for all around use, 5 w 30 is too much like water for my taste but i know that's the way things are now days. an older well used engine should be fine running a little thicker oil

bud40oz

this... is another good thought for sure. maybe take that sensor back out and run a coat hanger .. or other solid type wire that will not break... poke it in that hole and see what is in there, shouldn't be plugged buy ya never know, maybe even some teflon tape is covering up the tip of the sensor???

Sunny6

Heavier weight oil helps.

ctmccloskey

Jiffy Lube used to do an engine flush and I tried it once on my dad's Old Ford Pick up as the engine was packed full of sludge. Jiffy Lube hooked up a pump which flowed through the oil system and backwards through a filter mounted so you can see what was coming out of the engine. The oil was disgusting. They used a solvent that smelled like kerosene and heated it up to close to 200 degrees before circulating it through the engine. The difference was incredible, I pulled a valve cover afterwards and I would have guessed they changed the engine as it was immaculate. It was the best money ever spent on an old ford.

There are other ways of cleaning the inside of your engine, some are additives that get put in the oil and then drained. I am a bit skeptical. I have emptied all the oil out of engines and filled them up with Kerosene. The start the car and let it idle for about 10-15 minutes with NO-LOAD on the engine other than the accessories. Then drain the kerosene out and re-fill with oil and you will make the engine much happier. I have not tried anything other than Kerosene so be careful and keep a fire extinguisher handy when doing anything like this.

Your oil passageways may have sludge or a buildup that is restricting your oil flow. I personally would not drive any car with oil pressure that low, changing to a thicker oil is a good idea but if you have sludge inside the engine it won't do much to solve the problem. Your engine has a problem someplace and it could be simple but likely more complicated than you might want to deal with. Try cleaning the oil system out and bring that oil pressure up!

Good Luck!

21boy

Update, tried higher weight oil 10W-30 doesn't seem to be a difference. Will hookup the mechanical gauge and check again. Believe the sensor is at fault as when it hits 200F it goes from what ever it had to 0 immediately. Im thinking it does not work well at high temp range? I ordered a new one that's the same as the oem brand. Probably should have in the first place.

Still have the door open for 20w-50.

mtwoolford

bad news ? old worn drive gear on end of oil pump drive + high volume / high pressure pump + 20/50W oil + cold start + "poppa wheelie" = stripped out gear on oil pump drive. Just be careful, pumping heavy oil before the oil has a chance to warm up and thin out puts a lot of strain on the oil pump drive.
good news? the oil filter gasket will probably blow out first.
.
first things first, check your oil pressure with a quality mechanical pressure gage.