I was driving around tonite and i had no oil pressure at stop lights. I drove like this for, maybe 15-20 min, and for 5-10 miles. I noticed it started to accelerate and idle a little rough, then i noticed the oil pressure was zero. When driving and cruising there was pressure present, zero pressure only when stopped. I added 2 quarts cause it was low. I have a pan leak and i add a quart everyso often, but lately i've been busy getting ready to move and for college and stuff and i forgot to check so i was low on oil. It drives fine, just at stoplights it vibrates a bit, and acceleration from stop is a rougher.

What damage did I do? How bad?

Thanks,

Matt

 

Have you ever changed your oil pressure sender unit?

 

No i havent. But i know i was low on oil cause the oil on the dipstick was only a few centimeters high. I put in 2 quarts and it was over the full mark by a 1/4" maybe. It also is running slightly different. And the exhaust note is different, more pulsing.

Thanks,

Matt

 

You better check to see if there are shavings in the oil. You could've hurt something. Pull the dipstick out, put the oil on your finger and rub it into your finger. If it turns silver, you've got some problems.

 

Crap!! I just changed the oil before reading this. Will I still be able to check with the new oil? I talked to a friend, he suggested a lifter may be stuck or hasn't rised fully yet. Is that possible?
Any other input is welcome. I already know I'm an idiot for not keeping the oil level good and for not getting the pan replaced.

Thanks,

matt

 

I have the same problem, my bro told me to change the sender.
Im gonna try that myself see if it does anything. Pop says if not the sender, perhaps the crank is bad or pump is pimped

 

If you had litterally no oil pressure (0 psi) then your engine would have locked up already. Its probably just the f*cking GM guage.

 

i was told once that a rule of thumb is somthing like 10 PSI for 1000 RPM...


i do know that a small block chevy with alot of miles on it can idle at 10-15PSI and be just fine..


i also know that the GM gauge is acurrate to + or - 20 psi ( since it really sucks)



so you probly just have a gauge reading zero, while the pressure was on the low side....



athough you may just want to run a slightly thicker oil if you have a high miliage engine...... while pressure isnt the most important thing (volume is) , it is needed to move the oil around the engine.. a thicker oil would do that.

 

nope probably not the sender. i did the same thing. forgot to check the oil, wondered why it was reading no pressure and found out it was to low. if ur engine is making noise like mine started to after that happened, you damaged it. however, im still driving mine. ill wait till it breaks to replace it.

my dad told me "you live you learn" its nice being young, make a few mistakes and dont do them again. now i check the oil every saturday morning.

 

Well it isnt exactly making noise. Maybe a little, mostly the exhaust note has changedl. It vibrates a bit more when stopped. When accelerating it sounds/acts bogged down but it feels only bogged a little. Could it clear itself up or is there permament damage? How can I tell what is damaged? I was told maybe a stuck lifter. Is that possible?

Thanks,

Matt

 

Matt,

Yes, you can still check your oil if you changed it. My stock oil pressure gauge read zero and it freaked me out. Then it started running bad, but it never froze up. I checked the oil, like I told you to, and it was silver. After I pulled the engine, I ended up wiping 7 lobes out, and all the bearings were trashed. What happened was the pickup on the oil pump had fallen out. The previous owner rebuilt the ending and didn't tac weld the pickup to the pump. Now, I'm not telling you that's your problem, but don't totally disregard your stock gauge.

 

Well, i checked the oil on the dipstick, no silver. I'll check again in a week. It hasnt been running bad, just different. I can notice but no one else can.
What could've been damaged?

Thanks for all who have replied.
Any more advice/suggestions are welcome. I've put in too much money for the engine to crap out on me cause of my stupid mistake.

Thanks,

matt

 

I had the same thing happen & 4 months later #'s 3 & 4 rod bearings spun. 2 qts low is a bad thing, the remaining 2-3 qts of oil can't drain back fast enough to keep the oil pump from sucking air, hence zero pressure reading.

 

How do I know if the rod bearings or the main bearings are bad/damaged? How expensive to fix? I hope to rebuild the engine next summer. What are the chances the car will last till then?

Thanks,

Matt

 

Well, I just replaced the Oil Sender, and at idle pressure is over 35 before it was under 30. And at 200degress in drive pressure was around 20 before it was in the red if not 0psi.
So, first things first. Change the damn sender, cheaper easier, and could be the issue

 

Weres the sender located? How hard is it to change? How much was the sender?

Thanks,

Matt

 

Back of the intake on the drivers side. Not on the intake behind it. It actually screws into the block. Get one of the oil prescreens that go on top of the oil filter and run it 500 or so miles and then change your oil and check the screen for metal. You could flaten a cam lobe or wipe out a main bearing in no time at all with no or low oil pressure...

 

If you want to be really ****, grab the old oil filter and cut the damn thing open.

 

I wish I checked before. I threw everything out right after I changed the oil. What would a flattened lobe feel like? How noticable would it be? What about a bad main bearing or rod bearing?

Thanks all. I want to be sure of what I done, cause I move out to college tomarrow and I need my car running. I dont have cash to throw around.

Thanks,

matt

 

In my '89 Formula, the oil gauge will go to zero if I hit the brakes hard. I know the gauges suck and it is full because I just changed the oil 3 weeks ago and not much has leaked on the floor. The factory gauge floats badly.

 

I had a 400 that had a wiped exhuast lobe on number 8 i think it was, the freakin thing would would run hot.
You could pull of your valve covers and run the engine, if you dont a rocker moving or moving as much as the others, its wiped.

formul8!! ........ Change that sender, only pain in the **** about changing it is the mess of wires that they decided to run right there.


Matto'85TA ... The sender is on the rear of the engine on driver side near the distrubtor. It should horizontal pointing to the driver side. Its bell shaped with 1 electrical conector on it( for gauges) not certain what it looks like or number of conectors for idot lights.

 

formul8!!

I don't mean to pick on you, but you could have your oil at the full level and still have no oil pressure. If your pump is bad or your bearings wore, there won't be much pressure. You could also be about 1 to 2 qts. low and pressure will still read the same, untill the oil splashes in the pan, and the oil pump pickup goes dry for a second, then your gauge will read zero. That isn't good either.

 

But, as the rest of you guys are talking about, start with the sending unit. If that doesn't fix the problem, atleast you have a new sender for the future rebuilt engine. It's cheaper and quicker.

 

The same thing happened to me, and I even thought it could be the pump, until a guy who owns a car shop told me "chevy pumps never fail"... and sure enough, the problem was the sender.
It was a PITA to remove, I had to cut it, so I could slip a wrench and remove it. I got a new one, installed it, just in case I changed my oil and filter, and it read perfect pressure as soon as I started it.

 

I had the same problem, after I changed the oil it slowly began to lose oil pressure, so just to see if the pressure would improve I put in some 20w-50 and I had a little more on the gauge. The next day I borrowed a autometer mechanical gauge and put it in, at idle I had 40 psi of pressure, oops. I replaced the sender and drained the 20-50 and all was well again.

 

I had the same prob too and it ended up being a bad sending unit. Mine is an 86 IROC with 305. Scared the crap outta me when I saw Zero oil Press at a stop light. My step dad hooked up his mechanical gauge to the Engine and sure nuff was sitting at 30 psi at idle. We got it good and hot and never went below 30 until we shut the motor down. :lala:

 

Thanks for all the replies. The sender is probably bad. But i did have low pressure cause i was down 2 quarts of oil. I really would like to know what possible damage i had done. The car is running differently.

Thanks,

Matt

 

I have a mechanical guage on my motor and at 1000 rpms it sits at 13PSI... at idle in gear (750 RPMS) it sits at 9PSI.

my bearing are a bit on the loose side, by design, but i do have a HV Oil pump (melling55) hope this info helps.

 

Matt,
I hate to tell you this, but we could give you our opinions on what is wrong with the engine all day long. Change the sender, see how your pressure is and then go from there. The only way to tell if you scored the bearings is to lift the engine, drop the oil pan, and take either a rod or main cap off and check the bearing.

 

Thanks. I am gonna change the sender. Thanks for the replies.


Matt

 

Hm; I've had that problem for 3 or 4 years already- and I have an aftermarket mechanical gauge. I probably just have excessive bearing clearance; 256,000 miles on my original 2.8 v6.

 

Use Straight 30 W, that will help. If it doesnt, use 20w 50. That will give you a little more life out of that motor before it starts knockin itself to death.

 

well if he ahd no oil pressure at idle and then put oil in it, and the pressure went up, it is probably becasue he was low on oil!!!!!!

now, for the engine, i did the same thing(let it get to low on oil) and the engine started to sound different. it still does like 5months later. you probably did damage like me, but so far ive been lucky. it still runs.