oil pressure sudden drop

[iamseth]

My 400 bigblk has never had low oil pressure. The gauge has no numbers so ill refer to it like the gas gauge: Idle: 1/4 full, Driving (highway): 3/4 full. Until today... This morning, after accumulating about 2 inches of snow in AUSTIN, TX last night, oil pressure was fine. Then when I left work around 2:30, oil pressure was at 1/4 full while driving and all the way to empty while idling.

Should I be fretting over this? I recently switched to 20w/50 oil. Could this be the problem?

I've read a few posts about this issue, I'm just a little concerned about the sudden drop, that's all.

[tubbedII]

Did you check the oil after it dropped? No oil pressure would freak me out and I personally wouldn't drive it until it's fixed...even if it is just the gauge/sending unit. The damage risk is too high and my pockets aren't that deep.

[dan76]

ditto /\

Did you rev it right after start up? With the heavier oil, the cam might be wiped due to having insufficient pressure due to the cold temps.

Get a mechanical gauge on it to check for oil pressure. Hopefully it's just a gauge problem.

[71 super]

Sounds like at best low oil level, worst bearing going way south

[Frkypunk70]

When my oil pressure dropped like that, the cam was wiped and the lifters, one lifter had a hole worn right through the bottom. I would take a valve cover off and check the rocker arms and or push rods are going up. If no or little movement I would assume the same that happened to me. Not trying to scare you but its easy to check. By the way if it is, rebuild the whole engine. I tried to just replace the cam and lifters and ended up blowing it in a couple of months anyway. Time and money wasted.

[iamseth]

The oil is full, I just drove around the block, this is what happened:

Park: it's around "1/4 full"
Idle in gear: sits just above the "low" line
Driving 30mph: sits around "1/4-1/2"
Driving 60mph: sits at "1/2" and goes up with mph from there.

[cdowns]

i'd look at where the oil line for the gauge comes out of the block and see if it maybe got kinked or broken maybe leaking

but with those readings i really wouldn't b overly concerned

[grandfisher]

I've just experienced the same problem on my 1990 TBI truck. I built the motor 3 years ago and it's been a great engine. Usually my oil pressure is 30 PSI at an idle and much more under throttle. A couple days ago, I noticed a significant drop in pressure. It's gotten worse the last couple days. At first I thought it might possibly be the 0-20 degree temperatures were experiencing here, but it has gotten worse. Today, I had 7-8 PSI at an idle and 15 PSI under throttle. Not good. It's parked until I've got time to fix it.
One side of my exhaust has been making a "chirping" sound for the last several months. I have no exhaust leaks anywhere. No brackets that are loose or vibrating. I'm thinking it might be in the head or the glass pack has somehow ruptured. Maybe the chirping and the PSI drop are related somehow. Luckily, I have a spare 4x4.

[iamseth]

btw, the truck is running fine. My carb needs to be overhauled, but other than that.... I haven't noticed any difference in performance. I'm going to get a mechanical gauge tomorrow and check it out.

[swamp rat]

Originally Posted by iamseth

btw, the truck is running fine. My carb needs to be overhauled, but other than that.... I haven't noticed any difference in performance. I'm going to get a mechanical gauge tomorrow and check it out.

I agree with putting a different guage on it before jumping to any conclusions as long as you have no unusual clatter.. Also with the cold could the viscosity be a little high?

[iamseth]

you know, when i pulled the dip stick to check the oil, it actually seemed kinda of thin... Though I had just gotten off the highway. I am using 20w50.

What sounds/performance issues should I be looking for, if this is a bigger problem?

[tubbedII]

Where do you get such a line? I had to get a new sending unit when I bought my blazer and the only one I could find was a plastic piece.

[jasonroman]

i have an 85. with what i was told is a 5.7 liter engine. not really sure about what engine is in truck, but i notice sometimes my gauge works and sometimes it stays near 0. how can i check to see if my gauge is going or something is wrong with connection.
sometimes im driving and it reads a little over 0, some times it dont move and others it moves.
thanks for any advice. and let me know if i should be starting a thread for this. if so, sorry for posting.

[swamp rat]

Originally Posted by jasonroman

i have an 85. with what i was told is a 5.7 liter engine. not really sure about what engine is in truck, but i notice sometimes my gauge works and sometimes it stays near 0. how can i check to see if my gauge is going or something is wrong with connection.
sometimes im driving and it reads a little over 0, some times it dont move and others it moves.
thanks for any advice. and let me know if i should be starting a thread for this. if so, sorry for posting.

The best way to check would be to install directly to the oil port on the block a known good pressure guage, fire up the truck and read the pressure, see i'm pretty sure on that year it would probably have a sending unit and electrical guage but not positive...

[Captainfab]

The one I've bought before is made by Autometer.

http://www.summitracing.com/parts/ATM-3224/

Originally Posted by tubbedII

Where do you get such a line? I had to get a new sending unit when I bought my blazer and the only one I could find was a plastic piece.