I might be in trouble

[78C30]

So i just finished making my 1978 chevy c30 look beautiful, motor was in good shape and decided to take it to my college on a 120 mile trip. i got down here safely and with no issues. a couple days after i took it on a short 15 min trip and while i was driving the oil pressure slowly went down and hovered above zero. the motor didn't change in sound. i just did an oil change and filter change today to see if changing the oil would effect anything and when i first started it it had great pressure then as the engine warmed the pressure went down. it has a new pressure sending unit ad the motor is the 454 so any advice and explanations for what is happening and if i drive the truck would it damage the motor would be very appreciated.

Thank, Jamison

 

[Georgeb]

So i just finished making my 1978 chevy c30 look beautiful, motor was in good shape and decided to take it to my college on a 120 mile trip. i got down here safely and with no issues. a couple days after i took it on a short 15 min trip and while i was driving the oil pressure slowly went down and hovered above zero. the motor didn't change in sound. i just did an oil change and filter change today to see if changing the oil would effect anything and when i first started it it had great pressure then as the engine warmed the pressure went down. it has a new pressure sending unit ad the motor is the 454 so any advice and explanations for what is happening and if i drive the truck would it damage the motor would be very appreciated.

Thank, Jamison

Is this a new problem that has developed or do you not have much history with the truck?

 

[mistaake]

Bad gauge? Can you verify pressure with a real mechanical gauge? Might save you troubleshooting a problem that may or may not exist.

 

[78C30]

Is this a new problem that has developed or do you not have much history with the truck?

Both, ive had the truck for a few months and the oil pressure was always holding steady on the white line in the middle until a few days ago. its possible its a bad gauge, where can i get a cheap on to verify?

 

[1973c10]

You can get a cheep gauge here

http://shop.advanceautoparts.com/p/...p8206/9030005-P?searchTerm=oil+pressure+gauge

 

[mistaake]

You can get a cheep gauge here

http://shop.advanceautoparts.com/p/...p8206/9030005-P?searchTerm=oil+pressure+gauge

I was thinking something like this would be helpful to him...

Engine Oil Pressure Tester Gauge Diagnostic Test Kit $13.99

 

[78C30]

well i took a video of the oil gauge but cant figure out how to attach when i try it says it has an error. but i will find a gauge but i am hearing a knocking noise when its (im guessing as tach doesnt work) 2000 rpm its almost like a loud rattle but a soft repeating knock. doesnt happen till i give it about a 1/4 throttle. i verified that the top end is getting oil and the pressure was (again guessing as gauge isnt marked well) it was holding steady on the line between the 0 and half mark until motor hit operating temp. that is when the pressure slowly went down to just above zero guessing thats around 5-10 psi. when i hit the gas it goes up and if i hold it there around a 1/4 throttle the needle starts to bounce from 0 to 60 then goes past almost spinning around on the gauge face. once the needle goes spastic the motor starts to develop a light knock.

any ideas?

 

[1973c10]

Does it sound like lifter rattling
is it only when your driving
can you open the hood and run the RPM's up
and see if you can hear the lifters

 

[Georgeb]

The needle jumping is interesting but the knocking is bad news! I have an 87 350 that has good pressure untill it's hot then its at zero. No knocking but an interstate run makes the oil pressure so low the lifters wont pump up. Sounds like a similar problem. I think other than the oil pump being bad you may have spun a bearing. Either way the knocking is bad news. Many small blocks knock when cold so you may get lucky and it's the pump. May be worth changing it out to see if the motor survived. Hopefully others will chime in here too!

 

[78C30]

I can make it knock by lifting up hood and hitting accelerator about a 1/4 down. If you say the word dot somewhat fast that is what the noise sounds like it's not only when I'm driving. The motor in question is a big block Chevy I can't drop the pan until next weekend to check but I have to make a 120 mile trip with it to get it back home.

 

[78C30]

What do you mean by spun a bearing?

 

[mistaake]

you can upload it to youtube and post a link

if truly have 0 oil pressure and it's knocking you have a major engine problem.

 

[Georgeb]

What do you mean by spun a bearing?

When an engine bearing spins in the journal due to loss of lubrication.

 

[Georgeb]

Does it still make pressure and not knock when cold? If so and you cant afford a tow you may get home by removing the thermostat so it wont warm up and driving home on back roads rather than the highway. Otherwise have it towed. This may or may not be good advice but it's what I would do. But if yoy are unsure at all about that tow it. You dont want to do any more damage that what may be done already.

 

[78C30]

https://m.youtube.com/watch?feature=youtu.be&v=nQz_7uFq7Q8

Here is the video when I tap the gas