AnniversaryZ28

iTrader: (5)

My car has a 40k shortblock in it, when the cam was put in a few years ago we also put new bearings and arp rod bolts.

At hot idle i always have 40 psi, wot throttle about 65.

Yesterday driving around i was climbing through the RPMS oil pressure was going up just fine, when i came to the light at idle, the pressure dropped to about 10-15...

I pulled over, popped the hood, heard no noise what so ever. I shut the car off, let it cool, checked the oil. I was about half a quart low due to my valve guides being warn(stupid .641 lift cam)

Not thinking that was low enough to cause a problem, i started it back up...0 pressure, gauge did not even lift from 0, immediate lifter clack also. Shut it down after about 5 seconds.

So i called a flatbed and had it towed home. Its a 98 drivetrain and from what i gather it sounds like my pump puked.

Any opinions?

EDS01SS

iTrader: (30)

Yup that could very well be your problem but I would check the pickup tube o-ring first. I have heard of those causing oil pressure problems also when they go bad.

crainholio

iTrader: (2)

When the new bearings went in, what clearances did you get at the mains and rods?

G Engines

check your oil filter first before you just tear the engine apart. I have had problems with Fram filters twisting inside cutting off oil pressure.

crainholio

iTrader: (2)

Amen about Fram filters, anyone running them hasn't done much reading.

FRUSTRATED T/A

iTrader: (13)

+1 on the o-ring most people use the wrong one and dont know it.
Make sure their is thread sealant on the rocker bolts also as oil will work its way down them.

AnniversaryZ28

iTrader: (5)

Not really sure, machine shop did it of course, stock clearances i assume.

94lt105

iTrader: (1)

Sounds like a bad pump, but as others have stated it could also be the O-ring! Let us know when u find out!

Vince

eallanboggs

iTrader: (1)

I don't believe the pump is going to make pressure on minute and 0 the next. These pumps are just about bullet proof. Pull it apart and examine the guts. What is there to wear out or break? I guess it could get damaged if you don't change your oil and you let trash circulate through the system, but then other things are being damaged too at that point.

AnniversaryZ28

iTrader: (5)

Well, i am open to other explanations or opinions. Odd how the car had tons of pressure then 0, i would think every bearing would have to check out at the exact same time to totally lost pressure all at one. I have lost a few motors in my time, even when the pressure is low, knocking, i had some oil at the top of the motor...I have NONE.

I guess the bypass relief valve is a pretty common failure point.

crainholio

iTrader: (2)

I have seen a stuck/seized bypass plunger cause near-zero oil pressure at idle, but was on a car that had spent 15 minutes or so on a road course running at very high revs for long periods of time. Everything was fine until he pitted out, idled down the hot pits, saw the oil press gauge at 0, and the lifters were rattling as he came to a stop.

The good news is that the engine came back to life w/ a new pump and was still running track events a year later.

orangeapeel

iTrader: (18)

Fram Filters are about good to use as a spitoon and thats about it. I was gonna say the sending unit went out on you but it may be the pump. You said .641 lift cam so maybe it had a little valvetrain noise prior and you just didnt listen close enough because you had normal oil pressure at that time. Never hurts to check that though. Just an additional thought along with the o-ring and the pump itself.

eallanboggs

iTrader: (1)

In order for the bypass piston to get stuck OPEN several things have to happen first. The oil pressure has to increase to the point that it excedes the spring tension that's trying to hold the pistion in the CLOSED position. Once the pistion gets there an obstruction much be suddenly present to keep the bypass hole open. This burr or obstruction can not be present while the pistion is moving in the direction or the bypass hole of it might inhibit the pistion from traveling far enough for the bypass hole to open. The bypass hole shouldn't flow oil unless the oil pressure goes for some reason like the oil filter is never changed, but the oil filter has it's own bypass. That's a pretty heafty spring in the pump. I haven't measured it with a spring gauge, but it take substantial force to compress it and many people shim it to try and keep the bypass hole from opeing.

AnniversaryZ28

iTrader: (5)

Well, it was the pump relief valve, i opened it up and the valve was stuck wide open, hit it with a screwdriver and it snapped shut.

New pump is in, i think i pinched or rolled the O ring though, gotta try again this morning.

AnniversaryZ28

iTrader: (5)

Here is my opinion on why that happened. After taking it apart, i did find the valve hung wide open. Maybe once i shut it off and killed the flow it was unable to actually suck oil up with the valve so far open?

I dunno, all i know is the valve was open and that makes me happy.