Oil Pressure Hits Zero And Stays There- JGC '96

CHECK GAUGES: Zero Oil Pressure reading-


First had this problem on my way back home, I stuck in traffic, in the
middle of the summer. It was a hot day, and I had been driving for 40
minutes. I was at 4,000miles with my oil, which is 5 part synthetic,
1 part Lucas.

I told my mechanic that I though the problem might have to so with
dirty oil, because I'd never let the oil go for that long and I'd never
had this problem before

Mechanic changed the oil and the sensor. Nothing Happened. The light
would come on after the car warmed up for a while. Replaced the Oil
Pump- No Dirt in the screen. No change except for higher pressure on
Start-Up. Used to be 40-45, now is 50-60.

The problem used to happen after 20 minutes. Now it happens within5
minutes. In addition, the pressure used to go back up with
acceleration, but when it hits Zero, it stays there.


The mechanics first suggestion was to pull the valve covers, and
replace them, after cleaning out the RETURNS. Now he says he wants to
have the CPU reset first, but that costs $100 and may not solve the
problem.

What's the deal?

First thing I'd do is put a real mechanical oil pressure gage on a 't'
fitting and see what the engine is really doing. If it really is
dropping to zero after it warms up, about the only thing that could do
that is a bad oil pressure relief valve on the oil pump. That is a drop
the pan job, a nasty project on yours.

NJPainter wrote:

> CHECK GAUGES: Zero Oil Pressure reading-
>
>
> First had this problem on my way back home, I stuck in traffic, in the
> middle of the summer. It was a hot day, and I had been driving for 40
> minutes. I was at 4,000miles with my oil, which is 5 part synthetic,
> 1 part Lucas.
>
> I told my mechanic that I though the problem might have to so with
> dirty oil, because I'd never let the oil go for that long and I'd never
> had this problem before
>
> Mechanic changed the oil and the sensor. Nothing Happened. The light
> would come on after the car warmed up for a while. Replaced the Oil
> Pump- No Dirt in the screen. No change except for higher pressure on
> Start-Up. Used to be 40-45, now is 50-60.
>
> The problem used to happen after 20 minutes. Now it happens within5
> minutes. In addition, the pressure used to go back up with
> acceleration, but when it hits Zero, it stays there.
>
>
> The mechanics first suggestion was to pull the valve covers, and
> replace them, after cleaning out the RETURNS. Now he says he wants to
> have the CPU reset first, but that costs $100 and may not solve the
> problem.
>
> What's the deal?
>

There is no engine knocking et al, so we think the oil pressure is
fine.

My mechanic told me it shouldn't be the oil pressure relief valve but
he never tested it. I've seen the dropping of the pan performed, by my
back-up mechanic who replaced the oil pump, but did nothing else.

Are you saying that the valve cover/gasket and the cleaning of the
"RETURNS" wouldn't fix this?
Should I cancel the $100 appt with the dealer to reset the CPU, or just
let them find out what the real problem is, and bring it back to my
mechanic to do the work. I have a good mechanic but he's can't figure
out the problem or he's too lazy too. I do trust him to do the work
though. He changed out my exhaust manifold before.

This whole ordeal, along with countless other bigger issues I've had
with cars have made me want to become a mechanic but as for now I can't
do anything but change the oil.

If you are sure the oil pressure is fine then it is most likely a
problem with the gauge or sender or circuits. You did not mention
checking the gauge itself and the wiring.




NJPainter wrote:
> There is no engine knocking et al, so we think the oil pressure is
> fine.
>
> My mechanic told me it shouldn't be the oil pressure relief valve but
> he never tested it. I've seen the dropping of the pan performed, by my
> back-up mechanic who replaced the oil pump, but did nothing else.
>
> Are you saying that the valve cover/gasket and the cleaning of the
> "RETURNS" wouldn't fix this?
> Should I cancel the $100 appt with the dealer to reset the CPU, or just
> let them find out what the real problem is, and bring it back to my
> mechanic to do the work. I have a good mechanic but he's can't figure
> out the problem or he's too lazy too. I do trust him to do the work
> though. He changed out my exhaust manifold before.
>
> This whole ordeal, along with countless other bigger issues I've had
> with cars have made me want to become a mechanic but as for now I can't
> do anything but change the oil.

nrs wrote:
> If you are sure the oil pressure is fine then it is most likely a
> problem with the gauge or sender or circuits. You did not mention
> checking the gauge itself and the wiring.
Thanks...

I guess what I'm trying to say is that there is an accurate reading at
start-up. The reading is consistent until the car really warms up. At
Start-up the pressure is higher than before, which tells me that
changing the oil pump was a good idea, and beyond that, the sensor is
getting an accurate reading. Why the oil pressure would bottom out
after warming really confuses me. After the problem was recognized it
would take 20-30 minutes for the pressure go to zero but now it
happens in a shorter time span. Whatever problem there is seems to be
getting worse with time.

The car seems to run fine, I've taken it on regular commutes and I
still don't hear any loud noises, but I do think that once it's warm
and hits zero, that I have less power and acceleration.

Would changing the valve covers/gasket and cleaning out the returns
be a remedy. I just seems to be that some sludge or crap is stuck
somewhere I really don't think it's a CPU issue, because I'd assume I'd
have a bad reading at all times.

If you restart the car when already warm, does it give a good reading
for a while? If so it would seem it is not a temperature problem but a
mechanical problem If not, then it seems it would be an electrical
problem, something getting affected by temperature.

As RoyJ suggested, a mechanical gauge would tell you if the oil
pressure is actually dropping. If it is not then it is an electrical
problem.

A can't see how changing the valve cover gasket could help.




NJPainter wrote:
> nrs wrote:
> > If you are sure the oil pressure is fine then it is most likely a
> > problem with the gauge or sender or circuits. You did not mention
> > checking the gauge itself and the wiring.
> Thanks...
>
> I guess what I'm trying to say is that there is an accurate reading at
> start-up. The reading is consistent until the car really warms up. At
> Start-up the pressure is higher than before, which tells me that
> changing the oil pump was a good idea, and beyond that, the sensor is
> getting an accurate reading. Why the oil pressure would bottom out
> after warming really confuses me. After the problem was recognized it
> would take 20-30 minutes for the pressure go to zero but now it
> happens in a shorter time span. Whatever problem there is seems to be
> getting worse with time.
>
> The car seems to run fine, I've taken it on regular commutes and I
> still don't hear any loud noises, but I do think that once it's warm
> and hits zero, that I have less power and acceleration.
>
> Would changing the valve covers/gasket and cleaning out the returns
> be a remedy. I just seems to be that some sludge or crap is stuck
> somewhere I really don't think it's a CPU issue, because I'd assume I'd
> have a bad reading at all times.

THe Valve cover and gasket is just because it needs it.

He said he was going to clean out the "Returns". I've heard of this
before.

Yes, when I restart it, after warm, the pressure goes to zero.

"NJPainter" > wrote in message
oups.com...
>
> THe Valve cover and gasket is just because it needs it.
>
> He said he was going to clean out the "Returns". I've heard of this
> before.
>
> Yes, when I restart it, after warm, the pressure goes to zero.
>

If the returns are plugged with sludge, then it could keep the oil from
returning to the pan and cause the low pressure reading. I have seen the
returns plug up on a few engines, but it is normally caused from severe
neglect of oil changes, coupled with lots of short trips that prevent the
engine from reaching operating temperature. I agree with the others, put a
mechanical gage on it first, and see what you get. It is possible that the
sending unit craps out when hot, or there is some other temperature related
electrical failure happening. I'm sure the gage will be cheaper than the
cleaning job from your mechanic.

Chris

Probably an electrical problem because commuting regularly with zero
oil pressure would have already destroyed your engine.


NJPainter wrote:
> THe Valve cover and gasket is just because it needs it.
>
> He said he was going to clean out the "Returns". I've heard of this
> before.
>
> Yes, when I restart it, after warm, the pressure goes to zero.

Perhaps I missed something..

Did the mechanic, or the back up mechanic, ever put a mechanical pressure
gauge on the engine or are you relying on the dash gauge?


"c" > wrote in message
...
>
> "NJPainter" > wrote in message
> oups.com...
>>
>> THe Valve cover and gasket is just because it needs it.
>>
>> He said he was going to clean out the "Returns". I've heard of this
>> before.
>>
>> Yes, when I restart it, after warm, the pressure goes to zero.
>>
>
> If the returns are plugged with sludge, then it could keep the oil from
> returning to the pan and cause the low pressure reading. I have seen the
> returns plug up on a few engines, but it is normally caused from severe
> neglect of oil changes, coupled with lots of short trips that prevent the
> engine from reaching operating temperature. I agree with the others, put a
> mechanical gage on it first, and see what you get. It is possible that the
> sending unit craps out when hot, or there is some other temperature
> related electrical failure happening. I'm sure the gage will be cheaper
> than the cleaning job from your mechanic.
>
> Chris
>