Oil Pressure Gauge

Jasonsupafly · April 18, 2010

01 Z71 5.3 119,000 miles..

A couple of days ago my oil pressure gauge has started to function abnormal. It doesnt drop past halfway but when giving gas it now flickers very fast up and then flickers back down slightly once at cruising speed.. Any ideas ? Truck is serviced as it should be..

Funny thing is we have four of these vehicles. All with same engine size. 3 2001's and a 2005 that all are doing the same thing.

Also a last week my fuel gauge is going from fuel to empty and in between ?

Thanks in advance

jro909 · April 19, 2010

your saying your oil pressure goes up with rpms? if you put a load on the motor it will rise slightly and go back down once the rpms stay stable...its normal, my truck when fully warmed will sit from 35-38 psi at idle and when i hit the gas to go climb up to 40ish...idk if that helps lol

Jasonsupafly · April 19, 2010

Right. Ive got that. The gauge does not move smoothly anymore. It springs or flickers very fast..

Thanks for th reply

jblakeney · April 20, 2010

I had problems with my truck for awhile.... Ended up using a flush to cure the problem....... Flushing is a really RISKY trick with a high mileage engine. Beware... But you problem is kinda vague....

What ARE THE READINGS? Both of my trucks idle with 40lbs and anything over 1500 rpm's nets 60lbs of pressure.

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IT IS DANGEROUS TO FLUSH ENGINES that are not flushed on a regular basis. Engine flush will break loose all sorts of sludge that you never really knew was there. And everybody that does not use an engine flush has some sludge that will break loose and head for the oil pump pick up screen!! If oil pressure falls below 30 and you change oil and filter and oil pressure does NOT RETURN to normal. YOU WILL HAVE TO PULL THE PAN AND oil pressure screen. And possible the pump. ALSO this will NOT FIX bearing wear!!

My problem was I had always go 60lbs and seems like OVER night i fell to 40 above 1500 and 30ish on idle..... Flushed the engine, in a crazy procedure and it cured it (HOWEVER I was quite sure that I did not have bearing wear enough to cause my problem before hand).

USE A HIGH QUALITY OIL FILTER. I will recommend WIX GOLD filters..... Or any filter that has metal end caps and at least a 15 micron rating for this job, as you WANT TO CATCH THE TRASH not float around....

1. Change oil & filter.. * I use Castrol Syntec normally but I changed it several times so I just used regular Castrol... *

2. Poor in 1/2 bottle engine flush in the engine. WATCH GAUGE LIKE A HAWK.. Less than 30lbs KILL IT ASAP, if not quicker. Allow to run for 5-10 minutes.

3. Change OIL AND FILTER again.

4. Drive for several hundred MILES (200 - 300), !!!!! WATCH OIL GAUGE LIKE A HAWK !!!!!

5. Change oil & filter.

6. Poor 1/2 bottle of engine flush in the engine. WATCH GAUGE LIKE A HAWK.. Less than 30lbs KILL IT ASAP, if not quicker. Allow to run for 15-20 minutes.

7. Change OIL and FILTER again.

8. Drive for several hundred MILES (200 - 300) YET AGAIN WATCH OIL GAUGE LIKE A HAWK !!!!

9. Change oil and filter, use the oil you have always used...

Note I simply used regular oil since the Syntec per oil change is about 42 US $'s.... and regular stuff is 24 US $'s...... If you use regular *conventional oil to start with make no OIL type changes*

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It is NORMAL FOR the oil gauge to have movement. As the RPM's go up the oil pressure should rise also. GM I believe says 10lbs per 1000rpms (somebody correct me if I have forgot the numbers here). As the engine wears it is normal for the pressure to drop slowly over time... Large drops in oil pressure are indications that she is fixn' to go down on you.... Beware.

With all of that said... You really have no clue how much oil pressure you have till you remove the oil sending unit and screw in a MANUAL gauge and check it out..... If it does not act the same pressure wise get a new sending unit.. Or when in doubt just get a new sending unit..... Or look at the stepper motors for replacement..

Sorry, it got quite lengthy.... Hope it helps ya out...

Jbo

jro909 · April 20, 2010

your guage motor might on its way into the ground, check it with a mechanical guage and see what the readings are...10 pounds per 1k of rpms is the minimum the engine needs, i second a good filter ive put frams on alot of beaters and the next time around the oil comes out like a melted snickers bar...i prefer ac delco filters, but i have heard alot of good things about wix...

Jasonsupafly · April 20, 2010

Thanks for the help guys. I use ac delco filters also and have always used synthetic oil and its been changed as it should be. Im hoping the gauge is just going bad. I know the tach would get stuck and not move a couple years back but this only lasted for a couple of months but its worked right every since. Ill keep an eye on the pressure. Also the gas gauge is acting screwy now. I assume it may be the sending unit on that though..