Oil pressure

[Mr URL]

Having a freakin wierd oil pressure readings that is driving me nuts with my T-Type!!!

I installed a new VDO oil pressure gauge couple months ago. Before I took the motor out and tore it down to the short block to clean it all up with new gaskets, HV oil pump, timing chain, 206/206 cam, lifters, ported and polished heads, etc. it had 15 psi oil pressure at hot idle and 55 psi WOT stock. Cold was about 60-65 psi. It now has stock cover, HV oil pump with new oil pump gear plate, and 70 psi relief spring. New oil pickup tube gasket torqued to spec.

Now when cold the VDO gauge reads buried at 80 psi. Driving it a little bit after reaching full temp it's about 70-75 psi with a little rpm and 20 psi at idle. Give it some rpm (heavy throttle) after a bit warmed up or steady highway cruising it drops down to 40-50 psi with rpm and 17-20 idle. Pretty much stays at 40 psi with some rpm after a while.

Any ideas?? Gauge or sending unit? Can you have the oil cooler lines cocked wrong or any problems with installing the gear backing plate? Motor looked perfect inside and was tight (57K miles and had an easy life).

Humm...

 

[PsychoBuickBoy]

Mine does the same thing, I certainly hope it is OK! After it is thoroghly warmed up my oil pressure will go to maybe 40-45 at higher RPMs and it will hang at about 12 at idle. I also have almost the exact setup as you.

 

[Mr URL]

What we are experiencing probably is an internal oil leak.

 

[bose]

If you have the gauge with the electric sender that may be your problem.I had one on a car and never did get the correct reading.I now use only oil pressure gauges that have tubinf that connects on the back of the gauge.This way high or low or a bad ground does not affect it.Bruce

 

[Black Car]

Another possibility is that the electrical sender is temperature sensivite (sp). Is it touching the lower radiator hose?
Gary

 

[Mr URL]

It is close to the header.

 

[PsychoBuickBoy]

Yep, mine is electric also and close to the header. That could definetly be the problem.

 

[GNVAIR]

I have an Autometer mechanical gauge in my car. I used a piece of -4AN braided line and hooked it up in place of the stock sender. The gauge seems very accurate, which could be a blessing or a curse.

 

[salvageV6]

What about the new readings don't you think is accurate?

Cold start numbers?

I don't think the numbers are that far off???


"Give it some rpm (heavy throttle) after a bit warmed up or steady highway cruising it drops down to 40-50 psi with rpm and 17-20 idle. Pretty much stays at 40 psi with some rpm after a while. "

Sounds like my car, salvageV6, with a mechanical gauge on it???

Booster plate too.

 

[Mr URL]

I'm installing a mechanical gauge Thursday night and see what readings I get. I'll let everyone know what I find out.

 

[Mr URL]

Does anyone know what ohm readings the oil pressure sender should be giving with engine off, idle, cruise, and WOT?

I found this info but not sure which. Gauge was purchased from Ramchargers.

80 PSI 2 1/16" Oil
Part No: 350-104 Notes: 10 - 180 Ohms (VDO Ohm range)

80 PSI 2 1/16" Oil
Part No: 350-105 Notes: 240-33 Ohms (U.S. Ohm range)

 

[Fat Nat]

My car does the exact same thing. Drives me freakin nuts!!!. I have the HV front cover and I have the exact same readings as you have. When my car is fully warmed after driving down the road for about 20 min. The oil press is 35# at cruise I hear of people having 50 and 60 at cruise and this blows my mind. How much oil press. do you have at 2000rpms about 38# here. Please let me in on any info you might find out.

 

[Mr URL]

It reads 10-20 idle (can vary but not fluctuate), 38-42lb at 2,000 rpm fully warmed up down the interstate, and between 40-55 psi WOT (varies also).

My GN with a very old VDO oil pressure gauge reads 20lb idle, 65lb cruise, and 80 (buried) at WOT consistantly.

I would like to know if the latest VDO oil pressure gauges are having accuracy problems? I can't see why my oil pressure can be doing this. If I knew it was inaccurate for sure I wouldn't worry about it and call anything over zero good.

 

[Mr URL]

Engine cold and key off. Wire disconnected. 2 ohm.
At the gauge wire it was 15 ohm.

Engine cold running and warming up: 430 ohm (80+
psi), 350 ohm (42 psi), 320 ohm (40 psi), 300 ohm (30
psi), 285 ohm (20 psi).

Fully warmed up and running for a while: 137 ohm idle
(20 psi) to 50 ohm reved up (70-75 psi).

Voltage 2-5 volts.

Steady highway cruising the readings will go lower on
the gauge. Wasn't able to check it tonight cruising with a volt meter.

2 sendors supposed to be 10-180 ohms or 240-33 ohms that I've found.

Seems like it switches backwards after a while??
Higher ohm when engine cold is higher reading. Engine warmed up higher ohm is lower reading and lower ohm is higher reading.

Is that strange or what??

 

[Fat Nat]

I see mechanical gauges in our future. MY oil press is Identical to yours. Im thinking this new motor is looser than when it was stock the only thing is everything is brand new so the bearings are all standard. There was no cutting done exept for when the thing was line bored for the new main caps. I wonder if this could play a part in it. I agree with the internal leak someone on the board said somthing about a plug behind the front cover that was missing when he had his motor rebuilt and that was causing a low reading.

 

[Mr URL]

Well, not good news but news that I know there is a
real problem. My buddy Doug hooked up his wonder calibrated mechanical gauge. It's reading the same as my VDO gauge.

Cold the oil pressure is high (75-80 psi). Once fully warmed up
it has a problem. 17 psi hot idle. At higher rpm's
it goes up to 50 psi then starts going backwards to
40-45 psi where it will flutter. The flutter matches
up to a lifter tick noise. Humm... Won't go past
40-45 psi no matter what the rpm.

The car had great oil pressure during cam break-in
period of 20 minutes 2,200-2,500 rpm of 65 psi. Idle
had 20 psi. Next day I changed oil/filter and drove
it down the interstate. Had great oil pressure of 65
psi cruising speed. Then I stepped into it for the
first time and oil pressure dropped to 40 psi. Since
then I've had this problem. Something is causing an internal leak.

I installed a new Melling HV oil pump with 70lb spring and pressure plate in original cover, 206/206 Weber cam, Ramchargers lifters, PTE Ported/Polished heads, stock style timing chain with steel gears, new stock chain tensioner, roller bearing cam button, neopreme front seal, Felpro valley pan intake gasket, Felpro pickup screen gasket (torqued to stock spec), Felpro pan gasket, and new water pump.

Any ideas on causes? My friends James and Doug think maybe a
collapsed lifter bleeding off pressure or pickup screen sucking air.

I'm ruling out the plugs behind the front cover cause I think that would cause even less pressure than I've got.

 

[lazaris]

Chad,

"Had great oil pressure of 65
psi cruising speed. Then I stepped into it for the
first time and oil pressure dropped to 40 psi. "

You said everything was fine till you stepped into it. This could indicate a spund rod bearing or cam bearing. Was the engine recently rebuilt?

 

[TurboMike]

What kind of oil pick up tube are you using?? DO NOT use anything but GM.

 

[ULYCYC]

Do you still have a stock oil cooler? If you do take off the adapter and try it with out it. The cooler my be blocked with gunk and engine material. Mine was full of timing chain plastic and causing similar problems

 

[Mr URL]

The radiator was redone by Holms radiator 700 miles ago. Stock timing chain when I took it out was perfect. Oil pickup tube was clean when I took it apart but I can double check that.

Basically what I did was strip it down to the shortblock and add performance and maintenance stuff onto it. Heads, cam, lifters, HV oil pump, timing chain, etc. Shortblock is original 57K mile stocker. Only raced a very limited amount. Was bone stock majority of it's life.

Mike, I've been thinking about that too. I kept the same one that was in it cause it was like new. Just replaced the gasket. Any way to tell a correct and incorrect pickup tube? Maybe in past history it was changed to a non-stock unit?

I have a friend that can analyse the oil. I'm thinking about sending him a sample to see if there's any bearing material or anything in it. Bottom end has been quiet.