Oil pressure sensing unit replacement
 

I have a 95 Pontiac Comp T/A, and a 1995 Pontiac Formula Firebird (I'm pulling the engine and putting it into a rock crawler project)

Back to the question at hand...I've preformed a K-member motor drop, new seals all the way thru the motor, Lt4 hot cam, new lifters, rockers, lashed valves (4 times, long story there), long tube headers, Borla exhaust, EGR and air delete, etc.

I've been completely through the top end, and checked all seals and RTV thoroughly. I had an oil leak since the top-end was completed, and I have removed valve covers a couple of times, and the intake twice...the only constant is the oil leak somewhere high on the back end of the motor.

Is there anything else that could possibly be leaking oil up high, behind the intake, near the steam tube?

Second question...what is a reasonable way to replace said oil pressure sensing unit? Pull motor, pull intake again, or is there a trick to such a tricky spot on the car?

Re: Oil pressure sensing unit replacement
 

if the heads were milled it is possible the intake manifold is no longer sitting flush against the heads & block. With that said I have had my heads milled/ported and intake port matched and bone dry on the seal. But I have seen threads where the intake no longer set right. IIRC the holes on the intake manifold were oblonged some to get it to sit flush.

rear intake leaks can be stubborn. Besides wiping all surfaces with acetone, using a 1/4" bead of RTV (I use Permatex Black "ultra") one additional step I have seen is dimpling the rear china wall on the engine block and corresponding intake surface then applying the RTV. Let RTV sit for about 10 min and then place intake manifold "dead nuts" straight down. if you wind up missing the alignment and sliding it back and forth you will almost be guaranteed a leak. Also let the RTV cure overnight before starting motor

the oil sensor unit and fitting on a F-body is buried. feel by hand and work blind with a wrench.

I had a rear leak I thought was RMS..no. Finally did the oil die thing using a black light and found the leak was the gasket between block and RMS adapter. If you do this for your rear leak a small mirror and blacklight may reveal the actual source

Re: Oil pressure sensing unit replacement
 

Shoebox's photos of stock 1995 setup - two elbows increases the number of potential leaks. Also easy to hit the sensor against the cowl/firewall installing the engine if you aren't careful.

http://shbox.com/1/oil_pressure_sensor.jpg

http://shbox.com/1/op_sensor.jpg

Re: Oil pressure sensing unit replacement
 

If needed, replacing the oil pressure sensor is actually easy. Noting it's position in the picture above, use an oil pressure sensor socket, an extension and a ratchet. Point the socket from the brake booster in the direction of the sensor along and parallel to the firewall. Once you engage and break the sensor loose, you can reach back and remove it by hand. Reverse to install.

What I did to help isolate what turned out to be a leak at the rear of the manifold, was to take a lot of pictures with my digital camera stuck back in there. It showed me the leak was at the manifold gasket and not the pressure sensor.

Re: Oil pressure sensing unit replacement
 

I put a gopro on a stick around the back of the motor to see what's leaking...the back of the intake looks fine, and a slow drip from the oil pressure sensing unit...

Thanks for the advice on replacement!