The most common but most unrecognized oil leak

[Dynomite]

The most common oil leak is an oil pan gasket leak which is often misdiagnosed. What is really leaking is the Oil Pressure Regulating Valve Cover Plate. It will appear as a drip of oil and oily surface on the right front of the oil pan. Often the tendency is to tighten the front oil pan bolts with no success on stopping the oil leak. The Oil Pressure Regulating Valve Cover leak can also be misdiagnosed as a Front Crankshaft Seal leak. The symptoms are a film of oil progressing rearward on bottom of oil pan or an actual drip of oil on the right front oil pan bolts.

1. Oil Pressure Regulating Valve Cover Plate (1990-1991 ZR-1).

The Oil Presure Regulating Valve is located on passenger side front of engine just above the oil pan. The two 6 mm bolts that hold the OPRV cover plate (and gasket) to the Engine sometimes come loose.



There is an OPRV Cover plate gasket but I just removed and cleaned the two 6 mm bolts (8 mm heads) one at a time and applied Blue Loctite (You could use Red Loctite as you like). I used Blue Loctite because I figured it was a temporary fix but appears to be a permanent fix. I reached in from the top front of the engine to get access to the two 6 mm bolts with an 8 mm hex flex head ratchet wrench. An easier method of access to the Oil Pressure Regulating Valve Cover Plate is from the bottom as described in item #2 below.

Since such a tight area to work in with engine in car I removed each 6 mm bolt one at a time so I did not drop the cover plate or gasket. So...no permatex on that gasket but both 6 mm bolts cleaned and Blue Loctite applied.

Since the bolts and plate were so loose I figured correctly just tightening the 6 mm bolts with Blue Loctite would solve the oil leak and loose bolt problem (The gasket was stuck to the engine block and not the cover plate). I tightened the bolts by feel as I could not get torque wrench even close to that area unless engine is out of car. No more oil leaks in that area at all.

The BEST fix, however, is to replace those two 6mm x 16mm bolts having 8mm heads with two 6mm x 16mm bolts with 10mm heads as described in item #3 below.

Torque for 6 mm bolts is about 89 in-lbs but in that area with no oil pressure to contend with less bolt torque with Blue Loctite or maybe Red Loctite is just fine

2. Oil Pressure Regulating Valve Cover Plate (1995 ZR-1).

On the 1995 ZR-1 the Oil Pressure Valve Cover Plate is impossible to get to from above because of the EGR. But....one can get to that Cover Plate from below by removing the Passenger side strut that the Passenger Side Motor Mount is bolted to (no pressure on that strut from motor mount). Remove two 15mm bolts toward front and two 13mm bolts on frame rail passenger side. Remove 18mm Nut from Motor Mount Stud and drop the strut. The Oil Pressure Valve Cover Plate can be easily seen toward front where Strut was positioned. The bottom 6mm bolt is easy to unscrew and the top 6mm bolt required a vice grips gripping an 8mm open end to tighten. Both 6mm Bolts with 8mm Heads were replaced with 6mm Bolts with 10mm Heads.

3. The Trick to STOP oil leaks from the Oil Pressure Control Valve Cover plate.

I replace both top and bottom 6mm bolts with 6mm x 16mm Flange Bolts that have a 10mm head for a 10mm Box or ratchet Box wrench. It is a lot easier to tighten a 10mm bolt than an 8mm bolt which sometimes strips in the small 8mm box wrench. I used Red Loctite on the 6mm x 16mm Flange Bolts. No need to remove the Oil Pressure Valve Cover Plate or associated gasket.



Two 6mm x 16mm Flange Bolts installed in Oil Pressure Regulator Valve Cover (10mm Heads)
replacing original 6mm x 16mm (8mm Heads) Bolts.
Top 6mm Bolt shown before tightening with 10mm Box Wrench



See Potential Oil Leaks and the OPRV Cover Plate