The most common but most unrecognized oil leak - ZR-1 Net Registry Forums

Dynomite · 08-20-2016

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

mike100 · 08-23-2016

Now you tell me, lol. I replaced my oil pan gasket a few weeks ago. It was still wet on the front so I jacked up the engine, removed the middle wheel well plactic cover by the shock and got at it with a 1/4 drive swivel and a couple of feet of extensions. problem solved.

now if I could just figure out if the sub-block girdle seal wetness can be fixed.

Dynomite · 08-24-2016

Well.......you got an oil change out of that deal........I wonder how many New Oil Pan Gaskets have been installed only to continue with the oil leak

But the best trick is the use of two 6mm x 16mm Flange bolts with 10mm Heads replacing the two bolts with 8mm Heads. Much easier using a 10mm Flex Head ratchet

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5ABI VT · 08-24-2016

excellent will double check this thanks !

Dynomite · 08-25-2016

Quote:

Originally Posted by 5ABI VT

excellent will double check this thanks !

I actually removed both 18mm Nuts from the Motor Mount Studs (the Passenger Side Strut was removed) and jacked the engine up a couple inches to help reach the top 6mm x 16mm original Oil Pressure Regulator Plate Bolt. Once loosened from below, I then reached down from the front of the engine and was able to unscrew that bolt by hand. I then inserted and screwed in the 6mm x 16mm Flange bolt finger tight (with Red Loctite) and finished tightening that top 6mm Bolt from underneath as shown. It was Much easier using a 10mm box wrench to tighten the Flange Bolt. Absolutely NO oil underneath the engine anywhere to be seen

If you have oil on the front passenger side of the oil pan where the 8mm bolts are located or that first 10mm Oil Pan bolt but the rest of the oil pan is relatively clean........you prolly have a loose Oil Pressure Regulator Valve Cover Bolt.

5ABI VT · 10-30-2016

Going to bump this thread .. still need to get to this but I was wondering .. can the egr system be removed ? Doesn't appear to be aluminum so am guessing it is not a part of the block. I'm wondering if removing the egr would give much more room to tighten the bolts.

Dynomite · 10-30-2016

Quote:

Originally Posted by 5ABI VT

Going to bump this thread .. still need to get to this but I was wondering .. can the egr system be removed ? Doesn't appear to be aluminum so am guessing it is not a part of the block. I'm wondering if removing the egr would give much more room to tighten the bolts.

I am thinking removing the EGR components would be a nightmare

For the 95'......just removing that Engine Mount Strut is very easy and gives you plenty of room.
You do need to do some reaching to get the front 8mm bolt on that Oil Pressure Regulator Valve however.

Billy Mild · 10-30-2016

How hard is this to get to with engine in place? Does the fender liner need to come out?

Dynomite · 10-30-2016

Quote:

Originally Posted by Billy Mild

How hard is this to get to with engine in place? Does the fender liner need to come out?

See Item #2 in the first post of this thread

5ABI VT · 10-30-2016

The pictures are excellent and accurate if a little confusing to figure out what you are looking at. I have a 94, and it is not visible because it is underneath the egr. I am trying to figure out how the egr bracket is removed, that would give line of sight otherwise the egr valve and its bracket/base that it bolts to is directly above.

I'm removing the egr valve now. Looks very easy. Looks like 2 10mm bolts. What it's bolted to however I'm going to try and figure out. I am taking pics and will post if anything is helpful

08-20-2016	#1
Dynomite Join Date: Aug 2009 Location: South Dakota/California Posts: 3,789	The most common but most unrecognized oil leak 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 __________________ Left Clickable links -Solutions- LT5 Modifications/Rebuild Tricks Low Mileage ZR-1 Restoration 1990 Corvette (L98) Modifications LT5 Eliminated Systems LT5 Added Systems LT5/ZR-1 Fluids 1995 LT5 SPECIFIC TOP END REBUILD TRICKS Last edited by Dynomite; 02-07-2019 at 12:08 PM.

08-24-2016	#4
5ABI VT Join Date: Jun 2013 Location: Toronto Posts: 782	Re: The most common but most unrecognized oil leak excellent will double check this thanks !

10-30-2016	#6
5ABI VT Join Date: Jun 2013 Location: Toronto Posts: 782	Re: The most common but most unrecognized oil leak Going to bump this thread .. still need to get to this but I was wondering .. can the egr system be removed ? Doesn't appear to be aluminum so am guessing it is not a part of the block. I'm wondering if removing the egr would give much more room to tighten the bolts.

10-30-2016	#8
Billy Mild Join Date: Aug 2014 Location: Kansas City, MO Posts: 838	Re: The most common but most unrecognized oil leak How hard is this to get to with engine in place? Does the fender liner need to come out? __________________ Looking for a ZR-1 1985 Yamaha RZ350-NOT STOCK 1971 Yamaha AT1-Middle of a restoration

10-30-2016	#10
5ABI VT Join Date: Jun 2013 Location: Toronto Posts: 782	Re: The most common but most unrecognized oil leak The pictures are excellent and accurate if a little confusing to figure out what you are looking at. I have a 94, and it is not visible because it is underneath the egr. I am trying to figure out how the egr bracket is removed, that would give line of sight otherwise the egr valve and its bracket/base that it bolts to is directly above. I'm removing the egr valve now. Looks very easy. Looks like 2 10mm bolts. What it's bolted to however I'm going to try and figure out. I am taking pics and will post if anything is helpful

08-23-2016	#2
mike100 Join Date: Feb 2011 Location: San Marcos CA Posts: 1,802	Re: The most common but most unrecognized oil leak Now you tell me, lol. I replaced my oil pan gasket a few weeks ago. It was still wet on the front so I jacked up the engine, removed the middle wheel well plactic cover by the shock and got at it with a 1/4 drive swivel and a couple of feet of extensions. problem solved. now if I could just figure out if the sub-block girdle seal wetness can be fixed.