1987C4

OK, this might be fun to deal with...

The other day I noticed a wonderful burning oil smell from my 53,000 mile 1987 Vette. Not a good thing. I also noticed oil on the ground beneath the car, also not a good thing. My immediate thought was that the rear main seal had gone out, so up in the air she went.

I loosened the torque converter shield and there is no leakage from the rear main. Everything in there is high and dry... this is a good thing. The oil is dripping onto the top of the precat and dripping out of the lower louvers on the precat shield...hence the burning smell... not too great from a fire standpoint!

I determined that the leak is coming from the driver's side rear of the engine, everything else is dry. Looking from above I can't see anything that looks like a leak. There is a microscopic amount of dampness around the oil pressure sending unit where it threads into the engine, but nothing to write home about. It is a real challenge to see anything in the back of this engine between all the wiring harness stuff and the proximity of the firewall!

Underneath, it's a different story. The oil is leaking down the wiring bundle (black wire loom around it) that the O2 sensor wiring comes out of. Since oil does not defy gravity, I looked for the highest indication of dampness. The oil filter and oil cooler housing are wet and the block above it. I can just barely see the edge of the valve cover and it appears to be moist but no drips hanging off of the small section that I can see, just moisture.

This is the first center bolt valve cover engine I've ever owned. I had been told that with this newer design that valve cover gasket leaks were essentially a thing of the past. I tried to gently tighten the hold down bolts, but it didn't help. Was I lied to about the valve cover gasket thing? I am thinking that this may just be the solution, but I can't be sure. The rear port of the exhaust manifold is also damp. This leads me to belive that the leak has to be above that and seems to point to the valve cover.

Has anyone else ever chased one of these leaks before and is there anything else in the rear of the engine that could leak beside the oil pressure sending unit?

I am praying that there is nothing wrong with the head gaskets, but since there is moisture at the exhaust manifold area, that it likely is the valve covers. Anyone else with similar experiences or suggestions? The valve covers appear to be a bit of a job, but not impossible. Thanks for any insights you can share.

Brad

Dads90

The rear seal of the intake manifold gasket could be bad. It leaks down around sparkplug #7. Its a time consuming fix but can be done on your own, stay organized and tag all the bolts as they come off. If its the valve cover gasket replace with Felpro gaskets, they are a rubber material and seal good. Shine a flashlight behind the distributor and above the driver side valve cover and look for shiny oil, I bet thats where its coming from.

staugur

There are two senders back there.The larger is the pressure switch,the smaller the oil warning light.The latter blew out on mine and I almost lost all the oil. Could also be where the intake fits to the block which again is hard to see.

CFI-EFI

Since you have ruled out the oil pressure sending unit and switch, there are really only two possibilities. The rear seal of the intake manifold and the valve cover gasket(s). The manifold gasket will leak more to the rear, down the bell housing area of the block than anywhere else. The valve cover gaskets aren't likely to leak on the higher side. With the exhaust port of the exhaust manifold and the oil filter wet, I suspect the valve cover gasket. With the cat wet, I suspect the intake manifold, also. See if you can reach your fingers back and down the rear of the intake manifold, at the china wall seal to feel for oil. If the manifold needs to be resealed, it would be foolish not to replace suspected valve cover gaskets at the same time, for little additional labor. The good news is that there is no pressurized oil that flows from the block to or from the heads. The oil is not coming from a blown head gasket.

RACE ON!!!

1987C4

Thanks guys! I really appreciate the insights. Guess what I'm doing on my next day off? Kinda obvious huh? I never thought of the rear of the intake manifold. I'll check that as well. I really like the car, but right now it appears that it needs to be house broken with all the oil on the garage floor! Again, thanks for the tips and I'll post back to let you know what I find.

Brad

Sean Brian Kirby

Due to a rear main leak - and a previous hydraulic clutch problem - my clutch ate itself in the beginning of July. Our having neither a lift nor tranny jack, we had our local shop do the job.

Went and got her back last week. They had the car nearly a week-and-a-half. Got her out on the road, took her to Mr. Tire for them to sort a rim leak; they couldn't help me that late in the day, and I took her home. Clutch initially felt a mite-bit chattery to me, by the way, with my reasoning I might not be accustomed to the new McLeod Street Pro.

Just as I'm about home - I sense a burning oil smell, and there's blue smoke billowing from beneath the sides of the clamshell. When I got in the drive, Dad was there, and I asked what was up with all the smoke. "I smell oil," he said.

Pop the hood... Dad sees a dampness in the grass below the left-front cat, near the oil filter. Called the shop, and was told to bring it by, where they would take a look in the morning.

Next morning, they call, say it's not their main bearing seal work, and not coming from the filter. He starts rattling off diagnostic costs, if I want them to check, and I tell him I'll just come get the car.

Dad seems to think it's not the sending unit near the distributor. It's really oily at the top of the filter housing, where there's a pipe or two. Where is this warning light sending unit mentioned here? She loses about a quart of oil in the short (about 2 mile) trip to the shop. So, this may be our culprit, given the above description. Oil leak occurred within 3-4 miles of getting her back. Any help will be greatly appreciated.

Sean Brian Kirby

Playing around with lit video - it looks like we've found what looks like a sending unit atop the oil filter housing. It itself is dry, while its pretty wet with oil beneath. Is this the warning light sending unit? Looks like it's something like a pale green plastic.

s carter

2 part question, do you have a engine oil cooler? if so get under car grab a hold of the oil cooler adapter see if it is loose (rotates back and forth) if yes remove the oil filter you will see a large bolt with a hole in it (your oil filter screws onto it) slug it up, but don't over tighten. if it needs a new seal I have used a oil filter gasket in a pinch who knows probably the right part any way, its still working.

if you don't have the cooler and the oil seems to be streaming down from around the and above the oil filter you may have a bad gasket on your oil filter adapter, literally a $4.00 gasket at a dealership when Bought one a few years back. got it at dealership because with part in hand the guy in parts store said it didn't exist.

856SPEED

This thread is back ............from the dead......

mlm0

Put some dye in the oil. Check it in dark with black light. You can get dye at any parts store along with light

Sean Brian Kirby

Got the car up on a lift. It turned out not to be the oil filter, its adapter, or anything like that. Seems it is the oil pressure sensor at the back of the manifold, sending frightening amounts of oil streaming down the drivers-side back of the block and all down the side. it's like a quart every two miles kind of leak.

When Mike, the mechanic who was kind-enough to help me find the leak, heard this leak occurred within three miles of getting the car back after a clutch job, he said there was absolutely no doubt that shop was responsible. My Dad, who is a sharp mechanic and has had a years-long relationship with the place, went down and talked with them; they said they would not take responsibility for it. Dad figures they're using the car's age as an excuse. "Just a coincidence." My backside. Used to be a reputable shop that did good work, too.

So, Dad and I are left to fix the problem. Thrills. If we're lucky - it'll just be the sending unit itself, and not any of the related plumbing. What are the chances...

Thanks for your help!

WW7

They probably let the rear of the motor fall down when doing the clutch...If the motor isn't supported when the trans is removed it can break the oil sender and also the distributor cap if the distributor isn't removed..If this is the case, go back and show them the mangled oil sender and tell them it is definitely their fault...Hopefully the sender is just cracked and the oil plumbing tubes aren't broken... ...Good Luck...WW

shootnstarz

Lucas Oil's Stop Leak

Rick