Vehicle purchased this summer (July) - numbers matching. Had small transmission and engine oil leak - both fluids were and remain in excellent condition.
(1) Hand-cleaned entire engine and undercarriage - evaluating where leaks may be originating;
(2) Re-torqued all accessible bolts - transmission, valve covers, oil pan, etc. Nearly none of the bolts were torqued to value - all were very, very loose - no biggie - it's an old car & I have no idea of previous maintenance - vehicle still has a minor engine oil leak but the transmission leak as stopped;
(3) Vehicle (both transmission and engine) runs strong (for a 41 year transmission/engine). Some minor hesitations I believe are carburetor related (RC Quad 7041251) - I know it's a carburetor which should be sitting on a 455cid - no biggie - not part of the leak. I'm going to rebuild the carburetor anyways;
(4) I was concerned and I am not certain how concerned I should be regarding the engine oil leak. The engine leaks oil after having been driven; yet, the amount of oil (as measured via the dip-stick is nearly negligible). The amount of oil which pools on the floor is maybe one ounce or two ounces (one to two teaspoons) in a couple small places. The places where it 'appears' to leak I am having an issue in determining. The oil leak 'appears' to be originating from the RH side of the engine rearward (behind) cylinder number eight. All of the oil pan bolts were very, very loose. I am unable to tighten and re-torque several of the oil pan bolts as the frame cross-member is in the way;
(5) I cannot readily see (to the best of my ability) any oil running down from the valve covers or from the intake manifold;
(6) I performed a compression test today to determine the general overall health of the cylinders - no issues w/ compression.

QUESTIONS:
(1) The oil pan bolts I cannot re-tighten/re-torque is the most likely reason?
(2) The engine rear main seal could be leaking?
(3) It might still be an intake manifold leak?
(4) Don't worry about it when it's this small of a leak - just keep an eye on it moving forward - forty-one year old engines have earned the right to leak some oil?

Thanks!

 

Get a bottle of UV die and put in the oil. Run it for a while and use a UV light and see if you can find the leak. That being said........ I would bet on the rear main seal. The 307 in my Wife's Riviera started leaking a little when the car was about a year old. Got worse over the years until I rebuilt the engine last year and put in a rubber 2 piece seal. Has not leaked a drop since

 

Ah...good suggestion on the UV die. I own a UV light & I'll give this a go. Thanks.

 

Remove the bell housing under the torque convertor, look up inside for the leak. I just had my 1975 350 engine rebuilt, it had a leaking rear seal before the rebuild. Put a new neoprene seal in. When I was breaking in the rebuilt engine, I was having considerable oil leaks. I thought it was the new seal because it was leaking up around the bell housing area. Not from the tranny, Took back to the rebuilders for inspection on the hoist, removed the bell housing for inspection. No leaks from the rear seal. The rear oil pan bolts had loosened off some , had to remove the starter to tighten some of them, valve covers retorqued, and oil filter housing small leak. No oil drips yet, only will show when the car was running and then parked. Check around the distributor seal as well.
Good luck on your investigation. By the way, I lost 2 quarts of oil in 3 tanks of gas.

Jeff

 

(4) Don't worry about it when it's this small of a leak - just keep an eye on it moving forward - forty-one year old engines have earned the right to leak some oil?

I just put a piece of cardboard under the car where i park if the small amount of leak changes it easy to see

 

Interesting. When I purchased the vehicle, I did not go over every inch with a fine-toothed comb. I was satisfied with what I was purchasing based upon general running condition, visual inspections, etc., etc. The first time I put it on jacks (for various undercarriage/engine/transmission visualizations), I noticed the torque converter cover was not bolted on the LH side where (what appeared) someone may have broken the torque converter cover (the LH corner of the cover was not there). Yet, upon removing the cover I could tell someone had installed a new torque converter. The engine oil does appear to run down the front of the torque converter cover - I think - I am not 100% certain. I have evaluated the oil and it's not ATF - it's engine oil. Yeah, I'm not losing that amount of oil. I've lost maybe 10-12 teaspoons in four tanks of gas.

 

That's what I'm currently doing to get a handle on this, and how I know how much is leaking. I'll give the UV dye a shot since that makes good sense and continue to monitor. Thanks.

 

That looks in good in the compression department. That sounds very minor, it could be seepage from all of the places mentioned, the dye will pinpoint it.

 

You have a great point - it could be minor seepage from all of the places. Looking forward to the dye test. Thanks.

 

Did you check the oil filter and adapter at the rear passenger side of the block? And yes, it would not be uncommon for the rear main to be leaking, but usually that manifests itself as a leak directly out the bottom drain hole on the torque converter cover.

 

I checked around the oil filter & adapter a couple times & appears fine after initial cleaning. The oil is coming to lowest point when it drips - the center of the TC cover. I've been cleaning the areas (oil pan, rear of engine, all metal) whenever it's on jacks - more often recently. Since it's difficult to determine if the leak is any number of places previously mentioned, I'll pay more attention to the bell housing/TC area - removing the TC cover, wiping everything down and following oil in this location. Then perform a UV dye test. If the leak originates inside the bell housing, it would almost certainly suggest the rear main seal is suspect - yes?

 

Let's just say that a leak from the rear main certainly wouldn't be a surprise. That's when you invest in a drip pan for the garage.

 

I had to get one for the first time in my life for my Wife's Riviera about 10 years ago. It is still under the car but perfectly dry now

 

I have several of different sizes I use when working under vehicles or my Indian motorcycle while on the lift. One of them may have found a more permanent location is what you & Joe are saying.
They didn't have any UV dye at my local Carquest. I live in a small town (3700 residents). They had several different fluorescent dyes - each for a different application i.e. PS fluid, AC coolant, radiator coolant & engine oil. They had one of each. I bought the only engine oil fluorescent dye they had on the shelf, they said they sell one about every 6 months. I'm not sure of the shelf-life of a fluorescent dye - I asked them to order me two more - they arrived this morning & I'm heading out to pick them up. If the fluorescent dye doesn't visualize well, I'll head over the bridge to the BIG TOWN where I believe AUTOZONE has some UV dye in stock.

 

Thanks for the suggestion.

 

Performed the UV dye test. I can visualize a very minor amount of seepage from the rear main seal - it's more like condensation (of course it's not condensation) kind of adhering to the metal as it oozes out the rear main seal. That is going to be addressed (for the time being) with eight ounces of BlueDevil REAR MAIN SEALER.
I have a minor leak - more than simple seepage (IMO), emanating from the rear of the intake manifold - more pronounced on the passenger side than the driver side. In my mind I can visualize those corners where the intake manifold gasket meets the cylinder head. It doesn't appear the intake manifold gasket has ever been replaced - both the front & rear of the gasket demonstrate what I'd consider normal amounts of engine oil seeping & accumulating along the perimeter of the intake manifold gasket - the same might be said of the valve cover gaskets.
I'll R&R the gaskets & remove (plug) that bloody DVCS switch from the intake manifold while I'm noodling about in the (engine oil) valley of darkness.
I've changed out intake manifold gaskets several times in my youth, & I never found it difficult - mostly time-consuming. This is my 1st 350 CID engine but it looks like your typical 'engine'. I'll need to research & gather the proper gaskets.

Thanks everyone for reading and/or contributing to this post.
I changed out the AT gasket on my 2003 Ford F250 6L diesel a couple years ago while changing the AT filter - I can tell you aftermarket is sometimes pure & simple - crap. The bloody gasket which came with the so-called 'kit' was garbage - which had me heading to Ford for an AT gasket which was of much better quality and fit.

The only serious thing (I'll research) which I can't directly recall is the part about removing the distributor while removing the intake manifold only. It's a simple task to find TDC by turning the crank and watching the number one intake valve go from the open to the closed position (to align the distributor shaft into the oil pump shaft), but as I recall, I should be OK with removing the distributor and simply re-installing the distributor into it's same orientation?

I know how to read & comprehend (despite having grown up in the 60's), so I'll address the CSM & keep any posts to a minimum.

None-the-less, if anyone has suggestions on the best vendors/manufacturers for Olds 350CID intake manifold & valve cover gaskets by all means I'll review any suggestions. The same applies to the distributor orientation.

 

Additionally, if anyone knows of a good place to get updated - what GRADE 5(?) - intake manifold bolts and valve cover bolts, that would be sweet. Thanks.

 

The only serious thing (I'll research) which I can't directly recall is the part about removing the distributor while removing the intake manifold only. On an oldsmobile, while it may add clearence, it's not necessary to remove the distributor.

 

Oh well, heck - I'd probably have figured that one out but thank you Dave26 - sweet.

 

[QUOTE=Dave26;1139352]I guess I should examine the distributor seal while the manifold is off and determine if that seal needs replaced, as well. Thanks again.

 

UPDATE: Intake manifold scientergic renoberation (Homer Symptom).
(1) Will pull the manifold this evening;
(2) Probably found a modification/repair to a cracked intake manifold (between cylinders #3 & #5);
(3) Appears someone probably sought to contain the crack & arrest possible elongation of the crack?;
(4) Appears someone took a 20lb steel/iron sledge hammer to the top of the head between cylinders #3 & #5. Who knows why, I find stuff & move on.

Pictures tell a thousand stories. I found this issue while cleaning the intake manifold prior to removal to reduce contaminants from entering the oil valley during removal.
I have several questions to ask (in a follow-up post) forum members regarding this issue.

 

My leak (the issue I'm resolving & reason for replacing intake manifold/valve cover gaskets) has always been very minor - yet, it's there.
QUESTIONS:
(1) I believe my 'feature' is above the intake manifold cross-over?
(2) Based upon location, size, etc., I'm leaning towards installing this same intake manifold back onto engine. Thoughts?
(3) I have solid compression, I have solid water cooling, I have solid transmission functioning (the AT modulator works like a charm - therefore, I suspect [but I haven't validated via a vacuum gauge test - yet]) I have good vacuum. While examining/cleaning the head, are there any 'areas' on these stock iron 350 intake manifolds I should pay more careful attention while examining?
(4) I can see the metal intake manifold gasket as it borders the manifold - I'm assuming it's the metal turkey-type gasket (not sure if they made one-piece or two-piece for these manifolds). This is entirely a 'guess' at this point - this 'issue' might very well be addressed via replacement of a new metal turkey-type gasket with the appropriate type & amount of gasket sealer?
Thanks!

EDIT: I should mention I don't believe this is the 'source' of my leak - I believe the source is most likely at the rear of the of the intake manifold gasket.

 

Intake manifold, aside from 47 years of significant coking, is intact & appears solid. The cross-over member has minor coking (evidently the valley gasket has done a good job).
The metal valley gasket is coked with 47 years of both wet (rear) & dried (front) oil (rotisserie drippings of 350-400 birds). The front of the valley gasket has significant amounts of dried coke. There is significant dried coking everywhere - in particular some large 'clumps'. One very large clump (3"x3") just below the apparent crack/cut-away (pictured above). The rail gaskets are the rubber type & 'appear' original. I'd say for sure the turkey valley gasket is original.Lots of cleaning to address next.

 

Clean the intake well and paint it what ever colour you like, may as well make it purdy, extra high temp silver or black would last the longest. R+R of an iron intake sucks due to the weight. Use RTV around both sides of the 4 corner water ports. I also use a tall bead, multiple layer, not wide bead of RTV in place of the rubber end rails. Ultra Black or The Right Stuff works the best.

 

307/403- I'm leaning towards your suggestion - clean it up well & reuse. Understand about the rubber end-rails, RTV & Right Stuff. I have found a used OEM 1971 350 intake manifold - so, currently deciding which way to go. Thanks for your feedback.

 

Condition of the valley of darkness after pulling the iron manifold.

 

Not bad for nearly 50 years old.

 

I've pulled a couple heads from various engines (455, 396, 307, 327) in my youth - primarily because we blew them up - I've never seen the valley of a 47 yr old vehicle. I didn't know what to expect. I appreciate your comment. A very thorough cleaning, new gaskets, a couple oil changes w/ MMO @ 50 miles & 100 miles after putting it back together before a final oil change & I think it might see another 100K.

 

Page 6B-8, Fig. 6B-111 - Intake Manifold Torque Sequence of my 1971 Oldsmobile CSM demonstrates a peculiar Torque Sequence, IMO. I am replacing the OE intake manifold gasket w/ a Victor Reinz MS15925 Intake Manifold Gasket. The recommended torque sequence is from the Front outside perimeter to the Rear outside perimeter moving inward. This is contrary to most intake manifold torque sequences I have encountered and reviewed elsewhere; where, most intake manifold torque sequences are performed from the inside/center towards the outside perimeter.
I generally always follow OE specifications, but this one has me baffled. Does anyone have any thoughts regarding this recommended torque sequence?
NOTE: I realize the gasket is upside-down, I couldn't find a picture of the gasket right-side up; so, I simply flipped it horizontally for the purposes of discussion only. The recommended torque sequence is the one from the CSM I have illustrated.

 

Whats to discuss ? If you had become accustomed to Oldsmobiles, would you then consider the "others" torqueing sequences baffling ? I would follow the Oldsmobile CSM.
.......Just my two cents worth

 

I used a small parts blaster from Harbor Freight with the attached reservoir, and walnut shells for the medium. It takes off almost anything, does not damage metal, and the residue washes off with almost anything.

For those who are installing a cast iron or aluminum manifold, I developed a tool that makes it easy. I installed a 35 lb. manifold on a Chevy BB in 10 minutes with the engine in the car (91 Olds Custom Cruiser transplant) by myself. I did not have to worry about aligning it, because I had one hand free, and could position it with the other while hovering it over the valley. I could even put a few bolts in their respective holes before finally placing the manifold. I am 70, about 5'6", both of my rotator cuffs are damaged, and I have limited motion with my right arm. It took me longer to put the gaskets in place, and put silicone on the end rails, then the actual placement of the manifold. I made a few extra, and am willing to sell them.

 

I am accustomed to Oldsmobiles. What I find baffling is your comment.

 

Hi Fred- I've cleaned under the manifold in the (oil) valley & the rocker arms bay under the valve covers - basically plugged all the holes, vacuumed liberally, wire-brushed w/ xylene, a couple dozen shop rags of wiping, vacuumed, wire-brushed, wiping, etc. Turned out very good.
When I place the intake manifold back on with the seals prepared to receive the manifold, I cut a couple pieces of 5/16″ A2 Round Bar about 5" in length (just long enough to rise above the intake manifold when seated) - they kind of act like dowel rods in guiding the manifold into place. I insert these two pieces (on one side - either LH or RH) into a couple of the intake manifold bolt holes, then install the manifold using the rods as guides. After dropping the manifold into place, I remove the dowel rods & screw in the bolts.

Just my luck, I get prepared to pressure wash the intake manifold, drag out the 3000 psi pressure washer & it won't start - now, I'm in pressure washer rebuild mode. LOL

 

Oil pan removed, thoroughly cleaned & painted, new oil pump & driveshaft. The end seals were very hard & brittle. Timing chain looks very good - actually, crank looks pretty decent. I took a 2', 1/2" drive breaker bar to the rear main seal bracket bolts & they wouldn't budge. I considered getting my impact hammer drill out which may have loosened them up. The seepage is so small, I've elected to find a permanent home for one of my drip pans. I'm not keen to breaking off bolts laying under the car on a floor creeper drilling out bolts struggling with an easy-out. I have to pick my own fights - I lost this one.

 

THREAD UPDATE: More information regarding the R&R of my oil pan gasket is located here >350 Engine Lift Question.

(1) My suspicion the rear main seal was leaking is proving to be incorrect - after 100 miles of driving, I can find no oil leaks whatsoever - no where - none, anywhere on the engine or trans.
(2) I did a poor job on my initial R&R of the oil pan gasket using a cork gasket (which blew out in several locations). I used the neoprene/metal gasket on my 2nd attempt & it is, IMO, a much better gasket, see 350 Engine Lift Question for part number.
(3) When removing the distributor, there was no rubber O-Ring distributor mounting gasket installed. Much of the oil leakage was emanating from this area of the engine. While performing the R&R of the intake manifold gasket, I disassembled & rebuilt the distributor (which certainly required a thorough cleaning with some new minor parts & a new primary wire I created - and, or course a new rubber O-Ring mounting gasket).
(4) R&R of intake manifold - no leaks.
(5) R&R of valve cover gaskets - no leaks.
(6) Dwell angle of distributor was incorrect. Reset dwell angle to 33* @ 1100 RPM per CSM.
(7) Timing was incorrect - was set @ ~16*-20* BTDC. Adjusted to 12* BTDC per CSM.
(8) R&R of all vacuum lines & R&R with new oil pump and drive shaft. R&R of fuel pump>carburetor line.

Have carburetor rebuild kit. Next on my agenda.

At the end of the day - I no longer have oil leaks - and, what I thought (initially) might be a rear main oil leak has not presented itself (thus far).