Author Topic: Persistant Oil leak 500 motor. How do I find the source? - Update  (Read 946 times)

Offline chrisntam

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I have had an oil leak (drops) at the front of the engine ever since it was rebuilt.   Oil is dripping onto the front cross member that is under the front of the engine.  I thought it was the oil pump gasket.  After changing that gasket, no difference.

I can see oil dripping off rubber titty that is pulled through the oil pan.

I now think its the front seal of the oil pan that seals against the front cover (timing cover?) of the engine.  Clearly, I'm not very good at diagnosis or else I wouldn't have monkeyed with the oil pump.

Any recommendations on confirming the source of the leak before I start pulling parts off needlessly?

At least my front cross member is well lubed and won't rust.   >:(

« Last Edit: June 11, 2017, 04:10:51 PM by chrisntam »
1970 Deville Convertible  MTS 507
Dallas, Texas

Offline Jeff Rose CLC #28373

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  • Name: Jeff Rose
Re: Persistant Oil leak 500 motor. How do I find the source?
« Reply #1 on: March 19, 2016, 10:44:35 PM »
Well, I am no expert but I have a couple of ideas.
First, clean the engine well. Then see how long it takes to reappear. It may be dripping from there but it may start somewhere else and just end up there. Typically, oil will not travel up or foward. If it shows up immediately then that is probably your source, but if it takes a while then it starts somewhere else and just migrates there. 
If that is where it is, I would pull on those rubber  a bit. Maybe one of them is just not seated well.
Good luck.
Jeff
Jeff
CLC #28373
1970 Coupe DeVille
1955 Series 62

Offline Scot Minesinger

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Re: Persistant Oil leak 500 motor. How do I find the source?
« Reply #2 on: March 20, 2016, 07:30:11 AM »
An oil leak in that location means it is likely emanating from the front cover.  There are three places on the front cover that it can leak, seal at oil pan, front crank seal, and between block and cover.  The most difficult seal to make is the pan to cover seal, and so that would be my first guess.

As a side issue, there is a plug that takes an Allen wrench right above the oil pump and below alternator that is used if you want to add an oil pressure gauge.  Make sure that is installed tight.  It sure would be nice if you just had to tighten that up and problem solved.  Also presuming that it is not at the fuel pump because you checked that and it is leaking from other side.

If the plug above oil pump is not it, then after oil has leaked a bit, remove the belts, fan and drive pulley.  You should be able to see if it is leaking at the front crank seal.  That would be almost the highest point that oil could leak.  Then you can check the pan to front cover seal, which is made by that rubber seal that has the rubber spikes sticking through pan.

Did MTS rebuild your engine?  I cannot remember, but thought it was a real reputable place.

If you have to pull front cover, you will need to make a tool to pull harmonic balancer (using fine thread 9/16" threaded rod - let me know if you don't have one I can cut you a piece from mine).  The water pump can stay in place attached to front cover (do not remove the four small 1/4 bolts that use a 7/16" socket).  If you want to avoid removing oil pan, drive the two pegs into the block and catch them, then when cover is put back drive them back in.  If a peg goes into the pan, std 5/16" stock will suffice as a replacement.  This is really not a bad job, easy to do in a Saturday afternoon.

I had to do this job on a 72 Eldorado because the leak took out the front engine mount.  Since the chain and sprockets were original I replaced the set too.  Your chain should be good, but check it anyway if cover is off.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

Offline savemy67

  • Posts: 705
  • Name: Christopher Winter
Re: Persistant Oil leak 500 motor. How do I find the source?
« Reply #3 on: March 20, 2016, 08:07:45 AM »
Hello chrisntam,

Both Jeff's and Scot's posts should help improve your diagnostic skills.  As Jeff indicated, gravity will cause oil to migrate to the lowest surface in the vicinity of the leak before the oil drips off the car.  You may want to look higher up the front of the block to be sure that oil is not leaking from someplace else (valve cover, A/C compressor, ?).  As Jeff suggested, clean the entire front of the block well to hopefully improve your chances of spotting the source of the leak.

As Scot suggested, the oil passage plug should be checked for tightness.  Along these lines, all the oil pan, front cover, and valve cover fasteners should be checked for correct torque - be careful not to overtighten.

When diagnosing a problem, it helps to look at the big picture and review how the components fit together and operate, then narrow potential causes to the most likely.  Repair attempts should be started with the simplest. least-expensive, least-time-consuming repairs first, thus cleaning the front of the block, and making sure all fasteners are properly tightened.

When the engine was rebuilt, was the crank snout examined closely for wear in the area of the front seal?  Many high-mileage cranks are worn in this area, and an external sleeve is used to ensure a good seal at the front cover.  If evidence points to the front seal as the culprit, and you remove the front cover, run your fingernail over the crank snout in the area of the seal.  If you feel any wear, you may need to install a sleeve.

Hopefully your resolution will be no more complex than tightening some fasteners.  Good luck.

Respectfully submitted,
Christopher Winter
Christopher Winter
1967 Sedan DeVille hardtop

Offline Dr. John T. Welch

  • Posts: 57
Re: Persistant Oil leak 500 motor. How do I find the source?
« Reply #4 on: March 20, 2016, 01:54:00 PM »
After positively ruling out the crankshaft seal and  oil plug as the source of the leak,  you will likely find it to be at the junction of the front lip of the oil pan and the front cover.  Aftermarket seals (Fel Pro, Victor) are not always the exact size of the GM OEM original  .Even when the pan bolts are torqued repeatedly to spec, they do not seal completely.

The fix is simple. Thoroughly clean the entire oil pan front lip area and exposed adjacent front cover lip with acetone using a solvent resistant natural bristle brush and clean rags or paper shop towels. You will know that the cleaning is complete when the paint is removed and bare metal is exposed. You must expose  bare metal and the area must be completely dry when finished.  Using your finger, apply the sealer indicated below to the forward edge of the front lip of the oil pan, filling in the gap (ditch) between it and the front cover. Using a razor blade, trim off   the seal tit nearly flush with the pan  and make a new one with a dollop of  sealer that covers the hole in the pan and the seal tit stub. You must use the product below.  It is a proprietary Ford formula that contains urethane for adhesion as well as silicone  for gap fill. Follow instructions for cure times and temperatures. This stuff is expensive, but it works.  You get what you pay for. Do not try this with "Ultra Copper",  "Ultra Blue", " Right Stuff" or plain black RTV. If you are anal about judging, you can paint over the Ford product with Duplicolor formula engine paints.  I have no experience with other paint brands. 

http://www.amazon.com/Genuine-Ford-TA-31-Silicone-Sealant/dp/B000NUD02W   
John T. Welch
 CLC   24277

Offline chrisntam

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Re: Persistant Oil leak 500 motor. How do I find the source?
« Reply #5 on: March 20, 2016, 02:53:57 PM »
Yes, the engine was rebuilt by Marty at MTS.  I took my motor to him and it was built/assembled @ MTS in '14 and shipped to me. it came fully assembled including oil pump & oil pan. In the spring of 2014, I installed the motor, primed the oil pump and apparently, the pick up tube wasn't cleaned out properly; a small piece of the old timing gear got sucked in to the oil pump while I was priming it.  I Removed the pump, got the debris out, reinstalled the pump (using the old gasket (was in a hurry to get it started)) and ever since then there as been an oil leak, oil dripping off the front cross member.  I always thought the oil pump gasket was leaking.

Recently, I pulled the pump off, cleaned both surfaces very well, installed the new gasket (no sealer), packed it was petroleum jelly, put a very small amount of the jell on the surface to keep the gasket in place, got it primed and started it. No active/excessive leaks for the 15 to 20 minute run time, but a few hours after it was shut off, oil was dripping off the cross member (again).

I see a bit of a drip at the hex plug for the oil pump regulator, but the pump around where it mounts is dry.  I don't think the crank seal is leaking.  The front of the engine is fairly clean, the motor only has about 300 miles on it since it was installed.  The fuel pump is not leaking oil.  I'll look for the hex plug that Scot speaks of and check that.

A big reason I took the motor to MTS was so this wouldn't happen.  Marty was always adamant that the motor would not leak oil.

Anyone ever pulled the oil pan on one of these cars?  The FSM make is sound fairly simple, just drop the steering components out of the way and it should come off.

I'll keep looking to see where it is and let you know.  I work very slowly on it, regular work and other obligations get in the way.  I have a good mind just to take it to the local mechanic and have him do the work.  I prolly wouldn't get to it for a month or three.

Thanks for all your responses, they are appreciated.
« Last Edit: March 20, 2016, 03:06:39 PM by chrisntam »
1970 Deville Convertible  MTS 507
Dallas, Texas

Re: Persistant Oil leak 500 motor. How do I find the source?
« Reply #6 on: March 20, 2016, 04:36:02 PM »
Chris,
I would suggest the sealant at the front end of the oil pan as Dr. J describes, first.  If you still have oil showing in that area (and not a trail of oil from above) there is a good chance it is the front crank seal, and typically it is because of wear on the sealing surface of the crank hub.  What I do as a mater of course when there is any doubt about the hub's lack of a worn groove where it meets the front seal is install a crankshaft repair sleeve.

http://www.rockauto.com/en/catalog/cadillac,1973,deville,7.7l+472cid+v8,1025402,engine,crankshaft+repair+sleeve,10524

The tool that comes with the kit is useless, so I made a deeper one for the Cadillac hub.
Another "old school" trick that I learned from Marty was to move the crank hub out something like 1/32 of an inch so the groove (if it is small) is no longer at the seal.  Doesn't seem to affect the pulley alignment enough to be noticed.  You need to take it one step at a time. I don't see any need to do any major disassembly if the leak is in either of the two locations discussed here.
Incidentally I have another idea, but I would like you to PM me to discuss it.
Greg Surfas
G
Cadillac Kid-Greg Surfas
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

Offline chrisntam

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Re: Persistant Oil leak 500 motor. How do I find the source?
« Reply #7 on: March 20, 2016, 05:28:45 PM »
PM sent.
1970 Deville Convertible  MTS 507
Dallas, Texas

Offline Jeff Rose CLC #28373

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  • Name: Jeff Rose
Re: Persistant Oil leak 500 motor. How do I find the source?
« Reply #8 on: March 20, 2016, 06:18:33 PM »
Chrisntam,

I know what you mean.  I took my engine to a reputable place too, and have had issues.  Mine has not idled well (I think it may be carb so not the builder's fault) but I am looking at having to replace a lifter.  I guess it isn't that hard, but not looking forward to pulling the manifold........Let alone having to explain to my wife why, after all the $$ we spent, I still have issues.
You will get it figured out.
Good Luck,
Jeff
Jeff
CLC #28373
1970 Coupe DeVille
1955 Series 62

Offline chrisntam

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Re: Persistant Oil leak 500 motor. How do I find the source?
« Reply #9 on: March 20, 2016, 06:47:51 PM »
Oil galley plug is dry, valve covers - dry, fuel pump - nope. Timing cover seal is dry.  Only thing left is the front oil pan / timing cover seal, which is moist. Oh, and the regulator for the oil pump also has a drop of oil on it.  Hopefully I can address that without removing the pump.

Jeff, hate to hear about the lifter.  You'll need two people to lift that manifold off.   I too have carb issues, specifically the choke.  I can't drive it until it's fully warmed up.  I did get a FSM for the year of the carb ('76), so that is also on the list to work on.

I didn't have this much trouble w/ a rebuild ever, except when I was 16 and I put the pistons in upside down in my small block chevy.  They were 11 to 1s and the top of the piston hit the head once it got to the top of the stroke.   ::)
1970 Deville Convertible  MTS 507
Dallas, Texas

Offline Scot Minesinger

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Re: Persistant Oil leak 500 motor. How do I find the source?
« Reply #10 on: March 20, 2016, 07:07:42 PM »
Chrisntam,

Let's hope it is the front crank shaft oil seal and not the pan to front cover, but unfortunately it probably is the pan to front cover and Dr. Welch's advise should work great.

If you have to drop the oil pan as I had done on my 1970 Cadillac, you will have to remove the exhaust Y pipe, starter, center link and flywheel cover.  Here is where dual exhaust are nice - no Y pipe removal.  Anyway the oil pan has to scrape the frame to be removed and installed, there is zero clearance, plus you have to rotate crankshaft so front pistons are closer to top dead center.  Best to use an engine crane, loosen the two front engine mount nuts down to the last threads and raise engine up just a half inch or so, that will really help.

Good used chokes are not hard to find, I would get one of those and 15 minutes later - good to go.

If you do this work, it will be fine.  No one loves your car like you.  I just replaced a timing chain and rear main seal on a super nice and original 1975 RWD Cadillac.  After it started so nice and ran so well with no leaks there is almost nothing better.


Jeff,

Removing the intake manifold is not a big deal, especially if it was just removed.  You should be able to do this job (replace lifters) over the weekend with all parts costing less than $150.  The manifold is not really heavy, maybe 40lbs tops and it has pegs to position it perfectly.  Just make sure you RTV the corners where block/head/and intake manifold meet thoroughly or leaks will make it difficult to set timing.  When I put my manifold down on the RTV sealed gaskets there was no metal to metal sound and it sealed so nice, timing was easy to set.


Best of luck to both of you!  Are either of you guys going to LV for GN2016?  Be great to meet you guys.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

Offline chrisntam

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Re: Persistant Oil leak 500 motor. How do I find the source?
« Reply #11 on: March 20, 2016, 08:47:38 PM »
Hey Scot, thanks for the tip about lifting the motor up and turning the crank a bit.  I do have a hoist so I'm good to go with that.

Won't be going to GN, for some reason I fantasize about driving the car there but it's just not ready.  I can't afford a crew cab dually & trailer, so if the car is to attend, it will have to be driven.  Seems like since I've been an owner, the GNs are on the north coast, the right coast and now, the left coast.  I'm in the middle, so to speak.

As said before, I'm still sorting it out.

chris.
1970 Deville Convertible  MTS 507
Dallas, Texas

Offline Scot Minesinger

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Re: Persistant Oil leak 500 motor. How do I find the source?
« Reply #12 on: March 20, 2016, 09:12:48 PM »
Welcome.  If you see one my cars rolling out of a trailer it has been stolen, please call the police.  When I pour myself a well earned drink on Friday after work, it is not placed in a glass case to admire, I drink it.  And so I drive all my cars.  Need a truck for work, but have not nor will I ever price a trailer that will swallow a Cadillac that the truck could tow.  Get your car ready for GN2017 in DC.  I'm helping a lot with that, as it is just 30 minutes from my house.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

Offline chrisntam

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Re: Persistant Oil leak 500 motor. How do I find the source? - Update
« Reply #13 on: June 11, 2017, 04:21:21 PM »
Well, finally got around to doing what was suggested here.  Yes it was more than a year ago, I've been busy, life gets in the way and the issue was more of a nuisance than anything, and it kept my front crossmember from rusting.   ;)

I have to thank Dr. John T. Welch, his recommendation was spot on.

Got the product he suggested, cleaned it really, really good, puckied it up really, really good and it's been about 6 weeks and the leak has stopped.

So if any others with a 472 / 500 motor have a leak at the front of the engine and it's not the oil pump, fuel pump or crank snout seal, this is the fix for you!

I no longer have to carry cardboard with me to put under the car to keep driveways clean, nor do I worry where I park now.

 8)

One more thing off the list.
1970 Deville Convertible  MTS 507
Dallas, Texas

Offline kkkaiser

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Re: Persistant Oil leak 500 motor. How do I find the source? - Update
« Reply #14 on: June 11, 2017, 04:31:19 PM »
i did same thing,, worked for me too

30326

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Re: Persistant Oil leak 500 motor. How do I find the source? - Update
« Reply #15 on: June 12, 2017, 02:15:51 AM »
I always follow the doctors advise!    :)

Offline Dr. John T. Welch

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Re: Persistant Oil leak 500 motor. How do I find the source? - Update
« Reply #16 on: June 15, 2017, 01:48:07 PM »
Chris,

Glad to know that things worked out well for you.

John
John T. Welch
 CLC   24277