Eldo 500 with Low Oil Pressure

[mummyjohn]

Hello all, first time poster here.  I apologize for the verbose post, but I figure some background will be useful:

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A little over a month ago I purchased a 1971 Eldorado coupe with the grande 500 engine.  I don't know if anyone who reads this'll be from LA, but there's a Cadillac specialist in Santa Monica (near the intersection of the 405 and the 10) with half of a big pink '59 on the roof, maybe you've seen it?  Anyhow, I had the car inspected there before purchase, and while they found a couple thousand dollars worth of work to do, fortunately none of it had to do with the engine/transmission!  (Well, aside from replacing gaskets & fluids, of course).  Anyhow, I was buying a car before a couple days later heading off to my final year at university.
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The car, my dad, and I made the 2200+ mile trip across America over the course of a few days quite flawlessly and -- as you all well know -- in extreme comfort!  About a week ago I drove to a store, but when I started the car to come back home the "Stop Eng. - Oil" light illuminated at idle.  With very light revving, the light flickered, and with a feather-touch more on the gas it'd go out completely.  I checked the oil level, which appeared sufficient, and ventured the short ride home.  Since then, I've only run the engine for a couple minutes combined and only driven around the block, once after the initial incident, for testing.  The light now stays on regardless of engine speed and I was able to hear a slight tapping noise, which I'm guessing is the lifters?

I telephoned a local mechanic - who, it should be mentioned, replaced the brake booster and a front wheel hub on this car not three weeks ago now - and inquired what sort of oil should be used.  He suggested "thicker" (a-la 20W-50) for "an older car like this."  Much Internet investigation has not rendered a consistent opinion on this, some saying thicker some saying thinner.  I ended up choosing 10W-30 Valvoline; I asked the fellow at the Auto Parts store about ZDDP and he said the Valvoline would be appropriate.  Hoping upon hopes that I might get 'lucky' and have the pressure problem be something cheap like a clogged filter, I proceeded to change the oil and the filter on the Eldorado (as recommended in the manuals, 5 quarts for an oil change + 1 more quart when replacing the filter too).

Since I'm here posting this right now, something so simple was not the problem.  And, after much ado that's my question:  what's causing this low oil pressure?  Rather, what order of steps should I go about tracking down the problem?  My next guess would be the pump itself (could it be as simple as that it's not "sucking" oil and just needs to be primed?).

Helpful tidbits: I drove across the hottest parts of the United States, in the daytime, in late August and had no lubricating or cooling problems.  I have the shop manual (both Cadillac and Fisher body) for this car.  I am a college student, so I don't have a sprawling garage with an engine hoist; I've got a toolkit, a brand new torque wrench, ramps on which the front of the car is presently raised, and the great resources of the Internet.  I'm glad to finally be a member of the Cadillac family, but it ain't much fun to watch it sit there motionless!

[TJ Hopland]

First thing I would do is try to get a mechanical pressure gauge hooked up and see what the pressure actually is.   The accompanying noise does seem to indicate that it may actually be low.

Trying the 20w50 may be worth a shot to see if that seems to improve things.  If it does that would point to things just being kinda tired.

10w30 for a well used engine in the summer seems a bit on the thin side to me.   10w40 was much more commonly used in the warmer climates and warm seasons in the cold climates.   IF its got a ton of miles on it the 20w50 may be fine if you never try to run it under cooler or cold ambient conditions.   A diesel rated 5w40 full synthetic or synthetic blend is pretty easy to find these days and may be a good choice. 

With a lot of miles, warm conditions, it would not surprise me to see the oil light flickering running a a 30 weight.   Did you change the oil before the cross country trek?  IF so what weight was used?  How quickly did the fresh oil turn dark?

The oil pump is external on these engines, its what the filter screws onto.  Original pumps I believe had an aluminum housing so with poor maintenance they can wear and become less efficient.    You can fairly easily replace the pump but its pretty rare to see the pump being the only issue.  A new pump may improve things but there is likely going to be wear in all the bearings too which also effects pressure.  Another contributing factor with these engines is the valve guide seals and cam timing sprockets were plastic covered.  Mileage and age were not kind to those things.  Most likely the oil pan and pickup tube are pretty full of these bits of plastic which makes it harder for the pump to suck the oil through.   One bummer about the Eldo is you can not drop the oil pan without removing either the engine and or transmission from the car. 

Melling is a big company that still makes oil pumps for these cars but it appears that they still have not corrected a slight machining or casting flaw that has killed many Cadillac engines.  If you decide to buy one I would get it from these guys www.500cid.com.   They take the new pumps and make the corrections so you don't have to figure out how or worry about it.    I had one do some damage to a new engine.   Second one I bought from those guys and its working great.

Since this car is new to you and sounds like you have a limited budget I would verify the pressure.  If it is indeed low I would try running the thicker oil and see if that at least temporarily helps.  Like I said above I would be concerned about anything over a 10w for cold starts if you are in an area that gets cold.  Going to a synthetic will usually get you a wider range like the 5w-40 I mentioned.  If it does help I would likely just drive it that way for a while and enjoy it.  See what else goes wrong and save some money and come up with a semi long term plan.   I would hate to hear that you pulled the engine for a timing chain and oil pump to then hear that a week later you had to pull the trans for a rebuild.  If you get some miles on it and experience you will have a much better idea what all will be needed.   Who knows you may find that the engine is overall very tired and you may then want to plan on a rebuild or a better used engine.   Most places in the USA these engines are not too hard to find in decent shape so if a rebuild is not in the budget you can perhaps score a parts car that will get you a better engine.   You can get an engine from a RWD car, you just have to swap the oil pan and pickup tube.   A new timing chain set and some gaskets you could end up with a good used engine.   You can pretty easily spend $3500 rebuilding one of these now days.   They are not small block Chev's you can do for $1000.   MTS 500cid. does complete engines so if you get to that point you can see what they get for a stock rebuild just so you know.   

[dplotkin]

....cam timing sprockets were plastic covered.  Mileage and age were not kind to those things.  Most likely the oil pan and pickup tube are pretty full of these bits of plastic which makes it harder for the pump to suck the oil through.   

Given your description of what is happening and your cross country trip I'm willing to bet you that the teflon that was once on your timing gears is now in your oil pan and fouling the pickup screen. Common problem with this vintage and mileage on may V8's. I would NOT run it until you fix it. Starve those cam, main or rod bearings and it will get a hell of a lot more expensive.

Dan

[TJ Hopland]

Do you know what the previous recent driving history was of this car?  If its been sitting a lot Dan could be right that its suddenly really started falling apart.   I have never seen anything come out in the pan during changes but sure have seen the chunks when I got it apart. 

If you want to get an idea how bad the timing gear is you can kinda get a look at it if you remove the distributor.  It kinda depends on how clean the engine is.  If its fairly clean you can get a pretty good idea what sort of shape its in.   If the engine has a thick crust of scum in it it can be pretty hard to tell what you are looking at.  I had one that was so bad we had trouble telling even when we looked with a bore scope.  We finally ended up sticking a cleaning brush down there with some solvent on it to clean a spot so we could see what we were looking at. 

Before you pull the distributor I would take timing readings just to see where it is at now so you can easily get it back to where it started. 

[Dave Shepherd]

I find sludged up oil pans in every one of these older cars of any make that I have in my shop for major work, pulling the pan or at least getting a sample of what is in the pan is a must before setting out on any venture, this assumes the engine hasn't been gone through recently.Checking the oil press. with a gage is also required, or pull a valve cover and look at the upper end for sludging also. Sorry to repeat some of the advice already given,

[mummyjohn]

Of course, I leave out that one critical fact, mileage!  The car has 132,759 miles...at least, the information I received from the seller was that it's only rolled over once.  That's an awfully low number for a '71 car, but that having been said, not unbelievable...read on: I bought the car from a local mechanic who'd had it a very short time.  A fellow who the mechanic described as "a traveler" by occupation purchased the car in Minnesota, then drove out to LA and proceeded to sell it as quickly as possible so that he could continue his journey, which as the story goes was to South America.  The keys that I have for it came with a keyring from a Cadillac dealer in Edina, Minnesota.  Of course I'm making a big leap here, but it stands to reason that The Traveler bought the car from the original owner, who very well might've been a little old lady who rarely drove more than fifty miles at a time.


I am somewhat hesitant about an exceedingly thick oil because, as you say, it's not so good for cold starts.  While I'm not dealing with that issue yet, I'm in Ohio and below-freezing nights are going to be an inevitable reality in a few months.  Before the road trip I had every filter, gasket, pad, drum, and fluid changed, along with a slew of components replaced (master cylinder, power steering pump, fuel lines, several suspension components, etc...).  However, I do not know what type of engine oil he used.  It was something less than 2600 miles on that oil; it became dark, dark brown but far from black.  Regardless, he had the oil pan off to replace the gasket, so at the least it was all clean then.

From what all I've gathered so far (including reading on other websites as well), these timing gears are sounding like the most likely culprit.  Looks like there's no way to get around getting into the oil pan to inspect that suction filter for contaminants and clogging particles.  I'm sure you guys know how much fun that'll be with the front wheel drive on the Eldorado.  How many hours would you all say that job takes, assuming you've the proper equipment?  Is there a way to do it w/o removing the engine from the car?

P.S. IMMENSE thanks for the rapid replies, everyone.

[TJ Hopland]

The Cadillac dealer in Edina MN is Key Cadillac.   They have been around for a long time.   230k on a car from that era would be showing a lot of wear in a lot of places.   130K on the highway could show little wear on things like pedals and drivers seat. 

How much did you pay for this pre trip tune up?  If you crawl under there and look you will see there is no easy way the oil pan is coming out.  One way or another you have to split the engine and trans apart.  Its quite a job in an Eldo and does not seem like the sort of thing you would do on a quick freshening up.  Do you have any sort of detail on what that shop did?  If they got that deep into it I would have thought they would have seen the debris if it was there.  If you were paying them that much I would think they would have came to you and suggested something like the timing chain if they were already in that deep.   The plastic gear was a common thing for many GM cars in the 70's and early 80's so any shop that works on stuff from that era should be aware of the possible issue.  If they checked it and it had already been replaced I would think they would have mentioned that they checked it. 

Its also interesting that it was once owned by a mechanic.   Who knows what was done under his care.   It does seem like stuff has been done or its been well cared for since the oil is staying reasonably clean.

It may be worth pulling the distributor for a look.  If its a plastic gear that is shot you know its going to have to come apart just to deal with that.  If its been replaced then you may want to do some more exploring before yanking the engine.       

[bcroe]

There is a quick check of the chain, without pulling anything.  Line up on the
timing mark & remove the distributor cap.  Now manually move the crank
back and forth, to see how many degrees it must go before the rotor begins
to follow it.  My rule is 2 degrees is some wear; 6 degrees means replace that
chain set NOW. 

That said, any GM timing chain set of that era needs to replaced with an all
metal set, the sooner, the better. 

If the oil pickup is plugged by plastic, thicker oil will make it worse.  Bruce Roe

[35-709]

"That said, any GM timing chain set of that era needs to replaced with an all
metal set, the sooner, the better."

Bottom line!  And I agree that it is very likely the plastic from the timing chain gear is plugging up the oil pickup.

[dplotkin]

Yes...and forget about using thicker oils or other remidies in a bottle. Thick oils work like over-the-counter cold remidies, they temporarilly hide but do not fix the problem. Using 20-50 in cold weather will not flow well on cold starts and help finish your engine off. (Won't do much for your starter or battery either).

Dan

[mummyjohn]

     Reviewing the work that was done, it turns out that the mechanic was NOT, as I'd previously stated, in the oil pan at any time.  It was the gearbox gasket that'd gotten replaced, not the oil pan gasket (if it's worth mentioning, valve cover gaskets were also replaced at this time.).

     He also said he put 20-50 oil in it.  A bit thick for the Caddy's taste, I suspect?

     In other news, I've been doing some research around the 'Net and other folks have been saying that [this era's] Cadillac engines were somewhat known for having their oil pumps "go" relatively early.  How veritable that information is I can't say for sure (for that matter, what's "early" to the guy who said it?).  I removed the pump from my 500 and at visual inspection there aren't any nicks on the gears, housing, engine block, valve, or anywhere else I could see.  That isn't to say that I'm sure there is no problem with wear in the gears' axial direction.

     Which leads to the next round of questions...in these pictures attached, what is the small hole identified by the purple arrow (no one's using a B/W computer screen out there, eh? )?  The sprung cylindrical slider in the chamber it's connected to is the pressure regulator/relief valve, yes?  It looks to me like this hole dumps oil from the unfiltered side of the oil filter (output side of the pump gears) back to the input side of the pump gears, but it also seems that this little passageway would close up as pressure gets higher on the output side of the pump gears.  Am I getting that correct?
     Secondly, what is the [much stiffer] valve shown by the green arrow?  I imagine this is a bypass valve in case someone's oil filter was completely clogged.

     It suppose it's worth noting that the brand-new oil filter was full of the new, clean-looking oil - I wouldn't think oil from up above drips down back into the filter normally, does it?  This would appear to indicate that at least some oil's making it past the pickup screen and through the entire pump.  'Course I'm not sure if it's good news or bad news that the problem might be downstream from there...

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     Onto another arena entirely...how do you guys manually rotate the engine (for timing purposes or when working with any part synchronized to the crankshaft, such as removing the distributor)?  There's not much room to get a socket wrench in there on the crank-pulley nut (not to mention it takes a large socket).  Another new-guy question: do the spark plugs have to be removed before turning the engine?  The concern is from a pressure standpoint, not an electrical one (the primary wire on the distributor cap is disconnected already).

Sorry for the onslaught of questions!

[bcroe]

From what all I've gathered so far (including reading on other websites as well), these timing gears are sounding like the most likely culprit.  Looks like there's no way to get around getting into the oil pan to inspect that suction filter for contaminants and clogging particles.  I'm sure you guys know how much fun that'll be with the front wheel drive on the Eldorado.  How many hours would you all say that job takes, assuming you've the proper equipment?  Is there a way to do it w/o removing the engine from the car?       

I have had 3 of these FWD cars, and I have changed the timing chain on
every one plus all my RWD cars.  Not a fun job, just a "must do".  It can
be done with the engine in place, if the pan isn't plugged up.  If the slack
test or inspection down the distributor hole shows a problem, it sure beats
having to get another engine.  good luck, Bruce Roe

[TJ Hopland]

It makes a lot more sense that the oil pan did not come off.   Gearbox?  Meaning transmission?  Or the final drive (differential)? 

I would have to go look at a pump to refresh my memory on the valves.  One is the bypass for the filter and the other is the regulator.   The manual says the regulator is the one behind the 5/16" head plug.    It says the spring free length should be between 2.57 and 2.69 inches in length.  It should take a force of 7 1/2 to 8 1/2 pounds of pressure to compress it to 1 7/16 inches.   That's all the detail the manual has.   

Is yours aluminum?  Or iron?   I think the originals were aluminum and I know the replacements are iron.  The flaw in the new ones was with a valve sticking and bypassing all the pressure all the time.   

When they are bad / worn its obvious.  The tips of the gears will look more like saw teeth than gears and the housing will have grooves cut into it all the way around.    It sounds like either yours is in good shape or has been replaced.

I happen to have a 73 manual handy.  The engine oil specs are:

20*F to 100*+  20w-20, 10w-30, 10w-40, 20w-40, 20w-50
0*     to  60*     10w, 5w-30, 10w-30, 10w-40
- -20 to  20*      5w-20, 5w-30

notes are:
5w-20 not recommended for sustained high speed driving
sae 30 may be used at temps above 40*F
5w-30 recommended for vehicles operated in Canada.     

That kinda implies these had pretty healthy clearances and could tolerate quite a wide range of oils.

My memory of the 70's in my area was 10w-40 was the normal oil even in the winter.   I have been running 10w-40 in my Eldo till this year.  At the moment I am running a 5-40 synthetic blend diesel oil.  It was partially because it is what I had around but it really should be a decent oil.   The 5w should give good start up characteristics even in cooler weather and the 40 seems to be well within the original hot spec especially now that I noticed they say it was Ok to run a 20w-50. 

[mummyjohn]

A'ight, I'm back...got the distributor out.

Following the earlier advice, I checked the maximum amount the crankshaft could be turned before the distributor rotor moved.  Almost embarrassed to say...about a solid seven degrees!  Though I have a question regarding the toothed piece on the front of the engine that is used to line up the timing mark on the crankshaft pulley.  There is a mark on every "tooth" and every "valley" between teeth; every other mark is labeled with a number and the numbers are four apart.  However, these numbers seem really close together for degrees of rotation.  Do they in fact represent degrees of camshaft rotation, not crankshaft rotation?  Either way, the slop was ~7 degrees according to the timing marks on the front of the engine.

So while I'll definitely be replacing the timing chain & gears, I've got another question: how in the world is someone supposed to torque the nut on the clamp that holds the distributor in position to spec?  The distributor housing overhangs that nut, which means you'd have to not only get the height of the torque wrench and the socket to fit in that small space, but you've also got to have a direction for the wrench's handle to stick out.  As far as I can tell, there's no way that's going to happen - the coil and manifold are in the way to the rear, the distributor itself is in the way to the front and driver's side, and the air con compressor is in the way to most of the left.  In short, this thing's in a hole.  How do they expect someone to tighten this thing?

Of course to get to those gears the engine front cover would have to come off, which would necessitate taking off all the belts, at which point it wouldn't be a big deal to move the compressor out of the way and not reinstall it before finishing up with the distributor.  Someone said they've done the gear/chain replacement without pulling the engine; what special procedures/precautions should be observed when doing that?

[The Tassie Devil(le)]

Many people have done the cam gear change with the engine in, but the chance of major oil leaks after is always a possibility.

Personally, I always recommend pulling the engine and do the job correctly on an engine stand.

This way, you drop the sump and remove all the plastic pieces that are in the sump, and can remove the oil pickup to clean out the bits that are in there as well (Photo 76 shows everything that was caught in the oil pickup screen, and yet, the engine still showed 40 psi Oil Pressure.).   IMPORTANT   Drain the oil and drop the sump BEFORE rolling the engine over, as this way nothing of the rubbish at the bottom of the sump will get caught up under the pistons.

When pulling the engine, I always refer to the Workshop Manual as Gospel, and it directs you perfectly in everything to do for a seamless removal and re-installation.   EXCEPT, I remove the Left Exhaust Manifold if possible to make things easier, and I made up my own lifter using the Intake Manifold carby area to bolt to.

There are a couple of awkward bits to get off, and these are the Flywheel Cover, and the Diff to Engine Mount Bracket, but they are not insurmountable.

As for the Distributor wrench, Photo 17, I made my own using an old ring spanner and screw driver.   No need for a torque wrench for this nut, just tight enough to stop the distributor from moving after you have timed the engine.   Love making up special tools.

Photo No. 18 is the expensive rightangle screw driver I purchased just for those odd screws, and works well for the carby mixture screws.

Bruce.

[mummyjohn]

Thanks for the info and images, that's all good stuff to know.  I'm a mechanical engineering student, which is a dangerous combination of the interest and enthusiasm to know how the engine and its systems work, but the youth to lack significant experience repairing automobiles.  This is also my first GM car (for that matter, my first American car).  In other words, I do EVERYTHING by the Service Manual

I figure I would include these pictures I took down the distributor hole this afternoon.  They don't reveal much (to me at least), but maybe expert eyes will glean more from them.  Can you tell from here if these are the original gears, and how much (if any) Teflon is left on them?  I'm going to have to pull the engine so I'll find out soon enough anyhow, but I was curious if you guys could tell from these pictures.  The hole on the far side is of course where the shaft driving the oil pump goes.

[The Tassie Devil(le)]

I take it that you have removed the Oil Pump, as it is impossible to remove the oil pump drive shaft from the top.

Looking at the chain, it is difficult to make out the timing gear, but it looks like a replacement Morse Chain and associated cam gear, as the chain looks too clean to be an original, and the shininess of the gear looks to be a solid steel one.

If you poke a long screw driver, or a piece of wire with a slight hook on the end to manipulate the chain, if it is tight, you shouldn't be able to "flop" it around.   If it is very loose, then it has stretched.

I purchased one of those cheap Video things that look like a cheap hospital endoscope, and you would be surprised what you can see inside holes with these.   If you do buy one, get the one with the 9mm. end, as these go in more places than the one I got with the "huge" end.   The small ones fit down Spark Plug holes, etc.

Bruce.

[TJ Hopland]

I can't tell for sure either.   It does seem really clean in there.   It does kinda look like a replacement.  Many times there is still some plastic bits on there and I don't see that on yours.  I suppose it would be possible that its all gone in the area you are taking the pictures of but usually when that happens the chain is a terrible fit into the teeth because with the plastic missing the diameter is too small so the chain spacing is too wide.  It looks like in Bruce's picture where the chain just does not settle into the teeth.  The teeth that are left after the plastic is gone are not meant to be teeth, I think there were just there to keep the plastic part from spinning on the hub. Yours looks like it fits alright, not new but alright. 

Then again looking at Bruce's picture of the cam gear at about the 10 o'clock position (which would be around the distributor gear area) it does look like the chain is kinda seated like yours and I don't see much for signs of plastic on that hub.

[mummyjohn]

A while ago I got her over to a nearby mechanic (who has done a couple other jobs on this car, has been working on all sorts of makes since long before this car rolled off the production line, and who is quite familiar with the Teflon GM timing gears).  He quickly identified that the gear had already been replaced by a previous owner.  He claims that on the many GM cars of the era he has encountered with the 'teflon-chunks-in-the-oil-screen' problem he has (using external pressure) pumped oil the opposite direction down the pump pickup tube to blow any chunks on the screen off of it and ultimately out the open drain plugs.  The oil pump itself was scored and worn, so I had that replaced as well.

Long story short, he asserts that the lubrication system's channels all throughout the engine are clear, and the light/sending unit are not the problem, meaning this is a worst-case scenario: bearings are going to need to be replaced.  As I said many posts ago, I'm entirely unsure whether this car has 100,000+ or 200,000+ miles on it with the 5-digit odometer.

My three questions:

• Is that a proper diagnosis?  I have no reason not to think so, but I like second opinions.
• When I have the engine out (going to be taking it somewhere, since I've not the time, equipment, nor place to do it myself) what else should I have looked at [in addition to main & con-rod bearings]?  Camshaft bearings?  Piston rings?  Other bits I haven't thought of?
• To any members in Columbus, Ohio: I have found, through a friend that repairs automobiles, a gent who has been doing repairs/rebuilds of all shapes and sizes for quite a while now.  Before contacting this fellow to work on my Cadillac, I figured I would ask if anyone in the area knows or recommends a particular shop/individual for work this intensive.

Many thanks, all.

[Dave Shepherd]

Oil pressure relies  on internal engine clearances,and oil pump condition. Mains should be plasti-gaged, also the rods, Pistons and rings have no effect on oil press.  Cam bearings of course.  The condition of the pump, proper weight oil and quality filter are all in the formula.  So all the internal bearing clearances  must be gone thru to pinpoint the problem before any engine work is done.