49 Plymouth excessive oil consumption?

[Tim Larson]

My 49 Plymouth has consumed a considerable amount of oil since May. 2 gallons of oil have been added to the crankcase besides the fresh oil change this spring. I have driven it about 2500 miles up to this point and by my estimate I seem to need to add a quart of oil every 120 miles (approximately) in order to keep the oil level at the add mark. I have been told that keeping it at add is fine since many of these cars would lose the oil between the full and add mark anyway and just stay at add. 

 

Well, mine goes below add... 

 

I notice an oil smell when driving - mainly on acceleration, I think.

 

When I park anywhere there gets to be a oil spot in my parking space under the engine and my garage has developed a large area of oil over the course of the summer. 

 

I noticed on Sunday that after I parked in the garage I could see a drip of oil coming out the vent hole in the bottom of the bellhousing - is that possible? 

 

There is no trouble (that I notice) with acceleration and the oil pressure always stays up above 40 when driving. Probably around 50-60. It goes down a bit when idling after warming up, but never all the way down to zero. 

 

If I can get by with just continuing to add oil for now, I will. I'll monitor to see if it gets worse, but this seems to be consistent as long as I've had the car (just over a year).

 

My assumption is that the engine has never been rebuilt - just over 50,000 miles. It had not even 2000 miles added to the odometer since about 1986 if the sticker on the door is correct. 

 

[Hamilton]

It seems as though you already know this, but your car's issue isn't consumption, its a leak (or more likely, leaks).  Your description of a drip at the bell housing would suggest a rear seal, although it's probably not the sole source.   And not only is it possible, it's common (the drip is coming out of an inspection plate that bolts to the bell housing and covers/protects the flywheel).

 

If indeed the rear seal is your primary leak source, replacing it (the bottom section, anyway) isn't as challenging as you might think.  You'll have to pull the oil pan first (really simple on these cars, given the access) which is fine, because you can then replace that gasket at the same time.   Once the pan's off it's just a matter of removing the two bolts securing the rear main cap to access the bottom portion of the rear seal.  The top section is another story, as you have to remove the flywheel to get at it, which means pulling the gearbox and clutch assembly.  For this reason, you wouldn't be the first guy to do the bottom and cross his fingers.  Chances are, you'll still experience some leakage, but likely at a much reduced rate.

 

While you're under there anyway, might as well replace the valve spring cover gaskets on the passenger side of the block.  Once again, they're easy to get at ... and cheap.

 

Good luck.  Let us know what you find.

 

_

 

 

 

 

 

 

Edited October 2, 2020 by Hamilton
typo

[Sam Buchanan]

33 minutes ago, tjlarson88 said:

 

 

I noticed on Sunday that after I parked in the garage I could see a drip of oil coming out the vent hole in the bottom of the bellhousing - is that possible? 

 

 

Very possible, probably due to rear crankshaft seal failure.

 

(Hamilton beat me to it....   )

Edited October 2, 2020 by Sam Buchanan

[Tim Larson]

13 minutes ago, Hamilton said:

While you're under there anyway, might as well replace the valve spring gaskets on the passenger side of the block.  Once again, they're easy to get at ... and cheap.

 

I do notice that the covers over the valve spring gasket side of the engine does appear wet so that is probably part of the issue too.

 

Thanks for the suggestions!

[Worden18]

Hopefully you can fix the issue by patching up the leaks.  Just want to throw in my 2 cents.  Your car's oil consumption sounds almost identical to my Meadowbrook before the engine rebuild.  I was using a qt./100 miles or so.  The car had sat for 25 years then had about 700 miles put on it during the next 20 after that.  59k on the odometer.  When my builder pulled the pistons out the rings just fell apart on 5 of them.  No wonder I had no compression.  Drove it that way for 3,000 miles that summer.  Do a compression test and let us know what you find.

[Tim Larson]

21 minutes ago, Worden18 said:

Hopefully you can fix the issue by patching up the leaks.  Just want to throw in my 2 cents.  Your car's oil consumption sounds almost identical to my Meadowbrook before the engine rebuild.  I was using a qt./100 miles or so.  The car had sat for 25 years then had about 700 miles put on it during the next 20 after that.  59k on the odometer.  When my builder pulled the pistons out the rings just fell apart on 5 of them.  No wonder I had no compression.  Drove it that way for 3,000 miles that summer.  Do a compression test and let us know what you find.

 

I'll definitely check compression. Is there a specific tool you'd recommend to test this? Also, do I need to disconnect the fuel line or anything when doing this test? 

[Sam Buchanan]

9 minutes ago, tjlarson88 said:

 

I'll definitely check compression. Is there a specific tool you'd recommend to test this? Also, do I need to disconnect the fuel line or anything when doing this test? 

 

Do a Google search on "How to Do a Compression Test"......you will find a multitude of videos and documents.

[knuckleharley]

1 hour ago, Sam Buchanan said:

 

Do a Google search on "How to Do a Compression Test"......you will find a multitude of videos and documents.

And if you are a slow learner like me,there is nothing that beats a "how to" video.

Still,do yourself a favor and buy a Motors Manual that covers the year your car was made. Lots of photos there too,and they tell you what to do using simple terms the non-professional mechanic can understand.

[greg g]

Get under there,wipe everything down the best you can. With the air that moves around these engines the source could be any where.  I had a persistent oil leak on my recently rebuilt engine finally traced it to the oil filter return line. The tube had cracked under the flair nut.  Problem was it only leaked with the engine running above fast idle. There is still a leak somewhere to the tune of a pint every 500 miles or so.  Think it probably the valve galley covers that have been over tightened and spring so as not to seal when hot.  And rear mains are a pretty common fault even with fresh rebuilt engines.

[Tim Larson]

1 hour ago, greg g said:

Get under there,wipe everything down the best you can. With the air that moves around these engines the source could be any where.  I had a persistent oil leak on my recently rebuilt engine finally traced it to the oil filter return line. The tube had cracked under the flair nut.  Problem was it only leaked with the engine running above fast idle. There is still a leak somewhere to the tune of a pint every 500 miles or so.  Think it probably the valve galley covers that have been over tightened and spring so as not to seal when hot.  And rear mains are a pretty common fault even with fresh rebuilt engines.

 

I do notice some sort of possible leakage under the oil filter. There are really too many options - ha!

[Andydodge]

Strongly suggest that you degrease the whole engine then see where its leaking from.......as for the rear seal apart from the lower half of the seal there are a pair of side gasket or rubber seals that also should be replaced at the same time a s the rear main seal.......as for the valve spring cover gaskets, I'd also suggest when replacing these to completely clean the steel plates then use some contact glue to attach the gaskets to the plates which will help to stop the gaskets moving off the area on the block that the gaskets seal against........and when replacing the sump pan gasket make sure to allow for the side gaskets to protrude against the rubber end gaskets as this also helps to seal the sump..........when doing a compression test you take the plug leads off and disconnect the coil lead pull the spark plugs and screw the compression tester into the spark plug hole, use the starter to turn the engine over a couple of turns and the tester will read what the compression is.....write this down and your done........andyd

[plymouthcranbrook]

And have the engine warmed up before doing the compression test.

[Loren]

My thoughts on oil consumption.

If you think oil consumption is only for old cars think again!

The manufacturers experimented with "Low Pressure Piston Rings" thinking they could squeeze more gas mileage out of their cars.

The result  is cars burning a quart of oil every 600 to 800 miles!

 

Of course the 49 you have had a recommended oil change interval of 1,000 miles.

 

Once way back in the 1950s as a little kid I was sitting on my bike on the sidewalk and a cloud of black smoke came down the street.

When it got directly in front of me it stopped and a man emerged from the cloud.

Just as it started moving again I got a glimpse of a car under the smoke cloud.

Being a car fanatic at that young age I identified it as a 49 or 50 Ford.

It was making so much smoke that I couldn't tell it was even a car till that moment!

In spite of being able to identify the brand, the cloud closed up so fast I couldn't tell if it was a four door or a two door!

No telling what the oil consumption of that Ford was but I'll bet it wasn't as good as your's! lol

Looking back on that incident I wonder why the thing didn't burst into flame.

 

[Tim Larson]

7 hours ago, Loren said:

My thoughts on oil consumption.

If you think oil consumption is only for old cars think again!

The manufacturers experimented with "Low Pressure Piston Rings" thinking they could squeeze more gas mileage out of their cars.

The result  is cars burning a quart of oil every 600 to 800 miles!

 

Of course the 49 you have had a recommended oil change interval of 1,000 miles.

 

Once way back in the 1950s as a little kid I was sitting on my bike on the sidewalk and a cloud of black smoke came down the street.

When it got directly in front of me it stopped and a man emerged from the cloud.

Just as it started moving again I got a glimpse of a car under the smoke cloud.

Being a car fanatic at that young age I identified it as a 49 or 50 Ford.

It was making so much smoke that I couldn't tell it was even a car till that moment!

In spite of being able to identify the brand, the cloud closed up so fast I couldn't tell if it was a four door or a two door!

No telling what the oil consumption of that Ford was but I'll bet it wasn't as good as your's! lol

Looking back on that incident I wonder why the thing didn't burst into flame.

 

 

I don't leave any black clouds of smoke behind me, but there is a nice patch of black laid down behind the exhaust pipe on the cement floor - ha! My 52 Mercury started that when I had it parked in the same stall. 

[DJK]

On 10/2/2020 at 6:49 PM, Andydodge said:

Strongly suggest that you degrease the whole engine then see where its leaking from.......as for the rear seal apart from the lower half of the seal there are a pair of side gasket or rubber seals that also should be replaced at the same time a s the rear main seal.......as for the valve spring cover gaskets, I'd also suggest when replacing these to completely clean the steel plates then use some contact glue to attach the gaskets to the plates which will help to stop the gaskets moving off the area on the block that the gaskets seal against........and when replacing the sump pan gasket make sure to allow for the side gaskets to protrude against the rubber end gaskets as this also helps to seal the sump..........when doing a compression test you take the plug leads off and disconnect the coil lead pull the spark plugs and screw the compression tester into the spark plug hole, use the starter to turn the engine over a couple of turns and the tester will read what the compression is.....write this down and your done........andyd

Throttle should be open also.

[Loren]

I haven't tried this but on another forum it was suggested to degrease the engine and dry it real good then get some Talcum powder and sprinkle it where you think it might be leaking. It will lead you right to the source. Talcum powder turns dark in the presence of wetness.

 

I was tasked once to find an oil leak on a brand new car once. I did not want to invest a whole lot of time on the job as it was a flat rate warrantee job.

So without taking one thing apart I took a half can of Freon I had left over from another job and flooded the crank case with the gas.

Then I went over the engine with a leak detector. Bingo!

On this engine there's a gable plate behind the flywheel, it holds the flywheel seal and provides a passage to drain the oil from the cylinder head. During assembly they forgot (?) to install the gasket between the plate and the block.

I had the service manager check my methodology and got approval for the repair.

What could have taken forever to find was identified correctly without taking one part off.

I got paid for my labor (if not my brilliance. lol) and the customer got his car back the same day.

 

[Merle Coggins]

Interesting diagnostic approach. That’s certainly thinking outside the box.