Too heavy of oil

Too heavy of oil

ftwflh

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Crossville,IL
Vehicle(s)
1976 CJ 5, 232 6cyl 3spd lots of rust,good frame,Dana 44s w/373 gears,ProComp 4in lift kit
Would 20w50 oil make a rear seal leak in cold weather?It didnt start leaking until the weather cooled off.:confused: Think 10w40 would do better?
 
20w50 is for a very hot running engine (such as racing). But it would not cause the engine to leak.
Use 5W30 for winter.
The bigger the number the thicker the oil is. For cold weather use lower numbers. Most motor oil today is multi-weight and therefor has 2 numbers. The first number is when the oil is cold. The 2nd number is when it is hot.
So for winter the first number should be low - use 5W30 or 5W40.

Edit - the temp may have nothing to do with the leak. It just might be getting worse.
 
Last edited:
20w50 is for a very hot running engine (such as racing). But it would not cause the engine to leak.
Use 5W30 for winter.
The bigger the number the thicker the oil is. For cold weather use lower numbers. Most motor oil today is multi-weight and therefor has 2 numbers. The first number is when the oil is cold. The 2nd number is when it is hot.
So for winter the first number should be low - use 5W30 or 5W40.

Edit - the temp may have nothing to do with the leak. It just might be getting worse.

I know how multi viscosity oils work but I am afraid to go too light of an oil with this old engine.Hate to spin a bearing and mess up a crank.May try a 10w30 or 10w40.But I bet I end up putting a rear seal in.
 
Would 20w50 oil make a rear seal leak in cold weather?It didnt start leaking until the weather cooled off.:confused: Think 10w40 would do better?

Bad oil doesn't make the seals leak. Bad seals make the oil leak. :)
 
I know how multi viscosity oils work but I am afraid to go too light of an oil with this old engine.Hate to spin a bearing and mess up a crank.May try a 10w30 or 10w40.But I bet I end up putting a rear seal in.


It seems to me that you might be running a greater risk of spinning a bearing with a thicker oil. With an old and tired engine you will have an old and tired oil pump. An oil that is heavier when it is cold is going to have a higher resistance to flow when you first start the engine after it has been sitting and much of the oil has settled into the pan. With a heavy oil and those balmy Il. nights, you stand a chance of starving some fo your bearings for oil for the few moments that it takes you pump to get the oil to them.

I had an '83 s10 with a 2.8L v6. The engine had a knock at every cold start. I tried an oversized bearing, but it was still there. A buddy suggested a heavier oil. I went from a 5w30 synth to a 10w40 synth blend. The cold start knock only got more pronounced until I went back to the 5w30. When I did the knock went back to the way it was and stayed about the same until I traded the truck off. The full synthetic oil was probably a bit of overkill on that engine, but try as I might I could not 'finish' that engine through normal driving and wheeling. I had hoped that the 2.8 would give up the ghost so I could justifythe cost and effort of a new 3.4L long block.
 
You probably have an oil leak simply because its cold now and the seal has shrunk.....look at your oil pressure gauge it should have 10psi for every 1000rpm minimum I suggest using whatever weight oil it takes to acheive near that so if you have it with 10w40 go with it if not try the 20w50 this is only my 2cents :chug:
 
You probably have an oil leak simply because its cold now and the seal has shrunk.....look at your oil pressure gauge it should have 10psi for every 1000rpm minimum I suggest using whatever weight oil it takes to acheive near that so if you have it with 10w40 go with it if not try the 20w50 this is only my 2cents :chug:
Before I changed the oil to 20w50 it would drop to almost nothing when hot and at idle and go up to 40psi when driving.With 20w50 it idles with 20psi and runs around 50psi.
I and thinking about changing the seal after looking at the manual and it shouldnt be too big of a deal(now watch all hell break loose with it)



Next question is I am going to put a clutch in but planned on that later.
Would it be easier to change the seal with the tranny and clutch out or just as easy with it still mounted?
 
WOW......my 2cents worth again sounds like you need new bearings more than a new seal my suggestion on the cheap get an engine gasket kit and main bearings rod bearings and an oil pump/pick up pull the motor swap the bearings replace your seals and truck on with 10w40 oil you are loosing a lot of oil in the motor to have no oil pressure at idle again my 2cents
 
I agree with most of what Gert is saying. You need a new rear main seal and a new oil pump. Heavy weight oil will give higher pressure but that's not the way to fix it. New oil pump is what you need.
Before you tear into this make sure the leak is coming from the rear main. Those strait sixes also have a problem with leaking valve covers. make sure the oil isn't dripping down from there.
I am not sure if you need to replace the bearings yet.
When you replace the rear main seal check out this link:
Jeepin.com » Replacing your rear main seal
It's good instructions but one more tip. When it comes to removing the upper half of the seal it's good to loosen up the bearing caps. this will allow the crankshaft to loosen it's hold on the seal.
 
I agree with most of what Gert is saying. You need a new rear main seal and a new oil pump. Heavy weight oil will give higher pressure but that's not the way to fix it. New oil pump is what you need.
Before you tear into this make sure the leak is coming from the rear main. Those strait sixes also have a problem with leaking valve covers. make sure the oil isn't dripping down from there.
I am not sure if you need to replace the bearings yet.
When you replace the rear main seal check out this link:
Jeepin.com » Replacing your rear main seal
It's good instructions but one more tip. When it comes to removing the upper half of the seal it's good to loosen up the bearing caps. this will allow the crankshaft to loosen it's hold on the seal.


I had a valve cover leak when I first got the Jeep and fixed it by tightening the bolts(most were finger tight).I have no oil on the sides of the motor or on top the bell housing.But I will check again.Leak seems to show more on the bottom of the bell housing.What gets me is when you loosen the flywheel cover and feel inside it doesnt feel very oily.
I know the bearings may be a little loose but this is a AMC 232 i6 and I plan on going with a AMC 258 i6 / 4.2l later on.So I dont really want to drop any more cash into this than I have to.
My manual said to loosen the main bearings before changing the top part of the seal.
Thanks for all the help on this project.All input is very appreciated.
 
Another possibility is a leaking oil pan. I just wanted throw that out there so you wouldn't replace the main seal and find that's not it. Give the bottom of your engine a good cleaning and later look for fresh oil.
I don't think you ever got an answer on the clutch job. I would do that separate. Working on the clutch wont make the main seal any easier (or visa versa).
 
Another possibility is a leaking oil pan. I just wanted throw that out there so you wouldn't replace the main seal and find that's not it. Give the bottom of your engine a good cleaning and later look for fresh oil.
I don't think you ever got an answer on the clutch job. I would do that separate. Working on the clutch wont make the main seal any easier (or visa versa).


The motor is dry of oil(just some baked on the pan)Most of the oil is on the bell housing and drips off the bottom.Top of bell housing is dry.
I am going to check fluids again this weekend.I filled the tranny and trans case last weekend.The motor is a qt low for the first time since I have owned this and since the oil change.
 

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