1970 Chevrolet C20 Pickup - Motor Leaking Oil

[ggalv]

I have a 1970 Chevrolet C20 350, 5.7 pickup truck. The motor is leaking oil. I am trying to get an idea of possible places were the motor is leaking oil and what is required to fix it.

If I was to clean the motor to have a clean motor and look for oil leakage, what is typically used to clean the motor? Also, what parts need to be covered if water is used?

What are the places the motor would leak oil? Valve cover gaskets and head gaskets? Any other places?

What is typically done to fix motor oil leakage? Replace valve cover gaskets? head gaskets? Anything else? Might it require removal of motor?

Just trying to be well informed as I look for a mechanic or mechanic shop.

Appreciate the help.

[Getter-Done]

I would start with cardboard placed under the Engine.

Then you can see a local point of the Major Leak.

There are lots of cleaners and processes.

Simple green or Purple power work.
A person just has to be cautious about spraying on Wiring and electrical stuff.

[HO455]

Any ideas on the age or mileage on the motor? On high mileage motors any gasket may be leaking. Cheap gaskets will fall before quality gaskets will. And any gasket can fail if improperly installed.

Common points that leak but don't cause other problems (Like a leaking head gasket may)
The front and rear intake manifold gaskets.
Rear main seal.
Oil pan gasket.
Front main seal.
Fuel pump.
Valve covers. This can be from bent or deformed covers as well gasket failure.
There are more but these are the most common ones I've seen over the years.

Replacing the PVC valve and hose can help as a collapsed hose or stuck valve can allow pressure to build in the crankcase.

Generally if I have a really dirty engine I will take it to the DIY car wash and use their engine wash and the high pressure spray. Just stay clear of the upper part of the engine with the spraying. And wear some safety glasses.

Old plug wires are susceptible to grounding out when wet so it's best to avoid the car wash if your plug wires are old or questionable. Taking some WD40 to spray the plug wires down after cleaning the engine is a good idea.

You didn't mention what style of transmission. The front seal on automatics can leak as well as the seal around their dipstick tube adding to the mess.

There are dyes you can add to your oil that in combination with a black light can help locate leaks. Some professionals swear by them as they make it easier to find the leak when clean oil is leaking.

Good luck on your search.

[GASoline71]

Small Block Chevy's just leak... it's what they do. Especially if it's the original engine with high miles and all original gaskets. A lot of them leaked in spots very shortly after leaving the show room floor.

A lot of leaks at the rear of the engine are caused by leaking valve cover gaskets, or the oil pressure sending unit on the back of the block behind the intake manifold.

Gary

[mr48chev]

Best idea is to grab a can of WD-40, a roll of paper towels and a flat blade #2 screwdriver and your favorite engine degreaser and a pocket full of quarters and head to the quarter car wash and clean the engine and engine compartment as well as you can. WD-40 and towels and screwdriver are to dry the inside of the distributor cap out if it gets condensation in it. get it good and clean and start checking closely .

I've got a 68 292 that ran great but was given to me because in a 180 mile road trip it leaked more oil than it used gas dollar wise. The guy bought the truck drove it home and pulled it in the garage and did an engine swap. That one is going in my 48.

[Steeveedee]

Originally Posted by mr48chev

Best idea is to grab a can of WD-40, a roll of paper towels and a flat blade #2 screwdriver and your favorite engine degreaser and a pocket full of quarters and head to the quarter car wash and clean the engine and engine compartment as well as you can. WD-40 and towels and screwdriver are to dry the inside of the distributor cap out if it gets condensation in it. get it good and clean and start checking closely .

I've got a 68 292 that ran great but was given to me because in a 180 mile road trip it leaked more oil than it used gas dollar wise. The guy bought the truck drove it home and pulled it in the garage and did an engine swap. That one is going in my 48.

Wow. That would be his loss. A few dozen dollars for gaskets, and yer done. Crazy.

[mr48chev]

Originally Posted by Steeveedee

Wow. That would be his loss. A few dozen dollars for gaskets, and yer done. Crazy.

He bought it with the very nice ready to drop in engine sitting and waiting for it. The truck was a nice original 4 speed truck that ran great but leaked oil everywhere that one can leak.

This was after they pressure washed the engine and engine compartment before pulling it.



It's getting painted 48 Chevy truck engine gray with a serious amount of finned cast aluminum on it.

[Steeveedee]

Brutal! "Take a Saws-All to that exhaust pipe! I want that engine out of here, now!" BTW, I hope you are doing away with that puny air filter.

[BROWN 70]

Quarter car wash??? my local one is 4 bucks. lol

[Getter-Done]

Originally Posted by BROWN 70

Quarter car wash??? my local one is 4 bucks. lol

For sure.

48 Chev did say a Pocket full So He Knows.

[ggalv]

Thanks, appreciate your help. Going to use this, as I work on fixing this issue.

[72c20customcamper]

I really like the Dawn Powerwash for degreasing . Didn’t think it work all that well but I was impressed. If you really want it clean use a heated pressure washer. I rented one and it was well worth it never even took it off the trailer hose was 20 ft long . Like others have said it’s most likely the intake /valve cover or oil line .

[lil hoodlum]

Originally Posted by 72c20customcamper

I really like the Dawn Powerwash for degreasing . Didn’t think it work all that well but I was impressed. If you really want it clean use a heated pressure washer. I rented one and it was well worth it never even took it off the trailer hose was 20 ft long . Like others have said it’s most likely the intake /valve cover or oil line .

I also agree, sbc usually like to leak around the intake and/or valve covers. My 327 still likes to mark it's spot wherever I park. Recently replaced valve cover gaskets and that helped a bunch.

[72c20customcamper]

Originally Posted by lil hoodlum

I also agree, sbc usually like to leak around the intake and/or valve covers. My 327 still likes to mark it's spot wherever I park. Recently replaced valve cover gaskets and that helped a bunch.

The motor I took out and replaced ran well but was leaking a lot . Guess the prior owner tried to seal it up . Big ol gob of RTV on the valley of the intake front and back and it still was leaking . I’m going to reseal it and put it in the Anniversary truck

[ggalv]

Hi, regarding the how many miles question the odometer has 40426, then it has an 8 with a white background. Not sure how many miles would this be?

Below is a picture I took today, not sure if this might be where it is leaking oil. I had the starter replaced recently, and it was covered with oil. Should some hose or some kind of cap go in the valve cover opening (circled in red)? Also, there seems to be a decent amount of oil in bolt (circled in red).

Appreciate your advice, on where this oil might be leaking from?

[Greasey Harley]

Best engine degrease I have ever found is Totally Awsome from the Dollar store.
I'm dead serious, this stuff will amaze you!!
With a cold engine mist everything with cold water.
While it's still wet start spraying Totally Awesome everwhere.
Let it set for about 5 minutes then spray it off with cold water and watch the grease and grime melt away.
Depending in how nasty the engine is, you may need to hit it several times, but it WILL come clean.
https://www.familydollar.com/las-tot...20oz/FD1412251

[WorkinLonghorn]

Looking at your picture, are you running it with that hose missing? There is supposed to be a metal connector that plugs into that hole and a tube that runs to the air cleaner. There is another hole on the other side nearer to the front that has a PCV valve and a vacuum hose to the base under the carb. If you are running it with this missing, you will have oil possibly coming out the hole (s) or in other places too. Get those two hoses and the little PCV valve ($10) hooked up and check again.

[72c20customcamper]

Originally Posted by WorkinLonghorn

Looking at your picture, are you running it with that hose missing? There is supposed to be a metal connector that plugs into that hole and a tube that runs to the air cleaner. There is another hole on the other side nearer to the front that has a PCV valve and a vacuum hose to the base under the carb. If you are running it with this missing, you will have oil possibly coming out the hole (s) or in other places too. Get those two hoses and the little PCV valve ($10) hooked up and check again.

There is a hose connected to the air breather . Odd that it has another grommet on the same cover . I would get a breather cap for the rear hole it’s looks like the oil is spraying out of it onto the valve cover and manifold

[54blackhornet]

Get yourself a repair manual for your year pickup. It will show you all the items on your engine and their intended purpose. You mention oil leaking but how does the engine run ?

[Rust_never_sleeps]

I really like this kind of plastic scraper. They don't tear up the paint or leave a ton of scratches behind, the handle delays my hand cramping up into a claw, and you can sharpen or reshape them on the garage floor in a minute.
You can get these in sets anywhere, this is just an example:
https://www.oreillyauto.com/detail/c...aper/pwt0/qss1

[WorkinLonghorn]

Originally Posted by 72c20customcamper

There is a hose connected to the air breather . Odd that it has another grommet on the same cover . I would get a breather cap for the rear hole it’s looks like the oil is spraying out of it onto the valve cover and manifold

Ok, I missed that. I agree with your post. He should post up a picture of the other (driver's) side. In my limited experience, that front hole (passenger side) is for the oil fill cap. Back passenger hole is the breather (baffled internally) and front driver's side is the PCV valve. It's just how mine have been (both California '69s).
This is step #1, get those sorted. THEN if it still leaks, look at the valve cover gasket, oil pressure line connection, etc. From the looks of it, he's running around with engine blow-by shooting oil out the open breather like Ol' Faithful.-BA

[ggalv]

Here are additional pictures. I have had the truck for awhile, but don't drive it too often and I assuming that missing hose/cap has been there all this time (see "Revision" below). The truck has ran well, but right now it's not running too good. I have been driving it around a few blocks every week for about 2 months. When I press on the gas pedal, at 10-20 mph I noticed the truck does not respond well, feels like it needs more gas, not getting the power. I am assuming this opening in the valve cover gasket does not have to do with this, since that opening has been there all this time? "Revision" - actually I had a new carburetor installed about 2 years ago, not sure if the hose that is supposed to go their might have not been installed, but I don't know, maybe it has been without the hose/cap since I got the truck. A two barrel carburetor was replaced with a four barrel carburetor. Might provide a separate thread with more detail about the truck not seeming to be getting enough gas/power and the work that has been done.

Based on the additional pictures, might this help to figure out if what is currently there correct and what I need to put in that valve cover opening?

Appreciate your help.

[WorkinLonghorn]

The way that is set up, all you need to do is plug that hole. You might want to replace the grommet on the PCV (front driver's side) because it looks cracked. FYI, you've got two right side covers. this is what you should have;

[Willshook]

Engines don't have to leak But it may be more work than you're after to fix the leaks you find. The question kinda becomes if the leak is a Big Deal - is it irritating or something that's gonna get worse or fail completely.

Don't drive yourself nuts. Clean the engine then use a UV dye kit from your local parts shop. Tells you *exactly* where it's leaking in a pretty short time.

But yeah...gotta put a plug in where that open grommet is. May not be your leak, but definitely is chuffing out oil spray. Your local parts place will have a plug, or Summit.

[HO455]

Here is a primer on the crankcase ventilation system. If the system has leaks from bad seals and/or a defective PVC valve it can cause several problems including old leaks. The system is pretty simple and the cost to repair it is low.

https://www.mechanicaleducation.com/...ion-pcv-valve/

Basically low pressure is created in one valve cover so air flows from the breather on the other valve cover into the intake manifold through the PVC valve.