Help! Oil Leak.. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

HotRod73 · 05-31-2006, 01:21 PM

I have a 73 Chevy C20 3/4 ton pickup. Has a 350 motor and is leaking. Its leaking by the flywheel cover, it has a hole in the bottom i guess to let oil drain, well its coming from there... its not leaking from behind my block i looked at the intake etc and no oil leak, its got to either be my oil pan gasket at the back, or a rear main seal, or both or i was told something about oil sending unit or something could be possibility? it isnt leaking a whole lot but its noticable on the ground and smells when truck is hot... what do you think it could be? i know my oil pan is leaking a tiny tiny bit around a few of my bolts could this be it? i havent taken my flywheel cover off to inspect but thats were the oil is dripping from.... if its my oil pan gasket, will i have to lift the motor to take the pan out or will it slide out without messing with lifting motor?

Nolowrider · 05-31-2006, 04:42 PM

Usally if it is leaking from the flexplate cover it is the rear main seal. I guess it could be the oil pan gasket, but very doubtful. I would place my money on the main seal.

jberkeley · 05-31-2006, 04:43 PM

from experience, it sounds like rear main seal.. go around the oil pan and tighten all the bolts.. that might stop some of the leaks... this might fix the main leak..if it isn't the rear main, some chevys you have to lift the engine to drop the oil pan..i have a 4x4,mine just pulls off...good luck

HotRod73 · 05-31-2006, 06:55 PM

is rear main hard fix? does this require disassembling the whole motor?... is it something i should fix or find a replacement engine? this motor only has 91k original miles and runs like a top just leaks a little... shoot it can be cold or hot and ill go out and start it, most older vehicles i see they gotta crank it... i turn my key and it barely cranks and fires up just like a new car...of course i still got points i am planning on changin to hei soon...

jberkeley · 06-01-2006, 06:26 AM

rear main seal can be fixed, if it runs that good keep it, just have the seal replaced.. older engines come with a two piece seal, the newer comes with a one piece.. i can't remember the year they changed,,,,

Slonaker · 06-01-2006, 09:12 AM

The change to the one piece rear main seal was in 1986.

Here is swervin's instructions for changing the seal:

http://www.73-87.com/7387garage/drivetrain/rearseal.htm

Slonaker

Chevrolet4x4s · 06-02-2006, 11:48 PM

My money is also on rear main seal
Shane

BigDan3131 · 06-06-2006, 03:39 PM

And yes you have to pull the motor to change it. That and they have to pull the crank to do it as the seal fits around the crank to seal it.

larry may · 06-06-2006, 03:46 PM

Be sure to check the cam plug while you are in there.It could be leaking. Mine did .

Slonaker · 06-06-2006, 05:18 PM

Quote:

Originally Posted by BigDan3131

And yes you have to pull the motor to change it. That and they have to pull the crank to do it as the seal fits around the crank to seal it.

I have never replaced one, but I am pretty sure you don't have to pull the crankshaft to do it...

Slonaker

Nolowrider · 06-06-2006, 06:27 PM

Quote:

Originally Posted by larry may

Be sure to check the cam plug while you are in there.It could be leaking. Mine did .

Larry, What is a cam plug? Never heard that before.

I have replaced the rear seal without pulling the engine or the crank. As long as you can get the oil pann off you are good to go.

Chevrolet4x4s · 06-06-2006, 11:45 PM

Quote:

Originally Posted by BigDan3131

And yes you have to pull the motor to change it. That and they have to pull the crank to do it as the seal fits around the crank to seal it.

?????Are we talking about a 1 piece seal or 2 piece? also If you can get the pan off i see no need to pull engine.
$.02
Shane

HotRod73 · 06-27-2006, 01:35 PM

well here is another thing, when i let the truck sit a few days non running doesnt seem to leak, only when i got the engine for a while then ill come out few hours later and see a little on the ground not saying it doesnt leak when non running but seems to only do it when its running for while

boatpuller · 06-28-2006, 11:31 AM

mine does the same thing...only get about a drip the size of a quarter.only drips after running it.looks like the rear main,but ends up drippin off the starter.i just put down cardboard on the garage floor,till it gets real bad.

Nolowrider · 06-28-2006, 02:17 PM

When the engine is not running there is no oil pressure and the oil is not being circulated within the engine.

HotRod73 · 06-29-2006, 02:20 PM

okay so it is the rear main seal?

89 crew · 06-29-2006, 08:19 PM

Are you sure it is engine oil? I have had one converter break the welds and leak. I have also had the converter seal leak. Most likely it is the rear main seal. If it is yes the engine will have to be lifted to get the pan off. It won't clear the crossmember. and watch the distributer when you lift it! They like to get into the firewall. Are you sure the smell is comming from there? Most of the time on the 70's 350's it is the rocker arm cover gaskets leaking that stinks things up.

HotRod73 · 06-29-2006, 11:48 PM

its engine oil... the smell is burnt oil burning from when it hits my exhaust... converter? as in catylic converter? if so i dont have converter im almost certain now its rear main failing

89 crew · 06-30-2006, 12:15 AM

What is a 73 doing with a converter? I didn't think they were factory till 75-76. As long as you have decient oil pressure the seal is the only thing failing. If the oil pressure has dropped, I would replace the oil pump and probably rods and mains since you are going to have it open. They shouldn't be trashed after 91k, but they will have some wear.

boxrodz · 06-30-2006, 12:45 AM

Quote:

Originally Posted by 89 crew

... Most likely it is the rear main seal. If it is yes the engine will have to be lifted to get the pan off. It won't clear the crossmember...

89crew,
I didn't have to lift the engine when I removed the oil pan on my truck. I've taken it off a couple of time. If you crank the engine so that the crankshaft is a position so that you have clearance for the oil pan to clear the crossmember when you slide it out. You do have to remove the bell housing first.

89 crew · 06-30-2006, 01:28 AM

I have a 76 c20 and the engine had to be lifted a few inches to clear. Mine is a 4 bolt main, don't know if that makes a difference but there wasn't any way for mine to come out without lifting.

magnethead · 06-30-2006, 02:59 AM

Quote:

Originally Posted by 89 crew

What is a 73 doing with a converter? I didn't think they were factory till 75-76. As long as you have decient oil pressure the seal is the only thing failing. If the oil pressure has dropped, I would replace the oil pump and probably rods and mains since you are going to have it open. They shouldn't be trashed after 91k, but they will have some wear.

reffering to torque convertor....

HotRod73 · 06-30-2006, 02:36 PM

oh yeah its black so its oil not tranny fluid..

HotRod73 · 06-30-2006, 02:38 PM

my oil pressure needle is right in the middle

xfsketch · 07-06-2006, 10:54 AM

I have the same problem Hot Rod 73! Ive been keeping an eye on this post as I have wondered whether or not the engine will have to be lifted to get the oil pan off. (350 4 bolt main here) My truck leaks from the flywheel cover when it is running only and smells of burning oil from it hitting the exhaust as well. Same as you my motor has low miles and runs excellent and starts cold like a new vehicle. My oil pressure is high when driving for the first 1/2 hour or so and then it drops to half way. Sometimes at idle and slow speeds it is under half. Im not a mechanic but I think my RMS is bad too. I sure hope the oil pan will come off without lifting the motor! Does anyone know if my oil pressure should fluxuate like I mentioned or should it be at half way normally? I plan on getting the #s off my engine so I can post a Q whether or not its one or two piece rear main seal. I feel for ya Hot Rod 73 keep us updated on your progress. CYA

05-31-2006, 01:21 PM	#1
HotRod73 Registered User Join Date: Mar 2006 Location: Norman, Oklahoma Posts: 553	Help! Oil Leak.. I have a 73 Chevy C20 3/4 ton pickup. Has a 350 motor and is leaking. Its leaking by the flywheel cover, it has a hole in the bottom i guess to let oil drain, well its coming from there... its not leaking from behind my block i looked at the intake etc and no oil leak, its got to either be my oil pan gasket at the back, or a rear main seal, or both or i was told something about oil sending unit or something could be possibility? it isnt leaking a whole lot but its noticable on the ground and smells when truck is hot... what do you think it could be? i know my oil pan is leaking a tiny tiny bit around a few of my bolts could this be it? i havent taken my flywheel cover off to inspect but thats were the oil is dripping from.... if its my oil pan gasket, will i have to lift the motor to take the pan out or will it slide out without messing with lifting motor?

05-31-2006, 04:42 PM	#2
Nolowrider Senior Member Join Date: Jan 2005 Location: New Orleans Posts: 1,365	Re: Help! Oil Leak.. Usally if it is leaking from the flexplate cover it is the rear main seal. I guess it could be the oil pan gasket, but very doubtful. I would place my money on the main seal.

05-31-2006, 04:43 PM	#3
jberkeley 86 chevy k-10 Join Date: Jun 2004 Location: nashua, nh Posts: 121	Re: Help! Oil Leak.. from experience, it sounds like rear main seal.. go around the oil pan and tighten all the bolts.. that might stop some of the leaks... this might fix the main leak..if it isn't the rear main, some chevys you have to lift the engine to drop the oil pan..i have a 4x4,mine just pulls off...good luck __________________

05-31-2006, 06:55 PM	#4
HotRod73 Registered User Join Date: Mar 2006 Location: Norman, Oklahoma Posts: 553	Re: Help! Oil Leak.. is rear main hard fix? does this require disassembling the whole motor?... is it something i should fix or find a replacement engine? this motor only has 91k original miles and runs like a top just leaks a little... shoot it can be cold or hot and ill go out and start it, most older vehicles i see they gotta crank it... i turn my key and it barely cranks and fires up just like a new car...of course i still got points i am planning on changin to hei soon...

06-01-2006, 06:26 AM	#5
jberkeley 86 chevy k-10 Join Date: Jun 2004 Location: nashua, nh Posts: 121	Re: Help! Oil Leak.. rear main seal can be fixed, if it runs that good keep it, just have the seal replaced.. older engines come with a two piece seal, the newer comes with a one piece.. i can't remember the year they changed,,,, __________________

06-01-2006, 09:12 AM	#6
Slonaker Insert Witty Text Here Join Date: Oct 2002 Location: San Antonio, TX Posts: 3,415	Re: Help! Oil Leak.. The change to the one piece rear main seal was in 1986. Here is swervin's instructions for changing the seal: http://www.73-87.com/7387garage/drivetrain/rearseal.htm Slonaker __________________ '86 Chevy C10 (Sold 04/19/13 ) Stock '01 Silverado

06-02-2006, 11:48 PM	#7
Chevrolet4x4s Registered User Join Date: Nov 2005 Location: WV Posts: 227	Re: Help! Oil Leak.. My money is also on rear main seal Shane __________________ 1993 K1500 350 5 speed 1985 K10 Silverado Vortec 406 5 speed (in body shop) "I been drivin' this '85 pickup truck Them buddies of mine call it a bucket of rust She's a little beat up but she still runs like the wind Yeah, kinda like me I been banged and bruisedBeen around the block a time or two But I'm runnin' like new goin' places I never been No, I ain't broke I'm just broken in" 1963 Dodge Townwagon(its amazng what 30 years and zero miles will do to a vehicle ) Member#20327

06-06-2006, 03:39 PM	#8
BigDan3131 Registered User Join Date: Jun 2006 Location: Maple Valley, WA Posts: 1,913	Re: Help! Oil Leak.. And yes you have to pull the motor to change it. That and they have to pull the crank to do it as the seal fits around the crank to seal it.

06-06-2006, 03:46 PM	#9
larry may Senior Member Join Date: Jul 2005 Location: MISSOURI Posts: 3,256	Re: Help! Oil Leak.. Be sure to check the cam plug while you are in there.It could be leaking. Mine did .

06-27-2006, 01:35 PM	#13
HotRod73 Registered User Join Date: Mar 2006 Location: Norman, Oklahoma Posts: 553	Re: Help! Oil Leak.. well here is another thing, when i let the truck sit a few days non running doesnt seem to leak, only when i got the engine for a while then ill come out few hours later and see a little on the ground not saying it doesnt leak when non running but seems to only do it when its running for while

06-28-2006, 11:31 AM	#14
boatpuller Registered User Join Date: Sep 2005 Location: Sun City West, Az Posts: 3,822	Re: Help! Oil Leak.. mine does the same thing...only get about a drip the size of a quarter.only drips after running it.looks like the rear main,but ends up drippin off the starter.i just put down cardboard on the garage floor,till it gets real bad.

06-28-2006, 02:17 PM	#15
Nolowrider Senior Member Join Date: Jan 2005 Location: New Orleans Posts: 1,365	Re: Help! Oil Leak.. When the engine is not running there is no oil pressure and the oil is not being circulated within the engine.

06-29-2006, 02:20 PM	#16
HotRod73 Registered User Join Date: Mar 2006 Location: Norman, Oklahoma Posts: 553	Re: Help! Oil Leak.. okay so it is the rear main seal?

06-29-2006, 08:19 PM	#17
89 crew Registered User Join Date: Mar 2006 Location: Kansas Posts: 865	Re: Help! Oil Leak.. Are you sure it is engine oil? I have had one converter break the welds and leak. I have also had the converter seal leak. Most likely it is the rear main seal. If it is yes the engine will have to be lifted to get the pan off. It won't clear the crossmember. and watch the distributer when you lift it! They like to get into the firewall. Are you sure the smell is comming from there? Most of the time on the 70's 350's it is the rocker arm cover gaskets leaking that stinks things up.

06-29-2006, 11:48 PM	#18
HotRod73 Registered User Join Date: Mar 2006 Location: Norman, Oklahoma Posts: 553	Re: Help! Oil Leak.. its engine oil... the smell is burnt oil burning from when it hits my exhaust... converter? as in catylic converter? if so i dont have converter im almost certain now its rear main failing



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06-30-2006, 12:15 AM	#19
89 crew Registered User Join Date: Mar 2006 Location: Kansas Posts: 865	Re: Help! Oil Leak.. What is a 73 doing with a converter? I didn't think they were factory till 75-76. As long as you have decient oil pressure the seal is the only thing failing. If the oil pressure has dropped, I would replace the oil pump and probably rods and mains since you are going to have it open. They shouldn't be trashed after 91k, but they will have some wear.

06-30-2006, 01:28 AM	#21
89 crew Registered User Join Date: Mar 2006 Location: Kansas Posts: 865	Re: Help! Oil Leak.. I have a 76 c20 and the engine had to be lifted a few inches to clear. Mine is a 4 bolt main, don't know if that makes a difference but there wasn't any way for mine to come out without lifting.

06-30-2006, 02:36 PM	#23
HotRod73 Registered User Join Date: Mar 2006 Location: Norman, Oklahoma Posts: 553	Re: Help! Oil Leak.. oh yeah its black so its oil not tranny fluid..

06-30-2006, 02:38 PM	#24
HotRod73 Registered User Join Date: Mar 2006 Location: Norman, Oklahoma Posts: 553	Re: Help! Oil Leak.. my oil pressure needle is right in the middle

07-06-2006, 10:54 AM	#25
xfsketch 72 fleetside longbed 350 Join Date: Feb 2006 Location: Ohio Posts: 169	Re: Help! Oil Leak.. I have the same problem Hot Rod 73! Ive been keeping an eye on this post as I have wondered whether or not the engine will have to be lifted to get the oil pan off. (350 4 bolt main here) My truck leaks from the flywheel cover when it is running only and smells of burning oil from it hitting the exhaust as well. Same as you my motor has low miles and runs excellent and starts cold like a new vehicle. My oil pressure is high when driving for the first 1/2 hour or so and then it drops to half way. Sometimes at idle and slow speeds it is under half. Im not a mechanic but I think my RMS is bad too. I sure hope the oil pan will come off without lifting the motor! Does anyone know if my oil pressure should fluxuate like I mentioned or should it be at half way normally? I plan on getting the #s off my engine so I can post a Q whether or not its one or two piece rear main seal. I feel for ya Hot Rod 73 keep us updated on your progress. CYA Last edited by xfsketch; 07-06-2006 at 11:01 AM.

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