Is it possible on a LS engine? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Vintage Windmills · 01-02-2013, 08:14 PM

To have a leak from the rear main seal and not have oil on the flywheel/flexplate? My Lq4 6.0 has been leaving a little spot on the driveway for over a year now always thought it was the rear main since the whole area around the cast inspection cover was wet. I pulled this cast aluminum cover today and the flexplate is dry. The inside of the upper trans housing where it bolts to block is also dry. I would think a leaky main would fling oil all around the bellhousing? There was a small puddle in the inspection cover but the whole area from one side of the oil pan to the other is wet so it could have seeped in I suppose. I could see the oil pan leaking on one side but the odds of both sides would be pretty low I'd think. Looks pretty dry up high by the valve covers. This has me frustrated

Vintage Windmills · 01-03-2013, 12:34 AM

Some pics from underneath looking up

ls1nova71 · 01-03-2013, 12:37 AM

Anything is possible I suppose, but if the rear main was leaking bad enough to drip on the ground, I would think it would be on the flexplate. Are your oil cooler lines seeping or are they dry? Also the bypass block off above the oil filter will leak sometimes, as well as oil pressure senders. Just some thoughts.

Littletony · 01-03-2013, 12:40 AM

Jud,
How does the oil pan gasket look? If I recall right the oil pan seals against the rear main so it maybe coming from the pan.

v62go · 01-03-2013, 01:27 AM

mine was doing the same thing,turned out to be the dipstick tube...

**LEEVON** · 01-03-2013, 01:53 AM

Oil pressure sending unit can look like a rear main leak as well.

Vintage Windmills · 01-03-2013, 12:02 PM

Since you guys have identified so many possibilities, is there a dye I can put in the oil to see where the origin is?

Quote:

Originally Posted by ls1nova71

Anything is possible I suppose, but if the rear main was leaking bad enough to drip on the ground, I would think it would be on the flexplate. Are your oil cooler lines seeping or are they dry? Also the bypass block off above the oil filter will leak sometimes, as well as oil pressure senders. Just some thoughts.

Lines are dry. It could be the bypass block, seems wet around there too. Is there a gasket or O ring behind that? Any idea how hard that is to remove and replace gasket?

Quote:

Originally Posted by Littletony

Jud,
How does the oil pan gasket look? If I recall right the oil pan seals against the rear main so it maybe coming from the pan.

Hi Tony, its hard to see the gasket, pan fitment looks normal.

Quote:

Originally Posted by v62go

mine was doing the same thing,turned out to be the dipstick tube...

Interesting

Quote:

Originally Posted by LEEVON

Oil pressure sending unit can look like a rear main leak as well.

It seems fine but I will check out.

Littletony · 01-03-2013, 12:08 PM

Yes there is a dye kit you can buy. But you have to be careful when using it. Because under the UV light that comes with the kit coolant will show up just like the dye.

you can buy the kit from any tool supplier or napa.

ls1nova71 · 01-03-2013, 11:29 PM

I would get under there with a couple cans of Brakleen, and spray it off real good then drive it and see if you can tell where it's coming from. How many miles does it have on it? What year?

Vintage Windmills · 01-03-2013, 11:45 PM

Right on guys, I picked up some oil dye today at Oreillys for $8 and a black light bulb at Walmart for $4. So as soon as I recover a little more from this cough i'm fighting I hope to pinpoint the leak. Looking forward to trying this technique out! Engine is 11 years old with 80k on it. Just broke in for these motors.

brad_man_72 · 01-04-2013, 02:11 AM

I came in to say oil pressure sending unit also. If it is BUY THE TOOL!
I also had a prob w the dipstick tube but it showed up on the starter more than anything.
Good luck, I hope its something simple.
Posted via Mobile Device

Vintage Windmills · 01-05-2013, 09:15 PM

No luck with the dye today. I used the whole bottle which was the proper amount according to instructions. Its either still too diluted in my oil or my oil is too dirty or the bulb isn't good. I didn't see anything flourescence, even on oil dripping from the drain plug when I loosened it. This is frustrating.

towbar · 01-05-2013, 09:27 PM

I think you need a UV light to see the florescent glow of the die.....not sure the Wal-Mart black light is UV? Someone else may have a better answer?

dlh760 · 01-05-2013, 10:02 PM

It does need to be a uv light which is not the same as a black light even though they look similar
Posted via Mobile Device

Pzary3233 · 01-05-2013, 10:33 PM

There is an oil galley plug on the back side of the block inside the bellhousing. I'll find a pic for you.

Littletony · 01-06-2013, 01:22 AM

Quote:

Originally Posted by towbar

I think you need a UV light to see the florescent glow of the die.....not sure the Wal-Mart black light is UV? Someone else may have a better answer?

HE is right, plus you need a pair of glasses that have yellow lenses in them. They will help block out the other light source's. Once you have them you maybe able to see the die with your black light.

russellmarling · 01-06-2013, 04:12 PM

X 3 on the oil pressure sending unit. Common failure. I replace one of these every couple weeks at work. Unplug it and see if the electrical connector is full of oil.

Vintage Windmills · 01-06-2013, 06:12 PM

Quote:

Originally Posted by russellmarling

X 3 on the oil pressure sending unit. Common failure. I replace one of these every couple weeks at work. Unplug it and see if the electrical connector is full of oil.

Just did this, connector was dry. Does this rule it out? Theres some oil back around it on this part of the engine but it doesn't look too wet. Was hoping this would be the culprit since it would explain why both sides down the back of the block are wet. Theres a dripping off the starter bolts on one side and the oil filter bypass block on the other.

I bought a tracer products light and glasses kit from Oreillys that is being shipped to my house from their warehouse. Looks like its good for A/C diagnosis as well so that will be nice for my 71 with the 402. Should be here tuesday.

01-02-2013, 08:14 PM	#1
Vintage Windmills Vintage 4x4s Join Date: Sep 2010 Location: Prior Lake, MN Posts: 4,305	Is it possible on a LS engine? To have a leak from the rear main seal and not have oil on the flywheel/flexplate? My Lq4 6.0 has been leaving a little spot on the driveway for over a year now always thought it was the rear main since the whole area around the cast inspection cover was wet. I pulled this cast aluminum cover today and the flexplate is dry. The inside of the upper trans housing where it bolts to block is also dry. I would think a leaky main would fling oil all around the bellhousing? There was a small puddle in the inspection cover but the whole area from one side of the oil pan to the other is wet so it could have seeped in I suppose. I could see the oil pan leaking on one side but the odds of both sides would be pretty low I'd think. Looks pretty dry up high by the valve covers. This has me frustrated __________________ 67 GMC K1500 Custom- 305V6 SM420, PTO, Ram Assist, yellow (the outcast) (project period correct upgrades) 67 GMC C2500 351V6 TH400, AC, PS, PB (can't decide what to do with. Update, decided to keep and will restore ) 86 CHV K30 502 th400, apple red NEW 71 CHV K20 350 SM465, ochre (saved work truck) 71 CHV K20 292 SM465, white, tach, PTO, (future project) 72 CHV K20 350 350th, medium blue (project stocker) 01 CHV K2500hd crew, indigo blue ^3 dont run and the others don't see winter either '86 K30 Cummins "Fireside" thread: http://67-72chevytrucks.com/vboard/s...d.php?t=649649 '71 K20 "get driveable" thread: http://67-72chevytrucks.com/vboard/s...d.php?t=590642 '72 K20 Build Thread: http://67-72chevytrucks.com/vboard/s...=493477&page=6

01-03-2013, 12:34 AM	#2
Vintage Windmills Vintage 4x4s Join Date: Sep 2010 Location: Prior Lake, MN Posts: 4,305	Re: Is it possible on a LS engine? Some pics from underneath looking up Attached Images __________________ 67 GMC K1500 Custom- 305V6 SM420, PTO, Ram Assist, yellow (the outcast) (project period correct upgrades) 67 GMC C2500 351V6 TH400, AC, PS, PB (can't decide what to do with. Update, decided to keep and will restore ) 86 CHV K30 502 th400, apple red NEW 71 CHV K20 350 SM465, ochre (saved work truck) 71 CHV K20 292 SM465, white, tach, PTO, (future project) 72 CHV K20 350 350th, medium blue (project stocker) 01 CHV K2500hd crew, indigo blue ^3 dont run and the others don't see winter either '86 K30 Cummins "Fireside" thread: http://67-72chevytrucks.com/vboard/s...d.php?t=649649 '71 K20 "get driveable" thread: http://67-72chevytrucks.com/vboard/s...d.php?t=590642 '72 K20 Build Thread: http://67-72chevytrucks.com/vboard/s...=493477&page=6

01-03-2013, 12:37 AM	#3
ls1nova71 Registered User Join Date: Dec 2009 Location: Independence Mo Posts: 4,118	Re: Is it possible on a LS engine? Anything is possible I suppose, but if the rear main was leaking bad enough to drip on the ground, I would think it would be on the flexplate. Are your oil cooler lines seeping or are they dry? Also the bypass block off above the oil filter will leak sometimes, as well as oil pressure senders. Just some thoughts. __________________ My '72 short bed build. http://www.ls1tech.com/forums/conver...6-0-4l80e.html 5.3 swap into my RUSTY '71 C10 http://ls1tech.com/forums/conversion...71-c-10-a.html

01-03-2013, 12:40 AM	#4
Littletony Registered User Join Date: Sep 2010 Location: Jacksonville, NC Posts: 596	Re: Is it possible on a LS engine? Jud, How does the oil pan gasket look? If I recall right the oil pan seals against the rear main so it maybe coming from the pan. __________________ "Some people spend an entire lifetime wondering if they've made a difference. The Marines don't have that problem." President Ronald Reagan,1985 "The Marines I have seen around the world have the cleanest bodies, the filthiest minds, the highest morale, and the lowest morals of any group of animals I have ever seen. Thank God for the United States Marine Corps!" ..............Eleanor Roosevelt, 1945

01-03-2013, 01:27 AM	#5
v62go Registered User Join Date: Feb 2012 Location: davidson north carolina Posts: 105	Re: Is it possible on a LS engine? mine was doing the same thing,turned out to be the dipstick tube...

01-03-2013, 01:53 AM	#6
LEEVON Moderator Join Date: Jul 2006 Location: Ozark, MO Posts: 4,888	Re: Is it possible on a LS engine? Oil pressure sending unit can look like a rear main leak as well. __________________ '20 Silverado Trail Boss ~ '17 Tahoe ~ '79 K15 Sierra Grande ~ '76 Blazer 2wd ~ '71 Cheyenne swb ~ '55 Pontiac Safari ~'50 3100 bagged ~ '80 Wife ~ Late model kids

01-03-2013, 12:08 PM	#8
Littletony Registered User Join Date: Sep 2010 Location: Jacksonville, NC Posts: 596	Re: Is it possible on a LS engine? Yes there is a dye kit you can buy. But you have to be careful when using it. Because under the UV light that comes with the kit coolant will show up just like the dye. you can buy the kit from any tool supplier or napa. __________________ "Some people spend an entire lifetime wondering if they've made a difference. The Marines don't have that problem." President Ronald Reagan,1985 "The Marines I have seen around the world have the cleanest bodies, the filthiest minds, the highest morale, and the lowest morals of any group of animals I have ever seen. Thank God for the United States Marine Corps!" ..............Eleanor Roosevelt, 1945

01-03-2013, 11:29 PM	#9
ls1nova71 Registered User Join Date: Dec 2009 Location: Independence Mo Posts: 4,118	Re: Is it possible on a LS engine? I would get under there with a couple cans of Brakleen, and spray it off real good then drive it and see if you can tell where it's coming from. How many miles does it have on it? What year? __________________ My '72 short bed build. http://www.ls1tech.com/forums/conver...6-0-4l80e.html 5.3 swap into my RUSTY '71 C10 http://ls1tech.com/forums/conversion...71-c-10-a.html

01-03-2013, 11:45 PM	#10
Vintage Windmills Vintage 4x4s Join Date: Sep 2010 Location: Prior Lake, MN Posts: 4,305	Re: Is it possible on a LS engine? Right on guys, I picked up some oil dye today at Oreillys for $8 and a black light bulb at Walmart for $4. So as soon as I recover a little more from this cough i'm fighting I hope to pinpoint the leak. Looking forward to trying this technique out! Engine is 11 years old with 80k on it. Just broke in for these motors. __________________ 67 GMC K1500 Custom- 305V6 SM420, PTO, Ram Assist, yellow (the outcast) (project period correct upgrades) 67 GMC C2500 351V6 TH400, AC, PS, PB (can't decide what to do with. Update, decided to keep and will restore ) 86 CHV K30 502 th400, apple red NEW 71 CHV K20 350 SM465, ochre (saved work truck) 71 CHV K20 292 SM465, white, tach, PTO, (future project) 72 CHV K20 350 350th, medium blue (project stocker) 01 CHV K2500hd crew, indigo blue ^3 dont run and the others don't see winter either '86 K30 Cummins "Fireside" thread: http://67-72chevytrucks.com/vboard/s...d.php?t=649649 '71 K20 "get driveable" thread: http://67-72chevytrucks.com/vboard/s...d.php?t=590642 '72 K20 Build Thread: http://67-72chevytrucks.com/vboard/s...=493477&page=6

01-04-2013, 02:11 AM	#11
brad_man_72 the boat guy Join Date: Jul 2007 Location: springfield mo Posts: 2,339	Re: Is it possible on a LS engine? I came in to say oil pressure sending unit also. If it is BUY THE TOOL! I also had a prob w the dipstick tube but it showed up on the starter more than anything. Good luck, I hope its something simple. Posted via Mobile Device __________________ 67, swb, fleet, tach, throttle, 5.3, 4l60e, 3.73's, fuel cell, 5 lug, p.d.b., 4-6 drop. great little truck 66, stevens drag/ski 18' silouette, 350, 2.02 doublehump heads. comp extreme marine 278 cam, vette 7 fin valve covers, old polished edelbrock intake, velvetdrive, casale v-drive, adj cavitation plate. 28, model a rpu project,

01-05-2013, 09:15 PM	#12
Vintage Windmills Vintage 4x4s Join Date: Sep 2010 Location: Prior Lake, MN Posts: 4,305	Re: Is it possible on a LS engine? No luck with the dye today. I used the whole bottle which was the proper amount according to instructions. Its either still too diluted in my oil or my oil is too dirty or the bulb isn't good. I didn't see anything flourescence, even on oil dripping from the drain plug when I loosened it. This is frustrating. __________________ 67 GMC K1500 Custom- 305V6 SM420, PTO, Ram Assist, yellow (the outcast) (project period correct upgrades) 67 GMC C2500 351V6 TH400, AC, PS, PB (can't decide what to do with. Update, decided to keep and will restore ) 86 CHV K30 502 th400, apple red NEW 71 CHV K20 350 SM465, ochre (saved work truck) 71 CHV K20 292 SM465, white, tach, PTO, (future project) 72 CHV K20 350 350th, medium blue (project stocker) 01 CHV K2500hd crew, indigo blue ^3 dont run and the others don't see winter either '86 K30 Cummins "Fireside" thread: http://67-72chevytrucks.com/vboard/s...d.php?t=649649 '71 K20 "get driveable" thread: http://67-72chevytrucks.com/vboard/s...d.php?t=590642 '72 K20 Build Thread: http://67-72chevytrucks.com/vboard/s...=493477&page=6

01-05-2013, 09:27 PM	#13
towbar Registered User Join Date: Jul 2012 Location: Marshall, NC....heart of the Appalachians.....aka, Gods country!! Posts: 537	Re: Is it possible on a LS engine? I think you need a UV light to see the florescent glow of the die.....not sure the Wal-Mart black light is UV? Someone else may have a better answer?

01-05-2013, 10:02 PM	#14
dlh760 Registered User Join Date: Oct 2012 Location: valley center,ca Posts: 124	Re: Is it possible on a LS engine? It does need to be a uv light which is not the same as a black light even though they look similar Posted via Mobile Device __________________ 68 Chevy c10 longbed 307 with 305 H.O. heads,edelbrock performer intake,edelbrock performer plus cam,hei,Holley 650 double pumper and th400. Daily driver. It hauls butt,it hauls my butt where I need to go

01-05-2013, 10:33 PM	#15
Pzary3233 Registered User Join Date: Apr 2012 Location: Memphis, TN Posts: 65	Re: Is it possible on a LS engine? There is an oil galley plug on the back side of the block inside the bellhousing. I'll find a pic for you. __________________ '55 3200 283 4 speed '68 Pontiac Firebird Poncho powered with a 6 speed

01-06-2013, 04:12 PM	#17
russellmarling Registered User Join Date: Jan 2006 Location: Highlands, NC Posts: 138	Re: Is it possible on a LS engine? X 3 on the oil pressure sending unit. Common failure. I replace one of these every couple weeks at work. Unplug it and see if the electrical connector is full of oil. __________________ '70 GMC SWB step-side- 454, 4 speed, air bags (in progress) '09 CTS-V M6 '03 Sierra SWB Z71 '82 Yamaha Seca XJ650R Turbo! '04 Yamaha FZ6



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