Oil leak Conundrum - The 1947 - Present Chevrolet & GMC Truck Message Board Network

72K10 · 11-08-2002, 09:53 PM

I have an oil leak in my rebuilt 350. I've gone back and replaced the intake gaskets and front seals (crank, timing cover). Still leaks. Hard to tell where it's coming from. Wondering if it might be the fuel pump. Would a poor seal at the fuel pump cause 1/2 qt leak every 200 miles?

Thanks,

Chris

chucks70 · 11-08-2002, 10:28 PM

I don't know if it will help or not, but previous posts on a mystery leak suggest an open bolt hole by the fuel pump. It's one where you can put a longer bolt in to hold the rod inside up and make reinstallation easier. Oil will just pump right out of it. If all the holes around the fuel pump don't have a bolt in them, try that. Make sure not too long though, may interfere with the push rod inside.

*Piston* · 11-08-2002, 10:45 PM

Double check the missing bolt as Chucks70 mentioned. Very common and will usually leak very bad at highway speeds and not so much while idling.

Degrease the engine and let it dry, make sure your oil level is good then find a nice clean/dry area to let your truck run a bit.

Once things are dry and you have a clean area, start the engine and let it idle for a few minutes while checking for leaks. See any leaks underneath yet? While the engine is still somewhat dry, you'll be able to trace back to the source of the leak. If no, raise the rpm to 1200 or so (first step on a Q-jet carb choke) while checking for leaks. Look closely at the intake end rails(where the block meets the intake). If after 10 minutes of run time and you still have no leaks, may be time to take it in. Find someone thats willing to do a dye leak detection. They will add a few ounces of oil dye and verify your leak using a blacklight. (this is the basic procedure I would take at the shop)

You mentioned the front seal/timing cover, did you check your harmonic balancer shaft? the seals create a very deep groove in the balancer sealing area and will leak. If so, install a harmonic balancer sleeve.

Longhorn Man · 11-08-2002, 10:53 PM

I dunno, if that bolt was missing, it'd leak more like 3 qts an hr.

*Piston* · 11-08-2002, 10:56 PM

Alot of it depends on how much crankcase pressure there is. If its a relativly new engine, there will be small amounts of pressure there until the rpm's come up.

Older engines will literally pump it out, like your saying. It's a tough leak to find for a person thats never run across it before. Oil EVERYWHERE lol.

11-08-2002, 09:53 PM	#1
72K10 Registered User Join Date: Dec 1999 Location: New York Posts: 288	Oil leak Conundrum I have an oil leak in my rebuilt 350. I've gone back and replaced the intake gaskets and front seals (crank, timing cover). Still leaks. Hard to tell where it's coming from. Wondering if it might be the fuel pump. Would a poor seal at the fuel pump cause 1/2 qt leak every 200 miles? Thanks, Chris __________________ RLTW 70C10 72K10 72K10 Cheyenne 72C10 Cheyenne Super

11-08-2002, 10:28 PM	#2
chucks70 Registered User Join Date: Feb 2002 Location: Cadiz, OH Posts: 628	I don't know if it will help or not, but previous posts on a mystery leak suggest an open bolt hole by the fuel pump. It's one where you can put a longer bolt in to hold the rod inside up and make reinstallation easier. Oil will just pump right out of it. If all the holes around the fuel pump don't have a bolt in them, try that. Make sure not too long though, may interfere with the push rod inside. __________________ 68 1 ton dually 292, 2001 Sebring, 2004 Trailblazer, 11 Camaro Convertible.

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11-08-2002, 10:45 PM	#3
Piston Account Suspended Join Date: Oct 2002 Location: Olathe, KS Posts: 2,301	Double check the missing bolt as Chucks70 mentioned. Very common and will usually leak very bad at highway speeds and not so much while idling. Degrease the engine and let it dry, make sure your oil level is good then find a nice clean/dry area to let your truck run a bit. Once things are dry and you have a clean area, start the engine and let it idle for a few minutes while checking for leaks. See any leaks underneath yet? While the engine is still somewhat dry, you'll be able to trace back to the source of the leak. If no, raise the rpm to 1200 or so (first step on a Q-jet carb choke) while checking for leaks. Look closely at the intake end rails(where the block meets the intake). If after 10 minutes of run time and you still have no leaks, may be time to take it in. Find someone thats willing to do a dye leak detection. They will add a few ounces of oil dye and verify your leak using a blacklight. (this is the basic procedure I would take at the shop) You mentioned the front seal/timing cover, did you check your harmonic balancer shaft? the seals create a very deep groove in the balancer sealing area and will leak. If so, install a harmonic balancer sleeve.

11-08-2002, 10:53 PM	#4
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	I dunno, if that bolt was missing, it'd leak more like 3 qts an hr.

11-08-2002, 10:56 PM	#5
Piston Account Suspended Join Date: Oct 2002 Location: Olathe, KS Posts: 2,301	Alot of it depends on how much crankcase pressure there is. If its a relativly new engine, there will be small amounts of pressure there until the rpm's come up. Older engines will literally pump it out, like your saying. It's a tough leak to find for a person thats never run across it before. Oil EVERYWHERE lol.



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