High Oil Pressure and Leaking After Oil Change

I've got an issue that has me stumped. I have a 1977 K10 that has a 350 Goodwrench crate motor installed by a previous owner so mileage is unknown. It's my daily driver and runs great. It has had a rear main seal weep for a while, but nothing more than a few drops overnight so I've put off changing it. I've been driving it every day for over a year and the oil pressure has consistently been about 20 PSI at idle and 30 PSI at highway speed and it hasn't used oil at all.

Recently I changed the oil and filter. 10w-30 oil and PF 35 oil filter. Immediately after the change I noticed the oil pressure was 30 PSI at idle and 45-50 PSI at highway speed. After sitting overnight there was a small puddle of oil under the truck, not a ton, but enough to concern me. The oil filter was tight and the drain plug was not leaking. It appeared the oil was leaking out of the flywheel shield as it would with a rear main seal problem.

I drove it a few days, probably about 100 miles and the higher than normal pressure and the leaking continued. I checked the oil and it was down about a quart. Since the only thing I had done was the oil change I suspected maybe an issue with the filter. I changed the oil and the oil filter again and the exact same condition continues. Higher than normal pressure and a fairly nasty oil leak out the hole in the bottom of the flywheel shield.

The engine runs great, isn't burning any oil or misbehaving at all. I'll be changing the rear main seal this weekend, but the high oil pressure indication has me worried that something else is going on.

Has anyone experienced anything similar or any advice on what else to look at? Maybe it was just coincidence, but it seems to have been caused by the oil and filter change and that makes absolutely no sense to me.

this may sound ridiculous but check your dip stick, i had a similar problem and it turned out when the motor was rebuilt the tube for the dip stick was just shoved in the hole and not driven in all the way, i was told it was a higher capacity oil pan so i didnt really think about the fact it would take 5 to 5 1/2 quarts instead of 4, i had the same issue high oil pressure and oil leaking from weird spots, was told the high oil pressure was from a high volume oil pump, i figured it out more or less by accident, the tube for the dip stick was allways loose and would spin around i finally got sick of it and tried giving it a gentle tap to see if it would snug up, turns out it needed to be driven in about 3/4 to an inch, once that was done i realized ive been over filling the oil by about a quart and a half, once i had the oil level correct my oil pressure went down to normal and it quit leaking due to the reduced pressure in the block.

If it were me, I would remove the air cleaner and look real good at the distributor. It is meant to have a gasket underneath it.
ADDITIONALLY, I would put some bamboo shoots under the fingernails of the oil pressure warning light thingy and find out W.T.F. his problem is. If it gives ya any sh*t? Whack it with a hammer.

If you have had perfect oil pressure up till you changed the oil. You have a bad oil filter. Its causing the oil pump to pump harder causing the pressure to go up which i turn is causing a bigger leak change it. I know you put an AC DELCO on it but ive had issues in the past. Put a k&n oil filter on it i know it cost more but it will fix you problem.

Jimmyperf400 said:

If you have had perfect oil pressure up till you changed the oil. You have a bad oil filter. Its causing the oil pump to pump harder causing the pressure to go up which i turn is causing a bigger leak change it. I know you put an AC DELCO on it but ive had issues in the past. Put a k&n oil filter on it i know it cost more but it will fix you problem.

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That was my first thought also, but I changed the oil and filter again and this time went with a WIX filter. It didn't help. I have exactly the same symptoms even after changing the filter for a second time.

Danderson said:

That was my first thought also, but I changed the oil and filter again and this time went with a WIX filter. It didn't help. I have exactly the same symptoms even after changing the filter for a second time.

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Certainly sounds like a blockage somewhere in the system to me. Do you have an external oil cooler with lines going up to the small oil radiator in front of the main radiator (I have one on my Suburban but don't know which models did or did not include this)? If so, thats the 1st place I'd check for a blockage since that is (as far as I know) the only configuration that intentionally has the oil exiting the engine block. Otherwise you could have an internal blockage which will be harder to find (but I would closely examine where the oil filter screws on for anything covering the openings).

Someone mentioned the bad oil filter.... But - did you make sure the plastic was taken off the oil filter as well before screwing it on?

I know, sounds crazy but it happens.

OR, the oil in it was thinner, now it's correct viscosity and running normal oil pressure? Fix the leak(s), and stop worrying about normal oil pressure readings.

DoubleDingo said:

OR, the oil in it was thinner, now it's correct viscosity and running normal oil pressure? Fix the leak(s), and stop worrying about normal oil pressure readings.

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was thinking the same thing if it was an oil issue.....but visa versa. Example the engine had thicker oil in it and you put thinner in it. Either way, can you mask a leak by putting thinner/thicker oil in an engine? Never heard that trick, just going by what happened.

Camar068 said:

was thinking the same thing if it was an oil issue.....but visa versa. Example the engine had thicker oil in it and you put thinner in it. Either way, can you mask a leak by putting thinner/thicker oil in an engine? Never heard that trick, just going by what happened.

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Thinner will leak easier, for sure. His leak could be valve cover gaskets, intake gaskets, distributor gasket, , oil pan gasket(s), maybe even oil pressure sender not being tight, or rear main(possible, but not worth changing until everything else is known to be non-leaking). Lots of places to look before tackling the rear main.

I had a leak that I thought was rear main, and it turned out to be intake gaskets.

Happens all the time.

45 psi sounds like a good "normal" oil pressure to me, better than 20psi for sure.

slammed84 said:

45 psi sounds like a good "normal" oil pressure to me, better than 20psi for sure.

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Yup.

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